Distance between socket outlets on different phases

[Mark42]

Hi
I can’t find this anywhere: what is the minimum distance between sockets wired to different phases in a large domestic installation?
I’m sure in the same room is OK (encouraged even, for load balancing - but never in the same enclosure) but I remember reading somewhere years ago about a minimum distance requirement.
Thanks, Mark.

 

[acat]

I dont think there is one least I cant think of it what you need to do is put a warning sign up of the high voltage if you are capable of touching both at the same time.


Chris

 

[SEC-Tom]

I think it has to be clearly labelled. Danger 400v. At college they have a light sw. with the Danger 400v obviously the lighting was on two different phases.

 

[Notsosmart]

As a rule of thumb (In a commercial or an industrial environment) we have always used 2 metres i.e. more than the average humans span.

 

[mogga]

I think that right Notty dont know if theres a reg tho

 

[Mark42]

Many thanks for the replies: much appreciated.

I’m sure I read a regulation years ago, but I may be imagining it.

I knew about the requirement for labels where voltages greater than 250V might be unexpectedly present.

But I certainly wouldn’t want to put scary ‘DANGER 480V’ labels in someone’s bedroom! (This is a rural, overhead, split-phase ‘Farm’ supply)

Nor would I be comfortable with having, say, two bedside lamps with 480V between the line conductors.

I think 2m is a sensible rule of thumb, plus not either side of a bed etc, so, with a bit of careful planning , I’ll carry on regardless

Thanks again, Mark.

 

[davelerave]

hi

you're the man with the 480v split-phase eh!

that's higher than the standard 3-phase line voltage obviously,

you could play it safe and stick to different rooms

i think that's the rule here for domestic 3-phase anyhow

 

[Notsosmart]

Yep totally agree In the case of domestic I would try to keep all of the sockets in one room on the same phase. To attempt to balance the load I would use a bit of diversity with an estimate of likely loads in the various rooms, i.e. the phase that the kitchen is on preferably would be lightly loaded elsewhere in the house.

 

[m25maintenance]

yea just keep human touch apart, 400 v tag

 

[davelerave]

is 2metre separation any benefit with sockets-i doubt it


so-if you have 2 final circuits on separate phases ( so to speak)


as long as one final circuit is on a SP 30ma rcd you're protected basically if you come into contact with 480v

 

[Mark42]

Thanks again, gentlemen.

I agree that if it were a complete rewire or a new-build, I would certainly have only one phase per room, at least as far as sockets were concerned.

BUT there’s a complication I didn’t want to bore you with: This is an upgrade to an existing installation in a listed building, built in 1510, and constructed primarily of steel-hard oak, in-filled with mixture of clay, chopped straw and bovine sierra-hotel-one-tango.

Running cables is an absolute pig. Excessive drilling and smashing is illegal and surface wiring is ugly in what is supposed to be a perfect installation, so I’m stuck with using parts of the previous ring. This was put in when the previous owner did a major restoration 15 years ago. There was only one ring for the entire (large) house, and the wiring goes up, down, sideways and everywhere, following no logical route.

I’ve split the huge ring into three radials on 20A RCBOs, but am stuck with having parts of different radials in the same rooms.

Some of these will supply lovely old 2 or 3kW Belling radiant fires so I don’t want to have all the sockets on the same phase.

Hence the original question…

No one said it would be easy J

ps Yes, Dave, I’m the chap with the 480V supply. I got a quote to change the pole transformer to a modern three phase, but at over twenty grand (!) I politely declined.
BTW, no one ever answered my question about whether it’s OK to run 480 into 415 boxes…

 

[Mark42]

...as long as one final circuit is on a SP 30ma rcd you're protected basically if you come into contact with 480v

Yeah, I know, what’s the real-world risk anyway? The only possible way to come into contact with 480V would be to insulate yourself from ground well enough to allow not even 30mA to flow to earth, then stick one finger in, say, a light socket, and reach over to another socket to pick up the other phase, delivering a lovely 480V trans-cardiac shock. Game over I think.

Not likely to happen by accident, though J

 

[davelerave]

rcd will trip between phases(so to speak)


you're covered for L-E contact and L1-L2 contact with rcds but not L-N obviously

 

[Mark42]

rcd will trip between phases(so to speak)
you're covered for L-E contact and L1-L2 contact with rcds but not L-N obviously

Oops! I stand corrected. My previous post is rubbish. Of course, L1-L2 is an out-of-balance current WRT neutral. Trips at 30mA, the hypothetical contortionist survives.
Temporary brain failure on my part.
Thanks for the correction!

 

[davelerave]

ya

the theory at home is easier than practice


trying to put more time into planning and design lately-fed up of walking into unforseen problems at work

 

[davelerave]

Oops! I stand corrected. My previous post is rubbish. Of course, L1-L2 is an out-of-balance current WRT neutral. Trips at 30mA, the hypothetical contortionist survives.
Temporary brain failure on my part.
Thanks for the correction!

prob 2 rcd's in series if you come into contact with 480v assuming both final circits are rcd protected-

so if one fails other will likely trip-not too bad eh!

 

[Guest123]

514.10 applies here, and 417.3.1, although not so much I feel.

I have always believed that as long as all outlets supplied form different phases and simultaneously accessible were clearly labelled warning the user of the presence of the voltage between them this is ok, if however they are not labelled then they must not be simultaneously accessible a minimum distance of 2.5 meters is the accepted rule.

 

[Alisdair]

hi

you're the man with the 480v split-phase eh!

that's higher than the standard 3-phase line voltage obviously,

you could play it safe and stick to different rooms

i think that's the rule here for domestic 3-phase anyhow

Thanks again, gentlemen.

I agree that if it were a complete rewire or a new-build, I would certainly have only one phase per room, at least as far as sockets were concerned.

BUT there’s a complication I didn’t want to bore you with: This is an upgrade to an existing installation in a listed building, built in 1510, and constructed primarily of steel-hard oak, in-filled with mixture of clay, chopped straw and bovine sierra-hotel-one-tango.

Running cables is an absolute pig. Excessive drilling and smashing is illegal and surface wiring is ugly in what is supposed to be a perfect installation, so I’m stuck with using parts of the previous ring. This was put in when the previous owner did a major restoration 15 years ago. There was only one ring for the entire (large) house, and the wiring goes up, down, sideways and everywhere, following no logical route.

I’ve split the huge ring into three radials on 20A RCBOs, but am stuck with having parts of different radials in the same rooms.

Some of these will supply lovely old 2 or 3kW Belling radiant fires so I don’t want to have all the sockets on the same phase.

Hence the original question…

No one said it would be easy J

ps Yes, Dave, I’m the chap with the 480V supply. I got a quote to change the pole transformer to a modern three phase, but at over twenty grand (!) I politely declined.
BTW, no one ever answered my question about whether it’s OK to run 480 into 415 boxes…

 

[Mark42]

Err … Hello … This thread was from thirteen years ago

I’d completely forgotten about it. I do now have a proper three phase supply. The 480V issues have long gone.