I HAVE A PROJECT WHERE THE MAIN BONDING JUMPER AND GROUNDING ELECTRODE SYSTEM HAVE BEEN INSTALLED IN A PAD MOUNTED TRANSFORMER AND NOT IN THE SERVICE EQUIPMENT. PAD MOUNTED TRANSFORMER HAS A GROUND GRID WITH 4 EACH GROUND RODS SURRROUNDING CONCRETE PAD AND STEEL REINFORCEMENT BONDED TOGETHER. GROUNDING CONDUCTORS OF THE PROPER SIZE HAVE BEEN INSTALLED IN ALL SERVICE AND FEEDER CONDUITS. BUILDING STEEL, COLD WATER PIPING, ETC HAVE BEEN BONDED TO SYSTEM ALSO. WE ARE THE LOCAL UTILITY AND THE AUTHORITY HAVING JURISDICTION ON A MILITARY INSTALLATION. I HAVE REVIEWED THE 2005 NEC AND FOUND THIS WOULD BE ACCEPTABLE IN A SEPERATELY DERIVED SYSTEM SUCH AS A DRY TYPE TRANSFORMER DOWN STREAM OF THE SERVICE EQUIPMENT BUT I DO NOT THINK THIS INSTALLATION ACTUALLY MEETS THE NEC. ANY COMMENTS?
GROUNDING ELECTRODE SYSTEM AND MAIN BONDING JUMPER
- Thread starter floyd
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: GROUNDING ELECTRODE SYSTEM AND MAIN BONDING JUMPER
First of all, please turn off the ALL CAPS feature. It makes the post harder to read, and is considered impolite (as though you were shouting at us).
Secondly, a question: Is this a ?service? (i.e., from the utility) to the building? Or is there a separate utility service (i.e., to a substation) somewhere else on the military base, so that the primary conductors to this transformer constitute ?feeders? from the substation?
First of all, please turn off the ALL CAPS feature. It makes the post harder to read, and is considered impolite (as though you were shouting at us).
Secondly, a question: Is this a ?service? (i.e., from the utility) to the building? Or is there a separate utility service (i.e., to a substation) somewhere else on the military base, so that the primary conductors to this transformer constitute ?feeders? from the substation?
Re: GROUNDING ELECTRODE SYSTEM AND MAIN BONDING JUMPER
Caps off. Primary service coming to the transformer is 12,470 volts and owned by the military installation. Secondary voltage is 120/208 volts, 3 phase. I do not think this is correct because the grounding electrodes and main bonding jumper is not installed in the service equipment that is fed from this transformer underground.
Caps off. Primary service coming to the transformer is 12,470 volts and owned by the military installation. Secondary voltage is 120/208 volts, 3 phase. I do not think this is correct because the grounding electrodes and main bonding jumper is not installed in the service equipment that is fed from this transformer underground.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: GROUNDING ELECTRODE SYSTEM AND MAIN BONDING JUMPER
It looks to me that 250.30 applies, that this is a separately derived system. The bonding jumper and the connection to the grounding electrode system can occur at the transformer, or at the main panel in the building, so long as it is not at both locations.
It looks to me that 250.30 applies, that this is a separately derived system. The bonding jumper and the connection to the grounding electrode system can occur at the transformer, or at the main panel in the building, so long as it is not at both locations.
kturner
Member
- Location
- East Tennessee
Re: GROUNDING ELECTRODE SYSTEM AND MAIN BONDING JUMPER
floyd,
You pretty much have answered your own question. This installation is a separately derived system rather than a service.
floyd,
You pretty much have answered your own question. This installation is a separately derived system rather than a service.
Re: GROUNDING ELECTRODE SYSTEM AND MAIN BONDING JUMPER
Who owns what? More importantly, where is the service point?
Even more important, Who is making the rules? Doesn't the Corps of Engineers have their own code that should be followed? This is kind of important cause it's their ball and their playing field. :roll: Note: May match the NEC most places, but does vary. For example, i understand the gound rod resistance is required to be 10 ohms - no give-me for an extra rod.
So, by the NEC/NESC, assuming the service point is ahead of the xfmr primary: A few of the sites I work are industrial installations where the service is HV from the utility. The HV disconnect is our's and that is the service. The transformer is ours.
That makes the transformer secondary a separately derived system. From there, the xfmr neutral can be grounded and bonded and five wires run to the 208 panel/switchboard - separate ground and neutral - and that meets NEC and I think is a good method.
If the transformer belonged to the utility, the practice, per the NESC, (note: not verified by me) is to ground and bond the neutral at the xfmr, four wires to the 208 panel/switchboard, with the neutral grounded and bonded again.
This also meets code (NESC and NEC). IMO this is not as good a method as the first. But it is the method used in every house in the US. (For the regimented, literal sorts, "Oddball exceptions noted."
So, what's not to like?
carl
floyd -
Who owns what? More importantly, where is the service point?
Even more important, Who is making the rules? Doesn't the Corps of Engineers have their own code that should be followed? This is kind of important cause it's their ball and their playing field. :roll: Note: May match the NEC most places, but does vary. For example, i understand the gound rod resistance is required to be 10 ohms - no give-me for an extra rod.
So, by the NEC/NESC, assuming the service point is ahead of the xfmr primary: A few of the sites I work are industrial installations where the service is HV from the utility. The HV disconnect is our's and that is the service. The transformer is ours.
That makes the transformer secondary a separately derived system. From there, the xfmr neutral can be grounded and bonded and five wires run to the 208 panel/switchboard - separate ground and neutral - and that meets NEC and I think is a good method.
If the transformer belonged to the utility, the practice, per the NESC, (note: not verified by me) is to ground and bond the neutral at the xfmr, four wires to the 208 panel/switchboard, with the neutral grounded and bonded again.
This also meets code (NESC and NEC). IMO this is not as good a method as the first. But it is the method used in every house in the US. (For the regimented, literal sorts, "Oddball exceptions noted."
So, what's not to like?
carl
- Status