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Cannot get RCD test to work?

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HappyHippyDad

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Evening chaps..

I have just fitted some downlights in a bathroom and needed to give them RCD protection as there was none. I fitted the following:

[ElectriciansForums.net] Cannot get RCD test to work?

The test button works fine and the unit trips when a fault occurs (touching neutral to earth) but I cannot get the MFT to test it for trip times which I need for the MWC. Its a fairy decent MFT and I've never had any trouble with it testing RCD's before but I have never tested this sort of RCD before, it has always been in the CU. I make contact with the live/neutral/earth of something which the RCD is feeding, I get the little 'tick' on the MFT and then it just wont test.

Am I missing something simple here? Is this unit tested in the same way as you would an RCD in a CU?
 
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In addition to Howards post above ^^^^ Have you tested the ELI prior to fitting the RCD ?, because if the earth loop is high resistance/non-existent, the tester will inhibit the test if the CPC rises above a pre-set touch voltage, usually set @ 50V, some testers allow this to be set @ 25V, so check this too.
 
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spark 68 said:
In addition to Howards post above ^^^^ Have you tested the ELI prior to fitting the RCD ?, because if the earth loop is high resistance/non-existent, the tester will inhibit the test if the CPC rises above a pre-set touch voltage, usually set @ 50V, some testers allow this to be set @ 25V, so check this too.
Click to expand...

I forgot that bit, thanks. prior to carrying out a RCD test, the earth fault loop impedance value must be confirmed as compliant. That is an answer in the 2394/5 exam as well.

Cheers............Howard
 
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happyhippydad said:
Evening chaps..

I have just fitted some downlights in a bathroom and needed to give them RCD protection as there was none. I fitted the following:

View attachment 23855

The test button works fine and the unit trips when a fault occurs (touching neutral to earth) but I cannot get the MFT to test it for trip times which I need for the MWC. Its a fairy decent MFT and I've never had any trouble with it testing RCD's before but I have never tested this sort of RCD before, it has always been in the CU. I make contact with the live/neutral/earth of something which the RCD is feeding, I get the little 'tick' on the MFT and then it just wont test.

Am I missing something simple here? Is this unit tested in the same way as you would an RCD in a CU?
Click to expand...
Yes, test the same way, it is just and RCD incorporated into a Switched Fused Spur. Double check polarity and ZS on load side of unit. Also prove your meter on another RCD. You may have a faulty unit.
 
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Murdoch said:
Did you test on the outgoing terminals or at the end of the circuit?
Click to expand...

The RCD feeds a junction box which feeds the lights and also a fan in the bathroom. I tested at the triple pole switch which I fitted. I tested on the coductors coming from the junction box and the MFT gave a tick 'measurement can be performed'.
 
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spark 68 said:
In addition to Howards post above ^^^^ Have you tested the ELI prior to fitting the RCD ?, because if the earth loop is high resistance/non-existent, the tester will inhibit the test if the CPC rises above a pre-set touch voltage, usually set @ 50V, some testers allow this to be set @ 25V, so check this too.
Click to expand...

Zs was 0.9, I'll have a look at the pre-set touch voltage.. Thanks Spark68
 
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Meggerman said:
Yes, test the same way, it is just and RCD incorporated into a Switched Fused Spur. Double check polarity and ZS on load side of unit. Also prove your meter on another RCD. You may have a faulty unit.
Click to expand...

Have triple checked polarity (as I was tired!), Zs is ok and I proved the meter on another RCD in the same house.
 
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If the Zs is 0.9 then I don't see the touch voltage being set @ 25V being the problem, I would check the continuity of the CPC all the way through the circuit though.

I would also try the test at the outgoing terminals of the RCD with the outgoing circuit disconnected first too, to narrow down where the problem may lie, it maybe simply that the RCD is faulty.
 
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jackhammerJIM said:
What tester is it .

What exactly does it say on the screen ?
Click to expand...

Sorry Jackhammer, missed your reply.

Its a Metrel MI3000 and I'm embarrassed to say I did not make a mental note of the error display.
 
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