Insulation Resisitance (quick question!!)

[glasgospark]

Hi all!

IR global test: line & neutral connected together and tested to earth @ 250v... (nothing disconnected) eventually climbs after 2 minutes to give a reading of 140Mohms. (dampness?)

When tested on 500v it just sits at 0.30Mohms ???

I have tried individual circuits in the same way but all seems the same values? Is it because nothing is disconnected as well as damp? (Its TNS 100ma rcd main board)

Thanks in advance

the way you have described the glogal IR test doesnt require anything to be disconnected in order to produce GOOD readings as you arent testing between live-neutral.

 

[somersetsparks]

the way you have described the glogal IR test doesnt require anything to be disconnected in order to produce GOOD readings as you arent testing between live-neutral.

Hardly ever works out like that and if youj do a lot of testing you will damage something eventually, the only way is to unlplug all!

 

[glasgospark]

Hardly ever works out like that and if youj do a lot of testing you will damage something eventually, the only way is to unlplug all!

?? linking the live and neutral together means the voltage isnt running through the 2 so how could it ?

 

[Guitarist]

?? linking the live and neutral together means the voltage isnt running through the 2 so how could it ?

Equipment which is designed to safely "earth" voltage spikes will sometimes do so with the 500v test when carrying out LN-E. That's why doing the global can throw up odd readings at 500v but rarely at 250v.

 

[somersetsparks]

Your theory is correct glasgow sparks, however I have unfortunately had a tv recorder which didnt survive an IR test (method 2), so for purposes of an I&T especially domestic I always unplug equipment to get true readings and to ensure no damage. obviously there are exceptions especially when it comes to more commercial situations