Insulation Resistance Testing of downlights

I'm testing my own house and am just wanting to learn.

Are insulation resistance tests ok to run on LED downlights or any types of downlights for that matter?  Am I right in thinking that I can just test my whole installation regardless of ELV devices if I carry out a COMBINED L+N to earth test,  free of worries of damaging equipment.  Should I test the installation at 250V instead of 500V?  

thanks very much

The "load" part of any electrical equipment, (lights/toasters/showers/boilers/T.V.s/garden pond pump/internet router/etc/etc/etc), is connected between the Live & Neutral conductors. So as you suggest a 500v DC test between Live & Neutral could damage any equipment vulnerable to IR test voltages, Or just give a low continuity reading through the equipment rather than testing the cable itself. Whereas if Live and Neutral are combined, i.e. they are both at the same potential and any tests between [Live & Neutral combined] to [Earth] will only give 500v DC to earth. So potential between L->N is still = 0v and zero volts can't damage much.  However it can still be good practice to test at 250v before doing 500v, Just in-case you have forgot something still connected, plus if you do get a low reading at 250v, you don't stand much chance of a clear test at 500v.

Doc H.

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It all depends on what you find when doing your continuity tests .......... L&N to earth is pointless unless you have confirmed earth / cpc continuity on all circuits first.

Then there is the small matter of the increasing numbers of "smart" devices connected .........and if you have RCD sockets or fused spurs these can give "odd" results too

I am interested in this thread as I have done my own wiring and done my own cable insulation and continuity testing as gone along. My first fix passed the inspection and next time inspector is back he will do the full installation test. As I have a couple of hundred halers installed I am concerned how these would be tested as its not a simple case of removing the bulb as in a pendant light. (Most will have dimmers eventually but won't be installed until post final test). I contacted Collingwood and they put a haler under test both at 500v and 250v and did not result in any problem. However to be safe they did suggest doing the test at 250v. I am concerned like jumpjamesjump that having so much electronic stuff especially my heating controls how can one ensure nothing gets damaged?.

There is little benefit and no wisdom in doing 'just for fun' insulation testing between L & N (unless there is a known fault you have isolated to one circuit and
are getting very close to) and much less so with any devices remaining connected to the circuit. ...  And in many houses with Smokes, Aerial amplifiers etc
scattered around it's increasing hard to be entirely sure nothing is connected even having asked !

Insulation testing from L+N to E can be done at 250v or 500v and while decent connected equipment will pass at either the existence of such 'still connected'
devices would make 250V the acceptable and preferred solution unless it became necessary to disconnect all the devices as some other problem is suspected. 

However you say you have a qualified inspector to do the test so you can simply give them a sheet of paper that lists the still connected devices per circuit and let them figure how to compliantly test the installation.