Hi every one got a question needing help with

Im tring to size my Grounding electrode conductor. I have a 146amp calculated load and im going to use #1 copper for this. The GEC cant be under two AWG sizes smaller than your main feeder lines right? so if I use a #3 will this be fine? by the way this is a 120/240v 3wire single phase service.

Any help would be great thanks

Seems to me you'll be needing a 150amp Main Breaker Disconnect, and you'll need to run at least a #6 copper conductor back to your water main, jump the hot & cold water pipes at the hot water heater, and #6 copper to a pair of grounds rods placed 6' apart from one another.

Article 250.66

[This message has been edited by ShockMe77 (edited 10-28-2005).]

Assume this to be a Service not a "feeder" for a residential problem. The size for the ungrounded conductors could be #1 AWG and the size for the grounded conductor should not be not smaller than #6 AWG. The overcurrent protection would need to be 150a maximum. The GEC to the water would be #6 AWG and I don't find a code rule that says you need two rods. Bonding of the piping systems is required but I don't see where in the code that it has to be at the water heater. All conductors are considered to be copper. These conductor sizes are only valid for residential. If this is a non-residential problem the sizes will be larger.

And another thing- I don't see in the code that you need to use a rod.

I feel much better now that I've vented



[This message has been edited by George Little (edited 10-29-2005).]

the 2 grounding rods are if you have two seperate voltage systems right?

In New Jersey, in residential work, (2) 8' copper ground rods are required for all new or upgraded electrical services. They are required to also be a minimum of 6' apart from one another (250.53 (b), or 250.56). The GEC jumper between hot and cold water pipes is the way I always do it, but I can't seem to find it in the NEC.

250.50 describes the grounding electrode system and goes on to say that if you are using a metallic water pipe it must be supplemented with an additional electrode.(250.53(D). You are not limited to a rod and it's certianly not required to be copper. 250.56 explains the need for a single rod to be <25 ohms. If it's not less than 25 ohms it's to be augmented by an additional electrode of the ones discribed in 250.52(A)(2) through (A)(7). The '05 code will have us using the rebar of the foundation to supplement the water pipe and we won't need to install ground rods.

Most contractors will install a bonding jumper at the water heater to accomplish two things. (1) It ties the hot water and cold water piping systems together and is needed per 250.104 and (2) it bonds across any dielectric unions typically found at the water heater.

Side note: Most hot and cold water piping systems are tied together at a faucet someplace in the home or a mixing valve but this jumper wire at the water heater avoids an inspector checking this out at the faucets. (George likes it)

Thanks for all the info, George.

i dont have a code book with 250.66 in it ,,im using a 93 code book do you know if the 250.66 table just might have a different # in this year book. also is there a web site i can go to get the most current codes like this and i could just read it of the web.thanks

The Table 250.66 in the '02 NEC is 250-94 in the '03 code. The codes are not available on line for downloading or viewing to my knowledge. Probably due to book sales and copy right issues.

In the index of your '93 code book, I would look in the index for Grounding, then Electrode System. Hope that helps.

The 2005 NEC is available for viewing at the NFPA web site.

Curt

Thanks Curt- But there is no downloading, copying or cut and paste. Darn. Oh well, I guess their not going to sell many books if you could get it free as a download. I've noticed that the CD version (Acrobat) also needs a key for copy and paste.