ECN Forum Forums Code Related Discussion NEC & other Code issues Ground Rod Woes Revisited...

Well, I guess it comes down to:

If I gotta work so hard at getting a particular part of the service installed, I want it to be something that actually works.

What would be the cheapest and simplist, yet effective way to install a ufer with a target of say, 25 Ohms?

I need to get a "megger" don't I...

*watches $100 bills fly out the window*

Great soundbites Steve, and I've already called AP, but haven't talked to an EE yet...

Maybe tomorrow.

*...meditates saying "Ohm" and thumping self in head with the 2002 NEC...*

Sparky66, the electrode can be at least 20 of #4 rebar in the bottom of the footing(at least 2" of concrete around it) or 20' of no smaller than bare #4 copper wire. The 20 feet is the horizontal length at the bottom and does not include the vertical portion that comes up and out of the foundation. New construction in CA requires them.

Hey spark,I scored a kik ass megger from ebay for $60!. They are the crank type.1000v 1000m-ohms. earth tester/megger/insulation .
not a bad deal for a guy on a budget. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1771774872

PS, I think you could drive a couple of 8' ground rods. looks that way from my house anyway

[This message has been edited by Sean WB (edited 10-01-2002).]

Sean, here's the kicker...

I don't know how to use one!

I've heard about fall-of-potential methods and the like, and I have been led to believe that the mega-expensive meggers designed for ground rods without external test rods are the most convenient.

How does one test grounding electrodes with an analog crank megger?

PS: Are you a journeyman yet, Sean?


[This message has been edited by sparky66wv (edited 10-01-2002).]

Hey Virgil

You don't want a megger to test your ground rods. A megger is used to test very high resistance. You need to test for low resistance.

I just wanted to say something before you went out and spent hard earned money and discovered you purchased the wrong thing.

Curt

Ahhhh!

Thanks, that makes sense...

Anyone read 250.53 A "Where practicable rod, pipe, and plate electrodes shall be embedded below permanent moisture level" What does this mean and who does this?

The operative phrase in that case is "at least." The reason for the restriction is that very small structures such as guard shacks and well houses could be encircled with less wire. Twenty Feet is the minimum length. The perimeter distance around most structures assures that the length will be adequate to provide a ground that is a lower impedance than the two driven rod minimum solution.

(4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.
--
Tom

The only electrodes that the code requires 25 ohms or less for are rod, pipe or plate electrodes. No testing is required by the NEC for water pipes, Ufers and building steel.
Don

Virgil,

Don't waste your $$ on a ground resistance tester. It is unlikely that you will find anyplace in WV that you can get 25 ohms or less, except maybe the bed of the Ohio or Potomoc river.

Tom