RCD Problems on new split load consumer unit

[Mike_H]

I have recently installed a new consumer unit and I'm having problems with the RCD

All the ring mains are wired on the RCD side of the unit, nothing else (I have gas cooker / heating and no elec shower).

The RCD will trip whenever I put any load on it above, say, a table lamp. I have also totally disconnected each circuit in turn (L&N) and tried again but the same problem occurs.

Further to this the test button doesn't work (I'm guessing because not enough load is on the RCD).

I have checked the connections into the RCD and even swapped it with a new unit, but the same problem occurs.

Help!!!

 

[securespark]

You need to go back to the beginning.

Disconnect all N's and E's belonging to circuits wired to that side of the board completely, and switch off the mcb's on that side, too.

As if the board were new and there was nothing wired into it at all on the RCD side. Then the RCD should reset. The test button should work regardless, unless the supply to the board is down.

Also check for loose connections in and out of the RCD.

Also check to see that the neutral output from the RCD is connected to the neutral bar serving the RCD side of the board, and not the neutrals of the circuits on the unprotected side.

If the RCD stays on, reconnect each circuit in turn (having unplugged (if they have a plug) or switched off (if they don't) ALL appliances on that circuit.

And I mean all! Don't forget the shed supply or pond pump etc.........

Let me know how you go.

 

[Mike_H]

Thanks, but that didn't seem to work, it's still tripping when I put any load above a table lamp on system, even on different circuits when all other circuits are not connected at all.

Also, the test button still didn't work when there were no circuits on the RCD side of the consumer unit.

The only thing I can think of is that somehow one of the connections into the RCD is not true, although I have checked and double checked the connections and they are all in contact.

Like I mentioned, I have replaced the RCD before and had the same problem.

Any other suggestions!??

 

[Lectrician]

I suspect you have a small N to E fault somewhere. The more load you put on, the more can flow between the shared return between N and E, causing the RCD to trip. This doesn't sort why the test button doesnt work.

 

[Mike_H]

The N / E fault would seem to be the answer, but since it is happening on all of the circuits (even when only one circuit is wired in on it's own) that means that it must be in the consumer unit itself and I cannot see how that is happening.

The test button problem occurs with both the RCDs I have tried so it would appear that this forms part of the same issue.

Hmm, at least there's enough power for the heating controls!

 

[Lectrician]

Any chance of a photo of the insdie of the CU??

 

[Mike_H]

Sorry, no can do (digi cam at work and rather old fasion phone!)

It is a Volex unit which came pre-wired between the 100A main switch, Neutral bars and the RCD.

It also came with the MCBs, of which I have not wired up all of them but will need them for future expansion. (I assume that this isn't a problem)

I have checked these factoty connections and there doesn't seem to be a problem.

Other than that, all the neutrals link to the correct bar, earths all go to the same bar and lives to the MCBs as expected. I have checked these a number of times now!!!

 

[andy]

the RCD sounds faulty. it should tirp when the button is pressed (load or no load - aslong as there is mains power to it)

 

[Lectrician]

Is there a small white lead from the RCD to connect to the earth bar?? Is it connected??

 

[Damocles]

The RCD must trip when the test button is pressed. There is plainly something wrong here, so I guess try to sort this out first.

In general tripping when a small current is flowing is due to an earth-neutral short somewhere.

The test button almost certainly connects a resistor between neutral input and live output, hence supplying an unbalanced current. This has to work assuming live and neutral are properly connected.

Nothing stupid like cable screws holding insulation? did you manage to run anything via the RCD? (i.e. it does actually have power on its output?)

If you have the equipment, you could remove the RCD and check that there is N-L connection of about 10K ohm when the test button is pressed.

 

[ban-all-sheds]

The CU doesn't ship with a link between the 2 neutral bars that should be removed for split-load use, does it?

 

[Mike_H]

Bingo. Yes this is the problem. Sorry for not getting back earlier but with the problem resolved, I moved on!!!

Thanks anyway B-a-S

 

[acater]

Bingo. Yes this is the problem. Sorry for not getting back earlier but with the problem resolved, I moved on!!!

Thanks anyway B-a-S

Mike_H, Can you tell us what the problem was, I have exactly the same consumer unit with exactly the same problem, thanks

 

[breezer]

Mike_H, Can you tell us what the problem was, I have exactly the same consumer unit with exactly the same problem, thanks

acater, please read the forum rules

also if you notice, Mike_H only ever made 5 posts. I think that will be because he asked over 4 years ago

 

[blondini]

It may be an old thread but the answer is here.

The CU doesn't ship with a link between the 2 neutral bars that should be removed for split-load use, does it?

Meaning there may be a link beteween the two neutral bars. If there is, it needs to be removed.