Insulation Resistance testing - again!

[chrisgc]

Hi

Getting used to Metrel tester and am getting used to testing and was just after advice on clarifying some points:

1 - FCU's with neon indicators on IR tests - whats the best way of disconnecting the neon lights on these if they cant be disconnected? Do I keep that particular FCU switched off so that the IR test only goes up to that point - or is it possible that 500v may still damage the neon? How do i go about testing the FCU to the next point if it is ok for it to be switched off as from the FCU onwards would obviously not be tested?

2 - On NICEIC test sheets under the IR test results they have result column for L-N, L-E & N-E where as other test sheets only have two columns ie L-L & L-E. Why is the N-E not listed in the test result columns?

3 - On a cooker circuit (new 10mm cable) IR test with cooker switch on (but disconnected from cooker obviously, got a test result coming up saying 963.0 Mohms - is this all acceptable?

4 - And finally if Number 3 above is correct with regard to the reading what do I put in the SMALL test box on test sheet as have seen some test sheets filled out just saying +2.0 in all the columns - is this so that its indicating that readings were above required amount but obviously that fits into the column easier?

Sorry if I have waffled on as its late and I need some shut eye.

Chris

 

[Strima]

Hi

Getting used to Metrel tester and am getting used to testing and was just after advice on clarifying some points:

1 - FCU's with neon indicators on IR tests - whats the best way of disconnecting the neon lights on these if they cant be disconnected? Do I keep that particular FCU switched off so that the IR test only goes up to that point - or is it possible that 500v may still damage the neon? How do i go about testing the FCU to the next point if it is ok for it to be switched off as from the FCU onwards would obviously not be tested? Link out the FCU using jumpers or choc block for the test, then the whole circuit is tested. The neon will give you a false reading.

2 - On NICEIC test sheets under the IR test results they have result column for L-N, L-E & N-E where as other test sheets only have two columns ie L-L & L-E. Why is the N-E not listed in the test result columns? That'll be live conductors to earth test, connect both line and neutral and test to earth.

3 - On a cooker circuit (new 10mm cable) IR test with cooker switch on (but disconnected from cooker obviously, got a test result coming up saying 963.0 Mohms - is this all acceptable? As long as it's over 1Mohm it's OK, 963 is positively gleaming.

4 - And finally if Number 3 above is correct with regard to the reading what do I put in the SMALL test box on test sheet as have seen some test sheets filled out just saying +2.0 in all the columns - is this so that its indicating that readings were above required amount but obviously that fits into the column easier? I always put the reading in the box, the next EICR carried out may come out with a lower reading, that would indicate the insulation is starting to fail and would merit a C£ for further investigation.

Sorry if I have waffled on as its late and I need some shut eye.

Chris

In red...

When IR testing I always start at 250v DC, unless it's a new circuit I've installed, just in case there are still some items still fitted that maybe damaged or give bad readings.

 

[Barry Rathbone]

In red...

When IR testing I always start at 250v DC, unless it's a new circuit I've installed, just in case there are still some items still fitted that maybe damaged or give bad readings.

The question is why is he asking? I and all qualified sparks of yrs 5-30yrs know ? this is a forum for electricians is it not????

 

[malcolmsanford]

Hi

Getting used to Metrel tester and am getting used to testing and was just after advice on clarifying some points:

1 - FCU's with neon indicators on IR tests - whats the best way of disconnecting the neon lights on these if they cant be disconnected? Do I keep that particular FCU switched off so that the IR test only goes up to that point - or is it possible that 500v may still damage the neon? How do i go about testing the FCU to the next point if it is ok for it to be switched off as from the FCU onwards would obviously not be tested?

2 - On NICEIC test sheets under the IR test results they have result column for L-N, L-E & N-E where as other test sheets only have two columns ie L-L & L-E. Why is the N-E not listed in the test result columns?

3 - On a cooker circuit (new 10mm cable) IR test with cooker switch on (but disconnected from cooker obviously, got a test result coming up saying 963.0 Mohms - is this all acceptable?

4 - And finally if Number 3 above is correct with regard to the reading what do I put in the SMALL test box on test sheet as have seen some test sheets filled out just saying +2.0 in all the columns - is this so that its indicating that readings were above required amount but obviously that fits into the column easier?

Sorry if I have waffled on as its late and I need some shut eye.

Chris

That is why he is asking and good on him for doing so and good on Strima for helping him ........................ why are you having a go at him BR, if you don't want to help him then just go to another thread

 

[mickys86]

You say sparks of 5-30 yrs should know this..... He's just getting used to the tester which tells me he's just starting to learn the trade, he sounds competent with testing but just needs some clarification.

 

[tigerpaul]

Everyone needs a little advice now an then. Especially on something new or something they haven't done for a while. That's what these forums are all about.

 

[Strima]

The question is why is he asking? I and all qualified sparks of yrs 5-30yrs know ? this is a forum for electricians is it not????

He may be qualified but as stated he's just getting into testing, I doubt he's very much Bob from the pub as he's got an MFT for a start...

I will do this ONLY if someones life support will go off if FCU is Disconnected.

How do you do IR tests on live circuits then?

 

[Guitarist]

Hi

Getting used to Metrel tester and am getting used to testing and was just after advice on clarifying some points:

1 - FCU's with neon indicators on IR tests - whats the best way of disconnecting the neon lights on these if they cant be disconnected? Do I keep that particular FCU switched off so that the IR test only goes up to that point - or is it possible that 500v may still damage the neon? How do i go about testing the FCU to the next point if it is ok for it to be switched off as from the FCU onwards would obviously not be tested?

2 - On NICEIC test sheets under the IR test results they have result column for L-N, L-E & N-E where as other test sheets only have two columns ie L-L & L-E. Why is the N-E not listed in the test result columns?

3 - On a cooker circuit (new 10mm cable) IR test with cooker switch on (but disconnected from cooker obviously, got a test result coming up saying 963.0 Mohms - is this all acceptable?

4 - And finally if Number 3 above is correct with regard to the reading what do I put in the SMALL test box on test sheet as have seen some test sheets filled out just saying +2.0 in all the columns - is this so that its indicating that readings were above required amount but obviously that fits into the column easier?

Sorry if I have waffled on as its late and I need some shut eye.

Chris

Best advice I can offer is to get yourself a copy of IET GN3 (latest edition). It will answer loads of your testing questions.

 

[chrisgc]

Strima when you say the following:

Link out the FCU using jumpers or choc block for the test, then the whole circuit is tested.​

What do you mean by linking out? Can you just give a brief explanation as the FCU neons I cant disconnect as the wire for the neon cant be removed?

Sorry if I sound like a numpty.

​

 

[Strima]

Remove the line cables from the FCU and connect them together, reconnect when you have finished your IR testing.

 

[chrisgc]

Remove the line cables from the FCU and connect them together, reconnect when you have finished your IR testing.

Would that be the same as just switching the FCU off?

And how would the remaining cable then be tested? ie the cable run from FCU to the appliance Switch?

 

[trev]

No Chris it's not the same as switching it off mate, it's putting the cables into a connector for the duration of the test so as not to get a false reading through the neon

 

[tigerpaul]

Just take the incoming and outgoing line conductors out of the FCU and join temporarily. You don't need to do the neutrals, just make sure the FCU is switched on. Then when you do the IR test, the neon won't cause a false reading.

 

[chrisgc]

No Chris it's not the same as switching it off mate, it's putting the cables into a connector for the duration of the test so as not to get a false reading through the neon

As that would then test the cable up to the FCU point - how would the remainder of cable (from FCU to appliance socket outlet) be tested or is this in general left untested?

 

[chrisgc]

All understood now As wasnt seeing all the new replies (refresh button is a great invention) - So obviously taking the line cables out of fCU and switching FCU to on will then keep circuit but bypass the neon indicator light.

Got it.

Thanks everyone.