RCD issue, or is it?

[the pict]

Changed a consumer unit everything fine all test came back hunky dory, but one RCD would not trip on the test button so swapped them around, same deal,I then got random trips from unassociated circuits IE kitchen ring plug in kettle and the opposite RCD would trip disconnect incoming earth RCD,s behave normally Ze .18 didn't clamp the earth to check any current flow did't think of it till on my way back, the only other thing I did after the tests was connect an outside light for the tenant to existing cable, so i am thinking a shared N any clues would be great
Dev

 

[telectrix]

or a N-E fault.

 

[the pict]

or a N-E fault.

Yep most likely, going back any way to fit a shed light, so my plan is to disconnect the earths one by one to get the RCD to behave and hopefully indentify the culprit, is there anything else you can suggest may be contributing

 

[hightower]

Unless I'm being a dipstick, shouldn't your plan revolve around proper testing rather than disconnecting conductors designed for safety? First place to begin is with an IR test....

 

[polo1]

As Hightower has suggested, IR tests are the first step (assuming rcds are ramping ok and within specified tripping times).
Please tell us you don't intend to leave cpcs disconnected

 

[hightower]

Please tell us you don't intend to leave cpcs disconnected

And to go one further than this, not only should you not be disconnecting CPCs whilst the installation is energised, your IR tests should be carried out with all CPCs connected to the busbar and all bonding in place.

 

[the pict]

As Hightower has suggested, IR tests are the first step (assuming rcds are ramping ok and within specified tripping times).
Please tell us you don't intend to leave cpcs disconnected

I think you have mis read my OP,

 

[hightower]

I think you have mis read my OP,

I don't think it's that the OP has been misread, than the fact you've explicitly stated you're going to be disconnecting CPCs with the assumption you will be re-energising (otherwise how would you be able to see that RCDs are behaving).

so my plan is to disconnect the earths one by one to get the RCD to behave and hopefully indentify the culprit

 

[the pict]

OK disconnect each circuit in turn,test RCD, if it behaves then the fault has been found

 

[DPG]

What dead test results did you get?

 

[hightower]

OK disconnect each circuit in turn,test RCD, if it behaves then the fault has been found

Or, and stick with me on this because it is a totally radical idea, you could plug in an IR tester and try and find the fault using the method every electrical book going would explain. You know, just a crazy thought?

 

[Bobster]

An I-R test will almost certainly find this fault. My money would be a N-E fault, hence why only higher loads are causing issues.

As someone who's managed to get 'trusted advisor' status on here, this is a little worrying then you're just disconnecting things randomly.

 

[the pict]

Like I said done that and all test come back ok, but, and this is the bit that aint playing ball with every circuit without anything plugged in, cooker,shower immerse etc etc all disconnected and all bulbs out and in the switched on position doing a global IR I get a X reconnected everything I get random trips, dis main earth random goes away

 

[the pict]

An I-R test will almost certainly find this fault. My money would be a N-E fault, hence why only higher loads are causing issues.

As someone who's managed to get 'trusted advisor' status on here, this is a little worrying then you're just disconnecting things randomly.

Thats because you assume I am some sort of idiot

 

[polo1]

I think you have mis read my OP,

Sorry if I have! It did seem a bit strange

 

[Richard Burns]

Disconnecting a cpc when there is a known fault to earth could raise the earthed parts of that circuit (or if you disconnect the main earth, then all exposed and extraneous parts) up to the line voltage which is not a safe thing to do.
I would recommend that if your IR tests are coming back OK and you cannot find the fault by dead testing that you disconnect a circuit entirely (i.e. at least line and neutral) to remove it from the installation. Then if you put a high powered load on another circuit and the RCD does not trip you have disconnected the faulty circuit and can start checking that one in detail.

In this way if a faulty circuit is still present the RCD will limit the risk.

 

[Midwest]

Mud slinging aside, if you've done the dead tests in the correct order, you should of discovered the fault before the live tests. Once on a rewire, I discovered a neutral earth fault on a radial and decided to put it to one side for later, to get the other circuits on. Except I didn't and mixed it up with another radial and connected it up. Got to RCD test and wouldn't function, neither would RCD test button. Went back to basics, and discovered my mistake.

Happy hunting

 

[Octopus]

Have you got an earth clamp meter?

I think you need to check the residual earth loss across the installation and I suspect you have a combination of a N-E fault and cumulative earth leakage from plugged in devices....

 

[the pict]

Yes sorry my bad tempered comments to one side,it is obvious I have missed something, Thanks all

 

[DPG]

All friends again. Good.