How to determine if a main breaker panel is grounded correctly?
Hi all -
I have a wood frame house on concrete slabs.
I have a main breaker panel in the garage, with the meter directly connected to the top of that panel (no spacer or conduit run to the meter)
I'm trying to determine whether or not the main panel is correctly grounded or not, by NFPA code (grandfathered or not)
There is a bare copper wire (looks to be #8, maybe #6), going down into a conduit entering the slab of the garage floor. I don't know where that goes, but it's the only thing in the conduit whatsoever.
It does start a turn just as it enters the slab, heading towards the back of the garage, where there is no other exterior wiring of any kind.
Other conduits contain the wiring going out to a light out in the yard, RV storage area, etc.
Just for sake of mentioning it, there are two subpanels
- one is a Square D panel with a 2" conduit containing four wires coming from the main manel in the garage - two very large wires and two smaller wires (probably #8/10 guage, not #6)
- The other panel is an old Edison fuse panel, which is fed by conduit with only three large conductors. The wiring in the original part of the house is 2-wire cloth covered 12/2
Most of it cannot be replaced due to no attic/basement, and wood panelling everywhere -- you'd have to demolish the house to replace it, since there are no alternate paths (ie, attic or basement paths)
I plan to replace that panel with a new breaker panel, and I'm told I'll have to install a #6 THHM ground wire for it - I've identified a pathway for that wire to run though.
Does anyone know a way I can test that solid copper wire I found in the outside panel? I can't figure out where the other end of it is -
You don't say when this was built but it does sound like what is called UFER ground. It is connected to rods installed in the concrete when it was poured.
The second sub panel does not sound correct. It should have four wires to it.
I had another electrician come out and look -
He thinks it's an UFER ground as well...
We're going to replace the entire line running to the inside panel when we put in the new panel, and will add the fourth wire then.
A previous electrician had suggested just adding a ground wire, but the second guy didn't agree with running a ground wire via a different route for various reasons.
I guess now I'll try to pound the ground rods I bought in and use them for my amateur radio gear which needs them anyhow!
I have the materials to water drill it, which is supposed to be just as fast
Installing Ground Rods the Easy Way.
That being said, you should also follow the NFPA NEC guidelines
Electrical Code vs. Good RF Grounding
(BlueJay, I imagine you know most of what I'm saying here, but since others will read this post later...it's for them)
Much of what is said (by the more knowledgeable) in that latter article
would also apply to checking your phone wiring and TV cable carrier's grounding.
Most of those guys are minimum wage contractor installers, and just go for the nearest metal for the traveller/messenger wire on their cable, and hope that's a ground. In many older homes, it's NOT a ground, but not their problem.
Yes, once you got your insurance company to care and spend the legal time, you might win a case against the cable company for a lightning strike on your cable burning your house down --- because they attached their messenger wire to something on your house that wasn't a ground at all...
that still won't replace your family...
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