Want to stop the A/C from dimming the lights in the house. - Page 1
Forum section: electronics / general

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 19, 2012, 11:25:55 pm
content: I have a 240v single phase split system aircon here that cools/heats half the house by pulling about 11 amps when it's running. The problem is the damn thing dips the lights for a split second when the condenser outside starts up. Once it's up and running, of course, everything's fine.Whilst I realise the simplest solution is to just pull out the fuse protecting the A/C, can you suggest any way I could stop this annoying light dimming from happening when the A/C kicks over?My AirCon guy said change it for a Daikin inverter. Not ready to change it yet, since it is still working.

author: IanB
author_rank: Super Contributor
timestamp: May 19, 2012, 11:45:28 pm
content: This is what happens when motors start up. The same thing happens even in big industrial plants. The control room operators look for the lights dimming as a sign that the motor has started up as expected.To solve it you either need bigger wires, or a soft-start device on the motor.For the bigger wires solution, trace the air-con power feed back to where it splits off the supply to the rest of the house. At this tee point you need thicker wires back to the main supply from the electrical utility. If the tee point is actually in the utility supply cabinet there is nothing you can do save to ask the utility company to beef up their wiring. Sometimes they will upgrade a 100 A supply to a 200 A supply if you ask them. Also have an electrician check all connections to make sure they are low resistance. Sometimes the accumulation of years and oxidation can add significant contact resistance in places where connections are made. Contact resistance and high currents will produce voltage droop.For the soft start option, talk to the air con guy. If the first one can't help, try another. There may be a solution (though I am quite a non-expert on the electrical side of this problem). What typically happens in industrial plant is that the compressor is started up with a recycle valve open so that it has very little load. Once the motor is up to speed the recycle valve is gradually closed to bring the compressor up to full load. However I doubt this level of complexity is found in a tiny domestic unit.Maybe if you close your eyes when you hear the compressor starting you won't see the lights dim so much?

author: Psi
author_rank: Super Contributor
timestamp: May 19, 2012, 11:57:09 pm
content: Move to LED lighting.Problem solved.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 20, 2012, 12:04:34 am
content: Quote from: Psi on May 19, 2012, 11:57:09 pmYeah thinking about it.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 20, 2012, 12:06:09 am
content: Quote from: IanB on May 19, 2012, 11:45:28 pmOr hide under the bed sheets and never come out.

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 12:07:32 am
content: The solution is easy (albeit expensive) Just add copper. Your lights don't dim when the neighbors A/C kicks in but would in some third world countries. It's volt drop from instantaneous starting current. Your cheapest practical solution is live with it.As for your A/C mates advice about Daikin Inverters, it's great advice for someone likely enough to earn a buck selling or installing the Daikin but in your best interests. Inverter systems are a con for the majority of Aussie applications.Inverter systems save you money by reducing capacity in an overdesign situation. They cost more to buy, more to repair and are more likely to fail prematurely. 99.999% of console type split systems in our wide brown land will be running at their maximum capacity for most of the time they are on. You've already stated it's trying to cool/heat half the house.Ever seen a 100% efficient inverter? No? That's probably because they don't exist! So those good old boys have your compressor drawing maximum amps at less than it's own efficiency. How much is that inverter saving now? How long will it be to pay back the cost premium over a non inverter model of similar age?Back to your light dimming you could have an electrician look over the size condition and ratings of your wiring. It will be much worse if you have any hot or bad joints in your switchboard or consumers mains. Other than that any solution other than only using the A?C during daylight hours is going to be expensive.

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 12:11:15 am
content: Quote from: Psi on May 19, 2012, 11:57:09 pmThat's a positive suggestion. Whether it will entirely eliminate flicker depends on the design of LED lamp selected and duration of the A/C start current. Will definitely improve the situation but may not eliminate flicker entirely.

author: Rerouter
author_rank: Super Contributor
timestamp: May 20, 2012, 12:28:16 am
content: my first though is, the A/C is on a complelty seperate fuse correct?if so then your lights shouldnt be dimming not unless either the connection to your incoming mains is more resistive than it should be, or the incoming wires where not sized for such a load (weird) when it was initially run, any other than these 2 scenarios and i would think your neighbour would equally be seeing a dimming of there lights,as the lights otherwise should be seperate to the ac with the mains input being the only common denometer

author: IanB
author_rank: Super Contributor
timestamp: May 20, 2012, 12:40:04 am
content: Quote from: Rerouter on May 20, 2012, 12:28:16 amIt's true, the AC should be on a separate and dedicated circuit from the fuse box (breaker box). This is why you may need to involve an electrician or the utility company.What is your supply arrangement? Are you on a town supply from a big substation that serves many houses in a block? Or are you in a more rural area with a utility pole transformer serving only a few houses?

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 12:52:47 am
content: Quote from: Rerouter on May 20, 2012, 12:28:16 amIt would/should be. Anything above a 10A run current would demand a dedicated circuit. In any case lights and powere would be on separate circuits in Australia.QuoteNot necessarily. A 16mm2single phase consumers mains from the street is usual, smaller sizes are now becoming more common in our cost cut environment. 16mm2is good for around 80A at 240V. Run a hotplate in the kitchen at 8A and say 3A of lighting plus another 1A for PC and hifi then consider what effect 65+ Amps of start current will have. This isn't under design, start currents like this are transient and will not overload or over heat the mains.QuoteOnly if the distribution grid is undersized/overloaded. There is generally a lot more copper up on those poles or underground than there is at your premises. Start-up of larger industrial loads however may well be visible in neighborhood mains. To solve this successive western governments have encouraged all industry to move to China thus eliminating any localised light flicker.QuoteOnly for gas or battery powered lamps. Mains lighting is (traditionally at least) connected to the mains.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 20, 2012, 01:00:53 am
content: Quote from: Uncle Vernon on May 20, 2012, 12:07:32 amThe lab chillers at work (each one is about the size of a file cabinet and it provides chilled water for a temperature control system) are inverter controlled and if anything, the inverter itself is the most reliable part of the machine. (The main point is not greater efficiency but better temperature control, very critical in a test lab.) The fact that BLDC motors are more efficient than induction motors more than makes up for the efficiency of the inverter, especially at part load. Not to mention that if you could throttle back the compressor, the heat exchangers are more efficient. (Or you could oversize the heat exchangers, but nobody really does that...)That said, the cheapest solution for your problem is to use good quality ballasts. The ones intended for commercial use will have PFC, which acts as a regulator.

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 01:13:10 am
content: Quote from: NiHaoMike on May 20, 2012, 01:00:53 amThe nameplate ratings on consumer A/C does not hold up your theory in commonly available real world retail product. Cheapest components every time. Part load? When does 2HP split trying to heat/cool half a house experience part load?QuoteNo! they are simply doing less work.QuoteThe better made Australian an NZ manufactured product does! But numbskulls and knowitalls who haven't done their sums will tell you an inverter is the savior of mankind.QuoteAnd if the lamps are halogen filament units?

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 20, 2012, 01:22:55 am
content: Quote from: Uncle Vernon on May 20, 2012, 12:52:47 amJust to clarify, the A/C manages to heat/cool half the house quite easily given the proximity and space it has to affect. Also, I've got beefy insulation on the outside wall which helps alot.The system does not run flat-out at all unless it's one of those freak hot summer Sydney days and if I get the room really cold in the morning on those scorchers, it doesn't crack a sweat.I will drag my butt outside to look more closely at my wire sizes. How many mm wide is 16mm2cable?

author: Rerouter
author_rank: Super Contributor
timestamp: May 20, 2012, 01:28:00 am
content: approximatly 5mm diameter

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 20, 2012, 01:29:48 am
content: Quote from: Rerouter on May 20, 2012, 01:28:00 amThank you. How do you work this out? Is there a formula?

author: vxp036000
author_rank: Regular Contributor
timestamp: May 20, 2012, 01:32:43 am
content: Area = pi r^2, so 16 = pi r^2, and r = sqrt (16 / pi) or r = 2.26 mm. r is half of diameter, so the diameter is 2*2.26 = 4.51 mm.

author: Rerouter
author_rank: Super Contributor
timestamp: May 20, 2012, 01:33:54 am
content: yep^, though thats the conductor size, insulation would probably add 1-1.5mm,

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 20, 2012, 01:37:31 am
content: Quote from: vxp036000 on May 20, 2012, 01:32:43 amAw gawd. As if my head wasn't already hurting enough this morning!Thank you.Quote from: Rerouter on May 20, 2012, 01:33:54 amI wont have to guess the insulation cos I should be able to see right into the switch housing on the front once I take to cover off. Thanks again.

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 01:59:56 am
content: Quote from: vxp036000 on May 20, 2012, 01:32:43 amAs long as your happy. Nothing to do with efficiency or capacity however. The fan in a split system is inadequate for a space as suggested even if the unit can hold temperature on a less than design day.QuoteHelps immensely, it's common sense to engage all passive measures before resorting to mechanical means.QuoteDefine flat out? How much extra work and over cooling does it have to do to maintain the extents of the conditioned space on warmer/cooler days?QuoteIE: over-cool the space with extra energy so that the combination of A/C and insulation can cope with demand. Again not too much scope for an inverter to provide much assistance.QuoteWhy?QuoteAround 10mm diameter. As its a multicore construction its rare it will be truely round at many points along it's length.Quote from: vxp036000 on May 20, 2012, 01:32:43 amWrong! Perhaps you were away the day they did insulation at a university in your country.?In Australia at any rate it is traditional to insulate mains cables for domestic applications. The 600V V75 insulation of course adds to the overall diameter of the cable.

author: vxp036000
author_rank: Regular Contributor
timestamp: May 20, 2012, 02:02:38 am
content: I gave the conductor diameter, which I assumed the question was about.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 20, 2012, 02:08:13 am
content: Quote from: Uncle Vernon on May 20, 2012, 01:59:56 amSo now I don't understand. How did you derive 10mm diameter out of a cable that is 16mm2

author: Rerouter
author_rank: Super Contributor
timestamp: May 20, 2012, 02:13:58 am
content: a 3 core (earth active and nuetral) wire bundle that is more commonly used in its round orange insulation, with the conductors and first layer of insulation forming a triangle, and the second filling in the shape to make it round, so would be able 10-12mm in diameter of the entire cable with insulation included,but that is somewhat irrelivant in this case, conductor size would matter more, still other than that, how did it check out?

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 02:26:07 am
content: Quote from: Ed.Kloonk on May 20, 2012, 02:08:13 amCable (or more correctly wire) diameter equals conductor diameter + 2 times insulation wall thickness. And remember to take into account that the wire will be constructed of seven or more insulated strands. The only place the cable is likely to be 4mm is at the uninsulated portion close to a crimp lug. But then most of those are liable to be HEX crimped, So yes your head will hurt. The other tell tale sign is the conductor size is often embossed onto the inner insulation and/or printed on the outer sheath. Don't get electrocuted trying to identify this within a live switchboard.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 20, 2012, 03:47:38 am
content: Quote from: Uncle Vernon on May 20, 2012, 02:26:07 amYeah Unc,I had the frightening image in mind of someone leaning inside a switch board,trying to measure the cable diameter with a set of metal vernier calipers!Some years back,a bloke got a fairly severe jolt trying to measure the dimensions of the tuning components in an FM Broadcast Transmitter using a metal tape measure with the Tx turned on,so these things do happen!

author: vxp036000
author_rank: Regular Contributor
timestamp: May 20, 2012, 04:06:10 am
content: That's just asking for it... A few years back I was tuning a dipole antenna and a colleague attempted to hacksaw off a bit of aluminum while I was transmiting. Boy, was he surprisedQuote from: vk6zgo on May 20, 2012, 03:47:38 am

author: T4P
author_rank: Super Contributor
timestamp: May 20, 2012, 06:35:51 am
content: Well i don't think inverters bring much advantage but partly most of the mad rotation cycles kick in when the A/C fan energizes but not in normal operation ... 100amps circuit hereWhat inverters (VFD) do is that they drop the motor's rpm in induction motors by lowering the frequency so that they don't draw that much power and then slowly ramp it up and then the motor wouldn't draw 65amps for 3 seconds which does on my daikin but it hardly dims hereAs you know inductors store less energy over a longer period when the frequency is lower then usual(Don't quote me here, i might be wrong)As for BLDC's they are really rare to find on a consumer unit because anyway inverters were intended to tackle problems with the induction motor starting up but yeah induction motors are cheap and reliable

author: SeanB
author_rank: Super Contributor
timestamp: May 20, 2012, 10:44:00 am
content: Ok, first things first.11A implies this is a 24000BTU heat pump, and these can theoretically be plugged in in the UK and SA, don't know about Aus/NZ though. It should have a separate power cable right to the outdoor unit, direct from the consumer distribution board, and, depending on the cable length, this will be a minimun of 2.5mm of copper. 4mm if the run is much over 10m, as this reduces voltage drop and improves the ac efficiency. Should have a disconnect by the outdoor unit (or indoors if the supply is fed there) to isolate it.If it is plugged in to a socket it needs to have a dedicated circuit installed for it only.The power cable should be on a separate breaker in the panel, and the connections should be checked that they are tight, and not overheating. The breaker should preferably be near to the input side of the bus. Note that you will need a sparkie for this in most cases, as you will be working in a mostly live panel. The power input to the panel should also have clean and tight connections, any poor connections will cause a voltage drop. If the voltage at the panel input connections drops when the ac is turned on it is a supply problem, and needs to be referred to the supplier for remedy, as it is either a loose connection on the meter or on the pole.For the AC it probably is an older unit, running on R22. If the switch on surge is high first replace the compressor run capacitor, especially if it is a few years old, as these do lose capacitance with time due to self healing. I find they will start giving problems after 3 years or so ( outside warranty of course) so keep a few tested new ones around. If you want add a "hard start" kit to the motor as well, it brings the motor up to speed faster, so the surge time is lower. It is basically a extra capacitor with a PTC disconnect that adds extra start current for a second or so until the PTC heats up and takes it nearly out of circuit. If you are replacing the motor capacitor do the fan one at the same time, most are 50uF 440VAC for the compressor and 4Uf 400VAC for the fan. Buy from the ac wholesalers, as they will have the right ones for the application.

author: Zero999
author_rank: Super Contributor
timestamp: May 20, 2012, 12:51:10 pm
content: Quote from: Uncle Vernon on May 20, 2012, 12:07:32 amI don't think it's that simple. The reliability of a system depends on many factors, one system maybe more reliable than another when used in one situation but the reverse will be true in a different one. A motor driven by an inverter is less likely to fail because the windings aren't so stressed by the huge starting current and the mechanical components will be less stressed because of the high starting torque. The disadvantage is an inverter is far more susceptible to high voltage spikes which will be more common on a remote installation, than in a well built-up area.QuoteYou're probably right there.QuoteIt's true there's a small power loss, typically 2.5% but not much. Although the consumer may not benefit (other than power saved when it's run at 50% speed rather than cycled on/off and not having a brownout when it's started) the power company and environment do because the inverter improves the power factor so there is less power lost in the distribution system.

author: Unknown
author_rank: Unknown
timestamp: May 20, 2012, 01:40:01 pm
content: Quote from: Hero999 on May 20, 2012, 12:51:10 pmTruebut we are talking lowest cost consumer equipment.QuoteAh but a motor driven by a low cost inverter is often more stress, by insufficient fan cooling at low rpm, heated windings from a less than sinusoidal feed, and bearing damage through excessive leakage to ground.QuoteAgreed again it's all down to design, you can throw almost anything at a Danfoss HVAC drive, but those same supply variation will soon fry POS OEM inverter boards.QuoteMy experience has been that the differences are more often than not a lot more than not much and generally in favour of the better made conventional systems.QuoteThose will benefit a lot more from a mechanically more efficient system. I am not against Inverter drives as a concept. What irks me is all the short lived garbage (including brand named garbage) that are being retailed as money savers. TCO of this stuff just doesn't add up.

author: Psi
author_rank: Super Contributor
timestamp: May 20, 2012, 01:51:21 pm
content: What about a low tech solution.A 5A dummy load, a 20A relay and a 555 timer.When the A/C starts up it's in series with the dummy load. 2 seconds later the 555 triggers the relay and the dummy load is shorted out. Should give the compressor time to start moving.May cause issues if the AC unit has electronics though, due to voltage drop.You'd want to put it on the compressor motor only.

author: SeanB
author_rank: Super Contributor
timestamp: May 20, 2012, 02:08:48 pm
content: Dummy load will not work. The starting surge is needed to start a large mass rotating. If it starts too slow it will stop turning.

author: Zero999
author_rank: Super Contributor
timestamp: May 20, 2012, 03:30:54 pm
content: A large synchronous motor driving a flywheel permanently plunged in would get rid of the problem but it'll cost you a lot in the first place and then there's the standby power.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 21, 2012, 01:55:07 am
content: It looks like the cheapest solution is to use good quality ballasts that have built in PFC/regulation. It's still a little expensive if you have to replace a lot of fixtures, but they'll outlast even good CFLs (or just about any other lighting technology except LED, for that matter). LED is another great option, but they're a little on the expensive side for now.

author: G7PSK
author_rank: Super Contributor
timestamp: May 21, 2012, 08:44:46 am
content: How old is the motor, is it a capacitor start or run and does it have a centrifugal switch for the start winding. Some times the centrifugal start switch sticks or gets slow due to dirt and grease also defective capacitors can also cause problems. What type of compressor is it piston or diaphragm if piston are the unload valves working. If the compressor motor is separate from the fan motor you could start one first and then the other. Induction motors will draw 4 to 8 times the run current when starting so a starting resistance can be used if the motor is starting unloaded or on light load.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 21, 2012, 08:54:21 am
content: Quote from: G7PSK on May 21, 2012, 08:44:46 amBasicly have no idea. Had the A/C installed ten years ago. Has dimmed the lights the same today as it did ten years ago. Thinking about it, I'm starting to think I don't want to mess around with the A/C too much, given the vagueness of the replies, I can't be sure of the consequences. I'll wait for it to die naturally and install a power system friendly A/C.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 21, 2012, 10:23:07 am
content: You should measure the voltage drop. Both at the Air Con and at the lights.I am assuming that they are on different circuits, but then I would also assume there also wouldn't be much voltage drop.But maybe I am wrong so it would be nice to quantify this transient effect.Do you have any equipment capable of measuring a transient or responding fast enough to detect it in some reasonably accurate way?If you can see the lights dim for more than a fraction of a second you should be able to measure something with any good meter.A digital cro would be even better.It would be good to know the inrush current too, if you have a current clamp meter.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 21, 2012, 10:51:42 am
content: I have an 1995 entry level CRO from Jaycar here under some dust. Got to be 15 years since I fired it up and I remember the the Y axis dancing around when selecting the voltage setting. Might just shout myself a new DSO.I do have Dave's old DSO kit and a few arduinos laying around. If only I could get the src of the original code for the project, I could get it running on a modern system and offer the updated src both for the PC and the arduino to anyone who cares. I'd even promise to make a windows version, if asked nicely.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 21, 2012, 11:37:08 am
content: QuoteSorry I should have read the thread a bit more carefully. I thought it was longer, it would be hard to measure a split second with anything that doesn't have storage.Yes 11 amps at 5-8 times during startup would be hard to ignore.Are you suburban or rural, if you had one of those little pole top step down transformers and a long run, I dare say things would be even worse.The led solution might actually be the cheapest.I am doing it for my house, 100 cree xte leds and my home designed mcpcbs and drivers. Hope it works.

author: SeanB
author_rank: Super Contributor
timestamp: May 21, 2012, 04:19:32 pm
content: If it is a home ac then the motor is a hermetic motor, and will be rotary vane. It has a start winding, a run winding and is permanent split capacitor. Piston aircon motors were last made in the 1970's, it is all rotary, or scroll on some. Fewer moving parts, higher rotation speed and no crankshaft to balance, plus the motor can be a simpler 2 pole unit instead of a 4 pole unit, rotating at 1500/1800RPM.No start switches unless added as an auxilary hard start kit.Only reason for the lights to dip is because the start current is in the range of 50-60A, for the first cycle or two, until the rotor comes up to speed. If you have a poor supply there is nothing you can do about it other than top get the supplier to improve it.

author: Time
author_rank: Frequent Contributor
timestamp: May 21, 2012, 05:40:56 pm
content: Could you not just put a few caps in parallel to the power input to provide the high instantaneous current?

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 22, 2012, 09:13:44 am
content: Quote from: Time on May 21, 2012, 05:40:56 pmI guess i could, but I don't where to start.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 22, 2012, 09:19:07 am
content: No, it isn't that simple.I think you're thinking of a DC system where extra caps would actually help.The problem could be summarized having a large rapidly changing load ( the Air con) sharing the same relatively high impedance distribution network.Simply a change in one load will effect the other load.Most of the solutions above such as VSD, soft start, bigger wire, new air con would help or maybe even fix it, but it comes down to a question of effort and money vs how big the problem is.Sometimes the best thing is to just put up with it, and spend your money on beer instead.

author: G7PSK
author_rank: Super Contributor
timestamp: May 22, 2012, 09:23:09 am
content: I spoke to an electrician I know, He suggested checking the connections are tight in the consumer unit, not just for the A/C but the lights as well also the incoming connections, the other thing are you on trips or have you got fuses still as they could be ageing as could the company fuses. He also told me of a case where the lights would dim and brighten as the oven thermostat cut in and out, that was traced to overhead supply where the crimps holding the service splice had slackened, apparent if you look at night very often you will be able to see arcing on them as heavy loads switch on and off.

author: johnwa
author_rank: Frequent Contributor
timestamp: May 23, 2012, 08:28:18 am
content: Quote from: HackedFridgeMagnet on May 22, 2012, 09:19:07 amThere is another possibility I can think of, while fairly impractical, it could work if you absolutely have to stop the lights flickering at all costs. This would be to build an active shunt regulator for the mains. You would need a standing load of several kW, and at the time the compressor cuts in, the load would be momentarily taken off line to compensate. Of course, you then have the problem of what to do with a few spare kW of heat - I am guessing this will not be too welcome at the time of year you are running the A/C. I suppose you could use an electric hot water heater as the load, but if it was on off peak electricity, it would only work while you were asleep, with all the lights off anyway!On a more practical note, a similar scheme is sometimes used for regulating small scale hydroelectric generators. Have a look at this one for example:http://ludens.cl/Electron/picelc/picelc.html

author: SeanB
author_rank: Super Contributor
timestamp: May 23, 2012, 05:20:07 pm
content: That is a motor generator set........

author: kolbep
author_rank: Frequent Contributor
timestamp: May 23, 2012, 07:01:10 pm
content: To the OPIf your house has split phases (i.e. 2 phases and a neutral),or 3 phases and a neutral,then it is just a matter of changing the aircon circuit breaker or fuse to be on a seperate phase to the lights circuit.

author: IanB
author_rank: Super Contributor
timestamp: May 23, 2012, 08:14:13 pm
content: Quote from: kolbep on May 23, 2012, 07:01:10 pmActually in 240 V countries like the UK and, presumably, Australia it is usual to supply just a single phase to a house--in part because each house gets one phase plus neutral, and the phase to neutral voltage is 240 V. The phase to phase voltage is 415 V and introducing two phases to a house would give the potential of 415 V being accessible. The safety code should not allow 415 V to be found in domestic premises.In 120 V countries like the USA there is a 240 V split phase supply with neutral at the center. Most circuits use one or other of the split phases at 120 V. However, heavy loads like ovens, clothes driers and air con units tend to be wired up to the 240 V supply to reduce the current load on the wiring.In either case there is actually no "other phase" to connect the air con to.

author: Unknown
author_rank: Unknown
timestamp: May 23, 2012, 11:34:28 pm
content: Quote from: IanB on May 23, 2012, 08:14:13 pm3 phase domestic supplies are not uncommon in our wide brown land. If you are running any kind of induction motor, a polyphase supply is by far the most efficient way to do it. You wont find multiple phases across a GPO but it would be quite common to have something like an electric cooktop on a different phase to the outlets in the same room. All our wiring is rated to safely handle phase to phase voltage.While potential between phases may be higher, electrocution risk is no greater with the potential from any phase to ground via an idiot remaining at 240V.

author: IanB
author_rank: Super Contributor
timestamp: May 24, 2012, 01:20:11 am
content: Quote from: Uncle Vernon on May 23, 2012, 11:34:28 pmOK, interesting. Three phase supplies may be found in the UK to farms, other light industrial premises, to offices, businesses, schools and suchlike, but typically not to a small house or home. It used to be (if I remember correctly) that electricians were permitted to work on single phase 240 V supplies while energized, but not on 415 V supplies.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 24, 2012, 01:32:03 am
content: I think anyone is allowed to apply to get 3 phase installed but the energy companies charge quite a bit more as part of the service fee, and they are probably a bit reluctant to do it.Most houses definately just have single phase, I only know of one neighbour personally that has 3 phase and that house was initially part of a larger business.That said it would be useful for some items.

author: IanB
author_rank: Super Contributor
timestamp: May 24, 2012, 01:45:33 am
content: Typically what happens in the UK is that a three phase service transformer supplies a group of houses in a street. Each of the houses gets one of the phases with an even distribution. Most of the time the transformer is a big one, like this for example:But in rural areas it may be a smaller pole-mounted one like this:Either way the output is three phase wye on four wires at 240 V phase to neutral and 415 V between phases.

author: Unknown
author_rank: Unknown
timestamp: May 24, 2012, 02:08:29 am
content: Quote from: IanB on May 24, 2012, 01:20:11 amGenerally you are talking larger houses. But anything upwards of 3 bedrooms a 3 phase supply is quite common. Yes you pay more for the installation. No you don't pay more for the supply. And you save buckets on the running costs of ducted A/C or pool pumps.There is no distinction with works. 240V and 415V both come under the LV classification and can be worked on by any licensed tradesman.Quote from: HackedFridgeMagnet on May 24, 2012, 01:32:03 amNo the extra cost is only the install cost. Of late there has been some reluctance to supply 3phase power and a worrying trend of reduced size consumer mains in spec housing. As if less copper ever reduced practical electrical consumption. Upgrading to three phase supply is quite common when fitting ducted A/CQuoteDefine most!Quoteso what you meant previously was "Mostof my neighborshousesdefinitelyjust have single phasesupplies"QuoteIt is common, larger homes needing larger supplies will often get multiple phase supplies even if they do not have any polyphase loads. Even the knobs at BASIX recognise the energy savings of polyphase over single phase. The graph on P55 shows that domestic 3 phase supplies are quite common.https://www.basix.nsw.gov.au/docs/monitoring/2005-2008/05_08_BASIX_outcomes_energy.pdf

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 24, 2012, 02:31:10 am
content: Ok, I didn't realise they were that common in NSW.

author: kolbep
author_rank: Frequent Contributor
timestamp: May 24, 2012, 05:12:02 am
content: I am an electrician on the Lower South Coast in South Africa.When doing new house builds (with the larger houses), and for renovations (where the customer almost always wants to add a Gym, Sauna, Couple of more bedrooms, etc), and when they are getting several Aircons installed, then we advise that they apply to the provider for a 3 phase supply.In the past (before SA's electricity woes), the single phase supplies for houses used to be about 60 / 80A. When the customer goes to 3 phase, the supplier charges an arm and a leg to do the installation for 3 Phase (40a / Phase). They also then charge additional monthly fees for the 3 phase supply.Sometimes, if the new house/alteration is not too big, but may expand, or add more a/c's etc, then we install a 4 Core +E Supply cable from the Suppliers Meter Kiosk to the house, as well as a Distribution board of at least 3 x 18 ways. We then double up on the cores (this halves the volt drop, hence less lights dipping).If this customer wants to go to three phase afterwards, then they get the supplier to upgrade in the meter box, and the electrician just has to partially rewire the d.b. - Not dig up and change the cable again.P

author: vk6zgo
author_rank: Super Contributor
timestamp: May 24, 2012, 07:29:27 am
content: In Western Australia,3ph supplies are quite common,both my current house,& my Mother's old house were fitted with them.Both houses originally had Everdure instantaneous HWS installed,which ran off 3ph.Mum's place had a big cast alloy box in the roof cavity,with a water flow switch that flopped over 3 mercury switches when the tap was switched on.When the element for one phase burnt out,it was just about as cheap to replace the whole unit it as to get it fixed.The new one was in a steel box on the outside wall,but the same guts.Our place had an earlier version of the wall one,which did the same trick,so we replaced it with a Solar HWS.The previous bloke must have used some serious machinery out in the carport,as there is a 3ph outlet there(which I've never used).We got our kitchen stove replaced recently----I thought it was a 3ph device from the cable into the back,but it turns out to be 2 phase,which is apparently quite common.

author: G7PSK
author_rank: Super Contributor
timestamp: May 24, 2012, 07:47:38 am
content: My house has a 3 phase supply we no longer use it the previous owner installed an electric hot water boiler for central heating in the 1970's we replaced that with oil but we still have 4 wires to the house and 3 company fuses although when the meter was replaced after a lightning strike fried the old one it was replaced with a single phase.