Ground Rod or Not? - Page 2 - Electrician Talk - Professional Electrical Contractors Forum

Lenny · 11-19-2009, 10:52 PM

Two things,

I dont really know the purpose of a ground rod at every site, what is it?

Does everyone feel that the NEC is a bare minimum, a grade of a D?

Thanks

Lenny

RIVETER · 11-19-2009, 10:52 PM

Quote:

Originally Posted by Lenny

As soon as you say bond, everyone {at least around here} assumes ground. But Bond, Bonded or Bonding simply means "connected". Reading through the NEC thinking bond=ground horribly screws up interpritations.

Bonding means BEING AS ONE. As far as electrical considerations, it means that if you have a grounded system...GROUND ROD... you have connected a circuit conductor to ground potential. You are limiting that voltage to GROUND. It has very little to do with BONDING.

sparks134 · 11-19-2009, 10:54 PM

A ground rod is good for one thing, lighting protection!!!

user5941 · 11-19-2009, 10:57 PM

Quote:

Originally Posted by wareagle

no where in the nec does it say you need a minimum 25 ohm ground rod. I do agree with you math. Thats why you install an egc.

250.56

user5941 · 11-19-2009, 11:00 PM

Quote:

Originally Posted by Lenny

Two things,

I dont really know the purpose of a ground rod at every site, what is it?

Does everyone feel that the NEC is a bare minimum, a grade of a D?

Thanks

Lenny

the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault.

Lenny · 11-19-2009, 11:06 PM

Riviter,

So, you agree that bonding refers to electrically connecting something, not tying it to ground, right?

In my case, we have bonded all the pedistals with a #2 alum. conductor and connected that to the ground-rods at the disconnects, which are also tied to the neutral. All disconnects are bonded also.

I value your opinion, I don't want to come off as a smartass. I get a lot of bad advice from local electricans. I do have, and can read and follow a copy of the latest NEC

thanks

Lenny

sparks134 · 11-19-2009, 11:09 PM

The main service disconnect is the only place that needs to be bonded

sparks134 · 11-19-2009, 11:10 PM

your ground and neutral should not be bonded at the subpanel!!!

Lenny · 11-19-2009, 11:13 PM

Rewire,

I think I understand "the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault." But how would a ground-rod at every pedistal add protection, especially if they don't get down to 25 ohms?

When you say "clear the fault" is that tripping a breaker or GFCI?

Also, as I understand no connection can be made between the un-grounded conducter and the bonding conducter on the load side of the disconnects. Do you agree?

Thanks

Lenny

Lenny · 11-19-2009, 11:17 PM

Sparks134,

I understand that the ground and the neutral cannot be connected in the sub-panel. I dont have a clear understanding why? Older wiring used to allow that correct? Why the change?

thanks

Lenny

Benaround · 11-19-2009, 11:18 PM

Quote:

Originally Posted by sparks134

your ground and neutral should not be bonded at the subpanel!!!

These are not sub-panels, the OP stated 'metered pedistals' as new services.

sparks134 · 11-19-2009, 11:21 PM

Well they still need a ground rod!!!

Lenny · 11-19-2009, 11:23 PM

Benaround,

I should clear that meter thing up. The meters are owned by the campground, to charge for monthly electric usage. There is one CT meter per transformer, one transformer feeds 4 disconnects, one disconnect feeds 5 pedistals. As far as the utility company is concerend there is 1 service.

thanks

lenny

sparks134 · 11-19-2009, 11:24 PM

Then I was right, no bonding and a ground rod!!!

wareagle · 11-19-2009, 11:24 PM

Quote:

Originally Posted by rewire

250.56

Suggest you read that again. It does not say you need a 25 ohm ground rod. It says that if the resistance of the ground rod is more that 25 ohms you need to install another rod and bond the two rods together. The resultant rod resistance is not mentioned or required. If the rod measures 1000 ohms you install another rod and walk away. Please read 250.56 again so you understand the requirement.

sparks134 · 11-19-2009, 11:27 PM

Quote:

Originally Posted by Lenny

Benaround,

I should clear that meter thing up. The meters are owned by the campground, to charge for monthly electric usage. There is one CT meter per transformer, one transformer feeds 4 disconnects, one disconnect feeds 5 pedistals. As far as the utility company is concerend there is 1 service.

thanks

lenny

Where do you buy meters from to charge custumers? I never heard of that, just wondering!!

RIVETER · 11-19-2009, 11:32 PM

Quote:

Originally Posted by rewire

the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault.

Can you tell me why everyone is concerned about IMPEDENCE...Rather than RESISTANCE?

Lenny · 11-19-2009, 11:37 PM

I belive Wareagle is correct on the ground rod requirement, i've read it several times- but a rod with a 1000 ohms isn't doing much is it? Another reason I dont like the idea of ground rodding every pedistal.

Sparks,

Meters are avaliable from many companys. Midwest Supply, Utility Supply Group and Travellers are some suppliers in this industry. It is common for a Campground or RV park to charge monthly customers for electric. Some parks also charge more for 50 amp service.

Lenny · 11-19-2009, 11:41 PM

Riviter,

I asked that also, got a lot of shady answers. I think the real answer is that a "Megger" is needed to test the effectivness of a ground rod, and no one has them so they use the ohm meter.

amptech · 11-19-2009, 11:48 PM

Quote:

Originally Posted by rewire

the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault.

That is a mostly true statement but incomplete. The purpose of a grounding electrode is to maintain earth potential(zero) at electrical equipment. Does each pedestal require a grounding electrode? I suggest you read 250.50 carefully then also read 551.74. If you have not read Soares Book on Grounding, I would highly recommend it. Soares explains grounding and bonding very well and clears up a lot of misconceptions and misinformation about grounding and bonding.