Need 13Amp variac device to 'modulate' a water boiler. - Page 1
Forum section: electronics / general

author: paulca
author_rank: Super Contributor
timestamp: April 18, 2024, 01:45:56 pm
content: I have previously been using a cheap Chinese variac(?) PCB claiming 40A (lol). However, after the wire clamps melted and I soldered them on instead, I still don't trust it. I decided I want to upgrade it to be far less janky.Has anyone seen a reasonably priced high power dimmer?I'm okay with AliExpress et. al. As long as there is evidence the thing won't melt at 13Amps for an hour doing a boil and will tolerate another hour at 30% output without melting.My next home brew beer is depending on this! Help me make beer!

author: amyk
author_rank: Super Contributor
timestamp: April 18, 2024, 02:00:16 pm
content: "PWM" over a very long timescale using a suitable relay/contactor may be much better than trying to modulate the current. Water has a lot of thermal mass.

author: tom66
author_rank: Super Contributor
timestamp: April 18, 2024, 02:58:44 pm
content: Yes, I am wondering why you are using a variac when nearly every thermal regulation system - even the electric shower in my mum's house - just uses slow PWM (1Hz) to control the water temperature despite flow rates being reasonably high. It will also be a lot more efficient than trying to do it any other way.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 18, 2024, 03:02:20 pm
content: Use a solid-state relay (avoid the cheap Fostek fake ones that are popular on AE/Ebay - a Crydom D2425 is about $50) with a reasonable heatsink. Drive it with a PID process controller (like the Omega CN32i) with a food-grade RTD sensor to measure the mash temperature. This is a common homebrewers' setup. If you're buying a new process controller, look for one with voltage outputs that can directly drive an SSR, this simplifies the design and lets you do PWM. Controllers are also available with relay outputs, these won't work for PWM and only do on/off.

author: paulca
author_rank: Super Contributor
timestamp: April 18, 2024, 03:11:55 pm
content: Interesting. To be clear though, I am not aiming at holding a temperature. I am interested in controlling the amount of latent heat of evaporation of water at boiling point. With the 3kW element alone it will of course hold 100*C fine. Unfortunately with a high enough evapouration rate that it literally rains beer afterwards from the cieling. About 5 litres of beer turns into rain.So temperature regulation is out. If I needed temp regulation I could use the built in bi-metalic thermostat.A PWM controller that supports a direct duty cycle setting would be more appropriate.I assume by "process controller" we are referring to the little modules with red led displays and outputs for driving relays etc.?There are the expensive real ones (is it STC1000?) and then there are the cheap copies. I assum the later still work fine as they are very popular?One of those which has a high enough output voltage to control, say, a 20A SSR ... just the question about "non-temperature manually variably PWM" availability.

author: fourtytwo42
author_rank: Super Contributor
timestamp: April 18, 2024, 03:47:22 pm
content: Everytime I make beer I wish I had a device like this but instead I have to lug my old 3Kva Variac out of it's storage and along to the kitchen, backbreaking!Anyway I think what you want Paul is a Simmerstat, an old fashioned PWM device simply based on a heater and bi-metalic switch, herehttps://www.ebay.co.uk/itm/300724984865?itmmeta=01HVRXQZQQMGYMZETHFSZBYWMS&hash=item46049b1c21:g:6kAAAOSwa3BaFoY7&itmprp=enc%3AAQAJAAAA4FRh4My3jbmkA8vEEgQScq3nIo%2BK%2BQlCU5szJjK97bJVn6Czs9MVR1V2mE%2Fg6FNhkBCggM4o3bXk3lgBbjQuT5T5J%2BmCgdOu9za%2FnsTPTuMYQ0ThQ0O3TK0WDUJDYNpqoo3UhFL1zzHUPtP6QNALmeLbHT9EYlPpJLue1a8%2FukRVRS1OxnbcPiNpYZTCU7lzMuPEttBCwl%2Ba4SShyGgbLArfe9Kc7woJi5E9FGJvNR%2BoBeworQgv%2BiCDO2dHQpLyVDnyClwCoaASO6Cl1EFQxAk80L9lrC3ugv%2BvUiUC%2BbRQ%7Ctkp%3ABFBMlPzfnd5jis one intended for a cooker ring that in a suitable case I am sure would do your job (and maybe mine if I get around tuit).I have a feeling the internal heater is in series with the load when the contacts are open (so there is a little bleed current to the load). Reckon the copper lug is earth so that means just two active terminals to switch the load.What beer are you making, and are you going the whole hog and mashing yourself ?I used to but I have sadly descended to kits lols

author: ejeffrey
author_rank: Super Contributor
timestamp: April 18, 2024, 06:41:29 pm
content: Most of those temperature controllers can also be set to do a fixed percentage. Often they are programmable with multiple stages, and varying complexity of program. For instance, full power to ramp up to boiling, followed by a simmer at 25% or something.Another way you can do this is by putting a temperature sensor above the boiling wort so that it is heated by the vapors. It will take some trial and error to figure out how hot the sensor gets but you can then directly regulate the boiling rate.

author: TimNJ
author_rank: Super Contributor
timestamp: April 18, 2024, 06:55:17 pm
content: I'm sure the solutions above are probably the way to go, but have you given Facebook Marketplace (or equivalent) a look for an old but reliable one? I bought a 2KVA Powerstat variac on FB marketplace for like $15.

author: themadhippy
author_rank: Super Contributor
timestamp: April 18, 2024, 07:27:51 pm
content: Quoteput the lid on yer boiler once youve got the boil started

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 19, 2024, 04:37:32 am
content: Quote from: paulca on April 18, 2024, 03:11:55 pmHmm, something like theSSRMAN boardwith a pot to control the duty cycle might work. You would pair this with an SSR that does *not* have a zero-cross switching circuit. Holy crap, those boards got expensive!Quote from: paulca on April 18, 2024, 03:11:55 pmYep. The fancy ones include features you likely don't need (ramp/soak control, etc). If you were using a controller, you'd pick one with a voltage output that's suitable for driving the industry-standard 3-32V input for an SSR. A cheap controller may cost less than the SSRMAN board linked above.

author: Andy Chee
author_rank: Super Contributor
timestamp: April 19, 2024, 06:55:40 am
content: Quote from: paulca on April 18, 2024, 03:11:55 pmThe proper way to do this is to install two heating elements, one double the power of the other e.g. 1kW and 2kWRun the 2kW element from a standard bi-metallic thermostat. Use the PWM controller on the 1kW element.

author: paulca
author_rank: Super Contributor
timestamp: April 19, 2024, 07:22:10 am
content: Quote from: Andy Chee on April 19, 2024, 06:55:40 amInteresting. I had been bouncing a similar idea around. As this is a "rush" job now, ideal can wait.If I simply take what I have now, the built in 3kw ring element in a "tea urn", but purchase a "Travel Kettle" with a 1kW immersion coil element.... then I can jury rid that 1kW element into the boiler to hold the boil.I expect 1kW (based on the variac position) would be grand to maintain the boil. At least in a pinch.By "jury rig" though I mean something your mum wouldn't like and your spark would disown. Like cut the element out of the kettle in it's full doubly insulated form and "dump" it in the wort, cable and all!At least it's "boil side" so it doesn't need that much sanitation first!The whole stainless steel boiler is earthed. "What could possibly go wrong?"The "Proper" and "Best" way I believe to solve this is actually a large 8kW propane burner and a proper stainless steel "kettle" on a stand. That would however force me to do the full 1-1.5 hour boil outdoors... and if I don't fancy carrying around 25 litres of hot wort, also the cooling, transfers etc. Trouble is, a "home brew" kettle is about £300. An industrial sized pot capable of taking first propane heat for hours is probably half that, but it will lack nice features like temp probes, proper ball values, filters etc.My £40 coffee/tea urn does just fine! Eventually it's bottom will rust out, but it's got a few years left in it yet.

author: themadhippy
author_rank: Super Contributor
timestamp: April 19, 2024, 11:24:12 am
content: Quoteguess youve removed the stat from the urn,pity as they usually have a simmer setting.Quoteadd a false bottom,grain basket ,ssr, pid and pump and make it into a grainfather clone.

author: paulca
author_rank: Super Contributor
timestamp: April 19, 2024, 12:09:17 pm
content: Quote from: themadhippy on April 19, 2024, 11:24:12 amLOL. I have spent enough already. Home brew specialised kit is offensively expensive.The original thermostat is still in the urn. It still works. It was not luck that I sourced one which goes to 110*C so it doesn't cut out at full boil.For example, the very first thing the urn will do at the start of a brew is take 10 litres of tap water up to 75*C and then I dump about 50g of chorline donor powder into it and proceed to pump that water (by gravity) through every pipe/hose, fitting, valve, strainer, etc. Then it gets dumped into the other equipment like the mash tun and fermentor.Use the thermostat for that and for giving me 70-75C "strike water" for mash. Although I confirm with 2 probe thermometers.There is no setting for 99.999.. *C. No matter how finely I adjust the thermostat "I canny change the laws of nature". It will be boiling at 3kW constantly set to 100C or not boiling at all at 99C.I'm going to find a "portable" water boiler element with a 1kW rating. I am however struggling with only finding things that look like candidates for the "Big Clive" "Death Heater" videos. I need a proper fully immersible immersion heater! Not one that has to hang out the side and stay dry. I am NOT taking that risk!EDIT: It leads me to question the need for the "boil". Is there something about the water actually vapourising and recondensing that is necessary? What if I did just leave it at 99C and not rolling?

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 19, 2024, 01:42:19 pm
content: A series diode would cut the power in half, use a SCR instead and trigger it just before the peak to get to 30% power.

author: tom66
author_rank: Super Contributor
timestamp: April 19, 2024, 02:04:26 pm
content: You will find that if you set the thermostat to 99C that, most likely, some of the water will still boil because the fluid is not totally uniform and your sensor will be taking just one sample from a large container and the heating element plus convection currents will ensure some of the water has exceeded 100C. Also, of course, environmental pressure variations and any tolerance in your sensor will need to be accounted for.

author: paulca
author_rank: Super Contributor
timestamp: April 19, 2024, 02:30:31 pm
content: Quote from: tom66 on April 19, 2024, 02:04:26 pmYeah. I was just running this buy some fellow brewers on reddit. Enquiring to the purpose and criticality of a "rolling boil for 1 hour".Turns out it is more an "ideal" and it's likely the thermostat set to 99.999C or as close as I can get it while still cutting out and not constantly boiling the wort away... it should be fine. I'm not going to ruin the beer, only drop a few percentile on my "ideals".

author: ealex
author_rank: Frequent Contributor
timestamp: April 23, 2024, 04:58:38 am
content: HelloI've used a dimmer from a "home improvement" store, with 2kw heating elements. I think I had crimp-on ferrules on the cables, and had no issues with overheating. (it was an experiment but lasted way more than expected).You need to boil it for 2 reasons:1. Loose some water, so you have a higher sugar % when you start the fermentation - might or might not be desirable - it depends on your recipe and the final volume you can ferment and bottle, but usually diy mashing is not that efficient - you tend to end up with a lot of low concentration worth if you try to wash out all sugars from the mash.2. Help the bitter compounds dissolve into the beer - might work under the boiling temperature as well - this is also where the 1h boiling time comes from. There are some formulas to estimate the final bitterness from the alpha acid content of the hops you add and the boiling time it sees - the "start of boil" addition will give most of the bitterns but no flavor (or even some unwanted flavors), the last addition will add almost no bitterness and a lot of flavor (for an IPA for example)I've build my gear from old stainless steel kegs - cut the tops off and re-use the "crown" ( i don't know the proper name ) for the handles that are already there.Those worked ok with electric and propane heating, but I had to insulate the boiler - a few layers of cardboard where enough to reduce heat loss and easily to replace.One issue with electric heating: the sugars tend to caramelize and burn on the surface of the heating elements -> you either need very good agitation or heaters that have a high surface area.One more thing to consider: rapid cooling after the boil - it prevents volatile compound loss and will reduce the time period when the beer can be infected - when it's too hot to pitch the yeast but cold enough for random spores / bacteria to survive.

author: paulca
author_rank: Super Contributor
timestamp: April 23, 2024, 12:01:34 pm
content: Thanks.I'm going for "dimmer-less". Working out the volumes I was just going to "wing it". But roughly the following:Take 25 litres of strike water at 70C, add to mash tun (7 (uk)gal water cooler tub). Adjust if necessary. Cover, leave alone for 1 hour.Drain the mash into the kettle. I expect maybe only getting 20 litres back with a reasonable drain time.There are options here, but adding 5 litres of 70C (pre-boiled) water to the mash tun in multiple "rinse/sparge stages" is usually what I do.So I would be back to 25 litres boil volume, which in a 30litre boiler is as far as I am willing to go.Technically I need only 19lt out of the fermentor, so ... as you point out... I either need to skimp on the sparge water, the mash volume or reduce the wort through evapouration towards the target "pitching" volume.To get 19litres comfortably, without too much waste, I probably need a pitching volume of about 22 litres.3 litres sounds about right for the boil "with" the dimmer.The boiler is a tea urn. The elements are rings which cover a good area of the base. I still do get some caramel debris, but it's not bad enough to melt the bottom out of a paint strainer bag, (I used to mash in the kettle in a bag)Instead the plan is to 100% it up to the protein hot break. Then manually alternate the thermostat to nurse it through the same. When it's clear of foam back to 100% towards the rolling boil. In with the hops and the thermostat I will "fiddle" with to get it as close to "pulse boiling" as possible. Where it boils for a 10 seconds starts to get violent, then cuts out and cools below the boil and repeats. (that or I end up fiddling with it constantly).If I end up with too MUCH evaporation, I can part cover it with a humidity hood (lid). If I end up with less, I just steep it longer or manual supervise a violent boil phase.I do have a copper coil wort chiller and protofloc which usually results in pretty clear wort at 25*C after an hour.The frustrating bit, it works exactly like LithiumIon chargers do! The first 50*C goes in minutes. The last 5*C takes over half an hour on it's own! Need colder tap water!Nice idea with kegs. I'm still not convinced with the need. If I wanted to go propane for pure power that would limit me to boiling in the garage or outdoors.EDIT: I have a propane cooker hob. But for some reason, using one of those 7kW burners indoors sounds like it would be a bad idea??

author: themadhippy
author_rank: Super Contributor
timestamp: April 23, 2024, 12:32:14 pm
content: Quoteor pour it from the boiler straight into a container that can be sealed air tight and let it cool naturally-aka no chill