Service neutral bonding location

[kmh]

Pitkin County in Colorado requires construction of residential services over 400 A to be designed and stamped by a P.E. Also, the utility requires a hot sequence meter socket with associated disconnect switch within 2 feet of the meter. For the disconnect switches the electrical contractor wanted 800 A gear with 2 circuit breakers and a CT enclosure for the meter. He also had two fused disconnects at the house 200 ft away from the meter, which my 1-line drawing showed as the service disconnects. The AHJ ruled that the service disconnects needed to be the 2 circuit breakers at the meter, based on their interpretation of 250.30. Therefore they wanted the GEC to be run 200 ft to the meter/disconnect gear before bonding to the neutral.
I pointed out that 250.30 only applies to separately derived systems, of which services were explicitly excluded per Article 100 Definitions. I also stated it was poor engineering practice to run a GEC 200 ft before ground fault current was returned to the neutral. However, they refused to listen to me as they had already made their decision.
Any opinions of the AHJ ruling?

 

[gaelectric]

I would seem like a grounding electrode system at the meter. IE: two ground rods. Two 4 wire feeders to the house. Water pipe and ufer at the house to equipment ground bar in the house panels. I've done one similar and done it in this fashion.

Edit. Actually we used a 400 amp 320 amp continuous meter and did not do a true 400 amp service with the CT's and primary metering. No cold sequence was required that way.

 

[gaelectric]

Reading closer. This was actually an 800 amp service for a house? Must be quite the place.

 

[Dale001289]

Pitkin County in Colorado requires construction of residential services over 400 A to be designed and stamped by a P.E. Also, the utility requires a hot sequence meter socket with associated disconnect switch within 2 feet of the meter. For the disconnect switches the electrical contractor wanted 800 A gear with 2 circuit breakers and a CT enclosure for the meter. He also had two fused disconnects at the house 200 ft away from the meter, which my 1-line drawing showed as the service disconnects. The AHJ ruled that the service disconnects needed to be the 2 circuit breakers at the meter, based on their interpretation of 250.30. Therefore they wanted the GEC to be run 200 ft to the meter/disconnect gear before bonding to the neutral.
I pointed out that 250.30 only applies to separately derived systems, of which services were explicitly excluded per Article 100 Definitions. I also stated it was poor engineering practice to run a GEC 200 ft before ground fault current was returned to the neutral. However, they refused to listen to me as they had already made their decision.
Any opinions of the AHJ ruling?

Since your AHJ is obviously confused why not use 250.30 to your advantage? Tell him per 250.30(A)(5) the system bonding jumper, grounded conductor (i.e. neutral) and GEC are to be bonded taking the least impedance (shortest) path to the electrode system, which is at the disconnects - not at the meter.

 

[kmh]

Mike Holt responded to this

Mike Holt responded to this

Since your AHJ is obviously confused why not use 250.30 to your advantage? Tell him per 250.30(A)(5) the system bonding jumper, grounded conductor (i.e. neutral) and GEC are to be bonded taking the least impedance (shortest) path to the electrode system, which is at the disconnects - not at the meter.

I'm honored that I just received a phone call from Mike Holt. He told me the AHJ is correct. The two 200A breakers at the meter (meter disconnects required by utility) are the service disconnects that protect the feeders to the house. He said use 250.24 and 250.32 in this case.
Yes, he agreed the 800 A gear at the meter sounds like overkill. But this is Aspen, Colorado.
My 4th conductor from the meter/disconnects to the house disconnects (which really aren't needed) is therefore an equipment grounding conductor, not a GEC.
I suspect if the contractor had only wanted non-fused disconnects at the meter, which is all the utility requires, which would not protect the conductors, I could have used the fused disconnects at the house as service disconnects.

 

[kwired]

Is this meter and disconnect you are talking about in or on the house? You mention running GEC 200 feet to get to it, does that mean it is on a pole or other structure 200 feet away?

If so that may or may not be considered the service disconnect, but if separate structure then the house, you don't need to run GEC to other structure. The house would be supplied by an Art 225 feeder part II feeder, and would need it's own disconnect where the feeder at or near the entrance to the structure as well as have it's own grounding electrode system - which would connect to the Equipment grounding conductor instead of a grounded service conductor in that situation.

If the disconnect is for POCO use only and especially if they would lock it or otherwise make overcurrent protection non accessible - it is not the service disconnecting means. In such cases POCO usually specifies non fused switch for such a disconnect. They don't want to give customer easy access to non metered conductors, and should it be fused - that means they get called out if the fuse blows because they will have a lock or seal on it. They would rather have a primary fuse on the transformer blow instead of having something on the secondary that is their responsibility to service.

 

[kmh]

Is this meter and disconnect you are talking about in or on the house? You mention running GEC 200 feet to get to it, does that mean it is on a pole or other structure 200 feet away?

If so that may or may not be considered the service disconnect, but if separate structure then the house, you don't need to run GEC to other structure. The house would be supplied by an Art 225 feeder part II feeder, and would need it's own disconnect where the feeder at or near the entrance to the structure as well as have it's own grounding electrode system - which would connect to the Equipment grounding conductor instead of a grounded service conductor in that situation.

If the disconnect is for POCO use only and especially if they would lock it or otherwise make overcurrent protection non accessible - it is not the service disconnecting means. In such cases POCO usually specifies non fused switch for such a disconnect. They don't want to give customer easy access to non metered conductors, and should it be fused - that means they get called out if the fuse blows because they will have a lock or seal on it. They would rather have a primary fuse on the transformer blow instead of having something on the secondary that is their responsibility to service.

The meter and disconnects are pad mounted 200 ft away from the house. The disconnects (I don't know why the contractor wanted 2 disconnects) are required by the POCO within 2 ft of their meter and they don't need to be fused or MCCB's. The POCO does not care if anyone else has access to the disconnects.

 

[kwired]

The meter and disconnects are pad mounted 200 ft away from the house. The disconnects (I don't know why the contractor wanted 2 disconnects) are required by the POCO within 2 ft of their meter and they don't need to be fused or MCCB's. The POCO does not care if anyone else has access to the disconnects.

If we are calling said disconnects the service disconnecting means - which they very easily could be if they contain overcurrent protection, then you have a violation of 225.30 if both feeders supply the house. Your AHJ apparently missed that and doesn't understand 250 part II and III very well either. You said they cited 250.30 - but that covers grounding of separately derived systems - which so far you haven't described having one. Your inspector does need to read 250.32 - it very much applies to what you have described.

 

[kmh]

If we are calling said disconnects the service disconnecting means - which they very easily could be if they contain overcurrent protection, then you have a violation of 225.30 if both feeders supply the house. Your AHJ apparently missed that and doesn't understand 250 part II and III very well either. You said they cited 250.30 - but that covers grounding of separately derived systems - which so far you haven't described having one. Your inspector does need to read 250.32 - it very much applies to what you have described.

Very good point on 225.30. Even Mike Holt overlooked that one. I'll have to ask the EC why he wanted two feeders from the meter disconnect, though at the time we didn't consider those feeders but instead as service laterals.
The AHJ did not respond to the misuse of 250.30 - there is no separately derived system a this residence.

 

[kwired]

Very good point on 225.30. Even Mike Holt overlooked that one. I'll have to ask the EC why he wanted two feeders from the meter disconnect, though at the time we didn't consider those feeders but instead as service laterals.
The AHJ did not respond to the misuse of 250.30 - there is no separately derived system a this residence.

Some places (and where I am is one of them) if that meter/disconnect is provided and maintained by POCO - we still consider what leaves them to be service conductors - partly because POCO's can and have changed them out at later time to something without overcurrent protection. So even if you are considering the conductors in question as service laterals - nothing would require the grounding electrode conductor of your building to go beyond the building itself. You use any electrodes that are present at the building - not at a structure that is 200 feet away.

 

[kmh]

Some places (and where I am is one of them) if that meter/disconnect is provided and maintained by POCO - we still consider what leaves them to be service conductors - partly because POCO's can and have changed them out at later time to something without overcurrent protection. So even if you are considering the conductors in question as service laterals - nothing would require the grounding electrode conductor of your building to go beyond the building itself. You use any electrodes that are present at the building - not at a structure that is 200 feet away.

I couldn't agree with you more. I have done other houses in the Aspen area where the meter was remote from the house and the meter disconnect was not the service disconnect, hence the GEC did not go beyond the building.
The POCO does not own the disconnect. The POCO only requires there be a disconnect within 2 feet of their meter.
The reason the EC used two 200 A breakers instead of one 400 A in the MDP is it's cheaper. And the reason he used 800 A MDP at the meter is the owner will have other buildings later on this property. The house next door to this has the exact same equipment, though the EC does not know where they grounded their neutrals.

 

[kwired]

I couldn't agree with you more. I have done other houses in the Aspen area where the meter was remote from the house and the meter disconnect was not the service disconnect, hence the GEC did not go beyond the building.
The POCO does not own the disconnect. The POCO only requires there be a disconnect within 2 feet of their meter.
The reason the EC used two 200 A breakers instead of one 400 A in the MDP is it's cheaper. And the reason he used 800 A MDP at the meter is the owner will have other buildings later on this property. The house next door to this has the exact same equipment, though the EC does not know where they grounded their neutrals.

Cheaper doesn't make it code compliant. Sounds like that MDP is definitely the service disconnecting means, is a separate structure from the house, and any future buildings, and two feeders to the house would violate art 225.30. The MDP structure needs it's own grounding electrode system and so does the house.

Your inspector needs to go to school or hang out here.

 

[kmh]

Cheaper doesn't make it code compliant. Sounds like that MDP is definitely the service disconnecting means, is a separate structure from the house, and any future buildings, and two feeders to the house would violate art 225.30. The MDP structure needs it's own grounding electrode system and so does the house.

Your inspector needs to go to school or hang out here.

The MDP will be the service disconnect since the AHJ will not back down on that. Both the MDP and house will have their own grounding systems. I suppose it could be argued that 225.30(B)(2) exception would apply with respect to two feeders to the house, as this is a very large residence. And as I mentioned before, the house next door has the same configuration and that was approved by the same AHJ.
The EC (my client) has asked me not to apply 225.30. The equipment is already on site and he is under pressure to get this done. He's the one that pointed out the precedent next door and would like to leave it up to the AHJ.

 

[Dale001289]

Cheaper doesn't make it code compliant. Sounds like that MDP is definitely the service disconnecting means, is a separate structure from the house, and any future buildings, and two feeders to the house would violate art 225.30. The MDP structure needs it's own grounding electrode system and so does the house.

Your inspector needs to go to school or hang out here.

The inspector doesn't need to go to school....he just needs to join the Forum

 

[jap]

If they truly want the 800 amp gear with breakers in it, and, it has to be within 2 foot of the CT meter, and, they want a 400 amp service to the house, then, by rights they should install a 400 amp breaker in the MDP and (1) 400 amp feeder to the house which would require an EGC to be pulled with the 400 amp feeder conductors to the house.

How they separate it at the house with taps and fused disconnects (If any) is a different story.

You have to make the decision of whether the conductors to the house are service conductors or feeder conductors before you can make the decision of how they need to be installed.

The customer is providing the 800 amp gear and the subfeed breakers, not the power company,which makes this a feeder scenario to the house, not a service lateral.

JAP>

 

[jap]

The MDP will be the service disconnect since the AHJ will not back down on that.

The AHJ is considering the MDP as the service disconnect, and , the first means of overload protection.

Otherwise he would not be requiring you to install (The 4th wire) or EGC to the house.

JAP>

 

[jap]

I also stated it was poor engineering practice to run a GEC 200 ft before ground fault current was returned to the neutral.

The AHJ is talking about an Equipment Grounding Conductor (EGC) being run with the feeder, not a Grounding Electrode Conductor (GEC).

The GEC serves no purpose to clear a fault.

JAP>

 

[Dale001289]

The AHJ is talking about an Equipment Grounding Conductor (EGC) being run with the feeder, not a Grounding Electrode Conductor (GEC).

The GEC serves no purpose to clear a fault.

JAP>

Granted the EGC is the primary fault path (ref 250.134), but saying the GEC serves no purpose to clear a fault is a bit of a stretch. What about a lightning strike to earth? What about a fault to the equipotential grid?

 

[jap]

Granted the EGC is the primary fault path (ref 250.134), but saying the GEC serves no purpose to clear a fault is a bit of a stretch. What about a lightning strike to earth? What about a fault to the equipotential grid?

What fault does GEC clear in a lightning strike?
What fault does and equipotential grid clear ?

Answer: Neither

In a lightning strike it only disperses, and , an Equipotential grid does not clear a fault either. It only keeps everything at the same potential.


JAP>

 

[Dale001289]

What fault does GEC clear in a lightning strike?
What fault does and equipotential grid clear ?

Answer: Neither

In a lightning strike it only disperses, and , an Equipotential grid does not clear a fault either. It only keeps everything at the same potential.


JAP>

Whether to the earth or to the grid, fault path will seek all resistances - but back to the Xfmr (via the GEC) will be the least resistance path for solidly grounded Wye systems which is usually around 1 ohm or less. If you have a High Resistance Ground on the Delta-Wye Xfmr that's a different story.