Hi,
One for the electrical chappies :)
I am about to undertake installation and testing of a fairly major pair of domestic lighting circuits - lots of lights, lots of 2 way, lots of electronic parts.
Aside: I *have* done an EAL Level 2 Installation/testing course - basically the 4 day "Part P" entry level qual.
What I was after was *in the real world*:
1) Do most people do the insulation resistance test LN->E (that is L+N bonded together) rather than the more extensive L-E, N-E and L-N tests which would require every bit of electronics to be either bridged (eg dimmer switch) or isolated (eg tube gear, SELV PSUs)2) Our rather basic course did not cover full testing on the SELV side. Could anyone confirm that SELV wiring should be insulation tested at 250V DC both between conductors (PSU isolated) and 250V betwen mains and SELV side of the PSUs (with inputs and outputs bonded)?
Re (1) - Of course, dimmers should be bridged to conduct a proper R1+R2 test, but I do have a fair few tubes, SELV PSUs and extractor fan controls.
Extensive testing is of course good, but if it becomes too "destructive" (ie the circuits must be broken/bridged for the test, then restored afterwards) then to my mind, it defeats the purpose as a lot of untested disturbances have taken place. A bonded LN->E test at 500V DC seems to make more sense as you are disturbing less and testing is including the insulation in tube gear and (possibly if Class 1) SELV PSUs.
Cheers,
Tim