I've been having some fun with a cooker, and wondered if others have experience of odd behaviour of the mineral insulation in the elements.
After an RCD trip,I found what I considered unacceptably low resistance in an element, (about 2 megohm) and purchased a replacement (at a price that hurt !). On checking the replacement I found it wasn't that much better, at about 5 meg. Now this is a good brand spare, supplied in a sealed polythene bag. I then tested it hot, and to my horror found it had dropped to under 1 megohm. When it cooled the resistance increased again, reaching a higher level than original. Cycling it several more times, over a couple of days, I now have a hot reading around 5 meg, cold greater than 20.
Now, I'm GUESSING that what is happening is that there is water in the mineral insulation, and that when the element heats up this is forced to the cool bits at the end, where the increased moisture presence causes the low resistance. Some is driven right out of the end "seals", so there is a gradual improvement.
However, has anyone else had similar experience ? Is this the expected behaviour of these elements ? And worst, have I wasted my money on the replacement? Should I have simply baked it for a while on a non-rcd circuit.
