Insulation resistance testing

[Sb8389]

Hi guys,
i have always wondered when doing insulation resistance testing is there a test you can do to see if there are any loads still connected (ie neons,equipment) to see if the readings are true or through loads connected in the circuit.

 

[Octopus]

Test at 230v first and check the results - thats the way I do it.

 

[telectrix]

resistance reading using a multimeter across L and N.

 

[Simonslimline]

Always best to do a test at 250V first IMO.

 

[R G]

Like they both said ^^^^^

 

[ipf]

Test at 230v first and check the results - thats the way I do it.

Got me with that one, M....:icon12:

 

[Sb8389]

Cheers for the info guys. If a load was connected would it only effect Live-Neutral readings and not Live-Earth and Neutral-Earth or would it. I know these are basic questions for you guys but never really asked the question.

 

[TJ Anderson]

Cheers for the info guys. If a load was connected would it only effect Live-Neutral readings and not Live-Earth and Neutral-Earth or would it. I know these are basic questions for you guys but never really asked the question.

Yes it would. You would also be testing the connected equipment. For the sake of your tests you want to eliminate that. However it can also be very useful to carry out a global IR with it all connected under certain circumstances.

 

[Octopus]

Cheers for the info guys. If a load was connected would it only effect Live-Neutral readings and not Live-Earth and Neutral-Earth or would it. I know these are basic questions for you guys but never really asked the question.

Do a test on your own place with half the "socket" load items plugged in, then gradually unplug them and watch the results change!

 

[R G]

Possibly, depends on the appliance , some loads might not register at all on any of the tests , other appliances may have some leakage to earth , Always best to unplug everything and ask the customer what they have and go round with them , you have to be careful and not just rely on readings to tell if everything is unplugged , anything electronic you have to watch , always use 250v range first on all 3 tests , but still if this reads clear and theres things still plugged in ,and you then try 500v tests its you or your insurance thats paying for damaged appliances ..

 

[trev]

However it can also be very useful to carry out a global IR with it all connected under certain circumstances.

A global IR with what all connected? Loads?
How would it be useful?
What would it prove?
You would get the lowest reading possible. IE reading through the first load. What possible use could this reading be?
Under what circumstances would this be useful?

 

[Sb8389]

Would testing live and neutral together connected to earth bypass any loads still connected and give a true reading of the circuit or is it just for the purpose of eliminating damaging equipment.

 

[trev]

Would testing live and neutral together connected to earth bypass any loads still connected and give a true reading of the circuit or is it just for the purpose of eliminating damaging equipment.

Have a think about what you're asking mate, I'm not saying it's a bad question here but if you think about it the answer will become clear.
If I gave you it on a plate you'd have learnt nowt
Sorry for being a git

 

[TJ Anderson]

A global IR with what all connected? Loads?
How would it be useful?
What would it prove?
You would get the lowest reading possible. IE reading through the first load. What possible use could this reading be?
Under what circumstances would this be useful?

L&N-E 250V IR Before a consumer unit change when there was previously no RCD protection. Then test with them disconnected. It highlights if there is any earth faults on the w/m, d/w immersion etc etc in.

 

[trev]

Before a consumer unit change when there was previously no RCD protection. It highlights if there is any earth faults the w/m, d/w immersion etc etc in one easy test.

BOLOX!, Before a CU change you want to know whether there's any problems with the FIXED WIRING.

 

[Octopus]

L&N-E 250V IR Before a consumer unit change when there was previously no RCD protection. Then test with them disconnected. It highlights if there is any earth faults on the w/m, d/w immersion etc etc in.

Or stick a earth leakage clamp meter around the tails!

 

[R G]

The I/R tests are to be done as per GN3
, this requires all appliances isolated/removed , the readings required are of the circuit not the loads as well , what you suggesting is really a way of trying not to damage appliances , this is not the point and besides you could still damage appliances anyway..

 

[TJ Anderson]

BOLOX!, Before a CU change you want to know whether there's any problems with the FIXED WIRING.

Sorry mate, I meant in addition to carrying out disconnected, otherwise it would be obviously pointless I updated after I posted.

 

[Sb8389]

Right trev I'm thinking that testing live and neutral ensures you are putting the same voltage down both conductors so they are of the same potential eliminating damaging any equipment, am I on the right track

 

[trev]

Sorry mate, I meant in addition to carrying out disconnected, otherwise it would be obviously pointless I updated after I posted.

Sorry TJ but you're going to DC all loads, test, then reconnect them all and test again to see if there's any appliance problems?
NAAAAH that's bolox again
A It's wasting time and effort
B What's the point? Unless you've got a sideline in appliance repairs of course