Extraneous conductive part testing.

[Traineeboy]

To determine if an metal work is classed as an extraneous conductive parts then I understand that a test is to be carried out between the metal work in questions and the MET. I know as a general rule if the reading comes back as 22Kohms of higher then the part doesn’t need bonding, however some people state it’s a continuity test between metal work and MET and others are saying it’s an IR test. 
 

I could see how both could he right but would like clarity. 
 

continuity test  - You are simply testing to see if there is continuity between that metal work and earth. 

IR Test - you are seeing if there is resistance between the metal work and earth. 
 

Any thoughts would be appreciated 

 

[Andy™]

both are testing continuity / resistanc. there pretty much the same thing. IR youre not expecting low readings hence the high readings and always in Mohms. its also at a higher voltage. continuity you want to check the lower resistances, for this you also want current (200mA flowing required)

you could do an IR test for checking extraneous or not, however im not aware of any MFT that have a Kohms scale unless the resistance is in the Mohms, it wont be any help. reading of 0.00 could still be well over 22K

 

[binky]

I think my Megger MFT goes down to 0.01MOhm which is about 10 KOhm, but I wouldn't trust it to be accurate at that low level. You would have to check the spec of your MFT to see if IR could be used. I always use continuity test for checking bonding.

 

[Traineeboy]

I think my Megger MFT goes down to 0.01MOhm which is about 10 KOhm, but I wouldn't trust it to be accurate at that low level. You would have to check the spec of your MFT to see if IR could be used. I always use continuity test for checking bonding.

thanks for this. So I’m 100% clear I could use a Megger MFT ( set to continuity) and one probe on the MET and one on the metal part in question. If I get a reading higher than 22Kohms then won’t need to bond. I tried today and I got about 40K ohms with continuity and 0.04 Mohms with IR setting. 

 

[Andy™]

yes

 

[Sidewinder]

thanks for this. So I’m 100% clear I could use a Megger MFT ( set to continuity) and one probe on the MET and one on the metal part in question. If I get a reading higher than 22Kohms then won’t need to bond. I tried today and I got about 40K ohms with continuity and 0.04 Mohms with IR setting. 

IF the continuity range on your Megger reaches 23,000Ω.

 

[Bruspark]

The thing is that a decent MFT or multimeter will have been checked or even calibrated severalplaces in the ohms and Kohms range while a megger etc was probably checked at 1 or 2 Mohms

If they all say 10 Megs I wouldn't worry, but if an insulation tester says its 0.03 Mohms I would not be relying on that as a 'calibrated and precise reading'    In fact the spec likely says +/-  1 count at least on top of +/- 5 or 10% 

 

[binky]

thanks for this. So I’m 100% clear I could use a Megger MFT ( set to continuity) and one probe on the MET and one on the metal part in question. If I get a reading higher than 22Kohms then won’t need to bond. I tried today and I got about 40K ohms with continuity and 0.04 Mohms with IR setting. 

Correct. You can get those sorts or readings through the fabric of the building, especially with wet plaster - I once drove myself slightly crazy chasing down a low insulation resistance reading due to that