Grounding

[abe]

Hello
I am working on an 800 amp service panel. It is overhead with single line that says 3 x 21/2 " C. 4 # 300 MCM
I am wonderin what size wire has to be used for cold water connection? Table 250-66 shows 3/0 but 250-66A talks about a smaller size wire. which is correct. Don't I need to install two gound rods 6 foot apart and a cold water connection? what is different how it is connected/ If a diagram is available I appreciate. Are there different methods to connect to cold water?
Thanks for a quick response.
Abe

 

[480sparky]

You say you have a 'single 300 mcm' service conductor, but you're working on an 800 amp service. 300mcm won't get you 800 amps, so you must be paralleling. If so, how many sets of parallel conductors do you have, and are they copper or aluminum?

250.66(A) only requires a #6 to the ground rod. The wire to the water pipe is based on the service entrance conductor size, so we need a little more info here

 

[celtic]

You say you have a 'single 300 mcm' service conductor, but you're working on an 800 amp service. 300mcm won't get you 800 amps, so you must be paralleling. If so, how many sets of parallel conductors do you have, and are they copper or aluminum?

I am working on an 800 amp service panel. It is overhead with single line that says 3 x 21/2 " C. 4 # 300 MCM

Translation:
Three 2.5" Conduits, each with 4 #300MCM

 

[eprice]

Abe,

3 x 300 MCM is 900 MCM. Assuming these are copper, Table 250.66 requires a 2/0 copper GEC. 250.66(A) allows a smaller conductor (6 AWG copper) to rods. This does not apply to a conductor between the service and the water line.

Don't I need to install two gound rods 6 foot apart and a cold water connection?

A metal water pipe, if present, is required to be used as an electrode and needs to be supplemented (see 250.53(D)(2)). However, the supplemental electrode doesn't have to be rod(s). Is there 20' or more rebar in the footings? If so, it is required to be used as an electrode and will satisfy the requirment for a supplemental electrode.