Help from a sparky please Tripping of RCD

[Ian1]

I am a bathroom/kitchen installer, cleared to self certify having jumped through all of the hoops. I do not call myself an electrician though. My work is very limited, (oven, hob, extractors, lights, shower)
Have installed an 8.5 Kw new shower on a new circuit. All checks carried out (Resistance, Insulation resistance etc).
The Entire house also just had a rewire.All main and Supp bonding in place.
Split load Consumer unit. Shower and all rings, protected with a 30ma RCD. The shower has a 32A mcb.The shower keeps tripping the RCD immediately it is turned on.Have also temporarily wired the shower up in another house, works fine.
Could the RCD be faulty, or could there be an undiagnosed fault elsewhere. Am at the reach of my knowledge. Struggling to solve. All other circuits, electrical items not causing a problem.
Any ideas please. Any way of trying to diagnose. All circuits appear OK.

 

[Steve]

For a start your shower pulls 37 amps. So replace that 32A MCB would be a good start.

If the RCD protects all the rings and the shower, then i dont think it is faulty. What is its load rating? Should be 60-80 amps.

Do you have the facility / knowledge to test the RCD? If not, ask a friendly electrician to test it.

Was the shower on an RCD when you tested it elsewhere?

 

[Jaymack]

Is your shower neutral connected to the rcd section of the bar? If not i.e. it is connected to the non-RCD neutral bar and the phase is connected to the RCD side, this will cause the RCD to trip on switch on.

Jaymack

 

[Steve]

Is your shower neutral connected to the rcd section of the bar? If not i.e. it is connected to the non-RCD neutral bar and the phase is connected to the RCD side, this will cause the RCD to trip on switch on.

Jaymack

The thought never crossed my mind, the OP being part p registered etc!

 

[Ian1]

Cant beleve how quickly you guys have replied. many thanks.
The RCD is 80A. The Get split load consumer unit (new)only has one common Neutral rail/bar.(I thought that was standard) All of the neutrals go into it. The Mcb does not trip(maybe does not have time,will replace with 45A)
The temp check on another house with the same shower did have RCD, did not trip (and also had a common neutral rail)
Am not at property at the moment. Yes, can run RCD test. Never seen a split load CU, with a separate Neutral rail for rcd side?
Why does RCD not trip with the rings in use, why just the shower. Also temp connected to Cooker circuit in Kitchen. That tripped the RCD again, shower works fine in another house?

Do not like being beaten, would love to solve with your help and ideas.
Think we all need to get a life on a Sunday afternoon!

Thanks in advance.

Ian.

 

[Steve]

The Get split load consumer unit (new)only has one common Neutral rail/bar.

The temp check on another house with the same shower did have RCD, did not trip (and also had a common neutral rail)

Never seen a split load CU, with a separate Neutral rail for rcd side?

ok, there HAS TO BE another neutral bar. Otherwise the whole board is RCD'd.

Some boards have a small neutral bar mounted to the top of the RCD (crabtree IIRC), some have 2 bars at the top of the board. Every CU brand does it differently.

 

[dingbat]

Never seen a split load CU, with a separate Neutral rail for rcd side?

If it ain't got separate neutral rails it ain't a split load board.

 

[RF Lighting]

The Mcb does not trip(maybe does not have time,will replace with 45A)

You first of all need to make sure the cable is suitable to be protected with a 45A MCB

What size cable is the shower wired in?

Do you know what make the consumer unit is?

Can you take a photo of the CU and post it on here?

 

[DESL]

Is it an MK CU as the two neutral bars are in line, numbered in sequence and at first glance it will look like a continuous bar.

http://www.mkelectric.co.uk/PDF/technical/SENTRY_prod.pdf

Take a look at pics

I assume that the RCD doesn't trip when shower connected but not switched and insulation resistance OK P-E N-E