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Testing a kettle

PostPosted: Fri Jul 22, 2011 11:02 pm
by LordAzrael76
I'm just playing with my Supernova XE at present whilst awaiting my C&G course (probably October as it's a free course due to pending MoD unemployment) and have been trying some of my household items, but I can't get either of my kettles to pass the initial earth bond test. The first kettle is a cheapy Tesco plastic jug kettle with easy access to an element (which is new and clean) and the second kettle is an expensive Prestige model with a flat heater plate which I can only hold the earth clip against.

When I run the standard class 1 test on these the test starts with the earth bond test and I always get a reading of >19.99 ohms giving me an instant fail.

Is there something blatantly obvious I'm missing with this or is there a way around it?
(I apologise in advance if it is covered in the COP, but I've only just ordered a copy and it hasn't arrived yet.)

thanks

Re: Testing a kettle

PostPosted: Sun Jul 24, 2011 12:35 am
by Grizzly
You have plugged the kettle's 13A plug into the Supernova, haven't you?
Obvious, I know, but I've seen people start test sequences without having done so.

Re: Testing a kettle

PostPosted: Sun Jul 24, 2011 6:30 pm
by LordAzrael76
Yes, definately remembered that :)

Re: Testing a kettle

PostPosted: Mon Jul 25, 2011 1:12 pm
by benson
The PAT I use doesn't support the earth bond test. The tester may perform an earth continuity test automatically before it performs the earth bond test. Some PAT's claim to perform earth bond tests although in r reality they are only capable of performing. earth continuity or screen tests.

Re: Testing a kettle

PostPosted: Mon Jul 25, 2011 2:29 pm
by Grizzly
Hi benson,

Interesting.
Which particular PAT units are you refering to, and what do you consider to be the difference between an earth bond test and an earth continuity test?
Are you refering to the test current used (25A as opposed to 100mA, for example) or something else?

Re: Testing a kettle

PostPosted: Mon Jul 25, 2011 2:35 pm
by Grizzly
To LordAzrael76,

Another thought: have you inadvertantly selected a lead earth bond test (via the onboard IEC connector) as opposed to an appliance earth bond test (via the test clip lead)?
Just a wild guess, but if that had occured, it could explain the total fail (>19.99 ohm)

Re: Testing a kettle

PostPosted: Mon Jul 25, 2011 7:24 pm
by LordAzrael76
Hi,
I just selected the test setup that's been programmed into the unit as a class 1 mov/stat item. The settings are:
Earth bond output 25A Limit 0.10 ohm dur 5s
Insulation 500v limit 1Mohm dur 2s
Leakage 230v limit 3.50mA dur 5s

The kettle is plugged into the unit and the earth lead is attached from the unit's main earth bond socket to the kettle element.
I've just tried it again and it still gives the same readings.

Re: Testing a kettle

PostPosted: Mon Jul 25, 2011 7:55 pm
by Grizzly
I take it that the Supernova gives an earth bond pass on other Class I appliances?
If so, it may well be that the kettle does have an earth bond problem. Have you tried checking for earth continuity with something like a multimeter, just to see if an earth is indeed present?

Re: Testing a kettle

PostPosted: Mon Jul 25, 2011 11:07 pm
by LordAzrael76
Hi,I was just trying a few other tests and have discovered the issue. On getting the same results on my iron, I wiggled the earth lead a bit during the test and it changed dramatically. So I removed the connector on the end of the earth lead to find the wires disconnected! The problem with buying second hand I suppose. Never mind, I've found the problem, but does anyone know which wire connects to each terminal in the plug (pat tester end, labelled 1, 2 & 3)? Many thanks
Derek

Re: Testing a kettle

PostPosted: Tue Jul 26, 2011 1:57 pm
by Grizzly
LordAzrael76 wrote:... does anyone know which wire connects to each terminal in the plug (pat tester end, labelled 1, 2 & 3)?


Glad you've got to the bottom of it!

It doesn't actually matter which wires in the 3-core flex connects to which pins of the 3-pin XLR connector. The Supernova uses the 4-wire method to ignore the resistance of the test lead, and so all 3 cores are connected to the same place on the croc-clip end of the test lead.
For info, my Supernova test lead is wired thus:

Pin 1 Blue
Pin 2 Brown
Pin 3 Green/yellow

but as I said, it doesn't actually matter.

More info on the 4-wire method here: http://www.allaboutcircuits.com/vol_1/chpt_8/9.html