Two phase power in a kitchen?

In article , "peteshew" writes: |> The previous occupants renovated our house and were obviously thinking |> at one time of splitting it into two as there are two gas meters, two |> water supplies and two electricity meters. However at some point |> (after first fix) they their minds about a) splitting it and b) where |> the boundary between the two halves would be. |> |> The result is that the large kitchen has mains sockets from both |> meters close to each other. In fact we often switch the dishwasher and |> washing machine between the Economy 7 / white meter supply which we |> use at night and the standard supply which we use during the day. |> |> I have not put my multimeter between the two, but is it likely that |> they are on separate phases, and are there any issues with having 450v |> in the kitchen?

No. Very few houses have more than a single phase coming into them in the first place. You can check the number of wires as the cable enters the house; if there are two such cables or there are three power cables (plus an earth), then you may have three-phase or two phases on separate supplies.

If you do, I recommend getting it looked at by a competent person; there may be more oddities lurking.

Regards, Nick Maclaren.

On 6 Mar 2007 10:08:44 GMT, snipped-for-privacy@cus.cam.ac.uk (Nick Maclaren) mused:

Read the OP again.

On 6 Mar 2007 02:02:02 -0800, "peteshew" mused:

You're thinking of 415V, ont 450.

It is likely, but depends on how the REC got the second suply in. They may have just come from the 1st supply and had both supplies from a singular single phase feeder.

Needs testing really, but make sure your meter is up to it!

There are two completely independant mains supplies that are at opposite ends of the property, with meters and consumer units sets. Each has a ring main consumer unit and a lighting consumer unit with circuit breakers and RCCBs. The mains wiring that I have inspected looks competently done.

The decision to alter the split of the building was made after first fix, and affects water, central heating as well so no reason to suspect that there would be anything wrong with the wiring, other than the possibility of having two phases in a "sensitive area". Pete

You can tell by looking at the riser - the line cables will come from distinctly separate holes and fuses. Remove the cover to be sure.

Basically, sockets on different phases ain't allowed in the same room.

I fear this may be irrelevant. If the supply comes in on two seprate cables, whatever the arrangement now, there's nothing to say one of the cables mightn't be connected to a different phase in the future after some problem or other, the assumption being that each house would only have one phase. I would move it all to one electricity meter.

On 6 Mar 2007 02:02:02 -0800 someone who may be "peteshew" wrote this:-

Probably a 50/50 chance.

Not if the appropriate notices are displayed.

However, there is a more fundamental problem, the house has two electrical installations, which runs into a number of problems to do with isolation and switching.

I suggest that you get someone competent to look at ways of resolving this.

Ah. That's not what you implied on your first post. Which suggested it was originally one supply split into two - not a new one run in.

I'd get it checked out by a competent electrician familiar with the regulations regarding more than one phase in a domestic property.

Why don't you try taking your own advice. It was a perfectly reasonable response given the scant info in the OP

MBQ

In article , "Bob Mannix" writes: |> |> I fear this may be irrelevant. If the supply comes in on two seprate cables, |> whatever the arrangement now, there's nothing to say one of the cables |> mightn't be connected to a different phase in the future after some problem |> or other, the assumption being that each house would only have one phase. I |> would move it all to one electricity meter.

Yes. If there are two separate feed cables, then you have to regard them as potentially different phases. Or even, in a really extreme case, different substations :-)

The number of meters is irrelevant - lots of houses have several meters supplied from a single feed cable.

Regards, Nick Maclaren.

Do you have an authoritative reference for that? Just out of curiosity.

Perhaps there are different rules in commercial premises. I know of several installations where there is more than one phase present in a room. Largeish rooms, admittedly.

The two parts of the house are almost autonomous - one part operates as a "granny annex" - and except for the late decision to move the effective boundary they would have been completely separable. I would not like to lose this option, which switching to a single electricity supply could do.

My options seem to be to:

a) Revert the boundary to the original design, with some changes to the kitchen layout, and loss of the impressive kitchen. Oddly, I am still permitted to do my own gas plumbing AIUI. Oh, and get Listed Building Consent for any changes.

b) Dig into the dry lining etc., and work out if the ring mains could be adjusted. Part P certification needed for any work.

(I just remembered the lights, which are on the "wrong" supply too, and not easy to switch without putting a potentially wrong phase under the floor of an otherwise correectly connected room)

c) Do nothing (until we decide to sell, maybe). Perhaps label the power points with the supply to which they are connected.

Pete

I thought that they were not allowed to be within six feet of each other, or had to be separated by a wall.

Colin Bignell

There is no such restriction. I've heard all sorts of rules quoted, including this, and that socket outlets on different phases must be more than an arm's reach apart. The regs have never contained any such restrictions.

The regs only require that anywhere where > 230V is present and not expected (which you could argue to be anywhere in a house where > 230V is present), a suitable permanent warning label (400V in this case) be attached.

There was a manufacturer of carpet cleaning machines who fell foul of this a few years ago. The machine had one cable to power the vac & pump and another to power the immersion heater. They sold a load of machines via the Crown Suppliers - now The Buying Agency to Govmint departments & had to change the lot because of the safety issue.

My view on this is that it's because multi-phase installations don't occur in domestic premises so aren't covered.

Which would mean nothing to the average punter.

GP 13 amp outlets?

This is the second house that I lived in with two phase power. The first had electric storage heaters on a separate supply on another phase to the ring main. There were no warning signs - this was in the

Pete

In fairness, you'd have to be stunningly unlucky to get a 400V shock wouldn't you? You'd have to simultaneously touch live wires from both phases. Even if you had socket 2 outlets within a couple of feet on different phases, I really can't see it happenning.

Obviously I wouldn't wire that way in the first place, but I don't think I'd spend a lot of time and hassle changing it either.

Jon.