Transformer located 500 feet from service equipment no water pipe or building steel available in nearby vicinity. I am going to use two eight foot ground rods spaced ten feet apart as the grounding electrode and a number 6 awg bare copper grounding electrode conductor connected to transformer XO terminal. This is a 150 kva 480 volt primary 208/120 volt secondary. The supplied factory strap from XO to the xfmr case is adequate as the bonding jumper?if not it should be sized as per 250-66? also the equipment grounding conductor on the eprimary is based on 250-122 size of primary ocp? Please advise i am working with an uncooperative coworker
xfmr grounding and bonding
- Thread starter buggsy
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bphgravity
Senior Member
- Location
- Florida
Re: xfmr grounding and bonding
What you are describing appears to be a separately derived system. Per section 250.30, all that you describe appears to be compliant. I also feel that factory XO-to-case bond strap is adequate. Just remember to not bond at the first disconnecting means.
The grounding electrode issue should be discussed with the AHJ. One could argue that the building steel or water pipe should be used even if nots in the "nearby vicinity". I personally feel the 2 ground rods are adequate.
What you are describing appears to be a separately derived system. Per section 250.30, all that you describe appears to be compliant. I also feel that factory XO-to-case bond strap is adequate. Just remember to not bond at the first disconnecting means.
The grounding electrode issue should be discussed with the AHJ. One could argue that the building steel or water pipe should be used even if nots in the "nearby vicinity". I personally feel the 2 ground rods are adequate.
Re: xfmr grounding and bonding
buggsy - Wait a minute. Look at your xfmr very closely.
I doubt very seriouslly that the factory has put a factory strap from X0 to the xfmr case!
Believe you will find that the factory strap is from the iron core of the xfmr to the xfmr case !
You must install the bonding jumper from X0 to xfmr case!
Otherwise, it sounds like a simple, very common, separately derived system.
buggsy - Wait a minute. Look at your xfmr very closely.
I doubt very seriouslly that the factory has put a factory strap from X0 to the xfmr case!
Believe you will find that the factory strap is from the iron core of the xfmr to the xfmr case !
You must install the bonding jumper from X0 to xfmr case!
Otherwise, it sounds like a simple, very common, separately derived system.
sandsnow
Senior Member
- Location
- Southern California
Re: xfmr grounding and bonding
I used to see factory bonding jumpers all the time on GE xfmrs. I haven't seen any in recent memory.
I used to see factory bonding jumpers all the time on GE xfmrs. I haven't seen any in recent memory.
fc
Senior Member
- Location
- New Jersey
Re: xfmr grounding and bonding
Correct me if I am wrong but you say you are using #6 wire for your GEC? What size wire are you using for secondary conductors? I would think your secondary wire would be larger then 3/0 and if so you need to install a larger GEC as per 250.66
Correct me if I am wrong but you say you are using #6 wire for your GEC? What size wire are you using for secondary conductors? I would think your secondary wire would be larger then 3/0 and if so you need to install a larger GEC as per 250.66
peter d
Senior Member
- Location
- New England
Re: xfmr grounding and bonding
The sole connection to a ground rod does not need to be larger than #6.
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