megging 24vdc and 120v circuits

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wllthwa1

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I have a spec that states all wiring is to be megged. Is is appropriate to meg 24vdc and 120v circuits instead of just the 480 volt power cable.

If yes what voltage 500?

wllthwa1
 
Yes, absolutely, as long as the voltage rating for the insulation is compatible.

Assuming the insulation is 300V or 600V, I'd use 500V on the megger.

Caveat - make sure there is nothing on the ends of the wire! A duplex outlet with nothing plugged into it wont mind being meggered, but a smoke or thermostat with electronic bits in it may have a total sense of humour failure.
 
You can stress insulation of any supply voltage. The unwritten rule is twice the rated V push of the application itself. Fluke's new meggers have lower stress' of 50V and 100V. You can see from your question where the 50V may be used/useful:wink:
 
i megger 600v rated insulation at 1000volts. 300v insulation at 500 volts. 250v equipment at 500 volts. 120 volt equipment at 250volt and so on and so fourth. minimum values for conductors vary with insulation types but generally you dont want to see less than 100 megaohms. some people say 500 megaohms but 100 is acceptable. on brand new wiring you should expect to see full scale hopefully. on equipment the rule of thumb is 1 megaohm for every 1000 volts or so. minimum 1 megaohm. manufacturers should beable to give you the information needed if im not mistaken. just watch out for any loads attached like capacitors on single phase motors
 
cadpoint said:
dbuckley, I assume your stating this for the low voltage testing and 1000 for the 120V circuits ?
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I'm with Electricalperson here, megger at about twice the insulation rating, so if you are using 600V rated cable then 1000V on the megger. 300V insulation gets 500V.

The voltage the cable will be used at eventually I dont really care about, its the insulation voltage that is important.
 
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