RCD Testing

[TJH]

I wired in an RCD for some underfloor heating. I know I wired it correctly and it tripped satisfactorily when tested. However the timer unit to which it was connected was not working. When I measured the voltage out of the RCD it was just 7 volts. It has 240v on the line side. I figured it was defective so bought another RCD. Same problem except that this RCD has 0 volts on the load side. I have checked the wiring continuity from RCD to the appliance and its all okay.

So 240volts in, RCD lights up okay and trips when test button is pressed. Fuse is okay but 0 volts out. It seems unlikely that I have two consecutive duds so can anyone advise how I test the RCD to establish whether it is indeed faulty. What else could I be doing wrong?

 

[Doc Hudson]

What test equipment are you using and where are you testing between? What were your dead test readings on the circuit Prior to energising?  I suspect you are not following industry standard testing methods as all circuit continuity would have been established before energising. And the RCD would have been tested with no loads connected.  Maybe cable or bus-bar not secured correctly inside a termination clamp?

Doc H.

 

[Murdoch]

I've read the OP several times and I'm still a little puzzled about what he has done.

Has the OP fitted a RCD to a fuseboard (inside)

Has the OP added a RCD outside an existing fuseboard

Has the OP added a RCD FCU to an existing circuit 

Clarification would prove useful

 

[ProDave]

I suspect this is an RCD FCU as he mentions a light being on. No other form of RCD has a light on it.

If you have tried two of them, and get the same results (0V and 7V both show no output) then you must be doing something wrong.

Tell us exactly where both probes of your tester were connected to when you made those measurements.

 

[SPECIAL LOCATION]

I am guessing Mr Dave-of-the-Pro is on the right lines......

But back to the OP....

Unless you have got an RCD that will only latch on with power applied, then you should be able to test the continuity thro Live 'In' to live 'Out' and Neutral 'In' to Neutral 'Out' directly on the RCD terminals without any power applied. 

That should either prove something or remove some bits from your fault-finding!!!

(You can use the same continuity tester used for R1+R2 readings...

OR.....   is this a DIY jobbie???

Not in the DIY section so I assumed not?????????????)

Guinness