Cannot get RCD test to work?

[HappyHippyDad]

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:



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?

 

[SirKit Breaker]

Are you testing it on the load side?

 

[jackhammerJIM]

What tester is it .

What exactly does it say on the screen ?

 

[HappyHippyDad]

Are you testing it on the load side?

Yep....

 

[Octopus]

Did you test on the outgoing terminals or at the end of the circuit?

 

[spark 68]

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.

 

[Meggerman]

Are you testing it on the load side?

You are not a lot of help are you.

 

[SirKit Breaker]

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.

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

 

[trev]

You are not a lot of help are you.

It's a perfectly valid question from a very helpful member

 

[telectrix]

You are not a lot of help are you.

i thought it was a sensible question.

 

[SirKit Breaker]

You are not a lot of help are you.

No i am a total waste of space and have absolutely no idea what i am on about.:tounge_smile:

 

[markc123]

You are not a lot of help are you.

Is that sarcasm?

Sirkit one of the most helpful members on here, the only downside is he supports Bradford but we can all forgive him for that.

 

[Meggerman]

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?

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.

 

[HappyHippyDad]

Did you test on the outgoing terminals or at the end of the circuit?

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'.

 

[Meggerman]

It's a perfectly valid question from a very helpful member

Not when the OP has said this it isn't
"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."

 

[HappyHippyDad]

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.

Zs was 0.9, I'll have a look at the pre-set touch voltage.. Thanks Spark68

 

[GLENNSPARK]

has any IR testing been carried out beforehand?...

check for neutal-earth fault...

 

[Octopus]

No i am a total waste of space and have absolutely no idea what i am on about.:tounge_smile:

4000+ posts versas 169 posts...... hum.... think the contributor with 4000+ gets my vote!

 

[HappyHippyDad]

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.

Have triple checked polarity (as I was tired!), Zs is ok and I proved the meter on another RCD in the same house.

 

[HappyHippyDad]

has any IR testing been carried out beforehand?...

check for neutal-earth fault...

Yep.. All IR tests ok (L-N, N-E, L-E), all at least 90Mohms...