A new smart meter is tripping RCD for 7 hours every night & I have a theory

[James18288]

The fact the economy 7 CU had its own neutral but now is shared with the main CU would be where I’d look first. Where is the neutral supplied from in relation to the RCD? More than likely it’ll be a really easy fix. A N-E fault would probably trip whether the board had a live feed or not. Ie, not just at off peak times.
Hopefully you get it sorted tomorrow, and as has been said I’d be interested to hear what the fault was. Whatever happens though, could possibly be time at looking at an upgrade for those CUs

 

[snowhead]

Edit to above,
It looks like that parked tail was a Live which was switched by a now removed contactor for the Off peak and it's origin was in somewhere in the Henlys by the Consumer units

 

[fearny26]

The fact the economy 7 CU had its own neutral but now is shared with the main CU would be where I’d look first. Where is the neutral supplied from in relation to the RCD? More than likely it’ll be a really easy fix. A N-E fault would probably trip whether the board had a live feed or not. Ie, not just at off peak times.
Hopefully you get it sorted tomorrow, and as has been said I’d be interested to hear what the fault was. Whatever happens though, could possibly be time at looking at an upgrade for those CUs

Yes an upgrade would be ideal but the cost right now is less preferable ha.

Okay apologies for messy CU so setup is as follows

Of the four meter tails 2 enter the RCD at the top, one enters the middle back of the Henley and one enters the E7 CU directly.

Henley block is set out from left to right as follows
1 & 2 on the left are both tails From On peak CU
3 (rear middle) is meter tail
4 (front middle) goes to E7 CU
5 & 6 on the right enter the bottom of the RCD

On the meter side of things previously two tails came from the meter and two tails came from a seperate heat contactor now 3 tails come direct from the meter and one tail has been parked in a Henley block

Thanks guys for the replies so far

 

[littlespark]

Maybe I’m confused.
If the off peak board only supplies storage heaters, and you don’t use them, turn off the OP board if the rcd holds like that until spark has a look.

it could be a fault on any of the heater circuits, never mind on the tails.

 

[fearny26]

Maybe I’m confused.
If the off peak board only supplies storage heaters, and you don’t use them, turn off the OP board if the rcd holds like that until spark has a look.

it could be a fault on any of the heater circuits, never mind on the tails.

Yes the OP board is kept switched off but off or on the fault remains

 

[pc1966]

The whole setup looks a bit disturbingly complex, and there seems to be more than one meter-set?

Hopefully the spark who visits can do a bit more systematic testing than we can guess from the photos.

 

[snowhead]

Got it.

The Live to the Off Peak Consumer unit was sourced via the RCD.
Now it isn't.
But the Neutral still is.

There must be a small L to N leakage in the Off Peak C.U, enough to off balance the RCD.
And it will be on the Live side of the Main Switch

 

[fearny26]

Got it.

The Live to the Off Peak Consumer unit was sourced via the RCD.
Now it isn't.
But the Neutral still is.

There must be a small L to N leakage in the Off Peak C.U, enough to off balance the RCD.
And it will be on the Live side of the Main Switch

Thanks so much for taking the time
Great work ill mention it to the spark when he comes over. I assume it would just mean replacing the fuse board then.


I'm really keen to use this as a learning exercise for myself I think I understand you're explanation but would you mind at all going over why this problem didn't happen before the meter exchange and what it is that's changed to bring about this problem. Sorry if its obvious

 

[Rockingit]

"Theres only 1 rcd for the whole circuit (i know, its an old setup) and 2 wylex fuseboards for on peak and off peak."
Source URL: A new smart meter is tripping RCD for 7 hours every night & I have a theory - https://www.electriciansforums.net/threads/a-new-smart-meter-is-tripping-rcd-for-7-hours-every-night-i-have-a-theory.189919/

Unless I'm being thick and missing something already covered, how can you have a single RCD covering two lines of supply?! In order for that to be it would have to be upstream of the meter, which it never would be unless the meter fitter had been smoking something herbal at the time.

 

[snowhead]

Unless I'm being thick and missing something already covered, how can you have a single RCD covering two lines of supply?! In order for that to be it would have to be upstream of the meter, which it never would be unless the meter fitter had been smoking something herbal at the time.

On the original setup the meter only had a Single L & N out to the C.Us
This went direct to the RCD, through it then to the Henley where it split.
1 L & N supply to the Main C.U
Another Live went out to the contactor by the meter and came back in off the switched side to the Off peak Consumer unit.
The L to the Off peak now comes from the meter and misses the RCD, but the Neutral doesn't