Split Consumer Board - R side RCD switching off L side cicuits

[45140]

Hi folks,

Would appreciate some thoughts.

Called to a friend's house earlier in week. No cooker or sockets.

She said that the cooker had tripped a couple of times when she tried to set up the electronic timer either before or during use. Timer needs to be live to allow electric oven to operate. Rangemaster double stove.

Checked CU and found Cooker CB and RCD tripped.

Reset and everything working, however lady is making a whole series of cakes and does not want continuing trips.

Disconnect pcb in cooker so electric ovens will operate and all OK.

Today she comes home from shopping and ALL electric is off

Check CU and find that the RCD on the right hand side had tripped, all CBs on that side of the split were up. Left hand split RCD was up as were all CBs but absolutely no electric anywhere.

Reset RH side RCD and everything comes back on.

Trip RH side RCD and all electric lost.

Reset and trip LH side RCD and only left hand side circuits lost power.

There was limited ability for me to do much research, however from what I can see without dismantling the CU, the RCDs for each split appear to be wired OK.

I have included a photo of the board.

Am I missing something obvious ? Anyone have come across this before ?

Advice on possible causes would be appreciated.

 

[littlespark]

Can you confirm?
It sounds like all circuits, including all on left hand side, are controlled by right hand side rcd?
There are only 2 circuits on left, so has there been a mistake there in what was on and what was off?

 

[45140]

Can you confirm?
It sounds like all circuits, including all on left hand side, are controlled by right hand side rcd?
There are only 2 circuits on left, so has there been a mistake there in what was on and what was off?

In effect yes all of the circuits on the left hand side are being controlled by the right hand side RCD. Left hand side RCD works fine and only left hand side tripped in original fault.

Only the washing machine was in use when she was out. The cooker was not I use.

The cause of the right hand side RCD tripping could be completely disconnected with the cooker but it is the fact that it seems to disconnect all the power on the left hand side of the split when operated. None of the left hand side CBs or the RCD trip in that situation.

 

[ashrow]

After you posted "Disconnect pcb in cooker so electric ovens will operate and all OK."
I would not offer you any help !
Sorry but the best way to save time would be to get someone that knows what they are doing.

 

[Wilko]

Hi - well if the tripping just started then a fault has likely just occurred... It’s possible that prior to the fault the CU RCD config didn’t cause issues. Now it’s known it should be sorted along with the likely NE fault.

 

[45140]

After you posted "Disconnect pcb in cooker so electric ovens will operate and all OK."
I would not offer you any help !
Sorry but the best way to save time would be to get someone that knows what they are doing.

Taking the on/off time control out of circuit has no safety implications, simply means that the on/off timer cannot be used pending replacement PCB. Surprised you didn't know this
[automerge]1575755571[/automerge]

Hi - well if the tripping just started then a fault has likely just occurred... It’s possible that prior to the fault the CU RCD config didn’t cause issues. Now it’s known it should be sorted along with the likely NE fault.

Yes absolutely agree with you. I don't think the two are connected to be honest.

Sounds like the second trip is a different fault, could even be transient - like the washing machine motor.. Whatever has caused the second issue though has now highlighted the fault I mention in the original post.

 

[littlespark]

You’ve already been into the cooker, so the next suggestion should be ok for you.

Isolate the board, and take the cover off.
Take a photo and post here. You don’t have to touch any of the terminals... just a photo and replace the cover.

There should be 2 pairs of cables coming out the bottom of the mainswitch on the right feeding the top of the 2 rcds.

If you get this all fixed... send us a cake as a thanks

?

 

[45140]

You’ve already been into the cooker, so the next suggestion should be ok for you.

Isolate the board, and take the cover off.
Take a photo and post here. You don’t have to touch any of the terminals... just a photo and replace the cover.

There should be 2 pairs of cables coming out the bottom of the mainswitch on the right feeding the top of the 2 rcds.

If you get this all fixed... send us a cake as a thanks

?

I do have electrical training, so yes the RCDs are both wired correctly and the RCDs and CBs all work correctly and individually. The Neutrals are connected onto the neutral busbar and are tight. There are no loose wires in the CU.

My next step will be to disconnect the line to the right hand side RCD and see if there is power to the left hand side RCD. That should rule out a feed issue.

The next stage in my opinion would be to test the two sides of the split circuit separately circuit by circuit to see if there is an earth fault on any of the circuits.

I am convinced that the fault can be tracked down through step by step testing but I wondered if anyone had experienced this before because it may give a pointer.

At the moment the lady will not agree to a step by step approach because of the amount of baking she is doing, and because the CU is relatively recent. I have suggested that she gets in touch with the guy who installed it but she would prefer not to.

She is happy to live with the occasional trip until she can allow someone to come back and then spend time testing.

As for a cake, I will buy you a pint simply for being helpful, which I appreciate.

 

[littlespark]

As for a cake, I will buy you a pint simply for being helpful, which I appreciate.

RESULT!!

(3 word rule)

 

[Pete999]

Hi folks,

Would appreciate some thoughts.

Called to a friend's house earlier in week. No cooker or sockets.

She said that the cooker had tripped a couple of times when she tried to set up the electronic timer either before or during use. Timer needs to be live to allow electric oven to operate. Rangemaster double stove.

Checked CU and found Cooker CB and RCD tripped.

Reset and everything working, however lady is making a whole series of cakes and does not want continuing trips.

Disconnect pcb in cooker so electric ovens will operate and all OK.

Today she comes home from shopping and ALL electric is off

Check CU and find that the RCD on the right hand side had tripped, all CBs on that side of the split were up. Left hand split RCD was up as were all CBs but absolutely no electric anywhere.

Reset RH side RCD and everything comes back on.

Trip RH side RCD and all electric lost.

Reset and trip LH side RCD and only left hand side circuits lost power.

There was limited ability for me to do much research, however from what I can see without dismantling the CU, the RCDs for each split appear to be wired OK.

I have included a photo of the board.

Am I missing something obvious ? Anyone have come across this before ?

Advice on possible causes would be appreciated.

New House? new CU? could be a borrowed N on the 2 lighting circuits

 

[45140]

New House? new CU? could be a borrowed N on the 2 lighting circuits

Hi Pete, 1930s house, not sure on CU but not recent.

It was obviously replaced to become a split board but there is no information as to when that was done.

The CU was moved to allow the installation of a smart meter, which has resulted in some earths having to be extended to reach the earth busbar but other than that it looks OK.

The original fault - tripping of the cooker when the cooking timer was being set up started in the last few months and all indications are that this is the fault. Pulling out one of the connectors to the PCB in the control unit isolates the unit but allows the electric ovens to be controlled as normal.

So far there has been no further tripping affecting the cooker. New PCB on order

The only equipment "running" when she left were the washing machine, the fridge and obviously the central heating. The cooker was not in use. I am guessing that the washing machine may have caused the right hand RCD protecting that socket to trip but as none of the CBs tripped this remains simply an assumption.

This was the point where it was realised that somehow there appears to be a one-way connection between the two split sides.

When the RHS RCD is tripped using the test button, and when it is switched off, it takes out the electric, supply to the whole CU beyond that point. When the same test is done on the LHS RCD only the LHS circuits are affected.

Did not get the opportunity to look behind or do any further investigation because she wanted to use the cooker, shower, etc, and I will not work live. Once there is an opportunity to take out the whole supply to the CU and take a proper look I can do some more investigation and testing. Until then she wants to leave things and will let me know is there is a further RCD trip.

In the meantime I thought I would see if anyone else had experienced this problem.

 

[Midwest]

I'm not suggesting the answer for this conundrum, but have read on here (and experienced it myself) of many threads, where these kind of fault(s) occur.

It could be an accumulative earth leakage issue, it could be a N-E fault that either prevents an RCD to operate, or can cause an RCD to operate on a circuit it does not protect.

@45140 what tests have you carried out to try and establish the nature of the fault(s)?

 

[45140]

I'm not suggesting the answer for this conundrum, but have read on here (and experienced it myself) of many threads, where these kind of fault(s) occur.

It could be an accumulative earth leakage issue, it could be a N-E fault that either prevents an RCD to operate, or can cause an RCD to operate on a circuit it does not protect.

@45140 what tests have you carried out to try and establish the nature of the fault(s)?

Thanks, Midwest.

So far no tests carried out as the lady did not want to let me do anything at the time because she wanted to use a whole range of items (4 pm on Saturday and they were cooking/using shower, etc), but will let me do a whole series of tests and inspections when the system can be switched off

 

[ferg]

It wouldn't be the first time the RCD's were connected wrongly.
I have seen the incoming side of RCD2 connected to the outgoing side of RCD1 before now.

Usually after an attempt at converting a split load board to dual RCD.