Discuss Equipment excluded for insulation test in the UK Electrical Forum area at ElectriciansForums.net

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I don’t think there is a comprehensive list of equipment that should be considered to be “neutralised” before doing insulation testing.

as a small starter:

dimmer switches
Pilot lights
Equipment with capacitor
RCD
USB sockets
Light bulbs
Sensitive equipment ?


really appreciate if the list can be added to and tuned to be as limited as possible.
 
It depends on what kind of test you are doing, and what you mean by excluded. Testing L&N to E is possible with most equipment as the test voltage cannot normally appear across the internal electronics. Any equipment that cannot withstand 250V from both live conductors to earth is not safe for use anyway. In the absence of surge protection, the same is generally true for 500V to earth.

Testing from L to N or between lines of different phases, should only normally be done with all equipment either isolated or disconnected, as it is likely to influence the test result regardless of possible damage. Once the insulation to earth is proven, it is often possible nonetheless to test L to N of the wiring even with just single-pole disconnection of the load. This is what often goes in when testing insulation of appliances during PAT, where some functional internal control system disconnects one side of a component such as a heater or motor, but that is still tested via the other pole.

Most of your examples are fine to test L+N-E, and would not be expected to pass a test L-N as they are loads (e.g. indicator lamps). Many items of equipment contain capacitors in various configurations; it does not make sense to list them as items to exclude. Lamps and dimmers - if you disconnect one or the other it should normally be possible to test the circuit L-N, although switched lines might get missed from the test. Initial / complete verification would require bypassing the dimmer.
 
Really useful reply. Don’t see like button etc so very grateful for the info.
It depends on what kind of test you are doing, and what you mean by excluded. Testing L&N to E is possible with most equipment as the test voltage cannot normally appear across the internal electronics. Any equipment that cannot withstand 250V from both live conductors to earth is not safe for use anyway. In the absence of surge protection, the same is generally true for 500V to earth.

Testing from L to N or between lines of different phases, should only normally be done with all equipment either isolated or disconnected, as it is likely to influence the test result regardless of possible damage. Once the insulation to earth is proven, it is often possible nonetheless to test L to N of the wiring even with just single-pole disconnection of the load. This is what often goes in when testing insulation of appliances during PAT, where some functional internal control system disconnects one side of a component such as a heater or motor, but that is still tested via the other pole.

Most of your examples are fine to test L+N-E, and would not be expected to pass a test L-N as they are loads (e.g. indicator lamps). Many items of equipment contain capacitors in various configurations; it does not make sense to list them as items to exclude. Lamps and dimmers - if you disconnect one or the other it should normally be possible to test the circuit L-N, although switched lines might get missed from the test. Initial / complete verification would require bypassing the dimmer.
I think you should add this
 

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