230.72(b) service rated transfer switch

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ShauwnC

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Fairfax virginia
We have a job with a 400 amp twin service ( two 200 amp main breaker panels ).
We installed a 20kw generator with a 200amp service rated ats. The inspector rejected the job quoting article 230.72(a) grouping of disconnects. I have spoken to the inspector quoting 230.72(b). I am having difficulty understanding the wording and intent of 230.72(b) and if I am in the right here. The inspector is saying that I have to either install a disconnect on the "non emergency" panel or move the transfer switch inside. I want to know if I am covered by 230.72(b) as both panels have main breakers. Please help.
 
ShauwnC said:
We have a job with a 400 amp twin service ( two 200 amp main breaker panels ).
We installed a 20kw generator with a 200amp service rated ats. The inspector rejected the job quoting article 230.72(a) grouping of disconnects. I have spoken to the inspector quoting 230.72(b). I am having difficulty understanding the wording and intent of 230.72(b) and if I am in the right here. The inspector is saying that I have to either install a disconnect on the "non emergency" panel or move the transfer switch inside. I want to know if I am covered by 230.72(b) as both panels have main breakers. Please help.
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Two services and one is an emergency only?
 
ShauwnC said:
We have a job with a 400 amp twin service ( two 200 amp main breaker panels ).
We installed a 20kw generator with a 200amp service rated ats. The inspector rejected the job quoting article 230.72(a) grouping of disconnects. I have spoken to the inspector quoting 230.72(b). I am having difficulty understanding the wording and intent of 230.72(b) and if I am in the right here. The inspector is saying that I have to either install a disconnect on the "non emergency" panel or move the transfer switch inside. I want to know if I am covered by 230.72(b) as both panels have main breakers. Please help.
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Based on your description, I'll assume this is a residential Optional Standby System, Art 702.

I think the inspector is correct. While 230.72(B) covers Optional Standby Services, I think this would only apply to a separate service being used as a standby service, not an on premises generator. Your service rated ATS is carrying the normal service not just the generator.

Maybe an option to fix this would be to add a 200 disconnect outside for the other panel. Then both discos would be grouped and would be your new service disconnecting point. Just remove the N/G bond on the existing inside panels and make sure you have a EG path compliant with 250.122 from the mains to the (now) subpanels, as you should have already done on the standby panel.

Let's see what others say.
 
To me, the breaker at the generator or the breaker at the structure that disconnects the generator power would be the one that is allowed to be in a remote location per 230.72(b). The breakers that actually disconnect the utility service would need to be grouped per 230.72(a).
Afraid I agree with you inspector.
 
I think the optional standby service disconnect located in the outdoor service rated transfer switch meets the rule in 230.72(B). The 200 amp main breaker panel fed from the ATS is now a feeder panel. So there is one main service disconnect inside and one additional service disconnect located in the outdoor ATS.
 
augie47 said:
To me, the breaker at the generator or the breaker at the structure that disconnects the generator power would be the one that is allowed to be in a remote location per 230.72(b). The breakers that actually disconnect the utility service would need to be grouped per 230.72(a).
Afraid I agree with you inspector.
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We came to the same conclusion, but I think you said it better. 230.72(B) would apply as you described or if the optional standby was actually another service.
 
The main breaker for the optional supply is a separate service not. Does it matter if it has a separate meter or off the same.
 
augie47 said:
To me, the breaker at the generator or the breaker at the structure that disconnects the generator power would be the one that is allowed to be in a remote location per 230.72(b). The breakers that actually disconnect the utility service would need to be grouped per 230.72(a).
Afraid I agree with you inspector.
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If the meter has double lugs and you ran each panel of off it's own set of lugs, you wouldn't have to group the disconnects. If this is the case, the conductors would be SE conductors and not feeders. You can do this at a dwelling with a detached garage or other building. One set of SE conductors to the dwelling and one set to the garage. I think this is exception 3 of 230.40.

If this is the case with the OP, one of the panels could be located remotely and not have to be grouped.
I will admit I don't know how the ATS (service rated) would come into play with the exception though.
 
I'll try again... IMO...You have one service supplying a building. You have two service disconnects. 230.72(a) states you need to group those disconnects.
If you have an emergency supply, be it another service or a feeder from a generator, etc you can, and in some cases must, locate the emergency supply disconnect at a separate location. His service rated ATS is one of his service disconnects and must meet 230.72(a). The generator supply overcurrent can be located elsewhere,
 
The part where this gets tricky for me is that in 270.72(b) towards the end of the article it says shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply . Now if my two residential panels both have main breakers and the automatic transfer panel has a main breaker ( it also simulates an outage if the breaker is off in the ATS and generator fires up ) why would you need two disconnects next to each other for one panel ? I understand the intent of grouping of disconnects however under this logic , any sub panel with a main breaker remote from the two main panels would have to have a disconnect instead of a main breaker .
 
ShauwnC said:
The part where this gets tricky for me is that in 270.72(b) towards the end of the article it says shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply . Now if my two residential panels both have main breakers and the automatic transfer panel has a main breaker ( it also simulates an outage if the breaker is off in the ATS and generator fires up ) why would you need two disconnects next to each other for one panel ? I understand the intent of grouping of disconnects however under this logic , any sub panel with a main breaker remote from the two main panels would have to have a disconnect instead of a main breaker .
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230.72 Grouping of Disconnects. (A) General. The two to six disconnects as permitted in 230.71 shall be grouped. Each disconnect shall be marked to indicate the load served.


Exception: One of the two to six service disconnecting means permitted in 230.71, where used only for a water pump also intended to provide fire protection, shall be permitted to be located remote from the other disconnecting means. If remotely installed in accordance with this exception, a plaque shall be posted at the location of the remaining grouped disconnects denoting its location.
(B) Additional Service Disconnecting Means. The one or more additional service disconnecting means for fire pumps, emergency systems, legally required standby, or optional standby services permitted by 230.2 shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply.
230.2 Number of Services. A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D). For the purpose of 230.40,
Exception No. 2 only, underground sets of conductors, 1/0 AWG and larger, running to the same location and connected together at their supply end but not connected together at their load end shall be considered to be supplying one service
(A) Special Conditions. Additional services shall be permitted to supply the following: (1)
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Fire pumps


(2)
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Emergency systems


(3)
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Legally required standby systems


(4)
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Optional standby systems


(5)
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Parallel power production systems




Your application does not fit any of the special conditions for 230.2
 
Remote control switch to disable the generator.

Remote control switch to disable the generator.

I don't know what your system looks like, but I have similar situation where I am proposing to use a remote control switch wired to the Automatic Transfer Switch (ATS) to disable the generator. Will your inspector allow this?
Sometimes other juristictions such as the Fire Department have more stringent requirements than the code (That's my situation). You don't want a Fireman to throw the disconnect and start the generator.
All you need is two wires and a big red mushroom head button labelled as such. I am considering using a small disconnect switch that looks like the rest so there is no confusion. Does anyone else have any comments about this.
 
clarified !

clarified !

Gregg Harris said:
230.72 Grouping of Disconnects. (A) General. The two to six disconnects as permitted in 230.71 shall be grouped. Each disconnect shall be marked to indicate the load served.


Exception: One of the two to six service disconnecting means permitted in 230.71, where used only for a water pump also intended to provide fire protection, shall be permitted to be located remote from the other disconnecting means. If remotely installed in accordance with this exception, a plaque shall be posted at the location of the remaining grouped disconnects denoting its location.
(B) Additional Service Disconnecting Means. The one or more additional service disconnecting means for fire pumps, emergency systems, legally required standby, or optional standby services permitted by 230.2 shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply.
230.2 Number of Services. A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D). For the purpose of 230.40,
Exception No. 2 only, underground sets of conductors, 1/0 AWG and larger, running to the same location and connected together at their supply end but not connected together at their load end shall be considered to be supplying one service
(A) Special Conditions. Additional services shall be permitted to supply the following: (1)
spacer.gif
Fire pumps


(2)
spacer.gif
Emergency systems


(3)
spacer.gif
Legally required standby systems


(4)
spacer.gif
Optional standby systems


(5)
spacer.gif
Parallel power production systems




Your application does not fit any of the special conditions for 230.2
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Thanks for the response this helps to clarify this situation and these articles .
 
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