"Bill Jeffrey" wrote in message
...
Paul Hovnanian P.E. wrote:
Nelson wrote:

Not really electronics, I know, but I'm hoping some one can throw me a
pointer. I'd like to test for both safety and shorts/opens/too much
resistance. The only thing I could find on the web is safety testing
by electric utilities.

Any DIY help would be appreciated.


Put a GFCI receptacle in where you plug this blanket in.

I'm not sure a GFI would do any good. All electric blankets I have ever
seen are two-wire devices, and there is no ground in or around the
blanket. No ground = no ground fault = happy GFI.

I did see a blanket fail once, out in the middle of the blanket (i.e., not
near the connector). I THINK the failure mechanism was a heating wire
that had been flexed enough that it was ready to break - but hadn't quite
broken yet. The fracturing wire got thinner, which increased the
resistance at that point, which overheated the wire at the incipient
break, which caused a hot spot that was hot enough to scorch the blanket
material (the material does not support flame, by the way).

This was NOT a short circuit. The heating wires are well separated, and
anchored in place quite well.

Bill

Ground fault current interrupters do not sense ground current directly -
they sense any difference between the current in the line and return wires,
if the line current exceeds the return current then it must be going
somewhere it shouldn't!!!