Online assistance for electrical trade people in New Zealand and Australia Login  |  Register  |   Forgot Password
Assistance for electrical trade people
 

 

 

 


Click here to send Ron a pdf document for publication on this Topic

Documents must be less than 200k in pdf format

Posted By Topic: Dominos Pizza oven earth leakage test 8.6millamp

Marius
Jan 15 2019 19:44

Hi
Today I failed a Dominos pizza oven on 8.6mA earth leakage current.
Another technician went and said he did a insulation Resistance test and earth continuity and said you don’t have to do a earth leakage test as it has got a drive controller and did a test and tag on it.
I just need your feedback if he was able to do a test and tag without a earth leakage test.
   

ryanm10
Jan 15 2019 20:19

Doesn’t PAT testing only check polarity, earth continuity and insulation resistance?

   

pluto
Jan 15 2019 20:53

AS/NZS 3760 permits the use of earth leakage test in lieu of an insulation test.

This had become necessary sue to electronic controls being the control switch for some or all of the equipment.


   

JamesMagnum
Jan 15 2019 21:23

8.6mA Earth leakage on an Oven.....Situation Normal I'd think?
   

Marius
Jan 16 2019 09:08

But isn’t earth leakage has to be less than 5 Milliamperes and it is mandatory
   

AlecK
Jan 16 2019 12:44

Not so much electronics as the fact that the test has to be of the entire appliance. A lot of equipment has relays / contactors (which may or may not be electronic), and the only way to bring the load under test is to have the equipment powered up. Exactly the same as you can't properly test manually-switched appliances without switching them on.

An IR test on equipment containing an open switching device will test only the line side wiring, and not the whole appliance.

Because "3760" is designed to avoid dismantling, the leakage test allows this aspect of safety to be tested. In fact it's mandatory; because clause 2.3.3.2 says "If the equipment must be energised to close or operate a switching device in order to test the insulation, then the leakage current test in accordance with Appendix E shall be performed."

The maximum permitted leakage current is 5 mA.

For equipment that have multiple functions controlled by a timer, each function needs to be tested. Which will often require a much longer test period than most PATs use.

So if there's a switching device that is electrically operated, there's NO option of doing just an IR test, and a tag issued on that basis is NOT valid. If that's what has happened here, then clearly the person who issued the tag is not competent to do so.

Unlike for testing work on installations, there's NO alternative that would allow either a different type of test or a different test result due to presence of a "drive controller". There is a variation for PRCDs that have a functional earth (pretty rare items); where IR can be as low as 0.05 Megohm, but leakage still has to be max 5 mA. And there's a difference between Class I & Class II equipment. And there's a lower IR limit for Mims elements - but no difference for leakage.

Equally clearly the equipment should be removed from service and repaired. The 8.6 mA reading is over the maximum permitted leakage by 72%. That's not what I'd call "situation normal".

It's NOT an option to simply decide that low IR / excessive leakage is due to Mims elements; you'd have to prove it by testing them separately. That would require dismantling / disassembly; which is probably why there's no leeway allowed for the leakage test