Rccd Tripping

[pjelec]

Can anyone help I am really confused.
I am working on a camp site where Scattered around the small site is 5 fuseboards each supplying 10 caravans each. Each box is not connected to an RCCD. In each fuseboard there is a 20a Circuit Breaker and 30ma 40a RCCD feeding each caravan. Most of these RCCDs trip out at least once a day. Never once has the RCCD tripped in the fuseboard in the Caravans

I have done an Insulation Resistance tests on the caravans and the cable to the vans and all was clear. One caravan had a low reading in the caravan and on the main cable feeding it. I found the fault inside and replaced the cable to the van. It is still tripping.
As a test I disconnected all RCCDs in one fuseboard controlling 10 vans and in that week nothing tripped.

I can not understand why this happens. An Rccd will only trip if there is a fault after it. If the fault is in the van it should trip out the caravan rccd.
Could it be overload and it is missing out the 20a circuit breaker.

Any help would be appreciated Thanks

 

[stef]

Did you check out the appliances in the vans? are they OK?

 

[davelerave]

the rcds are in series then - is the rcd in the caravan protecting all circuits and is it the same type?


ie:standard 30mA

 

[ian.settle1]

Can anyone help I am really confused.
I am working on a camp site where Scattered around the small site is 5 fuseboards each supplying 10 caravans each. Each box is not connected to an RCCD. In each fuseboard there is a 20a Circuit Breaker and 30ma 40a RCCD feeding each caravan. Most of these RCCDs trip out at least once a day. Never once has the RCCD tripped in the fuseboard in the Caravans

I have done an Insulation Resistance tests on the caravans and the cable to the vans and all was clear. One caravan had a low reading in the caravan and on the main cable feeding it. I found the fault inside and replaced the cable to the van. It is still tripping.
As a test I disconnected all RCCDs in one fuseboard controlling 10 vans and in that week nothing tripped.

I can not understand why this happens. An Rccd will only trip if there is a fault after it. If the fault is in the van it should trip out the caravan rccd.
Could it be overload and it is missing out the 20a circuit breaker.

Any help would be appreciated Thanks

If you disconnect the RCD as you say then they will not trip?

Have you carried out trip tests on the RCDs in question?

Iis there discrimination between the DB RCD and caravan RCD?

 

[topquark]

Assuming they are all type 'B' (ie no discrimination between them timing wise), start by proving the RCD's in the vans are OK ie pass all the RCD trip currents (particularly 1x). If they do then I'd suspect a dodgy connection between the dist panels and the vans (check all terminations, polarity and continuity).

 

[pjelec]

Its quite difficult to a test with just an Insulation resistance tester on appliances. Could do with a PAT tester. But if there was a fault then it should take out the RCCD in the Van.

Did you check out the appliances in the vans? are they OK?

 

[davelerave]

assuming the rcds are identical and the rcd downstream is a main incomer(protects all circuits)

you'd be checking the supply cables to caravan and rcd testing at the caravan- as aready said

 

[pjelec]

The rcd outside in the fuseboard feeds the fuseboard in the van. Each van has an Rcd feeding it. The fuseboard in the van has a main switch then an Rcd. All the circuits in the van are connected through the rcd. Both rcds are 30ma 40amp.

the rcds are in series then - is the rcd in the caravan protecting all circuits and is it the same type?


ie:standard 30mA

 

[Guest123]

QUOTE...Could it be overload and it is missing out the 20a circuit breaker...QUOTE


An RCD does not give overload protection i.e, it doesnt trip out it just starts to overheat.

It only operates on earth fault.

 

[davelerave]

you should check L-E and N-E between the rcds and the trip test at caravan(load side of 2nd rcd) then

repairing the fault wont sort the discrimination issue-ie: the 2 30ma's in series

 

[pjelec]

May not have described properly but what i meant was when I disconnected the outdoor one for 1 week, the indoor one did not trip out. Each caravan has differnt makes of rcd but all the same rating. The rcds outside are all the same. General Electric and are about 18 months old.
I have not tested the tripping times

If you disconnect the RCD as you say then they will not trip?

Have you carried out trip tests on the RCDs in question?

Iis there discrimination between the DB RCD and caravan RCD?

 

[pushrod]

If the caravans have a 30mA RCD should the fuse boards not have time delay ones to provide discrimination???

 

[pjelec]

At the fuseboard outside the rcd feeding thevan is fed from a 20a mcb, which does not trip out. This means that the rcd is not even at its full capacity.

QUOTE...Could it be overload and it is missing out the 20a circuit breaker...QUOTE


An RCD does not give overload protection i.e, it doesnt trip out it just starts to overheat.

It only operates on earth fault.

 

[Guest123]

At the fuseboard outside the rcd feeding thevan is fed from a 20a mcb, which does not trip out. This means that the rcd is not even at its full capacity.

Then overload isn't your problem.

 

[pjelec]

This is a very good point. None of them are Time delay. This may make a diffence but still dont make sense why it should trip without having any faults.

If the caravans have a 30mA RCD should the fuse boards not have time delay ones to provide discrimination???