RCD wont trip with test button??

is the rcd a dc sense type and if so is the functional earth wire connected to the earth bar

other than that the only cause i can think of is a dodgy rcd i'd give mem a call and see if they will replace it directly (you really don't want to have to take the whole CU back to where you got it)

 

Make sure that live and neg are 100%. If yes then I rekon it's dodgy. I've seen an RCD spasm, sounded like an old alarm clock and wouldn't stop.

 

Its not common that a new RCD will fail to operate if installed properly, check that all the connections in the new CU are correct, a RCD will not operate if there is no voltage present so check that there is a voltage on the incoming terminals before you go any further

 

Err, you haven't wired the RCD in backwards have you? Like reversed the input and output . . . just a thought.

 

Err, you haven't wired the RCD in backwards have you?
Like reversed the input and output . . . just a
thought.

Good one fused, at first I wondered if I should ask if the main incoming switch was on or had the main cut out been refitted but thought I'd better not mention it

 

Sorry, I do not mean to be disrespectful in any way. You may be perfectly up to speed on all installation and testing work, and have merely presented a minimal amount of info, which unfortunately just doesn't sound quite right.

You suddenly mentioned another CU you are just going to swap tomorrow. Have you done this before, including all the testing, of the entire installation? And you propose to do this yet you have left the 'first' CU 'all working' tonight EVEN THOUGH the RCD is not functioning AND you have no idea what the problem is.

For instance, you mention just swapping the RCD, have you done this before? You shouldn't be too carefree about this. For instance this 'suspect' RCD may have already been swapped and the but-end of a serious fault-break for all I can tell. It may be now be unsafe to use, and not a brand new one that we have all assumed it would, and MUST be.

There are many alarming scenarios when you just throw in this second CU, borrowed neutrals for one, split-load neutrals incorrectly grouped, everything connected to the main earth but the main earth is floating, etc

I'm only trying to help.

 

so test button doesn't work and you reckon this might be due to mixing up the neutrals?Or to a duff earth?

If the RCD doesn't work then it wont help saftey, but then the installation never used to have one anyway.

 

No Damocles I do not consider borrowed neutrals or no earth is why this problem RCD won't trip. From my many previous posts, and reading this previous one in a more understanding way you would not have been in doubt. I was raising concern to an apparently over-casual approach by Marlboro. All in accord with some earlier postings about striking a balance between being helpful and being cautious.

I still hold that Marlboro sounded too 'rushed' with these instant-sounding one-a-day CU replacements. There was no mention of prior testing/inspection/design-intent etc.

If this RCD was internally dud, indeed I agree with you that it would not ADD to safety, but it could be a fire-hazard, for all we know.

If we are to give Marlboro total credit for his faultless CU-swapping then we all have to discount any possibility that he has not sorted and identified all the CU cables, and has not tested the split-load CU installation thoroughly, etc. In which case he could not possibly have N1 and N2 sort-circuit which totally by the wayside could produce this effect of a non-operative button.

Swapping with another RCD would not improve matters. Bench testing the 'faulty' RCD would find it works fine!

By I muse, as this could not be the real problem.

 

Sorry Housebasher, I have no idea where I got Marlboro from on this perishing computer.