Any 3 Phase Electricians On Here That Can Help??

[Chrishazle]

This is the first house we have ever owned that has a 3 phase electrical supply, normally not a problem but tonight for the first time we have had a power cut with a foible, so I'm hoping someone can advise.

Any power cut in the past - and there's been a few in our 12+ years here - once the power comes back on it's the whole lot. Tonight the power came back on, I noticed that our living room incandescents were dim, our oven and hob would not fire up, and a couple of other things. By investigation I figured that Red phase was on at lower than normal voltage, although the other 2 phases (Blue and Yellow) appeared to be fine. However, not being able to use the hob and oven when ready to cook dinner was awkward, to put it mildly! Reported it to Ukpowernetworks, over the next couple of hours Red phase was on and off, managed to get the veg's cooked and into the warmer, but ended up cooking the steaks on a camping-gaz stove!

So - in my consumer unit cupboard I have one consumer unit for each phase, plus a seperate circuit breaker for the cooker, which I'm now certain is only fed from Red phase.

Is it possible to install a selector switch upstream of the cooker circuit breaker so I can select which phase feeds it? How do I find an electrician qualified to work on 3 phase and install it? (I ask because a few years ago BG turned up to install Smart Meters, fellow took one look and said "that's 3 phase, I'm not qualified to work on that", then said "there's not a domestic 3 phase SMETS2 meter yet, don't know when one will be available!!", so we're still on an ordinary E7 meter (and not with BG!).

Any help appreciated!

 

[190]

There is nothing special about 3 phase as each phase is 240V to earth - the same as single phase. You only get 415 volts between phases. With 3 separate consumer units you can treat each one just as a normal single phase supply and any electrician should be able to work on one. I assume you don't have two phases supplying anything in the same room. If you do that would be bad practice because of the 415 volt risk but not actually against the regs provided there was I think at least 6 ft between them. The idea is that you shouldn't be able to touch both at the same time.

A selector switch would be an odd thing to do and risky if there is any possibility of shorting the two phases together. Leaving aside whether it could be done under the regulations because I'm not up to date on that, but if I did do it I would want the facility to securely isolate one phase before switching to the other.

 

[Stratman]

Our TV Outside Broadcast trucks had three-phase inputs, with switches to select which phase various groups of kit went to. Standard practice was the technical supply went to one phase, general (lights, heaters, kettles etc.) to another and air conditioning to the third, but each could be switched to any input should the need arise. So I'd say 'yes' you can do what you suggest with the caveats mentioned. As to who can advise on and do it, try a commercial electrician, one who works on large buildings, as it's likely they will have three-phase supplies.

 

[219]

It's slightly odd that a domestic property would have more than one phase run in - unless it was previously some sort of commercial property ?

At my parents old house , when my dad built the new garage , he had all three phases brought in , and three meters installed , because he was going to use it for his haulage business before he got separate premises .

Eventually , we got two of the meters taken back out , since despite only ever using one of the phases , we had a standing charge for the other two .

I agree that switching between phases could be a slightly dicey thing to do ; we have different rings on different phases in our studio , and have to be very careful if we had a camera or such plugged in to one phase and linked by cable to kit in the Edit Suite on a different phase ; eventually got long cables which snaked across the floor so that Camera Control Units were plugged in along with other kit on the same phase and nothing went across the phases . A bit like above , we then had all electronics on one phase , lighting on another ( we didn't have that much ) and non related items on the other .

We once lost a 30 grand data projector because a sparky in a hotel had wired something wrong and we ended up with two phases live on a single 13A socket ! The hotel paid for the loss , but we always plugged in socket testers after that before connecting any expensive kit .

 

[Benzowner]

Many moons ago, three phase in houses, was installed to run the night storage heaters in some areas of the UK and others areas chose to use a larger section mains cable single phase

 

[Ierton]

There is nothing special about 3 phase as each phase is 240V to earth - the same as single phase.

I think you mean 240v to neutral.

 

[190]

I think you mean 240v to neutral.

Well yes but I was thinking of the shock risk which is what might frighten people about working on 3 phase.

 

[Petrol Pete]

I helped out a mate of mine at one his pubs a while back, one of those big old (1950's) places. it had a 3 phase supply, one went to the kitchen, one went upstairs for the private accommodation area and the other phase supplied the public area of the pub.
It didn't seem to be particularly well balanced to me , but the pub is still there 20 years since I did anything to it, it hasn't burned down yet so it must be OK

 

[Gollom]

I used to have a house in France with 3-phase - at one time it was the level-crossings keeper house. We never ever saw a bill so guess it was still being paid by the railway company! Not sure it was up to spec though - was wetting/stripping wallpaper one day and got a shock from the wall!

 

[Chrishazle]

Same can happen with single phase. When we bought the family home in 1982 it was a 1936 build, the electrics were all in metal conduit in the walls and the wiring had vulcanised india rubber sheathing - which had degraded somewhat over the years. Like Gollom, I got an electric shock off a wall! A few months into ownership we had the whole house re-wired!

 

[Swotty]

I used to have a house in France with 3-phase - at one time it was the level-crossings keeper house. We never ever saw a bill so guess it was still being paid by the railway company! Not sure it was up to spec though - was wetting/stripping wallpaper one day and got a shock from the wall!

We have a house and barn in SW France which we joined together when we bought in 2007. Both have 3 phase 'leccy. I am told it was due to being an agricultural property and thus the need to run large machines.

The electric cumulus was 3 phase but when that went kaput, we had it changed to single phase. The pool has 2 pumps which are 3 phase as they are big hectors, and I kept 3 phase in the garage for the day I finally get my car ramp!