UK New smart meter, storage heaters now trip RCD

Brian N · Jun 19, 2021

I have just had a "smart" meter installed , and at night the electrics trips the RCD when the night storage radiator section comes on. I have had them out and they said installation was correct. I know a little about electrics (more over cautious and basic) but was suppressed when I looked at the lay out for the Night storage CU that the neutral goes through the RCD but the live goes direct - could this be a cause for the RCD to be triggered. I will have to get an electrician out to check all the wiring for the storage heaters if I cannot persuade them they have done something to suddenly make my electrics trip when that CU is on. Everything else seems to work fine. I have attached a simplified circuit diagram - electrics in the house have always been a little spaghetti junction, but never had any problems. Local electrician has always installed new stuff properly. Can anyone help? or suggest what my problem could be.

If I turn the CU for the night storage radiators off - then I get electrics 24/7 - if I turn that batch on then it pops overnight.

timhoward · Jun 19, 2021

Hi. If your diagram is right, and i have to say it looks to be, then I agree that isn’t going to work.
As you said the N split is the wrong side of the RCD (which is acting as fault production for the older consumer unit which has no RCD and you probably have an Earth rod - a TT setup).

My guess is that the henley block under the rcd was originally used to split the Neutral. It’s now used pointlessly to split a Live.
I’d try calling them again.
They have certainly messed up in my opinion but it might be quicker to get a sparks to fix it as the issues are all downstream of the meter tails. Then write a letter of complaint!

Brian N · Jun 19, 2021

timhoward said:
Hi. If your diagram is right, and i have to say it looks to be, then I agree that isn’t going to work.
As you said the N split is the wrong side of the RCD (which is acting as fault production for the older consumer unit which has no RCD and you probably have an Earth rod - a TT setup).

My guess is that the henley block under the rcd was originally used to split the Neutral. It’s now used pointlessly to split a Live.
I’d try calling them again.
They have certainly messed up in my opinion but it might be quicker to get a sparks to fix it as the issues are all downstream of the meter tails. Then write a letter of complaint!

Thank you, as I said my basic knowledge of electrics - and gazing at it - I think the people who install, and the person who came out to look at it are not electricians - more installers - if that make sense.

telectrix · Jun 19, 2021

Brian N said:
Thank you, as I said my basic knowledge of electrics - and gazing at it - I think the people who install, and the person who came out to look at it are not electricians - more installers - if that make sense.

Meter Monkey is a more accurate title.

littlespark · Jun 19, 2021

An rcd works by sensing an imbalance on the current on the live and neutral. If the difference is over the threshold of, I would presume, 30mA, the rcd trips…. As far as it knows, the spare amps are going to earth, and it’s doing what it’s meant to.

when your off peak comes on, whatever load on the live is not detected at all by the rcd, but the neutral is…. As it should be balanced, it’s tripping out.

Are you using any off peak heating just now? It might be worth testing by turning the off peak board off completely and seeing if the rcd holds as no load at all will be going through.

Brian N · Jun 19, 2021

littlespark said:
An rcd works by sensing an imbalance on the current on the live and neutral. If the difference is over the threshold of, I would presume, 30mA, the rcd trips…. As far as it knows, the spare amps are going to earth, and it’s doing what it’s meant to.

when your off peak comes on, whatever load on the live is not detected at all by the rcd, but the neutral is…. As it should be balanced, it’s tripping out.

Are you using any off peak heating just now? It might be worth testing by turning the off peak board off completely and seeing if the rcd holds as no load at all will be going through.

If I turn all CU for the night storage radiators off I get uninterrupted power for the rest of the house - only issue is if I leave the storage heater bit on - it then trips when the power to that bit kicks in. Your comments confirm my suspicion that sending the neutral through the RCD and the live direct is causing the problem.

timhoward · Jun 19, 2021

deleted

Brian N · Jun 19, 2021

Thank you all for your replies, I have contacted the meter installer lot, hopefully they can rewire the bit where they made the error. I expect they are not used to installing in an old property with old mechanical meters, three CU, one of which is for night storage radiators. I did jokingly ask if they could send an electrician this time, and they did say they did not have any of them, just installers. You would have thought they could have some trouble shooting electricians to help out.

timhoward · Jun 19, 2021

Brian N said:
Thank you all for your replies, I have contacted the meter installer lot, hopefully they can rewire the bit where they made the error. I expect they are not used to installing in an old property with old mechanical meters, three CU, one of which is for night storage radiators. I did jokingly ask if they could send an electrician this time, and they did say they did not have any of them, just installers. You would have thought they could have some trouble shooting electricians to help out.

Great, it isn't in fact too complicated to sort.
It just needs a henley block in the N from the cut-out BEFORE the RCD, then the N to the off peak CU removed from the top henley block, shortened and put in the new henley block.

(Though if they are pulling the fuse, they may prefer to run a new off-peak tail and re-purpose the block underneath that's there)
Up to them anyway!

UNG · Jun 19, 2021

These not so smart smart meter installers clearly are not trained to install on anything but the simple jobs and also work to the if you don't know ask principle
I wonder how many smart meters are actually installed where there are issues with the DNO equipment like main earths missing that are never addressed, the installation of smart meters would have been a good opportunity to get an overall assessment of the state of the installed distribution throughout the UK but the quality of the installers means it isn't going to happen

Dartlec · Jun 19, 2021

timhoward said:
Great, it isn't in fact too complicated to sort.
It just needs a henley block in the N from the cut-out BEFORE the RCD, then the N to the off peak CU removed from the top henley block, shortened and put in the new henley block.

(Though if they are pulling the fuse, they may prefer to run a new off-peak tail and re-purpose the block underneath that's there)
Up to them anyway!

I think I can see a slightly old TN-S setup under the main head, in which case this is the way to do it.

It's just possible that you are on a TT (earth Rod) - in which case you may need a functioning RCD on the storage heater circuits too to ensure fault protection is working. Alternatively it may be possible to get the DNO for your area to upgrade the earthing to PME.

It may be worth getting an electrician to check things over generally - it may be sensible at some point in the not too distant future to look at updating things a little, especially if you are likely to be doing any electrical work in the future....

Nothing wrong with what you have at the minute, assuming that the RCD is tested regularly with the test button. Just that it is probably >40 years old at this point.

Dartlec · Jun 19, 2021

UNG said:
These not so smart smart meter installers clearly are not trained to install on anything but the simple jobs and also work to the if you don't know ask principle
I wonder how many smart meters are actually installed where there are issues with the DNO equipment like main earths missing that are never addressed, the installation of smart meters would have been a good opportunity to get an overall assessment of the state of the installed distribution throughout the UK but the quality of the installers means it isn't going to happen

They will admit it themselves when I've talked to them - they have a plug in socket tester and a non contact voltage tester for verifying polarity - that's it...

I agree that it would have been a great way for the DNOs to update their records to actually comply with their legal requirement to provide the details of fusing and earthing on request...

UNG · Jun 19, 2021

Taking another look at the pictures if the meter tails were taken from the RCD and connected into the henley blocks above the CU and the CU tails taken from the henley's and connected to the RCD that would be a better fix as the CU to the right already has an RCD in it

loz2754 · Jun 19, 2021

This is the second recent thread where the smart meter installer has cocked up the off peak supply.
Duh!
Smart meter, dumb installer.

Brian N · Jun 19, 2021

Dartlec said:
I think I can see a slightly old TN-S setup under the main head, in which case this is the way to do it.

It's just possible that you are on a TT (earth Rod) - in which case you may need a functioning RCD on the storage heater circuits too to ensure fault protection is working. Alternatively it may be possible to get the DNO for your area to upgrade the earthing to PME.

It may be worth getting an electrician to check things over generally - it may be sensible at some point in the not too distant future to look at updating things a little, especially if you are likely to be doing any electrical work in the future....

Nothing wrong with what you have at the minute, assuming that the RCD is tested regularly with the test button. Just that it is probably >40 years old at this point.

Very sensible comments, I ought to get someone in to take a fresh look at the setup at some point, although the installation of a smart meter has not helped. The original unit was looking old when we moved in some 30 years ago! We do have an earth rod, massive thing stuck into the ground. The other thing I did not mention was the "smart" meter does not work as it will not connect to their network (is it mobile phone?) so all this fuss and it is not reporting back to base - expect I will have to read this meter somehow for them!

UK New smart meter, storage heaters now trip RCD

Brian N

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