Electric shower, anything I can do? - Page 1
Forum section: electronics / general

author: paulca
author_rank: Super Contributor
timestamp: July 23, 2019, 06:55:35 pm
content: So, new house, has electric shower. Shower has three settings, cold, low, high.On low, when I turn it up enough to get good temperature, I get sod all flow/pressure.On high, I have to turn it down to minimum or I get scalded and even then it can overheat and cut out occasionally.So I guess this is because my upstairs water pressure is absolutely rubbish. On low it uses a smaller element and when I turn it up it reduces the flow to make it hotter. However on high there isn't enough water pressure to supply the element with enough flow to keep the temp reasonable.I assume there is nothing I can do with that, like adjust the flow restrictor or something?I'm planning on upgrading the whole heating system to a pressurized setup, so this is a temporary problem, but an annoying one!

author: soldar
author_rank: Super Contributor
timestamp: July 23, 2019, 07:47:30 pm
content: I take it you are dealing with an "on demand" heater which heats the water as it goes by? In America they also call them "tankless".I have a natural gas tankless heater and they are crap. You cannot enjoy a shower with stable temperature. And if your pressure and flow are not stable it makes the situation so much worse.In my second home I have a big tank heater and it is much better. And you can even fit a thermostatic valve and temperature stability will be rock solid.For a good shower you want a good tank of hot water. It does not need to be very hot, just 40 or 45ºC will do so you only need to mix very little cold water. Excessively hot water temperature is dangerous and should be avoided.

author: Nusa
author_rank: Super Contributor
timestamp: July 23, 2019, 08:21:06 pm
content: Dangers of talking to an international audience. Terminology isn't clear, since in America most people would ask "What's an electric shower?" In this case, I'm assuming a point-of-use on-demand water heater, either in arms length from the shower or actually in the shower head itself.His other comments make me think he's on a gravity-fed system, using a cistern up in the attic space. Something else that's almost unheard of in American residences. Naturally pressure sucks if the vertical drop is small.I also presume that new house means old house that is new to him. Or he would have a more modern setup to start with.

author: ebastler
author_rank: Super Contributor
timestamp: July 23, 2019, 08:36:12 pm
content: Quote from: paulca on July 23, 2019, 06:55:35 pmAs others have pointed out, your terminology is not self-explanatory, especially to those in other countries. I take it that "low" and "high" are settings which affect the heating power? While, when you talk about "turn it up", you mean the flow rate - right?QuoteNow you have really confused me. If you set the heating power to high, I could imagine a situation where you have to crank the flow up tomaximum, because otherwise the water gets too hot. But you need to turn it (the flow?) down to minimum?! What's going on??

author: themadhippy
author_rank: Super Contributor
timestamp: July 23, 2019, 08:55:52 pm
content: try reducing the flow out of the shower,not the flow into the shower ,a washer between the pipe and rubber washer in the shower hose was the old skool way,or get an adjustable flow shower head

author: Brutte
author_rank: Frequent Contributor
timestamp: July 23, 2019, 09:07:26 pm
content: Quote from: paulca on July 23, 2019, 06:55:35 pmBefore you rip apart whole plumbing, I'd suggest temporarily installing a manometer (just screw it to a tap) and doing some measurements. It might be that your heater is going to work just fine if you reduce the pressure on the input and stabilize it. Include winter temperatures in your calculations, leave some headroom.

author: nctnico
author_rank: Super Contributor
timestamp: July 23, 2019, 09:12:45 pm
content: A more simple solution is to add a regular thermostatic valve to the output of the electric water heater. That way it will keep the water output temperature constant. These are pretty cheap if you can do with a temporary crappy one.

author: soldar
author_rank: Super Contributor
timestamp: July 23, 2019, 09:36:00 pm
content: Quote from: nctnico on July 23, 2019, 09:12:45 pmWill probably not work. I have some experience with these issues. A thermostatic valve will work when you have two streams at relatively constant pressure and temperature but an on demand heater, if you restrict the flow of hot water then the water just gets heated more.If you have unstable pressure then the best way to have constant water temperature is to have a full tank of water at the temperature you want. There is nothing that can upset that.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2019, 09:40:08 pm
content: Quote from: soldar on July 23, 2019, 07:47:30 pmTankless water heaters are great *if* the whole system is designed around one and everything is sized properly. The problems usually occur when one is retrofitted into an existing home that was plumbed to use a conventional water tank, or when the system is designed with less care than necessary. With a small household a conventional tank is fine, but for a medium sized family it can be a struggle not to run out of hot water frequently when you have people showering, doing laundry, washing dishes, etc. Both conventional tank and tankless systems have advantages and disadvantages but I don't think it's fair to call one whole category crap.

author: soldar
author_rank: Super Contributor
timestamp: July 23, 2019, 10:06:51 pm
content: Quote from: james_s on July 23, 2019, 09:40:08 pmOh, I agree. But a big tank of water is much more forgiving and will generally provide more stable temperature regulation.Providing stable temperature regulation with an on demand heater is much more complex because you need a feedback system that adjusts the power input in order to maintain a stable temperature. You can have an electric power control so that the water temperature remains stable. With a gas heater it can be done only within certain margins and is much more complicated.On demand heaters have the advantage of not needing a tank (which takes space) and not needing to maintain the temperature of the tank so there can be a savings in energy.On the whole I prefer a tank of water at a temperature very slightly higher than needed at the point of use. It is difficult to beat that for temperature stability and for simplicity.If you need lots of water, more than a tank can hold, you could place a on-demand heater in front of the tank and that way the tank provides a big temperature buffer.

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 23, 2019, 10:58:22 pm
content: I think Electroboom made a video about electric showers.

author: james_s
author_rank: Super Contributor
timestamp: July 23, 2019, 11:51:06 pm
content: I have a conventional tank which I have set quite hot as the hot water is nice for washing dishes and things and mixing it with cool water at the point of use allows a modestly sized tank to go a lot further. Definitely downsides to this too though, it's a safety issue for kids (which I don't have) and it's harder on the tank. Temperature surges were once an issue but when I redid the bathroom I installed one of those valves that regulates the differential pressure and that has worked very well.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 24, 2019, 01:02:04 am
content: Try putting a diode in series with the heater?

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 06:53:46 am
content: Yes, sorry, forgot the international audience.The shower is a wall fitted unit that takes cold water in, has 9Kw of heating elements, and hot water comes out of the shower head. It's on it's own circuit with a current breaker and RCD. So if the water ever conducts it will, hopefully conduct to earth and trip the RCD. Remember it's 240V, so 9Kw is circa 37 amps. Usually these are wired with 10mm twin and earth cable.The house is old, built 1968. It has an unpressurized, vented hot water system with a cistern in the attic keeping it full. So both the cold and hot water are gravity fed upstairs. The shower runs off the cold and apparently, according to a plumber has a priority valve trying to insure it gets the water pressure if other taps are turned on. This makes the water pressure really poor even when the shower is off.The temperature control seems to just change the water flow rate to alter the temperature. So when I say "minimum" I mean minimum setting for temperature which equates to maximum flow rate.The comment about winter temps is an interesting one as "Big Clive", during dismantling one reported the "Low" setting was for "summer" when the tap water is a few degrees warmer. So maybe, it will just be a bit like it is now for the next few months and when the mains water (and the water sitting in the warm attic) cools down it will be fine.The heating system is oil fired central heating with an heat exchanger coil in the "hot tank" in a cupboard upstairs. There is even less pressure from it. In fact the shower attachment on the normal hot tap won't even flow when you lift it up to showering height, it literally stops.The heating upgrade is basically to modernize the system. Modern systems that are being installed around here are natural gas (utility fed from the street, used to be known as "town gas" when it was made from coal) boilers and a mains pressurised system, so the attic cistern comes out and the whole central heating and hot water system is fed from a mains water inlet. So around here that's about 2-3 bar (I think). It's going to cost me about £3000 but £2400 of that is interest free credit for a year.

author: MosherIV
author_rank: Super Contributor
timestamp: July 24, 2019, 07:14:10 am
content: If I understand the plumbing correctly, the electric shower is fed from a water tank in the loftTry connecting the electric shower to mains water, run the water in let up to the electric shower heater. Most electric showers are designed to be run from mains water.Modern house plumbing no longer use a tank in the loft. The whole house is run off mains water.

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 08:21:05 am
content: Quote from: MosherIV on July 24, 2019, 07:14:10 amI'm aware of this, but the house has not (yet) been modernised. I am "assuming" it is run from the header tank in the loft as that's normal for a system of this age.So I'm resigning myself to put up with it until I can re-do the heating as a pressurized mains fed system. That's possible to get done this autumn as apparently it should only take 2 days to complete.On a related note the choice has been presented to me as to whether I want a "Combi" set up or a "System" setup. The former has no hot tank and water is heated on demand by the gas boiler. I have had this before and it's awesome; turn on a tap and you have scalding hot water in about 20 seconds. However the downside is, I have no hot tank and cannot later take advantage of solar PV water heating. It also has a more invasive and expensive install as the hot water tap circuit needs replumbed to the boiler. Going the system approach I have a heat exchanger in the hot tank so the gas can heat it, but I can put a DC immersion in the tank at a later time and as long as I can control the hot water/heating circuit valve and the circulation pump I will save on gas for heating not just the water but the radiators too. Of course 1kW of solar will not go that far, but it will heat the to tank to 60*C fairly easily during the day.

author: soldar
author_rank: Super Contributor
timestamp: July 24, 2019, 09:51:05 am
content: I have designed and modified a few domestic hot water systems of very different nature. My boat, homes with on-demand heaters and homes with tanks. Depending on your aim and needs some may work better than others and all can be made to work relatively well if you make it expensive and complicated enough.Domestic hot water systems are not complicated to understand for anybody who has the ability to understand electronic circuits and can be modeled very similarly.On-demand systems intrinsically suck at maintaining water temperature because basically they dump a fixed amount of energy into the water and any change in any parameter will result in a change in temperature. So you need to be able to modulate the energy and have a feedback loop that measures output temperature and modulates energy accordingly. This is possible and is done but adds initial expense and complication and risk of problems and failures.One advantage of tankless systems is you save a little space but that makes sense only if you have the tiniest of apartments. Another advantage for systems with very little use is you are not maintaining a tank full of hot water which means losses that need to be replaced.But, on the whole, by and large, a tank system is going to provide better results, better water temperature stability at lower initial cost.I have seen homes in England with both gas heaters and electric on demand heater. I never understood it. It seems salespeople sell stuff and homeowners buy stuff they don't really need because they do not understand the problem or the system.If you want to have an electric on-demand water heater and you require stable temperature then there is only one thing to do which is to modulate electric power with a feedback loop that measures output water temperature. And studying the system it will have certain limits, an envelope of pressures, flows, input temperatures, etc. This is what gas heaters do and they are incredibly complicated and expensive.Right now water arrives from the mains quite warm and needs very little warming up for a shower but my on-demand heater cannot provide so little heat. It is below the minimum it can do even at the minimum setting. A solution which works but might not be obvious to non tech people is to open the sink hot water and dump some hot water that way. Dump half or 3/4 of scalding water down the drain and use 1/4 in the shower mixed with cold water. Not very energy efficient but with a gas heater there is not much else you can do.With an electric heater it is trivial to insert a triac power control and regulate the temperature manually but it is better to sense the temperature automatically as it leaves the heater and insert a small tank or long pipe to stabilize any fluctuations.But, yes, I have seen plumbing and water heating systems in the UK that are hard to understand for anyone with a bit of understanding. I think it may be a combination of patching very old systems and not really understanding how things work.For a while I was staying in China in an apartment with a gas on-demand water heater which was impossible to get a decent temperature. The water was either scalding or boiling. I very soon learned to use two low stools. Put a tub on one and mix hot and cold water until I got the desired temperature. Then sit on the other stool and use a mug to shower water from the tub over myself. Works pretty well and saves a lot of water.I was doing the same thing on my boat until I fixed the system which has its own complications, including cycling pumps.

author: alanb
author_rank: Frequent Contributor
timestamp: July 24, 2019, 09:59:05 am
content: Quote from: paulca on July 23, 2019, 06:55:35 pmPut your efforts into upgrading the whole heating system. This annoyance is a great incentive to upgrade as soon as possible.

author: stevelup
author_rank: Regular Contributor
timestamp: July 24, 2019, 11:40:07 am
content: You can get better electric showers - one example is the Mira Advance - this is thermostatically controlled and modulates the heater. Means the temperature is unaffected by water pressure.Have a look at Triton as well - they do about half a dozen different thermostatically controlled ones.Triton also do one with a pump. So if your current one is fed from a loft tank rather than the mains, you could go for that.But to be honest, as has already been said, electric showers are a bit crappy anyway. Is there no way you can get a proper hot+cold feed to the location. The only advantage with putting another electric one in would be simplicity of installation.

author: richard.cs
author_rank: Super Contributor
timestamp: July 24, 2019, 12:08:18 pm
content: Quote from: paulca on July 24, 2019, 08:21:05 amYou should check that assumption. This kind of shower is essentially unusable on a header tank and I've never seen one plumbed that way. Even in houses with header tanks they usually tee off the rising cold before it goes into the tank, otherwise they just don't work at all, in most cases refusing to turn on due to low pressure. If it really is on the header tank then rearranging the plumbing is step 0 but I suspect as it sort of works you'll find it is on mains pressure just your mains pressure is crap.As you describe it you essentially have too big a gap between high and low, you need a "medium" which many of these showers have but not yours. It's probably one element or both with the two of similar power, better ones either have 3 elements or two dissimilar ones to give three power settings e.g. 3 kW, 6 kW and 6+3 kW. You may be able to create a medium setting of 1.5 elements by putting a diode in series with one of them, you'd then have cold, low and medium rather than cold low and high.They usually have a mechanical pressure regulator up front to take out the worst of the variation when someone uses water elsewhere in the house, and you'll find that changing settings between summer and winter is necessary. Some of the fancy modern ones do active temperature control by varying the input power rather than having a valve to restrict the water flow. Buying one of those or much cheaper buying a 3-step basic one would probably fix your problem, but any electric shower really needs connecting to mains pressure water.As a side note, be careful with your decision to go with a pressurised system and presumably a combi boiler (instant gas water heating combined with central heating for the international audience). They have a number of disadvantages over awell designedlow pressure system with storage and these are often skimmed over by installers wanting to sell the shiny and new.

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 12:53:33 pm
content: Quote from: soldar on July 24, 2019, 09:51:05 amInteresting comments. A few of them, from my experience...Having an on-demand electric water heater is common in most UK households with a hot tank. It's simply because you might not want to put the heat on in summer. Might be a surprise but none of the houses I have lived with a hot tank have had the ability to select "Hot water only" for the boiler. So in summer you simply wouldn't use the heating to get hot water as that would heat the house radiators too.The on-demand heater, usually referred to locally as "The immersion heater" and often a switch or pull cord in the kitchen is a 13A or 30A immersion heater. However it's not just an element stuck at the bottom of the hot tank. It takes water out of the bottom, heats it through a coil and via convection dumps it into the top of the tank where it will stay, heating the water from the top down. The hotwater outlet is designed to take water from the top of the tank if available. In my house if the water is cold because the heating has been off, the "immersion heater" will have it hot enough to scald your hands in about 1 minute. Obviously if you try and run a bath with that or have a shower it will use up the layer of hot water rapidly and it will run cold. You can heat the whole tank with the immersion heater but it would be wasteful.This issue is why people put electric showers in. It's so that they don't need to rely on running the heating in summer or using the immersion.Yes systems do exist with an electrical operated valve to select "Hot water", "Radiators" or "Both" but they are very rare here.A triac on a 7Kw water heater will never get past UK electrical codes. I expect it will be, large, noisy, expensive and likely to melt or go on fire at some point.Hot water in the UK comes out of the tap as hot as you can legally make it. The 65*C target is very often breached by gas boilers and electric water heaters. My previous apartment would happily produce water close to 80*C. You could almost make tea or coffee with it. All most all taps in UK homes are mixer taps. This is a rather recent thing as there are regulations stating that the hot and cold taps be separate anywhere the hot tank is coming from a header tank system as it can potentially contain stagnant water. This regulation has become lax however and many people fit mixer taps in the bathroom regardless of the regs.So you can expect the hot water to be absolutely scalding and expect to have to mix cold with it to get a temperature for bathing.

author: stevelup
author_rank: Regular Contributor
timestamp: July 24, 2019, 12:56:01 pm
content: You say very rare, I say I have -never- seen a house without independent control over heating and hot water!

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 01:04:14 pm
content: Quote from: richard.cs on July 24, 2019, 12:08:18 pmCan you elaborate a little?I was considering going for the System boiler approach which has just a hot water circuit flowing through the heat exchanger coil in the hot tank, which, assuming I fit an electrical routing valve giving me control of hot water only, radiators only and both gives me the best of all worlds.The main difference is that this system runs at mains pressure, so as soon as you pull water out of the hot tank it is replaced by the cold mains inlet.

author: richard.cs
author_rank: Super Contributor
timestamp: July 24, 2019, 01:12:13 pm
content: Quote from: stevelup on July 24, 2019, 12:56:01 pmAgreed, I've not seen one either. A choice between hot water only, or hot water and heating together is very common, i.e. many UK systems can't do heating without hot water but most can do hot water without heating. It doesn't even need an extra valve, many of them rely on gravity circulation for the hot water (boiler on, water tank gets hot) and a pump to circulate the heating water (boiler and pump on, hot water and radiators get hot).

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 01:19:09 pm
content: Quote from: richard.cs on July 24, 2019, 01:12:13 pmIs this a mainland thing? I have lived in about 5 different places in Northern Ireland with vented/pumped heating systems and there has only ever been one control, heating on, heating off. If it's on, you get both hotwater and radiators, if it's off you get neither.The coal fired system "did" have a circulation pump control, a spur switch on the wall. However that didn't have any effect on the heating/hot water it just sped the process up instead of it relying on convection alone.

author: richard.cs
author_rank: Super Contributor
timestamp: July 24, 2019, 01:21:07 pm
content: Quote from: paulca on July 24, 2019, 01:04:14 pmSystem boiler plus storage tank is essentially what you have now, only at the moment you have a low pressure storage tank and you're proposing a high pressure one. This is often a good system as you get mains pressure hot water without the downsides of a combi boiler. It's not a very common approach in the UK mainly because of historical inertia I think but there is not a lot wrong with it. You can generally expect it to behave like a mains pressure version of your current system. Disadvantages over low pressure tank are generally that it's normally a smaller tank holding less hot water and that the tank lasts less long (they're coated steel rather than copper so they corrode out). If your household tends to have baths rather than showers you might prefer a low pressure system (little else has the ability to fill a bath of hot water as quickly as a header tank and large-bore pipes), if your household is small and hot water usage is max one shower at a time then a combi might be better than either storage approach.Storage (either kind) also gives you free electric backup (immersion heater) and gives you some future options for solar heating.

author: richard.cs
author_rank: Super Contributor
timestamp: July 24, 2019, 01:24:47 pm
content: Quote from: paulca on July 24, 2019, 01:19:09 pmMaybe it is. I have lived in four places in the South of England, all had low pressure hot water systems with a choice of hot water only or hot water plus heating. All of my friend's and family's houses are either like this, have a choice of all three, or have combi boilers.

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 01:26:15 pm
content: Quote from: richard.cs on July 24, 2019, 01:21:07 pmThanks Richard, this confirms my thoughts. I expect the conversion plumbing will be easier going to high pressure storage "System boiler" than combi anyway. And I am interested later in attaching a DC immersion from a solar panel.

author: richard.cs
author_rank: Super Contributor
timestamp: July 24, 2019, 01:35:13 pm
content: Quote from: paulca on July 24, 2019, 01:26:15 pmThe one to watch there is the thermostat. They won't survive switching DC so an external contactor or similar is needed.If you have a plastic header tank you also need to have a high-reliability way of ensuring you never boil the tank.* Standard (modern) immersion thermostats have a second set of contacts which fire at about 90 C and are not self-reseting to get double fault to danger, you need to replicate that level of safety so a single contactor driven by the thermostat isn't really good enough.*There have been a couple of scary incidents in which stuck immersion contacts have boiled the storage tank, forcing circulation into the roof tank until it too is filled with very hot water. The plastic tank then gives way pouring 100 gallons of near-boiling water onto the poor sod asleep below.

author: soldar
author_rank: Super Contributor
timestamp: July 24, 2019, 01:47:35 pm
content: Every country has its own culture in everything, including solutions to common technical problems. It is interesting to see this as you live in different countries.In Spain gas water boilers (heaters) have a combined system where they can heat the house radiators and the domestic hot water. In the summer you can have domestic hot water without heating the house. The thought that you either do both or none seems rather crazy to me. If you want domestic hot water you need to heat the house? How crazy is that? What's the point?Still, these combined gas heaters are complicated and expensive and when they break down everything goes down.I like to have independent systems as much as I can and as simple as possible. But people love the idea of saving a little space and having a compact gadget that does five things although it does them all badly.A friend of mine bought a combined scanner-printer against my advice. Shortly after the printer stopped working and I got a free scanner.People love buying a laptop computer because they "don't have the space". Then they bitch when the smallest thing breaks and it is too expensive to repair. Or when they can't install that card or whatever.People love the apparent simplicity and later find out things do not work so well.For simplicity, low cost and reliable service it is hard to beat the American system of having a domestic hot water tank separate from the house heating.I always bitch about this to my friends. In Spain you can go to a really expensive, luxurious home but you can't take a comfortable shower there because water temperature is wildly unstable. WTF? What kind of luxury is that? I'd rather live in a shack with a good shower.

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 01:52:28 pm
content: Yes. I have a number of thoughts about the solar heating thermostat issue. You "can" get DC thermostats, they are expensive though. The option I have heard used most often is electronic switching. That presents it's own issues though.A lot of people just "match" the element to the power point of the panel and connect them direct. However as I live insunnyNorthern Ireland I need proper MPPT to get anything on cloudy days. So a controller will be required. This is were it gets complicated as these are not mass-produced consumer items yet. There are a few projects out there that will sell you a controller, or give you the design files and let you build one. Currently I am aiming towards that approach. The output of the buck converter would be made aware of the temperature, much in the same way a solar charge controller is aware of the battery voltage. It will basically open circuit the panel when the water hits 65*C or so.Obviously this needs done in a fail safe way and the idea of having a further bi-metallic non-reseting contact thermostat set to a much higher temp does sound like a nice fail safe device. Even though a DC version will be expensive, in retaliative terms it might be worth paying £50 for it.

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 02:00:53 pm
content: Quote from: soldar on July 24, 2019, 01:47:35 pmI also want independant systems for certain things. Presently in 99% of UK homes if the mains electric goes down you will have no heating, no hot water, no light, running water only while the local pumping station's generator runs. You might have gas, oil and god knows what else, but they all require electric to operate. Cookers, fridges, everything does. The electric is extremely reliable but power cuts of 1 or 2 hours once or twice a year do happen.There is of course the potential of a rare but extreme solar flare or other damage which could in the worst case take out a few sub-stations which might take weeks/months to repair. The local electric board will often use truck sized generators to cover these outages while sub stations are repaired, but following major grid damage how likely is this?So I already have a source for lighting by using batteries charged on off-grid solar to run small 3W LED lights. I intend to put a bottled gas hob in. I intend to put a wood burning stove in the living room. The only thing I need them is a DC operated freezer (or bottled gas) from a boat or caravan.It's not exactly prep'ing, but I think we all rely far too much on the electrical grid. I fear that without electric for longer than a few days and common order will start to break down and riots start.On the American system I think we have to really consider how much energy they use compared to the rest of the world, I believe the average US household uses 4 times the energy as a UK household. They pay next to sod all for their energy and probably think nothing of running an electrical heating element in their hot tank 24/7/365!

author: BMK
author_rank: Regular Contributor
timestamp: July 24, 2019, 02:33:27 pm
content: If this is your ubiquitous plastic tanked instant electric shower my Mira / Triton etc.. .There is no thermostat except a high limit safety to stop the thing from boiling. The outlet water temperature is completely dependent on incoming water temp, element power and flow rate. There are 2 fixed heater powers (hi/low switch) and the main knob actually just adjusts the flow rate. Depending on on the temp of incoming water and the flow rate chosen (seasonally variable as most attics are blazing hot in summer) you get steady water outlet temp. In my experience the flow gets restricted due to blocked inlet filter and/or scaling of the shower head itself. The effect of the adjustment knob is dominated by the other restrictions. It is a 2 minute job to remove and clean the filter. Google your model.

author: SteveyG
author_rank: Unknown
timestamp: July 24, 2019, 03:11:51 pm
content: Quote from: richard.cs on July 24, 2019, 12:08:18 pmI would go further and say the pressure switch would not activate on the shower if gravity fed at a height of probably 2m maximum.Firstly, confirm it is connected to mains water. Secondly, confirm the stop tap is properly open both at the water meter and at the incomer to the house. Finally, upgrade the shower to a Mira Thermostatically controlled electric shower.If it's been fitted to the header tank, I'd also check the electrical installation as the installer did not know what they were doing.

author: SteveyG
author_rank: Unknown
timestamp: July 24, 2019, 03:20:54 pm
content: Quote from: paulca on July 24, 2019, 01:26:15 pmDifference in effort between Combi boiler installation and Heat Only with a cylinder is minimal. The only thing which may need more work on the combi boiler is the gas supply will be undersized, so more likely than not will need a 22 or 28mm feed from the meter.Additional complexities from the pressurised tank are related to the safety systems which need plumbing to outside through specific means to comply with G3 regulations.Both systems have pros and cons, so don't just accept what an installer suggests. Energy costs for a combi boiler will be higher if you use a lot of hot water and for most of the combis available in the UK, there is both a lag between turning on the tap and getting hot water but also a minimum flow rate before you get hot water.With the unvented cylinder you do have standing losses and of course you lose out on space. You won't have unlimited hot water either, even with a fast recovery coil.

author: soldar
author_rank: Super Contributor
timestamp: July 24, 2019, 04:35:33 pm
content: There's no way I would run a water system without, at least, 30 m water pressure. 40 m is better and 20 m bare minimum. I want to see water coming out of the faucet when I open it.In the country home I have an automatic pump. It used to be you needed a pressure system with a pump that would cycle on and off and the water pressure would be like sawteeth, up and down, which is a pain if you are using a tankless water heater. Now I have a pump that automagically detects flow and starts itself and maintains constant pressure until flow stops. No pressure vessel, no pressure switches, no nothing, just the self-priming pump.It maintains a pressure of about 25 ~ 30 m which works pretty well. It is mounted in the garage, over the 1000 L water tank.Same at home as on the boat the first issue to resolve is maintain good and stable water pressure.

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2019, 04:48:08 pm
content: Quote from: BMK on July 24, 2019, 02:33:27 pmThanks, good info.It's this one:http://secure.tritonshowers.co.uk/media/custom/upload/File-1352735182.pdfI'll see if cleaning the filter helps. I also intend to replace the shower head as it's a bit knackered and doesn't actually have the "mode" I like.

author: Towger
author_rank: Super Contributor
timestamp: July 24, 2019, 05:17:55 pm
content: You have the wrong model shower for a tank feed system. Yours is designed for mains feed.The Triton T90 (+various sub versions) is their tank feed shower, it is much the same but has a small (noisy) pump. The new (si?) version moved to a DC pump motor and is supposed to be much quieter. In any event the T90 should have it's own feed point from the tank, not 'T'ed from the main outlet.

author: Someone
author_rank: Super Contributor
timestamp: July 25, 2019, 07:45:51 am
content: Quote from: soldar on July 24, 2019, 09:51:05 amThis is all dependent on the specific heater, instantaneous/continuous/on demand gas water heaters are widely used in Australia but they have closed loop regulation at the heater. When used with a controller to set the desired output temperature for each use there are no problems with stability other than low flow rates.

author: paulca
author_rank: Super Contributor
timestamp: July 25, 2019, 08:22:58 am
content: Quote from: Someone on July 25, 2019, 07:45:51 amI think it depends on how you want to use the hot water. I 'can' imagine that a shower could send a signal to the boiler to request a temperature so the shower only runs the hot water and varies it's signal to the boiler to achieve the temperature it wants. However I can't see this as practical unless that boiler is specifically for the that shower alone. If someone turns on the kitchen hot tap what temperature would the boiler deliver?The on-demand combi boiler in my last place produced water around 70-80*C and the shower had a bi-metal valve. As soon as the hotwater was flowing the heating circuit would be shut off, if active and the boiler would produce hot water as hot as it could get it. The shower bi-metalic valve then regulated the amount of cold water that got added to maintain a temperature.Anyway, I checked my mains inlet stop cock and found it not fully open, so my water pressure on the cold taps has increased. This included the bathroom cold tap which tells me the upstairs cold feed has been redirected to the mains and so the shower is most likely running on mains water pressure. I didn't get to test the shower last night or this morning (long story), but I also bought a new shower head to exclude the existing one was gunked up. I'll see how it goes tonight.

author: soldar
author_rank: Super Contributor
timestamp: July 25, 2019, 10:05:07 am
content: Quote from: Someone on July 25, 2019, 07:45:51 amYes, they are widely used in Spain too. They are the most used solution here. Some drawbacks I see:Compared to tanks they are complicated, expensive to buy, expensive to repair and prone to needing repairs. To do all that regulation they have complex electronic systems that can break down and if you are lucky you can find a replacement board very expensively. If you are unlucky you need to replace the whole heater. OTOH, a water tank just sits there for decades and knows nothing about electronics or repairs.On demand gas heaters can only modulate power within certain limits, say 35 or 40% at the lower limit and 100% at the upper limit. If it is going to actually modulate then you need your centerpoint to be, say between 50 and 80% of capacity, so you have range to move around. So, really, the modulation range is not that great.Add to that the great variation in power needs and you can see an on-demand heater is just not suitable for many circumstances.Assume in winter water arrives at 4ºC and you need 15 L/min at 74ºC.Assume in summer water arrives at 24ºC and you need 3 L/min at 40ºC.The ratio of power requirements is over 20 and no on-demand heater can do that or even come close while a tank can do that and more.The combined heating and domestic water on-demand gas boilers we have here resort to different tricks and they kind of work but they are more inefficient than simpler solutions.In summary, a complicated solution, expensive, prone to problems, inefficient, expensive to buy, expensive to run, expensive to maintain and repair.These days we are having a heat wave in Europe and water is coming out of the faucet at over 25ºC. The minimum amount of heating my gas heater can provide is way over what I need for a shower so the only way to take a shower is to open another faucet and dump heated water into the drain while I shower. Not something I like to do. Maybe I can take a bath instead.I understand the need for complicated solutions in a spacecraft where space is at a premium but I prefer not to spend hundreds or thousands of euros and endure crappy showers just to save a little space and have a nice heater hanging on the wall.Yes, we have on demand gas heaters here. I don't like them. Personally, I prefer a tank any day but that's just me. Other people have other preferences.

author: richard.cs
author_rank: Super Contributor
timestamp: July 25, 2019, 10:17:42 am
content: Quote from: soldar on July 25, 2019, 10:05:07 amYour incoming water temperature range is very wide, here we see much lesser variation though it is still problematic for on demand heating. In the UK our water temperature range is more like 10ºC winter to 20ºC summer.Are your water distribution pipes run on the surface of the ground (I have seen this a lot in Italy but I have never been to Spain) or very shallow buried? In the UK we bury ours about 1 metre deep to prevent them freezing in the winter and I suspect that may be why we see less variation in temperature. As you said before the variation between how different countries do things is very interesting.

author: soldar
author_rank: Super Contributor
timestamp: July 25, 2019, 11:01:11 am
content: Water pipes here are buried because we also get hard freezes here. I suppose it is fairly complicated to determine the factors in water temperature. First would be the temperature in the open reservoirs. I suppose there are huge pipes many km long that take the water to the city. I don't think those would add much. Then maybe big tanks and reservoirs and then thinner distribution pipes. I have no idea what the influence of each may be.It may be that the last riser from the sidewalk to the apartments has most influence as it is the thinnest and most exposed. I don't know.I am always measuring this kind of thing but it never occurred to me to ask other neighbors. They already think I'm weird enough and I don't need to make it worse.Receiving the water in winter just above freezing seems logical to me. In the summer I would expect more variation because if you have thin pipes exposed to the Sun the water can get very hot. The good thing then you don't need heating it.

author: Someone
author_rank: Super Contributor
timestamp: July 25, 2019, 11:25:15 am
content: Quote from: soldar on July 25, 2019, 10:05:07 amIn this country (before rebates or incentives) instantaneous heaters are around the same price or cheaper to buy and have been showing similar longevity to tank systems. But they cost significantly less to operate over their lifetime, so much so that they have a payback period of just 3 years if you replace a storage system. This will vary on your local energy pricing, tariffs, temperatures, etc.Quote from: soldar on July 25, 2019, 10:05:07 amAll the units I'm familiar with do have power control with ratios over 20, even beyond a factor of 30 so based on your choice of numbers they work fine. This is going back 20 years so its nothing new or exclusive, there are multiple suppliers of products which meet those requirements.Storage units can't deliver any temperature other than their current point, so most of the time they are being used with cold water mixed in at the load. You're keeping a big pile of hot water hot for the minority use case, its silly and outdated.Quote from: paulca on July 25, 2019, 08:22:58 amIts a simple system, the boiler unit has a well regulated output temperature which can be changed in a second or so. If you can't possibly wash you hands in the kitchen with 43 degree water while someone else is showering, or wait for them to finish their shower before running a washing tub at 60 degrees, then you've got some first world problems.

author: soldar
author_rank: Super Contributor
timestamp: July 25, 2019, 12:38:03 pm
content: Quote from: Someone on July 25, 2019, 11:25:15 amI am interested in this. I'd like to see a gas water heater that can modulate output from say 12 KW down to say 500 W. Sounds very interesting.Other than that there is no need to belittle my preference just as I don't belittle yours. You do whatever you want. I don't care. Just allow others their own choice.

author: richard.cs
author_rank: Super Contributor
timestamp: July 25, 2019, 12:55:09 pm
content: Quote from: soldar on July 25, 2019, 12:38:03 pmSame, in the UK I've not seen anything near 20:1, many are more like 4:1 and 10:1 is considered to be very good. Once you go below their minimum they either cycle and the temperature swings wildly, or just turn off and go cold.

author: soldar
author_rank: Super Contributor
timestamp: July 25, 2019, 01:45:41 pm
content: Storage tanks also are necessary and useful when using solar panels to heat the water. While I lived in America my house had solar panels and a big tank and I hardly ever needed supplemental heat, only a bit in the winter. In the summer though I had more heat than I needed and I would flush the toilet with buckets of scalding hot water.

author: Nauris
author_rank: Regular Contributor
timestamp: July 25, 2019, 07:06:33 pm
content: For reference I draw schematic how hot water and heating is arranged here traditionally. (altought these days heat pumps are very much in, oil not so much)

author: soldar
author_rank: Super Contributor
timestamp: July 25, 2019, 07:20:13 pm
content: Quote from: Nauris on July 25, 2019, 07:06:33 pmThe problem with using a heat exchanger in the big heating tank for domestic hot water is that (1) you need the big tank always hot, which makes no sense when you do not need heating, and (2) efficiency suffers.On demand combined heaters here do that and it works for certain values of "works". One advantage of not heating the domestic hot water directly with the flame but through an exchanger is that is adds a lot of temperature stability but, again, efficiency suffers a lot.Another thing I would add is that if they are not required by code I would still require thermostatic valves anywhere a person might get hit by that water. All bathroom, kitchen faucets, etc. Most people do not realize how dangerous hot water is and how fast it can scald. I know of a very serious case of a baby in a bathtub who pulled the control lever and got badly burnt. If you do not have Thermostatic valves installed and you have children, old people, distractable people, etc. in the house you should really consider lowering the heater temperature as much as possible.

author: paulca
author_rank: Super Contributor
timestamp: July 25, 2019, 09:19:01 pm
content: Quote from: Someone on July 25, 2019, 11:25:15 amSo you are suggesting that when I want hot water of X degrees for X purpose I put my shoes on and go out to the boiler and set the hot water temperature manually and when I then want to use the water at Y degrees for Y purpose I go and change the temperature at the boiler again?Who does that? In fact most combi boilers with on demand hot water are just set at MAX and you mix hot and cold at the demand with a mixer tap. They are of course differential, so if you want a low temp, it's mostly cold and very little hot is used. The boiler will put out hotter water with a lessened flow, but it's really not an issue and surprisingly easy to balance by moving the tap, or shower valve.The benefit of this approach with a shower is that you must mix a bunch of cold into the hot, which gives you even higher pressure.

author: Nusa
author_rank: Super Contributor
timestamp: July 25, 2019, 10:36:13 pm
content: Quote from: soldar on July 25, 2019, 07:20:13 pmI totally agree with you in general. However, the costs of that decision varies greatly with climate, since it's a pretty efficient solution when you DO need heating.Nauris's "here" is presumably Finland. The heating season encompasses the bulk of the year. It happens I am of Finnish heritage, and spent a year there as a child. That's when I learned to ice skate, although I was pretty inept compared to the local kids.Your here is presumably Spain, which I believe has a long hot summer. Not the same thing at all.Where I am currently (coastal southern california) my heating season is about 1 month long. It wouldn't make sense at all.The bulk of the UK is probably closer to Finland in climate than either of us.

author: soldar
author_rank: Super Contributor
timestamp: July 25, 2019, 11:48:38 pm
content: Well, yes, obviously any solution needs to be tailored to the specific circumstances and many factors come into play like different costs of energy sources, type of use, etc.

author: Someone
author_rank: Super Contributor
timestamp: July 26, 2019, 03:22:46 am
content: Quote from: soldar on July 25, 2019, 12:38:03 pmNot disagreeing with your preferences but you repeated provably false statements as fact, so just correcting your misinformed position that you make so loudly. 500W is down in the electric power level, most gas systems bottom out at a few kW but since they are all continuous flow models you can have multiple in series/parallel configurations for people with very special requirements for ranges or volumes of water.Quote from: paulca on July 25, 2019, 09:19:01 pmIts like you are living in the 19th century. We have controls inside the house to set the temperature, no messing with mixer taps to try and get the temperature where you want it.

author: sambonator
author_rank: Regular Contributor
timestamp: July 26, 2019, 04:08:27 am
content: I thought this thread was about this...

author: paulca
author_rank: Super Contributor
timestamp: July 26, 2019, 06:50:03 am
content: Quote from: Someone on July 26, 2019, 03:22:46 amDo you have multiple boilers too for when there are more than one person in the house and they want different water temp? What about when the washing machine fills (if it's a hot fill model)?In the UK the heating systems are fairly simple and as someone correctly pointed out the "heating season" is most of the year. In fact I run my heating at least 30 minutes every morning 365 days a year. In summer here, if it's sunny and/or warm then you really don't need the heating, but "summer" here in Northern Ireland is about one, maybe two weeks, before it returns to cloudy, rainy, cool and damp again and the heating will be needed the odd evening. From September to May it's needed at least 1-2 hours a day, more like 4-8 hours a day in winter when it's -2*C in the mornings, is dawn at 9am, dusk at 4pm and the temp barely gets above 5*C most days.19th century, no, but my house, like the vast majority of them was build decades ago (1968 actually). There are houses around here build 100 years ago. Sure they could be modernised (and I'm trying to modernise mine), but there are limits to what you can do depending on your budget. New builds with vast acreage are very rare here, unless you want to live in the middle or nowhere or can afford to spend millions on your house. I gather that is not quite the same as Aus. A 3 bed semi detached with a total of aprox. 100m2footprint is circa 150,000GBP, a large detached house with 200m2 is going to cost you 300,000GBP. Renovating that £150,000 house to be all modern tech like your image suggests will cost you 30,000-100,000GBP. Even just a new basic heating system will cost me 3,000-5,000.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 08:18:53 am
content: First you said:Quote from: Someone on July 25, 2019, 11:25:15 amNow you contradict that:Quote from: Someone on July 26, 2019, 03:22:46 amI think you may be overestimating your knowledge in this field.Quote from: Someone on July 26, 2019, 03:22:46 amThere is a bunch of us here having a pleasant exchange and your aggressive and unpleasant attitude just ruins it for me. Other people seem to be able to disagree without being disagreeable. I do not need this and will not be addressing any aggressive posts. I hope whatever is bothering you gets resolved and you can enjoy a good day. And if it is my posts that upset you I recommend using the "ignore poster" list. It works very well for me. Posters that I do not consider worth my time go on that list and it saves me a lot of scrolling.

author: paulca
author_rank: Super Contributor
timestamp: July 26, 2019, 09:37:03 am
content: Anyway, I have found this discussion interesting. Obviously as I am embarking on an expensive change to my heating system to modernise it I'm a little nervous about picking the wrong approach.While realising the international audience and different climates and different types of system out there, I thought I would ask for opinions on the merits between the options I have.1. Keep the same basic type of system, ie. a "System boiler" which has the heat exchange coil in the hot tank, ideally with an electric valve to choose between hot water only, heating only or both.2. Replumb the system to be on-demand hot water only, removing the hot tank entirely.To be honest, having lived with option 2 for nearly 15 years I do really like it. The downside is it removes my ability to later use solar PV water heating. Also the heat fed into the hot tank from solar pv would of course transfer to the radiators when the circ pump is on, it would save money (a little) in space heating too.

author: SteveyG
author_rank: Unknown
timestamp: July 26, 2019, 09:50:16 am
content: Quote from: paulca on July 26, 2019, 09:37:03 amPersonally, I would not choose a system boiler. If you're going down the route of an unvented cylinder then go for a heat-only boiler and keep the rest external - it'll be more maintainable.Have you measured your water supply to even know if a combi boiler is a viable option?

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 09:55:00 am
content: Quote from: paulca on July 26, 2019, 09:37:03 amWhat do you mean by "PV"? wouldn't you just use plain solar collectors? PV, photovoltaic, is to generate electricity.Regarding choices, you have to make your own. Nobody knows what suits you better than yourself. As you can see there are plenty of different views and tastes. If you are not entirely sure then do what I try to do which is to do things in a way they can easily be altered later.

author: paulca
author_rank: Super Contributor
timestamp: July 26, 2019, 10:29:36 am
content: Quote from: soldar on July 26, 2019, 09:55:00 amThermal solar doesn't work very well here. Sure it might work in summer, but in winter by the time they have started to warm up the sun is going down. They also require circulation pumps to be maintained and if they fail in summer the panels can burst. In winter if it gets very cold they have to be heated to stop them freezing, depending of course on how much anti-freeze you put in their loop. They require a dual coil hot tank here too.Solar PV -> MPPT Controller -> DC Immersion heater is more efficient here as at noon 1kW of panels will still produce close to 1kW of power, even in the dead of winter when it's -10*C outside.I'm not asking for people to make the decision for me, just looking for opinions and considerations that I may, or may not have considered.

author: paulca
author_rank: Super Contributor
timestamp: July 26, 2019, 10:33:18 am
content: Quote from: SteveyG on July 26, 2019, 09:50:16 amI have a heating company coming to do a survey on Monday, so I'm sure they will test this and present me my options.What do you mean "heat-only" boiler? Do you mean that the boiler heats only the radiators and not the water tank or do you mean a combi boiler with on demand heating?If it's "heat-only" I would of course need another way to heat hot water. Electric heater is not really an option due to cost and environmental aspects in that electric heating is the least efficient by a fact of around 3. Basically the utility company burns oil or gas to produce electricity at about 35% efficiency, making electric heating only possibly viable for heating a single room, where running the whole house heating would be wasteful.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 11:17:36 am
content: Quote from: paulca on July 26, 2019, 10:29:36 amInteresting. Never seen that.

author: Someone
author_rank: Super Contributor
timestamp: July 26, 2019, 12:48:33 pm
content: Quote from: soldar on July 26, 2019, 08:18:53 amNo contradiction, there are instantaneous gas heaters with 20x or greater dynamic range,andthere are small electric instantaneous heaters suited for low flow/low power requirements. Instantaneous gas heaters are not suited to low flow situations as you have pointed out as they have limited dynamic range, but those limitations are overblown as few people have need for low flow at a low temperature rise.

author: richard.cs
author_rank: Super Contributor
timestamp: July 26, 2019, 12:54:02 pm
content: Quote from: soldar on July 26, 2019, 11:17:36 amThat approach has been discussed on here a few times. Overall efficiency is much lower in terms of Watts per roof area, but unless you are space constrained you use a larger area of PV to get the amount of heat you want, and the total cost of ownership can be lower that an equivalent solar-thermal system because you don't have wet circulating loops, pumps, etc. to maintain and because PV benefits a lot from economies of scale.

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 26, 2019, 12:54:15 pm
content: Quote from: Someone on July 26, 2019, 03:22:46 amI knowI'm digressing, but that's what makes life interesting...I understand, but have alwayshated, the... "19th Century"...vsthe... "18-Hundreds" nomenclature!There's something unsettling in my 'brain' during quiz shows or what ever, getting it right !!An old German friends mother was talking to me once. I may be shot down here, but I was told she uses'old' German, to describe the timeTo me, if it was say "9:40pm", we would say it like that...However, she would say... "It is 5 mins until 3/4 of 10"... Aarrgghh xxx

author: paulca
author_rank: Super Contributor
timestamp: July 26, 2019, 03:17:01 pm
content: Quote from: GlennSprigg on July 26, 2019, 12:54:15 pmIt's okay, the entire world (or the vast majority of it) celebrated the new millennia a whole year early.There was no year 0. We started on year one, so the end of 2000 years happened on December 31st 2001, not 2000.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 04:07:56 pm
content: I never understood the problem or the confusion. I guess it is because I was taught the difference between ordinal and cardinal numbers.A baby in its second year of life is one year old.In 1859 18 centuries had been completed but it was into the 19th century.Different cultures count different ways. A baby is born into its first year of life so some cultures will say the baby is one, meaning it is in the first year of life.Jesus Christ died on a Friday and rose on the following Sunday "on the third day". We would say only two days transpired but the way they counted Friday was the first day, Saturday was the second day and Sunday was the third day.

author: Seekonk
author_rank: Super Contributor
timestamp: July 26, 2019, 04:22:53 pm
content: I have PV water heating at my camp and those little 6 gallon tanks are plenty for a shower. 500W of grid tie panels (+60V) is sufficient to power the heaters in light use. I use a simple circuit that keeps the panels at power point and efficient. Even get to use the tanks existing thermostat at that voltage without arcing. A fun way to do a little solar that actually pays for itself.

author: paulca
author_rank: Super Contributor
timestamp: July 26, 2019, 04:54:40 pm
content: Quote from: soldar on July 26, 2019, 04:07:56 pmI always had a pet hatred of inclusive/exclusive ranges. I still do. I 99.9% of the time get the right answer to questions like, "How many days are there until pay day?", pay day is the 25th, today is the 12th. 13 days. However I will 99.9% of the time refuse to accept the intuitive answer and disappear off the down the rabbit hole until I can mathematically prove to myself I've considered the inclusion or exclusion of the boundary numbers.... or counting the days on my fingers.It's exactly the same as the suspicion new programmers have upon seeing:for( int i=0; i<10; i++ ) {print i;}It will execute 10 times, but 10 will never be printed. If you rewrite it as a while loop it's even worse.i=0;while( i<10 ) {i++;print i;}How many times and will 10 be printed? 10 and yes.ori=0;do {print i;i++;until( i > 10);Sometimes I have to write a while loop in my head to work out how many days there are between two dates.(kidding)

author: Nauris
author_rank: Regular Contributor
timestamp: July 26, 2019, 08:17:14 pm
content: Quote from: soldar on July 25, 2019, 07:20:13 pmElectric tank not much loss, it has great insulation all around but the oil boiler - that really sucks in the summer. Some people actually have electric tank for summer so the oil boiler can stay off, that saves a lot of oil.QuoteI drew a better schematic, this gives both temperature stability and good efficiency.It is easy to integrate solar heating to it, also there is auxliary electric heater should the gas burner fail. Also solar power heats both water and radiators.Gas burner is controlled by tank thermostat so that if tank falls below 50 C gas heats it up to 60 C or so. And if there is plenty of solar then tank temperature never fall and gas burner don't need to run.

author: soldar
author_rank: Super Contributor
timestamp: July 26, 2019, 08:49:31 pm
content: For space heating I prefer, if possible, the greatest heating exchange surface and the lowest fluid temperature. That is the most efficient because the takes most heat out of the burning gases. If I could I would install subflooring heating but it is too expensive to retrofit.So the thing is that if you want domestic hot water at 55ºC then you need the water tank to be at substantially higher temperature which means lower efficiency because you could be heating the house with water at 45ºC and gaining in efficiency.All engineering solutions are compromises.Regarding the heat losses of a tank I guess they can be minimized as much as you want by adding insulation. I should measure how much my tank loses. In the winter it does not matter but in the summer it would add a bit of load to the AC.

author: paulca
author_rank: Super Contributor
timestamp: July 27, 2019, 07:49:48 am
content: Quote from: soldar on July 26, 2019, 08:49:31 pmI can't remember exact figures, but someone on here mentioned how much temperature their tank lost overnight in 8 hours and we worked it out as something like 90W of heat loss. Not much, modern insulated tanks are surprisingly efficient at holding heat. My own, old copper tank, with a tied on blanket to insulate it is still perfectly warm at bedtime when the heating was only on for 30 minutes at dawn.

author: soldar
author_rank: Super Contributor
timestamp: July 27, 2019, 10:39:06 am
content: Heat loss will depend on the size of the tank and, importantly, on the temperature of the water. 90W sounds like a reasonable figure from an engineering point of view but I would try to bring it down with additional insulation. 90W over a year can add up to more than 100 euro. To put it in perspective, my refrigerator uses less than half that. It has a 100W motor which is running on average less than 45% of the time.That is an advantage of on-demand heaters. No heat loss when not in use. I have a tank in my second home and when I am away I turn it off which means waiting some hours for hot water when I return. Not a problem for me at all but it might be for some people. Also, I may arrive for a weekend, heat the tank and leave so most of the heat will be lost and wasted.

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 28, 2019, 11:18:32 am
content: Quote from: paulca on July 26, 2019, 04:54:40 pmYep, the examples you quoted can be (are) tricky to the uninitiated, though each coding has it's purpose/use.I was going to respond here, 'next Tuesday', (Sunday here now), but I think I've been told that this will meanthat I wouldn't reply for9 days, instead of2 daystime !!My apologies to the O.P. for going off topic again...

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2019, 10:18:44 pm
content: Quote from: Someone on July 26, 2019, 03:22:46 amI've never seen anything like that before in my life, a standard mixer valve in the shower is virtually universal in the US, little has changed in the last 60+ years other than pressure compensating valves that will maintain a constant ratio regardless of pressure changes on hot or cold.

author: IanB
author_rank: Super Contributor
timestamp: July 28, 2019, 10:29:07 pm
content: Quote from: paulca on July 23, 2019, 06:55:35 pmThe usual solution to low water pressure is to install an electric booster pump. Since UK houses commonly have a header tank in the loft to supply the water there is not enough head available to drive water through an upstairs shower. The booster pump fixes this problem. Any competent plumber would be able to install one.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 06:58:56 am
content: Quote from: IanB on July 28, 2019, 10:29:07 pmI have now come to the conclusion that the bathroom does indeed run off the mains. I found the stop cock was partially closed, although opening it fully still didn't make the shower tolerable on HIGH mode but a new shower head did make it feel better pressure wise on LOW.Anyway, heating engineer is calling this morning to give me my options for the upgrade. I let them give me details for both Combi boiler with on-demand tank-less hot water and also the system boiler with hot-tank that I can solar-ify later.

author: DTJ
author_rank: Super Contributor
timestamp: July 29, 2019, 07:13:32 am
content: Someone has probably already said it (bit I have not read all the replies....).Try replacing the shower head with one with more flow (less back pressure). I think I have that right way around.This seems to be a common fix with what we call 'instantaneous' hot water systems here in Australia.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 09:49:50 am
content: So to paraphrase the heating engineer."If you have plenty of money to throw at it and want to redesign your heating system, you can do whatever you want. I recommend you go Combi boiler, it's easier, cheaper, more efficient and if you want to you can add a unvented reserve tank later for solar heating."Basically the system boiler would add over £1000 to the installation cost. Combi is circa £2700, system boiler circa £4000.So I can later remove the electric shower and replace it with a power shower replumbed onto the hot water. In the meantime there is a shower fitting on the normal hot tap which when fed from the combi boiler will be fine.

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 10:01:19 am
content: Quote from: paulca on July 29, 2019, 09:49:50 amI would be interested to see the evidence behind that statement. It's easier for the installer to put in a combi and offers greater profits. If it's a boiler replacement only, I would get additional quotes. Those are BG prices!As mentioned before, I'd also suggest a heat only boiler over a system boiler if you choose that route over a combi.What did he measure as the water parameters? (Flow, dynamic & static pressure etc)

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 10:15:26 am
content: Quote from: SteveyG on July 29, 2019, 10:01:19 amFor the benefit of us, non-UKdians, can we get definitions of those terms? Just to make sure we are all on the same page.And, yes, I find the prices of anything and everything in the UK absurdly high.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 10:20:17 am
content: Quote from: SteveyG on July 29, 2019, 10:01:19 amThe cost of the tank for a dual immersion, single coil is £600-800 alone. There is some additional plumbing required.He measured the mains flow rate just which was 14 lpm, the combi boiler requires 10 minimum.I'm still not sure what you mean by heat-only boiler.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 10:32:50 am
content: Quote from: soldar on July 29, 2019, 10:15:26 amAs I understand them...System boiler = a single out/return boiler that feeds through a heat exchanger coil in the hot tank before circulating the radiators, thus providing both hot water and radiators. With or without the "S plan" diverter valves to switch between hot water only and/or radiators.Combi = Combination boiler. Provides an out/return for the radiator circuit and separately a direct inline on-demand hot water heater. If you turn a hot tap on it immediately fires up and heats the hot water. Turn the tap off, it shuts off. There is no hot water tank or reservoir.https://www.worcester-bosch.co.uk/products/boilers/explained

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 10:34:31 am
content: Quote from: paulca on July 29, 2019, 10:20:17 amA system boiler has everything except the cylinder internal to the unit, so even if you just need to replace the diverter or pump, you have to disassemble the boiler to get to those parts (and also be gas safe...)A heat-only boiler just has the heat exchanger and a flow and return to the boiler. You have everything else separate making it more customisable and maintainable . You can buy an Intergas 24kW heat-only for less than £700. System boiler comes in around £1100 and a similar (Intergas Xtreme) combi is close to £1800. Unless massive work needs doing, both end up around the same £2000-3000 in total.The installer doesn't want the work if he's quoting £4000More often than not, you will pay a premium for a system boiler over a heat-only boiler. Even after buying the parts separately.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 10:44:30 am
content: Quote from: SteveyG on July 29, 2019, 10:34:31 amSo looking at that link I posted:https://www.worcester-bosch.co.uk/products/boilers/explainedA heat-only is what I currently have. Including the header tanks in the attic and a vented, non-pressurized system which is just poor on terms of upstairs water pressure, in particular showers.On the cost. The boiler itself is probably around £1300-1600, installation is probably 2 or 3 guys over 2 days. So the labour costs around going to be somewhere close to £800-1000 + addition parts, boiler control panel, radiator TRVs, 3 new radiators + fitting, etc. etc. So £2700 ball park sounds about right.Then add in the cost of the unvented tank which is £600-800 and we are already at £3500, so the plumber is only adding £500 for additional work for plumbing and setting up the hot tank. The £4000 was just when I asked him for a finger in the air estimate if I was to choose system boiler.https://www.screwfix.com/c/heating-plumbing/hot-water-cylinders/cat830956

author: richard.cs
author_rank: Super Contributor
timestamp: July 29, 2019, 10:56:26 am
content: Quote from: SteveyG on July 29, 2019, 10:34:31 amSo just to be clear, heat only and system boilers are functionally equivalent, the distinction is only in the detail of whether the pump and valves are internal or separate.Combi boiler is on-demand water heating at mains pressure, plus heating a circulating loop for radiators. The actual implementation is usually that it has pump and valves internally like a system boiler and that hot water mode takes priority over space heating and circulates water from the sealed heating loop locally through a water-water heat exchanger to heat the mains pressure cold water.Quote from: paulca on July 29, 2019, 10:44:30 amThe plumbing for an unvented tank is probably more similar to what you have now (vented low pressure tank) than the plumbing for a combi boiler is so I am very dubious about higher labour cost for unvented vs combi. Also a heat only boiler is cheaper than a combi (see SteveyG's numbers) by pretty much the price of the unvented tank. I'd tend to agree with him that the 4k quote is pretty high.In my experience plumbers tend to push you in the direction of doing what they're familiar with. I'm not saying a combi isn't best for you, it depends on your use case, but it sounds to me like he's pushing for combi for his own reasons.

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 11:13:27 am
content: Quote from: richard.cs on July 29, 2019, 10:56:26 amYes, both familiarity, ease and (depending on the manufacturer) heavy discounts to "accredited" installers.Just to be clear, I am not suggesting any system is better for you than another - the use case should be entirely at the centre of the decision. Remember to account for the future too (additional family members etc).

author: Towger
author_rank: Super Contributor
timestamp: July 29, 2019, 11:17:36 am
content: If the hot water cylinder is more of less replacing like for like (with just original pipes/electrics moved/extended) £500 seem high for labor. I have done this several times my self over the years.The going rate in Dublin is touching on €200 a day, wife has me spending 10Kon a new bathroom, pumps and plumbing etc... I would expect the labor rates in NI to be cheaper, since they follow the money and most builders vans down here have NI reg plates! Your labor rates will probably drop after 31st of October, if BJ and the DUP have their way. The price of a cylinder has gone up with the price of copper. Watch what happens to the old one, it will not be going into a skip

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 11:25:20 am
content: Quote from: Towger on July 29, 2019, 11:17:36 amThere would be additional pipework for the PRV and expansion valve given the move to an unvented cylinder, but not much else.Another thing to check would be if the installer is even G3 registered. He may not be, hence pushing the price high so that you do not go down that route.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 11:39:46 am
content: Well anyway, I'm going to get another company to do a quote also.As to which system I want I'm still undecided. If I wasn't considering the solar water heating at all, then it would be 100% combi. The house only has me in it with the option later of my daughter spending the odd night here and there is always the potential of a partner later. But the point is the hot water demand is small. On an average day I maybe use 5 litres of hot water in the mornings washing, a handful of litres rinsing some dishes before they go in the dishwasher or washing my hands. Every other day (yes, you can call me a smegger and judge all you want), a shower. Thus storing a full tank of hot water would not be that efficient.That's compared to a busy family home serving up three or four showers a day and the odd bath.The only thing leaning me towards a system boiler (or heat-only) is the ability to stick 1000W of solar on it and basically have free hot water with some of it taking a tiny bit of load off the space heating as a by product, although I haven't worked out just how much that would be. Install of the solar system is around £1000 + whatever a spark charges me to check it for safety + the plumber cost to install the immersion.

author: SteveyG
author_rank: Unknown
timestamp: July 29, 2019, 11:45:26 am
content: Quote from: paulca on July 29, 2019, 11:39:46 amJust as a reference point: Standing losses for a cylinder are usually between 35 and 55W depending on the cylinder of choice. So you lose around 1kWh per day if you use no water, or somewhere in the region of £10 per year. Worth also bearing in mind, heating a cylinder is more efficient than instantaneous heating of water as the boiler will not be operating at optimal condensing point.

author: richard.cs
author_rank: Super Contributor
timestamp: July 29, 2019, 12:02:56 pm
content: Solar aside, that sounds like a good use case for a combi.But, if you did decide to go for the solar do you even need a gas heated hot water at all? I suppose if you want a new gas boiler for space heating the extra install cost is fairly low. You could alternately keep your existing boiler for space heating, get an unvented electrically heated tank for the hot water and spend the difference on a larger solar array so as to get free hot water for much more (potentially all) of the year. It depends how elderly/inefficient your existing boiler is and if you therefore want to change it anyway for more efficient space heating.If you have a 60 L 45 C shower on alternate days, and otherwise use 10 L of 65 C water per day, then if your incoming temperature was 15 C your total heat required is well under 2 kWh per day, plus a kWh for standing losses. If you can angle your solar panels for bestwinterperformance (south facing and about 20 degrees from vertical) then in Northern Ireland you should be able to get over 1 kWh per average winter day per kWpeak installed. More panel area needed if they just have to go at whatever angle your roof is. A 2-3 kWpeak install would give you free hot water year round and minimal maintenance cost with the gas boiler only used for winter heating. Your big problem would be if you had a future partner who likes 30 minute showers every day.

author: soldar
author_rank: Super Contributor
timestamp: July 29, 2019, 12:39:11 pm
content: Quote from: paulca on July 29, 2019, 10:32:50 amOK, looking at that page, "combi" is what most homes here would have with the caveat that they need to be installed outside or take the air from the outside and vent the gasses to the outside.The thing when deciding which one is the best option is that it depends a lot on what kind of use it will get. A family with a steady usage is not the same as a single person with irregular usage and that is different from a week-end second home.I believe domestic hot water, heating, PV electric, etc are much better used and controlled in larger groups. They work well in large institutions like hotels, hospitals, etc. and compared to single home installations they would work better for groups of homes where it is much easier to balance production and consumption.

author: paulca
author_rank: Super Contributor
timestamp: July 29, 2019, 12:43:10 pm
content: Quote from: richard.cs on July 29, 2019, 12:02:56 pmI would be nervous about elevating the panels that much as it makes them into wind sails and we get 100mph+ gales every 10 years or so and 70mph gusts every year. The surface area of a panel stood up nearly vertical in 100mph winds will need significantly strong mountings to not rip off and that moves the potential to ripping the roof off. They even have strick regulations around them not over lapping the peak of the roof as it allows the wind to get under them and risk lifting the roof!Maybe I can turn my DIY(OW) to other uses and use solar + a hot water tank and small pump and radiator, to take the cold and damp edge off the garage. I can do this 100% DIY, especially if I can rescue my copper hot tank. however is putting a few kWh of heating into the garage in winter going to make the slightest different when it's not lined, sealed or insulated?EDIT: Of course, due to me storing a bunch of stuff in the garage, I will probably need someway to at very least keep it above freezing. Most people recommend sealing the edges of the garage door to stop direct drafts and using 2Kw oil filled radiator on a thermostat set to 2*C.

author: paulca
author_rank: Super Contributor
timestamp: October 10, 2020, 05:37:09 pm
content: Quote from: peacekeeperman on October 09, 2020, 12:10:11 pmIs that on ali express or your website?