Transfer Switch Non-Grouped Disconnect

[sunbelt1971]

Situation: (2) 200 amp & (1) 150 amp main breaker panels installed inside building (grouped together). (1) 600A Meter Can mounted outside (no disconnects).

Would like to install 200A transfer switch with internal disconnect outside by meter and intercept one of the conduits going from one of the 200 amp interior panels to the exterior meter can (this is run in the concrete slab).
We only want to backup one of the 200A panels (not the other two).

Now my concern with this is the requirement to group the disconnects in 230.72. Then when I look at 230.72(B) Add'l Service Disco Means: "the additional service disconnecting means for...optional standby services permitted by 230.2 shall be installed remote from the one to six service disconnecting means for normal service"

Thoughts?

 

[brother]

Situation: (2) 200 amp & (1) 150 amp main breaker panels installed inside building (grouped together). (1) 600A Meter Can mounted outside (no disconnects).

Would like to install 200A transfer switch with internal disconnect outside by meter and intercept one of the conduits going from one of the 200 amp interior panels to the exterior meter can (this is run in the concrete slab).
We only want to backup one of the 200A panels (not the other two).

Now my concern with this is the requirement to group the disconnects in 230.72. Then when I look at 230.72(B) Add'l Service Disco Means: "the additional service disconnecting means for...optional standby services permitted by 230.2 shall be installed remote from the one to six service disconnecting means for normal service"

Thoughts?

well from what i understand, the transfer switch is now the 'service' disconnect (it does have a means to disconnect the service right? and be sure its LISTED for a service), and now that 200 amp panel its feeding is the SUB PANEL and be sure the neutral and grounds are seperated.

Now to answer your question, I believe you do qualify for 230.72(B) since its an optional standby system. Be sure to double check the definition in 702. I say its ok, let others chime in.

 

[brother]

bump to the top. Hope to hear from others.

 

[tom baker]

What code are you under? In case I don't get back, the 08 NEC requires Art 702 generators to be able to pick up the entire calculated load per Art 220.
Your transfer switch needs to listed for service entrance use. Be very clear ahead of time on where the main bonding jumper(s) will be installed.
I don't like a transfer switch installed with no disconnect ahead of it, I have seen it done, sometimes its the only way

 

[brother]

What code are you under? In case I don't get back, the 08 NEC requires Art 702 generators to be able to pick up the entire calculated load per Art 220.

I just read this 2008 702, I was wondering was it really necessary to have this in there?? I mean, would not it just be common sense (for electricians)to be sure the generator can handle the load that you intend for it to supply????

 

[iwire]

What code are you under? In case I don't get back, the 08 NEC requires Art 702 generators to be able to pick up the entire calculated load per Art 220.

That only applies to Automatic transfer switches, it does not apply to manual transfer switches.

I just read this 2008 702, I was wondering was it really necessary to have this in there?? I mean, would not it just be common sense (for electricians)to be sure the generator can handle the load that you intend for it to supply????

IMO that section should never have gone in, it is very common to install a small home generator and have the homeowner pick and chose the load applied to it.

That can still be done with a manual set up but now if you decide to go 'full auto' you either have to size the entire setup for the entire calculated load or you have to place a separate panel with only certain loads and the generator has to be able to pick up that.

The fact is the NEC load calcs result in much larger figures then are really needed and this new rule is only another that helps manufacturers sell larger equipment.

 

[sunbelt1971]

Thank you all for your responses. The transfer switch with internal disconnect is service rated. And we are still on 05 code. The generator is 45KW.

 

[LarryFine]

That can still be done with a manual set up but now if you decide to go 'full auto' you either have to size the entire setup for the entire calculated load or you have to place a separate panel with only certain loads and the generator has to be able to pick up that.

What if you, say, equip your HVAC to drop out the compressor and/or strip-heat contactors during transfer? Does that allow eliminating those loads from the requirements?

 

[hillbilly1]

Load shedding can be done to meet this requirement, though I would think that you would have to add another service disconnect outside for the other panels to meet the grouping rule, unless special permission is given by AHJ. Make sure they know that it is an optional standby system, as an Emergency system opens up a whole 'nother can of worms.