Service entrance conductor overcurrent protection

[SHB]

120/240 volt single phase service. A 6-unit apartment building has a calculated demand of 250 amperes. House meter plus 6 units - 7 meters each with a 100 ampere disconnect.
Contractor ran 350 kcmil aluminum in conduit from weather head to meter cabinet.

The 350 kcmil aluminum conductors terminate at an 800 ampere disconnect. Allowable ampacity of these conductors is 250 amperes in the 75 degree column.

I believe this is a violation and cited 2014 NEC section 230.42(B). The contractor is insisting that this arrangement is permissible. Am I missing something? The commentary in the handbook following section 230.80 reads "A single overcurrent device must have a rating or setting that is not higher than the allowable ampacity of the service conductors."


Thank you for any help.

 

[charlie b]

I believe the contractor is right. The article you cited does not say that the conductors must have an ampacity at least as high as the service disconnect that you happened to choose to install. The article refers you to 230.79(B). That article tells you the minimum rating for the service disconnect. If you choose to install a service disconnect that is rated higher than the minimum, nothing requires you to install conductors that match that higher rating.

Welcome to the forum.

 

[charlie b]

The commentary in the handbook following section 230.80 reads "A single overcurrent device must have a rating or setting that is not higher than the allowable ampacity of the service conductors."

Don't confuse the requirement for a service disconnecting means with the requirement for providing overcurrent protection. You mentioned an 800 amp disconnect, but did not tell us whether it was fused, nor the rating of its fuses, nor whether the 7 individual 100 amp disconnects for the tenants and the house panel were fused. You will have to add some detail, in order for us to address the issue of overcurrent protection.

 

[don_resqcapt19]

230.90(A) is the section that requires the service overcurrent protective device to have a rating equal to or less than the ampacity of the conductors. If the disconnect does not contain an overcurrent protective device and if the seven 100 amp disconnects contain overcurrent protective devices, the installation is compliant per Exception #3 to 230.90(A).

Note that if the disconnect is a non-fusible disconnect, there may be a fault current issue....I don't think that there are any non-fusible disconnects with a SCCR rating of above 10,000 amps.

 

[david]

230.90(A) is the section that requires the service overcurrent protective device to have a rating equal to or less than the ampacity of the conductors. If the disconnect does not contain an overcurrent protective device and if the seven 100 amp disconnects contain overcurrent protective devices, the installation is compliant per Exception #3 to 230.90(A).

Note that if the disconnect is a non-fusible disconnect, there may be a fault current issue....I don't think that there are any non-fusible disconnects with a SCCR rating of above 10,000 amps.

Doesn't exception #3 say two to six overcurrent devices, the Op indicated 7

 

[don_resqcapt19]

Doesn't exception #3 say two to six overcurrent devices, the Op indicated 7

Good point. I guess that is really why there is a main in the first place.

 

[SHB]

Disconnect is an 800 ampere circuit breaker, non-adjustable. No fuses. 7 individual disconnects are 100 ampere breakers.

I believe the reference to 230.79(B) is not permission to protect 250 kcmil aluminum service conductors at 800 amperes. It seems to point to the minimum required capacity of specific occupancies.

The reference to 230.90(A) seems to only reinforce my position for overcurrent protection when the service conductors terminate at one overcurrent device. Without the 800 ampere breaker, there would be 7 disconnect switches which is not permitted.

 

[charlie b]

I believe this is a violation and cited 2014 NEC section 230.42(B).

There is no violation of 230.42(B) in this installation.

I believe the reference to 230.79(B) is not permission to protect 250 kcmil aluminum service conductors at 800 amperes. It seems to point to the minimum required capacity of specific occupancies.

Here again, 230.79(B) has nothing to do with overcurrent protection. It is all about the ability of the disconnecting means to handle the current that might be imposed upon it. That is a component rating, not an overcurrent protection rating.

Disconnect is an 800 ampere circuit breaker, non-adjustable. No fuses. . . The reference to 230.90(A) seems to only reinforce my position for overcurrent protection when the service conductors terminate at one overcurrent device.

So what you need to do is to cite 230.90(A) as the basis for the violation.

 

[david]

I believe this is a violation and cited 2014 NEC section 230.42(B). The contractor is insisting that this arrangement is permissible. Am I missing something? The commentary in the handbook following section 230.80 reads "A single overcurrent device must have a rating or setting that is not higher than the allowable ampacity of the service conductors."Thank you for any help.

you are correct in that, the over current exceeds the ampacity of the service conductors and is in violation of 230.90 (A) NFPA 70 / 2008

PA is under the Uniformed construction code the current reference is the 2009 IBC which the 2008 NEC is the reference in the that cycle.

So if we are under the 2008 NEC why are you referencing the 2014 NEC as a violation?

 

[SHB]

Thank you all for the clarification. I was originally pretty confident that the 250 aluminum going to the 800 ampere breaker was a violation but the contractor was extremely agitated and persistent in his assertion that this was permitted. I started to believe I was missing something but he refused to show me anything in the code book that would back up his view.

David, you are of course correct that we in PA are still using the 2008 NEC along with the 2009 ICC code books. Thank you for making that distinction. My references to the contractor are from the 2008 book.

 

[GoldDigger]

230.90(A) is the section that requires the service overcurrent protective device to have a rating equal to or less than the ampacity of the conductors. If the disconnect does not contain an overcurrent protective device and if the seven 100 amp disconnects contain overcurrent protective devices, the installation is compliant per Exception #3 to 230.90(A).

Note that if the disconnect is a non-fusible disconnect, there may be a fault current issue....I don't think that there are any non-fusible disconnects with a SCCR rating of above 10,000 amps.

POCO conductors (on the POCO side of the service point) need not be sized according to the NEC even if they are purchased and installed by the customer. You know where the service disconnect is, but that is not necessarily the service point.

 

[don_resqcapt19]

POCO conductors (on the POCO side of the service point) need not be sized according to the NEC even if they are purchased and installed by the customer. You know where the service disconnect is, but that is not necessarily the service point.

I would be very rare for the service point to be at the line side terminations of the disconnect for an overhead service. Around here, the service point would be at the transformer connections on the utility pole for that service.

 

[GoldDigger]

I would be very rare for the service point to be at the line side terminations of the disconnect for an overhead service. Around here, the service point would be at the transformer connections on the utility pole for that service.

I have seen members describe connections where the service point was the splices at the weatherhead.
I am sure this varies by area, since neither NEC nor NESC specify the location. Best for the OP to confirm with his own POCO before spending a lot of money.

 

[iwire]

I have seen members describe connections where the service point was the splices at the weatherhead.
I am sure this varies by area, since neither NEC nor NESC specify the location. Best for the OP to confirm with his own POCO before spending a lot of money.

As you say it varies but for me here in general for an overhead it is at the weatherhead.

For underground it could be the line side of the meter socket or with larger services at transformer.