Discuss RCD Aways tripping in the Electrical Forum area at ElectriciansForums.net

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Douglasmcc

I'm new to this forum. I've recently done a visual inspection of a campsite hall as a favour which has has had an extension built. It's all a bit of a mess electrically speaking. The consumer unit has a 100A main switch and 10mcbs divided across the two 30mA RCDs. The major problem is that when a significant load is placed on circuits 2 & 3 it trips the RCD2 of the other side of the board, not its own. The consumer unit circuits:

RCD 1 - 63A 30mA
  1. External Socket (40A)
  2. Socket, hand dryers, Shed & Gas Boiler (32A)
  3. Hall sockets (32A)
  4. Fire Alarm (16A)
  5. Hall lights & outside lights (6A)
RCD 2- 63A 30mA
  1. Kitchen Sockets (32A)
  2. External socket (32A)
  3. Gas isolator and fly zap (16A)
  4. Hall lights (6A)
  5. Kitchen & toilets & emergency lights (6A)
My initial observations:

My guess in regards to the tripping is that the neutral has been crossed over causing an imbalance between the two sides of the board?

The division of circuits above is not particularly intelligent and not how I was taught; divide the board between fixed and portable circuits.

There are two 13a spur units sitting about 20cm above a stainless steel wash hand basin. I'm sure this is not safe?

There is no earth bonding at all throughout the building especially in the kitchen, which has stainless steel sinks and tables. Nor is any bonding visible in or around the hot water tank or the gas boiler. The SWA cable earth tag has not been fixed to the consumer unit, although it is present.

I'd appreciate your input especially regarding the tripping.

Many thanks
 
almost certainly a neutral problem. either as davidM said, or some other shared/crossed N.
 
Agree re neutrals. Spurs need moving looking at zoning. Maximum demand seems to exceed main fuse. I would suggest to the people to get back the contractor who installed and discuss the matters. Is there a cert. for it all to look at? Looks like it trips when 2 and 3 load up, they are both rings so maybe swapped neutral there?
 
There are two 13a spur units sitting about 20cm above a stainless steel wash hand basin. I'm sure this is not safe?

There is no earth bonding at all throughout the building especially in the kitchen, which has stainless steel sinks and tables. Nor is any bonding visible in or around the hot water tank or the gas boiler. The SWA cable earth tag has not been fixed to the consumer unit, although it is present.

The spurs though not ideal, may not be a code 1 or 2 (if you read the description guides for the codes and then check with the regs for zoning if applicable, you can determine what code you feel is adequate, for this situation)

Supplementary earth-bonding is not always required, a simple test to determine this can be carried out. Main earth bonding is required for all incoming services that are conductive (i.e - aluminium, steel, copper, lead etc..) if you check the regs it is all explained in there.
 
Hi - the observed SWA termination concerns me. Is it a metal CU, is the SWA relied upon for installation earthing? Perhaps confirm Ze and a few Zs ?
You are right about outlets over a sink. Outlets should be min 300mm to the side of a sink with the aim of reducing water splashes onto them. To me, these need to be relocated. Maybe the outlets were there before the sink was added :)
 
I don't do EICR's, as I feel my level of experience would not enable me to scrutinise an installation to the correct degree. And I do not wish to take additional responsibilities at my age :). I also do not wish to have the additional indemnity insurance, although I expect that would be an additional few pounds a month.

However, with just a few lines from the OP, bonding metal tables, bonding hot water tank etc, I would just question his experience in carry out an EICR, if infact that is what is doing.

OP, not having a go at you and we are all can learn from each other, but do you think you should be doing this sort of work on your own, with your current level of expertise? If things do go wrong, your insurance might not protect you. Just saying.
 
Can't see any reason for supplementary bonding. Division of circuits across rcds seems fine to me. What is this zoning business? The hall lights are hall lights not a hallway. It is almost certainly crossed neutrals though.
 
Can't see any reason for supplementary bonding. Division of circuits across rcds seems fine to me. What is this zoning business? The hall lights are hall lights not a hallway. It is almost certainly crossed neutrals though.
unkess a builder has been "having a go".then anything is possible.
 
I don't do EICR's, as I feel my level of experience would not enable me to scrutinise an installation to the correct degree. And I do not wish to take additional responsibilities at my age :). I also do not wish to have the additional indemnity insurance, although I expect that would be an additional few pounds a month.

However, with just a few lines from the OP, bonding metal tables, bonding hot water tank etc, I would just question his experience in carry out an EICR, if infact that is what is doing.

OP, not having a go at you and we are all can learn from each other, but do you think you should be doing this sort of work on your own, with your current level of expertise? If things do go wrong, your insurance might not protect you. Just saying.

I do EICR's....been in the trade for getting on for 40 years....and am increasingly thinking they aren't worth the worry. The risk of missing something that'll come back to bite you seems very real to me. I think these obviously inexperienced guys carrying out EICR's are playing with fire.
 
I do EICR's....been in the trade for getting on for 40 years....and am increasingly thinking they aren't worth the worry. The risk of missing something that'll come back to bite you seems very real to me. I think these obviously inexperienced guys carrying out EICR's are playing with fire.
Couldn't agree more but like you I have been carrying out Periodics for years, you do the job to the best of your ability using your experience you have gained over the years. Unfortunately people who lack experience will do the job to the best of their experience and very often this isn't enough.
 
You need to make an assessment of the earth leakage, across ALL the circuits and the effect that turning off circuits has.

Last Summer I was tracking an issue on a high integrity board - it had 2 x RCD's and 2 x RCBO's - one of the RCBO's was tripping - (it covered lights and smokes ONLY) but would ONLY trip when the kitchen was used.

Using my earth clamp meter I could see that as more appliances were used in the kitchen, RCBO2 would trip - I eventually found a fault on the RCBO circuit - as soon as that was cleared the RCBO tripping stopped.

The earth leakage from the cooker remains..... until they replace it!

So there may be more to this than meets the eye.
 
Some of the more experienced chaps have said 'shared neutral', I can't see how this is possible so must be missing something? Doug says it trips when a 'significant load' is placed, if it was a shared neutral between rcd1 and 2 then it would trip immediately when anything on the circuits 2/3 on RCD 1 is used. Also, it would be a bit of a coincidence that circuits 2 and 3 have a shared neutral as well?

Doesn't it sound more like an accumulation of earth leakage? Richard Burns had a good diagram showing how a fault on one RCD could still cause the other RCD to trip (not a shared neutral).
 
I think crossed neutrals is the immediate default, said it myself. But as you say it may not be the case.
 
With a neutral earth fault on a circuit some current can be redirected from other circuits through the RCD protecting the circuit that has the neutral earth fault causing it to trip.
If only a small amount of current is diverted then only a large current loading on the other circuits could cause the trip.

Possibly this or this diagram?

RCD Aways tripping NE fault RCD trip on current use - EletriciansForums.net

RCD Aways tripping RCD Trip due to other side loadin - EletriciansForums.net
 
Circuits 2&3 have a poor neutral somewhere,
causing some of that neutral current to find a path thru the other side
which must have a better neutral.
Check ALL neutral and earth connections.
you could try using an IR camera, look for hot spots.
 

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