how low is it, and what is the neutral-earth IR? Is this just one circuit, a whole installation or what?If the reading live to earth is low what other causes besides a neon could there be?
It is probably "usually avoided' since it is often impossible to be totally certain/confident that "absolutely everything has been removed from the circuit" - but, if one feels that one is "totally certain/confident" that such is the case, then there's no reason why it can't/shouldn't be done.Is live to neutral testing usually avoided even if absolutely everything can be removed from the circuit?
Both have neon indicators.
It would take only a tiny amount of moisture, remnants of a dead insects or whatever to get an IR than 'low' - I don't think many people would be concerned about it.34 MΩ on the upstairs ring. The test showed this on live to earth. I had left two extension leads, one surge protected, plugged in. Both have neon indicators.
If one tests between L+N and E, a 'fixed load' will only affect the IR measurement if any of the loads have an L-E or N-E 'leak', and that's probably unlikely with the sort of loads you mention. In any event, there's no harm in trying - if one gets a very high result, then one is re-assured and, if not, one can 'investigate further'.He didn't want to do that due to some fixed appliances. Wired-in timer and alarm system were mentioned but there were others I think.
I have a couple of extension leads I got from a previous job when they were thrown out for failing PAT. Reason they failed was due to the neon being between L&E and hence failing at 500V. Could also be surge protected, in which case the MOVs would conduct before 500V is reached.Neons would directly affect Live to Neutral IR readings as they are connected between Live and Neutral and not to Earth
I must say I've never come across that one. As I hinted a couple of posts back, I've certainly see occasions on which neons have been installed L-E when there was no neutral available (e.g. at a light switch), but there's really no excuse with an extension lead - particular since, as you admit, there would be a major flaw in the possible 'thinking behind it' that you 'guess at' above!... thrown out for failing PAT. Reason they failed was due to the neon being between L&E and hence failing at 500V. ... I think (well guess, no idea if they came with destructions) the idea was that if there was no earth then the neon wouldn't light and the user would realise there's a problem and investigate. Hmm, there's a little voice suggesting there might be a problem with that idea
"L-N" is indeed, what I intended to type - so just a typo (now 'clarified') Thanks for noticing.Is that correct John I thought that the danger was when you test L to NThe 'danger' with (actually to) connected loads arises when one does IR testing between L and E - since a 500V IR test may (depending upon what they are) damage/destroy such loads.