rcd problems please help

[demkap]

hi there i need a bit of help basically the rcd trips and the shower mcb trips the same time. then its ok for a day then it randomly does it during the night etc even when the shower isnt in use, any ideas?

 

[stef]

Faulty supply cable, maybe?

 

[Landril]

Have you done an IR test to start with, if the mcb trips when there is no load on the circuit i can only assume there is a problem with the mains incoming side of the shower causing the short!

 

[GLENNSPARK]

is it doing it when people are walking around in the house upstairs...on the hallway perhaps?...
or just after using the bath or shower?

 

[demkap]

nope i will do though but it doesnt trip everytime... flicked breaker and rcd back up and then was ok but the next morning the rcd and shower mcb tripped.

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its weird that the mcb trips aswell that would mean theres a overload i believe?

 

[GLENNSPARK]

just have a look at the busbar will you under the breaker....make sure its properly located....also check the shower cable terminations...this goes for the RCD terminations as well...

 

[Edd]

Rodent damage, or crushed cable. Check in loft or under floor

 

[demkap]

nope just randomly

 

[GLENNSPARK]

well...it may be the MCB is tired....what rating is the shower....oh, and we need cable CSA, installation method and rating of MCB as well...

 

[demkap]

it would seem to be that shower circuit wouldnt it if its the only that keeps tripping guys? how about i do some tests on it r1 + r2 and zs tests?

 

[GLENNSPARK]

it would seem to be that shower circuit wouldnt it if its the only that keeps tripping guys? how about i do some tests on it r1 + r2 and zs tests?

wander lead out....method 2 on it...
and IR as well...
thats on the cable....if its clear then move on to the shower....IR cold....then warm it up...and IR again...

 

[MDJ]

how about i do some tests on it r1 + r2 and zs tests?

the first thing a spark would do is check via an instrument the continuity of the system via meggaring and continuity tests if nothing jumped out at him whilst investigating the fault.

 

[demkap]

i need to find out i know its a 40amp mcb and 10mm cable buried in the wall

 

[GLENNSPARK]

did you ask the person ordering the work if they have had any recent work done....this would be any recent work....not just leccy stuff

 

[demkap]

say it its anything over 10kw i should be a 50amp breaker shouldnt it?

 

[Landril]

If the shower is tripping when it is not in use then its would lean more to a faulty cable/connection due to the fact there is no load being used surely ?
Therefore check all connections you can access, do IR test then r1 + r2 see if any reading look out of place!

Zs test will probably not tell you that much in relation to the fault !
Has the shower been working for a while and this falut just appeared?

 

[GLENNSPARK]

If the shower is tripping when it is not in use then its would lean more to a faulty cable/connection due to the fact there is no load being used surely ?
Therefore check all connections you can access, do IR test then r1 + r2 see if any reading look out of place!

Zs test will probably not tell you that much in relation to the fault !
Has the shower been working for a while and this falut just appeared?

(R1 R2) before IR to ensure all portions of the circuit are being subjected to the test

 

[Landril]

(R1 R2) before IR to ensure all portions of the circuit are being subjected to the test

Fair point

 

[demkap]

yep shower was installed 6 years ago yea so if i disconnect the loads side and do a IR test if i get anything under >200mohms theres a cut or something in the cable?

 

[GLENNSPARK]

yep shower was installed 6 years ago yea so if i disconnect the loads side and do a IR test if i get anything under >200mohms theres a cut or something in the cable?

get continuity first....then IR....
continuity does what it says on the tin....
IR demonstrates dielectric strength....