House Socket Isolation

[kevmcdo9]

Hi Folks,

Just a quick question, is it normal to only be able to isolate your house sockets by switching the RCD off ? I ask because this is the only way on my CU i.e there is no MCB to isolate them.....well there is but it dosen't isolate them

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• kevmcdo9
• 21 Mar 2011
• 1

 

[mikhailfaradayski]

Hi Kev,

Sorry, can't quite read the labels on your CU. Any chance you could post another?

Whilst your at it, can you take a photo of the cu with the lid removed so we can see the wires inside, please.

(be careful when you do this)

BTW, those finger sized gaps in the front of the CU should be sorted out. Nip down to your local electrical wholesaler and ask for a couple of blanking plates to fill the holes (they'll only cost you a pound or two)

 

[JohnD]

you have a defective installation, or the labels are wrong.

one of the errors sometimes seen is that the two legs of the ring are put into two different MCBs, instead of both going into the same one.

If you can safely remove the cover and photograph the cables and MCBs we might see what's happened.

edited: too slow

 

[bernardgreen]

Hi Folks, Just a quick question, is it normal to only be able to isolate your house sockets by switching the RCD off]

NO and if there is no MCB that isolates them then very likely there is no over current protection either.

You need to have that checked out and the potentially dangerous fault or wiring error removed.

Do any of the MCBs turn anything OFF. A ring circuit may been wired with one end in one MCB and the other end in another MCB and both will have to be turned off IT IS STILL A HAZARD

Or maybe if none of the MCBs turn anything off the cables have been connected to the input side of the MCB ( where the busbar is ) and that is a very dangerous situation.

Someone here has a photo of a CU where that "error" was made.

 

[Monkeh]

Someone here has a photo of a CU where that "error" was made.

//www.diynot.com/wiki/electrics:hs:pic1

 

[kevmcdo9]

So I turned my RCD off to take the cover off cu for photo, when turning it back on the sockets didn't come on so I put the 'house skts' mcb on and they came on.......even though it wouldn't isolate them all the times before.

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• kevmcdo9
• 21 Mar 2011
• 1

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• kevmcdo9
• 21 Mar 2011
• 1

what do you make of the insulation tape ?

 

[kevmcdo9]

yes bernard all other mcb's isolate fine.

 

[ajrobb]

If turning one MCB on with all the others turned off activates the sockets but turning the same MCB off with all the others turned on does not isolate it, it might be you have the two rings crossed.

Check which sockets each of the rings MCB (2nd and 3rd MCBs from right) turns on with all the others turned off.

 

[kevmcdo9]

If turning one MCB on with all the others turned off activates the sockets but turning the same MCB off with all the others turned on does not isolate it, it might be you have the two rings crossed.

Check which sockets each of the rings MCB (2nd and 3rd MCBs from right) turns on with all the others turned off.

It turns on both with all others off and with all others on.
I would have thought that there would have been two seperate rings for ground and first floor. This is not the case.

2nd from right 'House Skts' turns all sockets apart from the kitchen and the 3rd from right turns on the kitchen sockets

The problem is when I turn 'House Skts' mcb off it dosen't isolate the sockets.

 

[ajrobb]

What happens when you turn of both the kitchen and house sockets MCBs?

 

[kevmcdo9]

What happens when you turn of both the kitchen and house sockets MCBs?

They both isolate..... honestly the 'house skts' mcb would not isolate the sockets for the past week ! it is now isolating when I turn it off .......? Confused.com

 

[ajrobb]

If you believe that the MCB ever failed to isolate its circuit, you should get it replaced.

 

[electronicsuk]

If turning one MCB on with all the others turned off activates the sockets but turning the same MCB off with all the others turned on does not isolate it, it might be you have the two rings crossed.

Check which sockets each of the rings MCB (2nd and 3rd MCBs from right) turns on with all the others turned off.

It turns on both with all others off and with all others on.
I would have thought that there would have been two seperate rings for ground and first floor. This is not the case.

I think you've misunderstood the potential problem. If the two legs of the ring are in separate MCBs then either MCB will be able to apply power to the circuit when the other is off. What you won't be able to do is turn off the circuit with any one MCB.

You need to confirm that turning off the downstairs sockets MCB alone isolates said circuit. If it doesn't, also turn off the kitchen sockets MCB at the same time, and then test the circuit for dead.

Either that, or it's a faulty MCB as has already been suggested.

 

[ajrobb]

Please perform the following tests and answer the questions:
1. turn off all MCBs
1a are the main sockets live?
1b are the kitchen sockets live?
2. turn on just the 2nd MCB from the right
2a are the main sockets live?
2b are the kitchen sockets live?
3. turn off the 2nd MCB from the right and turn on the 3rd MCB from the right
3a are the main sockets live?
3b are the kitchen sockets live?
4. turn on all MCBs except the 2nd and 3rd from the right
4a are the main sockets live?
4b are the kitchen sockets live?