What can cause a fridge freezer to fail a pat test?

[Gary111]

If a fridge freezer gives an indication reading of 0.00 Mohm what is the most likely cause?

 

[Harry Bloomfield]

If a fridge freezer gives an indication reading of 0.00 Mohm what is the most likely cause?

When measured across which wires/or terminals?

 

[RandomGrinch]

What voltage was used for the insulation test - 500V, or 250V?
Was the fridge freezer operational and didn't cause any trips, before the test?

 

[Gary111]

Hi, It was tested at both voltages, it is operational and doesn't cause trips.

 

[Harry Bloomfield]

Hi, It was tested at both voltages, it is operational and doesn't cause trips.

You still haven't answered the question - across which terminals, was 0.00Mohm measured?

 

[RandomGrinch]

You still haven't answered the question - across which terminals, was 0.00Mohm measured?

We don't know for sure, but a standard PATester will short L and N and probe on earth (through the plug).

 

[RandomGrinch]

Hi, It was tested at both voltages, it is operational and doesn't cause trips.

Do you have any other tests available to confirm? A few testers also have an earth leakage test available?

 

[Gary111]

I think that's right its a prime test 350

 

[RandomGrinch]

I think that's right its a prime test 350

Yes, standard for Seaward testers.
The Prime test 350 has a touch leakage test.
If I was to come across an appliance that failed an IR test, but was previously working, without tripping, I would try a touch leakage test next.

Edit: for a touch leakage test, make sure you get the probe on a good earth point on the fridge - the croc clips don't always bite through the panel coating!
If you can only access the front, the door hinges can be a good earth point.

It is likely that it would confirm the low IR, but there could be other factors at play.
I.e. a fussy power filter etc.

 

[Gary111]

Thanks very much for your help

 

[ericmark]

I would think more likely is the seals on the mineral insulated defrost heater have broken.

 

[RandomGrinch]

I would think more likely is the seals on the mineral insulated defrost heater have broken.

Yes, I wasn't suggesting sny specific causes yet - I was just suggesting a confirmation test for a very low IR result.
In the years I've been PATting, a 0.00MOhm IR, on an otherwise operating appliance is a very rare case!