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Discuss Insulation Resistance testing - again! in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

C

chrisgc

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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

-
Arms
Esteemed
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.
 
B

Barry Rathbone

  • Thread Starter Thread Starter
  • #3
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????
 
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
 
M

mickys86

  • Thread Starter Thread Starter
  • #5
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

-
Arms
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

-
Arms
Esteemed
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?
 
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.
 
C

chrisgc

  • Thread Starter Thread Starter
  • #9
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

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

chrisgc

  • Thread Starter Thread Starter
  • #11
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?
 
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

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Arms
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.
 
C

chrisgc

  • Thread Starter Thread Starter
  • #14
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?
 
C

chrisgc

  • Thread Starter Thread Starter
  • #15
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.
 
C

chrisgc

  • Thread Starter Thread Starter
  • #16
While we are on the subject of IR test just a question about R1 R2 jump leads. What cable size do you tend to use if you have made your own?
 
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.
You won't need to switch the fcu to anything. The cables will be joined outside the fcu.
 

DaveyD

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Arms
You won't need to switch the fcu to anything. The cables will be joined outside the fcu.
I think it's refering to TigerPaul's idea - he mentioned just linking the lines outside the switch so the neutrals are still in the SFCU and therefore to include the neutrals the switch will still need to be closed.
 
R

rare breed

  • Thread Starter Thread Starter
  • #19
Kind of related to the above thread.
I am doing the 2391 practical tommorow, to speed up my testing on a rig is there a problem with doing the Insulaion testing prior to the continuity for the Periodic?
 
To be honest unless it as changed dramatically over the years you are advised to test in the order they are laid out in the GN 3 and the continuity test comes before the IR test, so I would do it in order.

Also isn't it an EIC test you do not a periodic, or am I at cross wires when you mentioned "periodic"
 

topquark

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Mentor
Arms
Kind of related to the above thread.
I am doing the 2391 practical tommorow, to speed up my testing on a rig is there a problem with doing the Insulaion testing prior to the continuity for the Periodic?
Yes, if you don't know that you have continuity of conductors how would you know that your IR test is testing all of the circuit?
 
R

rare breed

  • Thread Starter Thread Starter
  • #22
Its still a periodic inspection and test but you use the EICR to make the report.
I know you need to do it in order for new installations but I don't think you need a particular order for the periodic, I was just trying to figure out if I would be penalised for trying to do the IR on the motor circuit first when I connect across the switch.
 
R

rare breed

  • Thread Starter Thread Starter
  • #23
Reply past in the ether thanks for your thoughts Topquark
 

Strima

-
Arms
Esteemed
The sequence of tests is logically formatted so you find any faults before moving onto the next test. If you did IR before continuity you would have to do the IR again if you found a break in a circuit and rectified it, saves you doing things twice.
 

topquark

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Mentor
Arms
Its still a periodic inspection and test but you use the EICR to make the report.
I know you need to do it in order for new installations but I don't think you need a particular order for the periodic, I was just trying to figure out if I would be penalised for trying to do the IR on the motor circuit first when I connect across the switch.
Don't confuse EIC (Electrical Installation Certificate--on first install) with EICR (Electrical Installation Condition Report--subsequent test).
 

ackbarthestar

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Mentor
Arms
Generally, the hybrid nature of the 2391 test rig would mean that you do continuity before IR. However, on a real job, where you know everything is working beforehand then you would be interested in the Zs, without disconnecting all the circuits. So its justifiable to IR test and then Zs.
 
R

rare breed

  • Thread Starter Thread Starter
  • #27
Generally, the hybrid nature of the 2391 test rig would mean that you do continuity before IR. However, on a real job, where you know everything is working beforehand then you would be interested in the Zs, without disconnecting all the circuits. So its justifiable to IR test and then Zs.
Thanks for the advice. I think I will do the continuity first to be on the safe side.
 

AndyL

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Arms
Generally, the hybrid nature of the 2391 test rig would mean that you do continuity before IR. However, on a real job, where you know everything is working beforehand then you would be interested in the Zs, without disconnecting all the circuits. So its justifiable to IR test and then Zs.
Just because its all working does not mean you have continuity of protective conductor which is what you test for.
As stated earlier, done in logical sequence so we dont have to redo earlier tests if a fault is found
 

ackbarthestar

-
Mentor
Arms
Just because its all working does not mean you have continuity of protective conductor which is what you test for.
As stated earlier, done in logical sequence so we dont have to redo earlier tests if a fault is found
In most cases it does. Once you know that the MPB's are Ok then a Zs is perfectly acceptable for each circuit. (Perhaps not so with domestic installations where the Numpties roam).

I often find cpcs are cross linked to other circuit cpcs so your R1 + R2 wouldn't give you specific circuit readings, and if you did disconnect everything you would have the hassle of reconnection at each point of separation of the cpcs.

You'll be spending week on a days worth of work if you chose to undo everything just to get your R1+R2 readings.

So its often better to get a R2 reading coupled with Ze and Zs
 
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