[ranger12]

I have 400 amp service to my house. At the meter base, this is divided into 2 200amp subpanels. One is for the detached shop, and the other for the house (passing thru a Generac whole-house transfer switch.

What I would like to do, and I believe to be permitted under NEC 225.30(A)(3), is to, in addition to the 125 amp service to the shop, run a 15 amp circuit, 12-2 UF-B to the shop, that comes off of that panel serviced by the backup generator. This would come under the exception of "optional standby systems".

This would be to supply power to a single outlet supplying the alarm system controller and video camera system, that would be backed up by the automatic generator.

If I read it right, all that is required is a disconnect of the secondary feed, and proper labeling and documentation of such.

Number of supplies

If more than one building or other structure is on the same property, each building/structure must be served by no more than one feeder or single or multiwire branch circuit [225.30]. However, there are five exceptions to this. You can have additional supplies for:

1. Special conditions [225.30(A)]. These are:

• Fire pumps.

• Emergency systems.

• Legally required standby systems.

• Optional standby systems.

• Parallel power production systems.

• Systems designed for connection to multiple sources of supply for the purpose of enhanced reliability.

2. Special occupancies. Multiple-occupancy buildings where there’s no available space for supply equipment accessible to all occupants, or a building/structure so large that two or more supplies are necessary — but only with special permission [225.30(B)].

3. Capacity requirements. Where the capacity requirements exceed 2,000A [225.30(C)].

4. Different characteristics. Different voltages, frequencies, or uses, such as control of outside lighting from multiple locations [225.30(D)].

5. Documented switching procedures. Additional supplies are permitted where documented safe switching procedures are established and maintained for disconnection [225.30(E)].

Right or wrong??

 

[ranger12]

Google finally found me something. This (from 2010) seems to support the plan:

https://forums.mikeholt.com/threads/nec-210-25-and-nec-225-30-a-3.74503/

 

[surferdude2]

<quote> I believe to be permitted under NEC 225.30(A)(3)</quote>

Perhaps you meant (1). I don't see a problem. Draw it up and submit it for plan check and permit. A simple single line hand drawn plan showing all devices and notes you may want to include will usually do for small jobs like this.

I did a similar job for a computer POS and security system that was derived from the main business to an annex building. I provided a surface mounted wall switch with a permanently attached sign beside it since it was a retrofit job. It was required to be a metal sign and mounted with tamper proof screws with spanner hole heads. Your inspector may not be that particular.

 

[Jim Port]

I don't your plan meets any of the criteria to allow your plan.

 

[ranger12]

I don't your plan meets any of the criteria to allow your plan.

The criteria is vague....

702.2 Definition.
Optional Standby Systems. Those systems intended to supply power to public or private facilities or property where life safety does not depend on the performance of the system. Optional standby systems are intended to supply on-site generated power to selected loads either automatically or manually.
FPN: Optional standby systems are typically installed to provide an alternate source of electric power for such facilities as industrial and commercial buildings, farms, and residences and to serve loads such as heating and refrigeration systems, data processing and communications systems, and industrial processes that, when stopped during any power outage, could cause discomfort, serious interruption of the process, damage to the product or process, or the like.

"typically installed"
"for such facilities as"
"or the like"

Reads to me like the end-user gets to define what is worthy of meeting code, not the code itself.

 

[Oldmaster]

Why not install the circuit from the main house panel since it's already on the generator?

 

[Fishbulb28]

If I read it right, all that is required is a disconnect of the secondary feed, and proper labeling and documentation of such.

Both disconnects would also need to be appropriately grouped. Other than that there would be no regulatory problem with your plan.

There is a practical one, though. Is this going to have the same 475' run as in your other thread? If so, even with #12 you're going to end up with a completely useless circuit due to voltage drop.

This would be to supply power to a single outlet supplying the alarm system controller and video camera system, that would be backed up by the automatic generator.

A substantial UPS would run such a small load for quite a long time and would cost considerably less than a 500' roll of UF.