ECN Forum Forums General Topics of the Trade General Discussion Area Testing damaged circuits

In cases where you are called to fire and/or water damage cases what testing do you typically do to assure yourself that circuits which are not destroyed are still serviceable? If megging what value is considered good?? WHat is your damage criteria for removing equipment completely and starting over?? Anyone had callbacks where there were problems down the road on reused circuits/equipment??

You might be able to get a megger and test all of the remaining circuitry. Just a thought.

Hi Harold,
What value of resistance would you consider 'good'?? How would you treat the problem from an inspector's standpoint with the EC??

Jes,

FWIW....I would like to see >10meg , but would probably accept anything over 1 meg.

GJ

Pardon my ignorance, but does a "megger" place voltages on the circuit that is tested?

Wouldn't that be dangerous in a situation where there is damage, and one is not certain if insulation is bare, etc?

Yes, a megger places voltage on the system. In England we typically test normal 240/415V systems at 500V DC.

It's a high voltage, but supplied through a high impedance so that the current is limited, typically 3 or 4mA into a dead short. The 500V level is achieved only if the circuit insulation is good.

I'd be looking for a value of at least 1 meg., although I'd rather let the wiring dry out some more and get it higher before re-applying power.