Multiple Optonal Standby Generators to Single Family Residence

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Leo1

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Los Alamos, NM
Does the NEC allows multiple optional standby generators to feed a single family residence? The residence currently has two main disconnects on the outside of the home. One is a single phase 120/240VAC, 400AMP main disconnect feeding a 400 AMP panel-board on the inside of the residence. The second main disconnect on the outside of the residence is a 200 AMP, single phase 120/240VAC feeding a 200 AMP panel-board on the inside of the the residence. (The 400 AMP and 200 AMP disconnects are grouped within one foot of each other.)

I know multiple services to structures are limited to per 230.2, do the conditions of number of services in 230.2 apply to multiple optional standby generators? The use of two generators will avoid the need to upgrade the 400 AMP and 200 AMP disconnects to a single 600 AMP service and the associated service lateral and feeders.
 
To start with, I think this is already a violation of 230.2. A building is only allowed one service, unless you meet one of the conditions listed in this article. I don't believe any of those conditions apply.

Now I was about to say that you can only have one service from an optional standby generator, and I do believe that is the code's intent. Then I read 230.2(A)(4), and noticed its use of the plural word, "systems." I see that this can be interpreted as allowing more than one generator. So you may have to get the AHJ to weigh in on this question. Please be aware, however, that the AHJ just might call the existing installation into question.
 
charlie b said:
To start with, I think this is already a violation of 230.2. A building is only allowed one service, unless you meet one of the conditions listed in this article. I don't believe any of those conditions apply.

Now I was about to say that you can only have one service from an optional standby generator, and I do believe that is the code's intent. Then I read 230.2(A)(4), and noticed its use of the plural word, "systems." I see that this can be interpreted as allowing more than one generator. So you may have to get the AHJ to weigh in on this question. Please be aware, however, that the AHJ just might call the existing installation into question.
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The residence is feed from one utility service with a single transformer that is double tapped with service laterals to the 400 AMP main disconnect and the 200 main disconnect both are next to each other on the outside of the residence. I think the two safety switches are OK, the residential main service disconnect handles do not exceed six handles and are group together being feed from a single transformer from a single utility service. Thank you for the review.
 
shortcircuit2 said:
I worked on a job the had three 20KW generators backfeeding 1 dwelling.
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Thank you for the input. Likewise I have seen multiple generators serving the same building but they were parallel feeds into a single large main disconnect and ATS. In the project above the owner and contractor plan to install two small gen sets with ATSs with one each to the existing 400AMP and 200AMP main disconnects instead of one large 600 AMP system. The larger single gen set along with the service rework to a single 600 AMP service likely cost more than the two small units under consideration.
 
JFletcher said:
Three panels or were they paralleled/synchronized?
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The dwelling had one 400-amp service and there were 3 transfer switches to separate panels with different loads distributed to different areas of the dwelling.

1 generator was backup for the solar with battery storage backup via an Outback Power System.
2 other generators were for different loads given there nature of importance. These 2 gen-sets were wired so the owner could start them when needed.

Set up this way with 3 gen-sets, fuel consumption could be extended for longer periods because you would not be running one larger 60KW generator all the time for power.
 
shortcircuit2 said:
The dwelling had one 400-amp service and there were 3 transfer switches to separate panels with different loads distributed to different areas of the dwelling.

1 generator was backup for the solar with battery storage backup via an Outback Power System.
2 other generators were for different loads given there nature of importance. These 2 gen-sets were wired so the owner could start them when needed.

Set up this way with 3 gen-sets, fuel consumption could be extended for longer periods because you would not be running one larger 60KW generator all the time for power.
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Was the one connected to the Outback system set up for autostart? And was the Outback configured for "generator support" so that generator and battery inverter could run at the same time?
 
I recently did a standby generator installation for a family with a disabled child. I installed 2 (8kw) Generac units. The load isn't so much the factor as the necessity to have backup power is. There are multiple pieces of medical equipment that are essential to the life of the child, which have battery backup but not for long. I described what I was doing to the building inspector and then the electrical inspection service. Both had no problems with the installation given the circumstances. I ended up having to split the main panel into 2 panels and have each generator feed their respective transfer switch. Which in turn backed up specific circuits within each panel. The most critical circuit in the living room , has a 2 20a receptacles fed from each panel.

Sent from my VS987 using Tapatalk
 
GoldDigger said:
Was the one connected to the Outback system set up for autostart? And was the Outback configured for "generator support" so that generator and battery inverter could run at the same time?
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I recall the generator for the Outback System was backup if the battery system drained down. Just like an off grid setup but this Solar was also grid tied for credits. The system was setup with enough onsite fuel for more than 3 months...Doomsday setup.
 
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