RCD tripping

An RCD is not looking for circuit overload.

There must be earth leakage somewhere in the circuit. When the shower was replaced did the plumber check to make sure that the pipe fitting at the shower end is not leaking? i had a shower tripping an RCD once that was caused by water spraying up from an old compression fitting onto the live terminals.

with the fault occuring after a few minutes of use, it sounds to me like a water issue, which dries up by the time you begin to use the shower the next time.

its just strange that it occured with both old and new shower. Hence why i ask if the plumber checked the fitting, as most would just reuse the old.

Thanks for this. I think you may have cracked it. I bet the plumber didn't check that and probably just used the old fitting, assuming as we both did that it was the shower unit at fault.

Thank you. I appreciate your help on this.
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conny wrote:
I'm not an electrician so could be wrong but I was under the impression that your main RCD is usually 100ma and then individual circuits are rated at 30ma to avoid this kind of occurence.

TTC wrote:
Yes you are not an electrician.The only time there should be a 100mA RCD as the MAIN SWITCH is if this is a TT installation. We don't know that and it adds nothing to the discussion by mentioning it.

Well pardon me for being honest and at least trying to help.
And seeing that you appear to have your nasty head on,

Yes you are not an electrician,

should actually state,

No, you are not an electrician.

Now maybe you know what it feels like to be a mere mortal. :evil:
What other circuits are on the 63 amp RCD? As with the shower pulling 41 amps it does not leave you a lot else to play with?

I am thinking that you are simply overloading the RCD and there is no live/earth fault.

Someone stated that an RCD is not looking for overload, this is incorrect, the secondary purpose of a 63A RCD is to trip at over 63 Amp.

If this is a split board the shower circuit should be on the larger rated RCD.

6mm cable is acceptable for upto 47Amp in certain circumstances (BS7671 table 4D5 page 282), however if it is anywhere near insulation it rapidly becomes unacceptable which is why 10mm is realistically the minimum for this size shower.

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Please explain,

I was always told that if you put over 63A through a 63A rated RCD after a short time it will trip!

Please explain,

I was always told that if you put over 63A through a 63A rated RCD after a short time it will trip!


The device which has that function is called an RCBO. The 63A on the RCD refers to how much current it can carry without damage.
I actually disagree but cannot at this time be bothered to look up the facts.
RCDs provide basic overcurrent protection by electronic determination of the load current via detection circuitry unlike the MCB's

I am concerned that the OP is overloading his RCD as he only has 23 or so amps left to play with, has he had a new piece of kit delivered that overloaded the circuit whilst using the old shower or someone puts the kettle/toaster on??

Dont want to get into arguement, I am an electrician with plenty of experience and know the difference between an RCD and an RCBO!

happy to beg to differ!

In the datasheet the 63A is in the column In. :?:

But another manu datasheets blurb states

Type RMG residual current devices provide the functions of isolation, switching and earth leakage protection of electrical circuits. They have a residual current operated electro-mechanical release which operates without any auxiliary source of supply to open a circuit automatically in the case of an earth leakage fault between phase and earth greater than or equal to a threshold of 10, 30, 100, or 300mA

Nothing about overload, well you learn something new.


Big red book has no trip times for BS EN 61008, which is the number they are made to.

So NO overload protection I can see :)

EDIT 3 BS EN 61008 RCD operated circuit breakers without integral overcurrent proteection for household and similar uses (RCCBs)

Appnd 1 p.236

Well looks like humble pie time!!!

Just been looking up on the net and it looks like I am wrong!

Sorry to 3036!

:oops: :oops: :oops:
Yes and no and maybe not another electrician ;)

Without patronising anybody, and especially not JBPElectrics.

You had better go back over your records and make some double quick visits to any of your old jobs if you have installed an RCD and expected it to provide any overcurrent protection.

As noted above RCDs (BSEN61008-1) only provide earth leakage protection

RCBOs (BSEN61009-1) provide earth leakage and overcurrent protection.
the OP has stated that the RCD trips when the shower is in use, so to me it means there is an issue with the shower or related circuit.
Thankfully I have never ever used an RCD for overcurrent protection!

I just (previously) had been led to believe that they would trip if overloaded.

Live and learn!
try this...

unplug EVERYTHING in your house, i mean pull the plugs out of the sockets, switch everything off that you cannot unplug, have the bathroom light on though by all means. once you have done this, have a shower and see how long until it trips.

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