RCD TRIPS ON MOST CIRCUITS ON NEW SPLIT LOAD CONSUMER UNIT

Hi,

I just installed a new MK Sentry K5686S Split load Consumer Unit and am having problems with most of the circuits attached to the RCD side of the consumer unit.

I had four circuits attached to the RCD - Downstairs sockets, upstairs sockets, garage sockets and the Shower. All of the circuits trip the RCD apart from the shower. I have temporarily moved these problem circuits over to the non-rcd side and they are all working fine.

I am suprised that I am having problems, especially with the garage circuit, as this was only fitted a year ago.

Any ideas on possible causes and how to resolve this problem greatly appreciated.

Thanks.

Reply to
KevCompton
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Slightly OT, but does anyone manufacture an "imbalance" current meter?

Reply to
Fred

Make sure that the neutrals for the RCD circuits are on the RCD side and not the neutral bar of the non-RCD side.

Dave.

Reply to
Dave

The usual problem is wiring the neutral of the RCD protected circuits back to the non RCD protected neutral bus bar, rather than the dedicated bus bar for RCD neutrals.

Reply to
John Rumm

You have connected the neutrals to the wrong connecting strip. The less likely problem is a faulty RCD but then the shower would trip it too.

Reply to
dennis

Thanks for all the prompt replies. I'm 95% sure that I had all the neutrals on the RCD protected neutral bus bar as I had to swap them over to the non-RCD protected neutral bus bar to get things working temporarily on the problem circuits. Are there any other possible reasons?

Reply to
KevCompton

Some CUs come with a link wire between the neutral bus bars. You need to remove that when using it as a split load unit.

A faulty RCD would be aother possibility. Difficult to test reliably without an RCD tester though. You could swap it out for another to be sure.

Or it may even be telling you that you have genuine circuit faults! A quick and simple test would be to check for any neutral to earth shorts at the CU end of the circuit wires, before you connect them back. You can get useful information with an ordinary multimeter.

When do you get the trip? If for example you connected a socket circuit and made sure there was nothing plugged into it, and any equipment directly connected was disconnected at its FCU, does it still trip with no load? If not does it then trip with a small load applied (like a table lamp for example)?

Reply to
John Rumm

Hmm, how do you get a neutral feed to it then ? do split CU's have separate incomers/isolators per side ?

I thought it had a single isolator and separate RCD.

Does it need a dedicated tail per side in this case ?

I can't envisage it as I don't have a split load CU.

P.

Reply to
zymurgy

Both the live and neutral go *through* the RCD.

Reply to
dennis

John,

Thanks for the reply.

I removed this prior to installation.

I don't have a spare but, I will ask someone who has a tester to check it for me.

I will check this when I get chance, is this simply a matter of testing for continuity between the neutral and earths for each circuit at the CU?

I will check this when I get chance, thanks for the assistance.

Reply to
KevCompton

The missing 5% of "sure".

Reply to
Ian White

I had to remove a power factor capacitor from a fluorescent lamp once. It was isolated and most definitely only connected to live and neutral yet virtually every time I switched it on it would take out the RCD.

I also had a computer which I learnt to leave permanently switched on and only turn it on or off at the wall.

Equipment with mains filtering can be an issue. I've isolated capacitors before now so there's no connection to earth.

Reply to
Fred

Re CU tripping on most circuits:

The other thing not yet mentioned is your house wiring may have connected neutrals between different circuits, or have loads that run from live on one circuit to N on another.

Or there may be silmilar N/E issues.

I would remove all problem circuits from the CU, disconnecting all 3 L,N & E, and test with a multimeter to see what connects to what. Each circuit should be entirely unconnected to each other one, except for earths which can connect to other earths no problem. For lighting circuits, switching all the unpowered lights on would enable the meter to spot lights connected from one circuit's L to another one's N.

You just need to work through the possibilities, confirming or eliminating one by one. Thats if you want to run them on an RCD. I dont know which circuits they are, but it may be fine to not RCD some or all of them, depends.

NT

Reply to
meow2222

Thanks for your reply, very useful. Earlier, I did a bit more checing and it looks like different circuits are connected to each other. I will do as you suggest and remove all wires on the problem circuits and see what is connected to what. All the problem circuits are for the sockets throughout the house.

You mentioned that the wiring may have loads that run from live on one circuit to N on another. I think that may be my problem as continuity between two L contacts on different circuits existed even though I had disconnected them from the CU, leaving only the N and Earth still connected. Why would this be done? Is it a normal thing to do in certain conditions?

Thanks.

Reply to
KevCompton

Its quite common, if not best practice. If it were me I'd be asking which of the problem circuits actually need to be on RCD. Either that or you've got a bunch of tracing and rewiring to do.

NT

Reply to
meow2222

Christ, something Fred does not know the answer to and posted in thread !!. Things are looking up.

Dave

Reply to
Dave Stanton

Live and neutral tails come into the incomer, thence go to the primary neutral and phase bus bars. The RCD normally sits in the middle of the CU and is fed both live and neutral from the primary bus bars (or sometimes dedicared cables inside the CU). The RCD in turn feeds a second live busbar for the protected MCBs and a separate neutral bus bar for the protected circuits.

Reply to
John Rumm

Aha, thanks, got it.

So not shared neutral, isasmuchas the main neutral is fed via the RCD. But with only one isolator.

Cheers

Paul.

Reply to
zymurgy

You need to disconnect neutral as well, otherwise you may be sing continuity from live to live through a pair of loads and their common neutral.

Reply to
John Rumm

Main neutral is fed direct from the isolater. The Secondary neutral is fed from the RCD (which is fed from the main neutral)

Same for the lives.

Reply to
John Rumm

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