Question for Electricians/Panel Builders

When you build a panel, do you megger the wires after you run them but prior to connecting them? What standard do you use to determine whether wires need to be meggered?

Maybe I am doing it wrong but I have never used one when building a cabinet... I have used them to troubleshoot but never when building

Hi

Maybe I am wrong to but I would use it the check a motor and I would use a meter to check the panel wiring.

Donnchadh

I always used my meter for ponit-to-point testing and troubleshooting. Some customers requre Hipot testing on control panels, usually for agency listings.

No.

In our panel shop our QC standard is that we meg our wires/cables that run higher than 220V ac/dc and greater than 60A or greater than 480V ac/dc or greater than 80A, after building the cabinet. hope that helps

Sparky said:

In our panel shop our QC standard is that we meg our wires/cables that run higher than 220V ac/dc and greater than 60A or greater than 480V ac/dc or greater than 80A, after building the cabinet. hope that helps

Click to expand...

Interesting... what is the reason (other then QC standard), safety, noise or other

I built a couple hi-pot testing machines and never used one, they were variable on the high side about 5k volts, for testing circuit boards and copper cladded dielectric laminates

in my past life, we had to megger all wiring for European panels and certain customers in the USA had us megger the wiring before shipping a panel.

their maintenance procedures had them megger the wiring every 6 months / year.

regards,
james

the panel needs to be meggered, after building and after complete installation, all wiring and motors are checked again.
this is only done in non electronic ones as for example power supplies are leaking like hell.
same vfd
on ships important as they are not using gnd.

So, in effect, 60% for not meggering (which is my experience), 40% for meggering (which is my co-workers position). This is pretty much the same results I've found on Google.

Unfortunately, it doesn't seem like there is any one "standard" that everyone uses (like the NEC). There are ANSI standards, IHS standards, IEEE standards.

My thought on it is this: it will add a decent amount of work. Our electrcians are overscheduled as it is. We've never had trouble because wire insulation broke down (especially in a 120V/24V control system).

We megger any wires/cables that we pull through conduit or raceway, motors, and megger heat trace several times when we install it. I just didn't think panel wiring needed it as the chance for damaging the insulation while installing was minimal.