Class 1 - Insulation Resistance lower legal limit?

[Blackstone]

Hi Guys,

Could you guys tell me what the lower legal limit is on Insulation resistance for Class 1 appliances?

We raised our own test limit some years ago to >5m ohm due to certain units failing when installed on site and us getting increasing warranty call outs to fix them. We narrowed it down to the heaters on these particular cabinets quickly failing if during the PAT test they read below 5m ohms.

Our MD wants to lower the limit again for certain cabinets but we cannot find the book thats states the lower legal limit for insulation resistance.

If anyone can help and provide a link so i can show him it would be much appriciated

Cheers

Glen

 

[spark 68]

=> 1 Meg ohms I believe

 

[telectrix]

lower limit is 1 Meg. afaik.

 

[ringer]

The Code of Practice published by the IET sets this out, cost £40, but I take it you are not into PAT per se. The info you want is 1M ohms is a pass but anything under 2M ohms warrants investigation. Not sure where you can find this on the web though.

Sent from my HTC Sensation using Tapatalk

 

[Deleted member 26818]

There is no legal limit.

 

[Blackstone]

Cheers guys,

spinlondon - No lower legal limit? So is the 1m ohm limit stated by those above just a recommended lower limit, maybe stated in the IET Code of Practice?

 

[Richard Burns]

For inservice testing (PAT testing):

For equipment that is a heater (or cooker) >=3kw the limit is 0.3Mohm
For other equipment that is earthed the limit is 1Mohm
For equipment without an earth 2Mohm
For Extra low voltage (<50V) the limit is 0.25Mohm

This is not legal it is recommended but is a useful level to work to to provide legal justification.

this site gives the correct information, though I cannot vouch for them:
http://www.pat-testing.info/test.htm

 

[Blackstone]

Thanks for your help guys!