If I measure the resistance between the live and earth terminals of my Russell Hobs stainless steel electic kettle I get a reading of about
9M ohms. (using my electonic multimeter)Is this normal or indicative of a fault which a higher voltage might be able to jump causing the fuse to blow?
Michael Chare
If that same impedance applies at mains frequency, it will cause a current of just under 30 micro-amps to flow to earth - which is a thousand times less than the current required to trip an RCD.
I would have thought that this was pretty good - and certainly wouldn't worry about it.
My problem is that the kettle has blown two fuses. Before fitting the 2nd fuse I checked for a short circuit, but not an earth fault. There is now no sign of an earth fault other than I have described in either the kettle or the supply lead. The plug that goes into the kettle is similar to that often used on computer equipment, it could just have had a fault which was burnt away by the fault current. Unfortunately although the plug appears to be made in two parts I can't get it apart to make an internal inspection.
It's possible that if there are pinholes in the element, the presence of water causes a mains-voltage earth leak which doesn't show up in your DC resistance measurement.
The fuse is blowing is because it's being asked to carry more current than it can. This might be going to earth - or it might be going through the element, back to neutral.
Have you got an RCD plug-in adapter, as used with garden tools? If so, use that with the kettle for a bit and see what happens. If the RCD trips, its an earth leak. If the fuse blows without the RCD tripping, the element is taking too much current for some reason. You are using a 13A fuse and not
5A, aren't you?On Thu, 18 Nov 2004 14:49:16 +0000, Michael Chare strung together this:
If you're trying to fault find it don't bother with a multimeter, use an insulation tester. Buying a new kettle would be cheaper though, they're not expensive.
Michael Chare wrote in news: snipped-for-privacy@chareDOTorg.uk:
You're not holding the croc clips, are you? could be *your* resistance.
TBH, I don't know, but 9 Meg won't hurt anyone, and I _theeenk_ heating elements may be leaky, and may trip RCDs
mike
You cant measure impedance with a a dmm
Peter
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