rcd trip on my shower

[mitchell0239]

Hi Guys,
I'm new on this site and have joined for some info on a problem which is driving me mad...
I have installed a 8.5kw shower, run a 11m 10mm t+e from the 40a MCB to a 45a on/off switch and then to the shower..but when i turn the shower on it trips the RCD on the splilt load CU and the MCB stays on..so i power it back on..removed the shower, checked the voltage and have 240Vac..but as soon as i turn the shower on again it trips..any ideas pls????

 

[Amp David]

Were your test results satisfactory?

 

[mogga]

your shower could b gubbed possibly the boiler part element

 

[mitchell0239]

Its the second shower as this was happening with the new one i put in last time, so i thought it was maybe the shower?? Bought a new one and the same thing happening to this one...can i use a 40a mcb and a 45a on/off switch or do they have to be the same??

Sky diving sounds good to me lol:d

 

[netblindpaul]

Crossed neutral on the split board?
Paul

 

[mitchell0239]

Thanks paul...but surely it can go on any neutral? Or does it have to match up with the phase side of the board? Is that waht you mean?
Mitch

 

[netblindpaul]

If you have a split board then each RCD has its own N bar, thus the N to the shower must go on the N bar corresponding to its RCD.
Paul

 

[mitchell0239]

Will double check it later when i get in from work..if it is on the correct n bar...any ideas what else it could be? Was thinking if its the rcd that trips then its gettin an earth fault from somewhere...could be the 10mm cable as i have fitted it under floorboards and wonder if i may have caught it with a nail or something else?? But if i had then i wouldnt get voltage would i? Im convinced its a problem in the cu

 

[netblindpaul]

If not wrong N bar, disconnect wiring both ends & do IR test.
That should show up any cable issues.
Let us know after that.
Paul

 

[WayneL]

If not wrong N bar, disconnect wiring both ends & do IR test.
That should show up any cable issues.
Let us know after that.
Paul

Should have done that before energising the circuit - but there you go

 

[netblindpaul]

Should have done that before energising the circuit - but there you go

Yep, along with Zs, but that is probably doubtful too?
Paul

 

[Amp David]

I thinks its the fact that the CPD and shower switch arn't rated the same

Priceless!

 

[Guest123]

Try checking the terminals in the pullswitch.....maybe something pinched.

 

[Yooj]

Safely isolate the shower...Electrically disconnect shower at shower end...Get suitable terminal block, and safely terminate into terminal block...Re-energise shower circuit...If it still trips, then it is a wiring/earth fault...start at CCU to see if N on correct neutral bar...work your way through the circuit, checking each connection at all points...

If the circuit energises ok when shower is disconnected, then fault will be at the shower unit, either incorrectly connected, damaged conductor insulation touching eathed point, or faulty internals in shower.

Yooj

 

[Modernelectric]

Will double check it later when i get in from work..if it is on the correct n bar...any ideas what else it could be? Was thinking if its the rcd that trips then its gettin an earth fault from somewhere...could be the 10mm cable as i have fitted it under floorboards and wonder if i may have caught it with a nail or something else?? But if i had then i wouldnt get voltage would i? Im convinced its a problem in the cu

Sounds to me like you need to do full test sequence on this circuit?

If you dont have access to test equipment then you can do as YOOJ has said but it is preferred to consult a proffessional electrician.