Two consumer units backfed

[mick b]

I have just come across a domestic installation that has two consumer units I was asked to wire extra sockets and do a board change as well. I found that the sockets of one board circuit are interconnected to a circuit from the other board, thus back feeding each other. This means that unless you isolate both boards or pull both relevant fuses then the whole installation remains live. I have wired my additional sockets to my own board , and explained to the client what the problem is. There is no way to find where these two circuits are interconnected without ripping up boards or going in loft and emptying it. And it's a possibility that it's been done more than once. Apart fron putting a warning notice for two sources of supply what am I meant to do. Mention of tearing the house apart was not well accepted.

 

[telectrix]

make sure you put it in writing and get customer to sign that he understands and does not want you to investigate.

 

[davesparks]

What you should do is advise the customer before you start work and if they don't agree to have it sorted then you should walk away and not do anything.

Why didn't you just move the offending circuit from one board to the other? Are these circuits ring finals? If so they may just be two legs mixed up.

 

[7029 dave]

^^^^ could be legs crossed or interconnection, needs testing to confirm.

 

[Deleted member 9648]

I have just come across a domestic installation that has two consumer units I was asked to wire extra sockets and do a board change as well. I found that the sockets of one board circuit are interconnected to a circuit from the other board, thus back feeding each other. This means that unless you isolate both boards or pull both relevant fuses then the whole installation remains live. I have wired my additional sockets to my own board , and explained to the client what the problem is. There is no way to find where these two circuits are interconnected without ripping up boards or going in loft and emptying it. And it's a possibility that it's been done more than once. Apart fron putting a warning notice for two sources of supply what am I meant to do. Mention of tearing the house apart was not well accepted.

Really cant see it being a major issue. Some basic testing and the source of the problem will be identified in less than an hour. Presumably your method of 'tearing the house apart' means you intended to find the problem visually rather than by testing.

 

[fall-apart-dave]

You could get some idea of what's what by doing a continuity check on all legs as Davesparks suggests, that will at least give a clue about what might be going on. In the event that does not show something simple like legs crossed, then there's still not a need to pull up floors straight away. Though it's unclear from your post what is actually happening... You say the whole installation is live unless fuses are pulled, could you clarify a little? is it one circuit or all circuits? Rings or radials?
If continuity checks at the board don't yield results, and it turns out one ring on one board is indeed connected to a ring from the other somewhere in the house, then before pulling boards up and tearing the loft apart, popping sockets off and disconnecting (trying to emulate something akin to the half split technique) will hopefully show where the offending cable is. It'd be tedious, likely not cheap for your time and boring doing continuity checks all day but it would go a long way to nailing the issue down and wouldn't need tearing a house to bits. Or do I have the wrong end of the stick here?

 

[telectrix]

Or do I have the wrong end of the stick here?

or the wrong end of the circuit?

 

[fall-apart-dave]

Or do I have the wrong end of the stick here?

or the wrong end of the circuit?

Unless it's a ring final... Then one end is as good as the other.

 

[telectrix]

unless the other end is the other RFC.

 

[joehat]

Currently then the circuits have to high of overload protection. Which is more dangerous


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[Octopus]

I have just come across a domestic installation that has two consumer units I was asked to wire extra sockets and do a board change as well. I found that the sockets of one board circuit are interconnected to a circuit from the other board, thus back feeding each other. This means that unless you isolate both boards or pull both relevant fuses then the whole installation remains live. I have wired my additional sockets to my own board , and explained to the client what the problem is. There is no way to find where these two circuits are interconnected without ripping up boards or going in loft and emptying it. And it's a possibility that it's been done more than once. Apart fron putting a warning notice for two sources of supply what am I meant to do. Mention of tearing the house apart was not well accepted.

Can you share with us the "notes" you put on your EIC concerning your initial findings?

 

[gnselectricals]

Bit of a poor show leaving the 2 interconnected circuits as they are and installing your stuff on anther board. Hardly 2 sources of supply either sounds like mixed up legs of 2 ring finals as mentioned earlier. Think I'd be on the phone to you if I was coming in behind you and it was left like that tbh


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[PEG]

If that was one of my "special" customers,they would get another spark in,after the last,and he would connect all three boards together...then,and only then,would i get the phone call...:icon11:

 

[mick b]

Why do I need a a report for an addition on my own board

 

[mick b]

Ok then what do you do