On Wed, 07 Mar 2007 10:41:13 +0000 (GMT) someone who may be "Dave Plowman (News)" wrote this:-
Yes they do. Usually larger houses rather than noddy boxes from volume house builders.
The notices are intended for those maintaining the installation.
On 7 Mar 2007 03:26:57 -0800 someone who may be "peteshew" wrote this:-
I don't think the requirement for warning notices came in until the early 1980s.
In message , David Hansen writes
Still never fully understood that rule. The only potential for 400/415V disaster is if two appliances have no earth, simultaneously develop faults to earth and the user touches the exposed metalwork on both of them at the same time. Since making contact with just one of the faulty appliances is likely to give at least a tingle at some point this scenario is very unlikely.
Of course, if you were really determined you could get two ES table lamps, put them on your lap, take the lamps out and stick a finger from each hand onto the middle contact........
415V stickers on switchplates.... To be honest, if I ever have to grub about with the back of a live multiway switchplate then just coming into contact with 240V is going to be most prominent on my mind.On a plus side the presence of two sockets on different phases in a kitchen could be jolly useful. Given that the theoretical resistance of a 3kW kettle element is 12.5 ohms, then by stripping the cable back and wiring live and neutral across the live pins of two separate plugs and whacking them into opposing phases would instantly turn the kettle into a 14kW kettle and tea would be ready in no time. Plus the plugs would have the potential to be full of tingly fun when one was unplugged. (That's backfeed for those who don't understand. It the same reason neutral CAN electrocute you.)
With sockets from different phases in the same room?
And just how many lights etc does a 'larger' house have that a 100 amp feed couldn't cope with? Unless of course you're talking about electric space heating.
So you'd be happy with notices stuck to all your sockets, etc?
Fixed installations like space heating isn't the same as socket outlets.
On Wed, 07 Mar 2007 13:49:13 +0000 (GMT) someone who may be "Dave Plowman (News)" wrote this:-
The assertion was that houses don't have more than single phase supplies. It is incorrect, though there are not that many houses with three phase supplies.
If a house has sockets on different phases then these are no different to sockets on different phases elsewhere. Discouraged in the same room, but where provided they should have the appropriate notices on them. Of course a room could cover everything from a small cloakroom to an indoor games court.
That rather depends on what else electricity is being used for. As well as the space heating you have mentioned there may be workshops, big cookers and so on.
Trying to personalise things is not productive to discussions. I don't have any need to stick such notices on all my sockets.
True but not the point from the OP's pov - some readers may misinterpret although you know what you mean. One should be clear that this isn't a house with a three phase supply (where things are arranged, ab initio, properly in that knowledge and the supply is recorded somewhere as three phase). This
*may* be a house with two, different, single phase supplies, an entirely different kettle of fishes and one that might cause future problems.
What do you mean by GP?
If you mean 'General Purpose', as opposed to dedicated outlets for permanently-installed apparatus, then yes.
I'm surprised. I don't have the regs for such things but know in places like a TV studio the sparks are careful to keep all floor lamps etc on the same phase as the technical gear.
The rooms in question are in residential properties above shops. They might have been considered commercial premises once upon a time, but are now residential. ( several seperate premises on seperate floors. ) The distribution boards are obviously fairly old, and are 3-phase. The various rings in the premises come off different phases, and some of the larger rooms have sockets from more than one phase. It's possible that the rooms in question were each originally more than one room, which have been knocked together.
So the situation may have evolved into this, rather than having been designed this way.
However, I'm still not aware of any actual regulation that prohibits this.
( These premises were the subject of a thread I started some time back, where bulbs were blowing all the time. It turned out to be a Neutral problem in in the cabling in the communal stairwell. The high-resistance N was 'rotating' around the phases, causing cyclic >>>240 phase-N. )
In message , "Dave Plowman (News)" writes
Many of the film industry generators in the UK are one big single phase supply for safety. I think this is probably more due to the grief caused if a neutral floated and all the big lamps went boom just before an expensive shoot. The fact that most film industry "electricians" learn by word of mouth as opposed to a formal apprenticeship doesn't help.
The same inappropriate rule is still dragging it's sorry ass in the theatre industry with the belief that you can't have more than one phase on a lighting bar. Given that the bar is earthed itself and that each fixture probably has some scorched semblance of an earth too, the only way you can get a 415V shock is by opening two lights and poking your index fingers into the holders. I've never actually tried this or seen it done.
In message , Ron Lowe writes
The electricity supply companies usually prefer for a complete installation to be fed from a single meter. The use of more than one phase is only likely in a huge residential premises or one that was used as accommodation with showers in every room.
Each of the upper floors is a seperate premises, and each has it's own 3-ph meter, covering that premises.
I guess each of the commercial premises on the ground floor also has it's own meter.
These are all fed from a 'rising' main that runs up the stairwell.
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