any help would be great

[prgil74]

just had quick look at ccu 12 way 100a/30ma hager isolator, problem seems to be that the rcd/isolator trips when all mcbs are on and when its wet, now turn off any two or three mcbs and the problem stops could under stand if one of the mcbs solved the problem but seems you can turn of any and it has to be two or more have done no testing as yet as it really was a quick look was thinking of neutral to earth fault but then it would still trip all the time ,faulty rcd any help would be great large house so could be in for the long hall if no ideas

 

[trebor]

just had quick look at ccu 12 way 100a/30ma hager isolator, problem seems to be that the rcd/isolator trips when all mcbs are on and when its wet, now turn off any two or three mcbs and the problem stops could under stand if one of the mcbs solved the problem but seems you can turn of any and it has to be two or more have done no testing as yet as it really was a quick look was thinking of neutral to earth fault but then it would still trip all the time ,faulty rcd any help would be great large house so could be in for the long hall if no ideas

Could be a loose main neutral or a neutral earth fault at the RCD or mains position, in both cases the inbalance would get worse as load is increased so turning off load regardless of order would stop the inbalance, cant undestand the wet though unless its an overheads service

 

[Des 56]

Without any tests eveything is guesswork

The first thing I would do is eliminate the chances of 1 or more loads causing the problem
The installation tripping when its wet suggests external problems

There may be an outside light or such that is the sole cause or it may be low when wet and coupled with appliance leakage or other circuit leajkage,it is enough to tip it over

Turning off an mcb wont isolate a faulty circuit,it will eliminate load paths that may be contributing

With a neutral earth fault on the system,the load on the problem circuit may not in itself be enough to trip the rcd,but may do so with the load of a good circuit making the fault show up

As I say without testing all guess work

 

[andekoch]

loose connection or insul damage but conductors not touching until moisture on them or wet inside the board causing N/E fault.

 

[trebor]

Another thought, might be worth doing a ramp test on the RCD b4 going too far

 

[prgil74]

thanks chaps got some good ideas worth trying

 

[bugsy]

Worth doing N/E IR test from CU , check any external circuits, PIR's Photocell's etc.

 

[m4tty]

Worth doing N/E IR test from CU , check any external circuits, PIR's Photocell's etc.

Excuse my ignorance bugsy but do you connect one probe to neutral bar and other to earth bar to do this test?

Cheers

 

[marksparky]

make sure main switch is off or ul get a short, i personally would disconnect each circuit and carry out ir test

 

[bugsy]

Excuse my ignorance bugsy but do you connect one probe to neutral bar and other to earth bar to do this test?

Cheers

Yes - but make sure you isolate board first. after the initial test you will still have test each circuit, but a least you get an overall picture to start with.