Is a service rated ATS required?

[Coppersmith]

I have been asked to install the wiring for a 20Kw generator at a residence with a 320 amp service and two 150 amp MB panels back-to-back with meter. They are supplying two 200 amp non service rated ATS's.

If I insert an ATS between the meter and each panel, do the ATS's have to be service rated? I think I will be able to keep the feeders very short. My jurisdiction requires a main breaker by the meter if the feeder is more than 5 feet long. However, seems like I would need a service rated ATS just so I could simulate a power outtage for test purposes.

Secondly, Since the service is 320 amps, would 200 amp non service rated ATS's be OK? What if they were 200 amp service rated?

As an interesting aside, the UG conduit going into the meter can is 2" PVC. It's a 320 amp meter can, but I'm wondering if it's really being fed with a 320 amp service. I know the POCOs tend to undersize their wires, but I usually see 3" conduit for 320/400 amp services.

 

[texie]

To install as you describe, the ATSs would have to be service rated to comply with the NEC .Also the listing of the ATS would not allow this. You will also have to make the existing 150 amp MB panels sub panels. This will mean that you will need an EGC from the ATS to the panel, unbond the neutral, separate the neutrals/grounds in the panels, etc.
Making the ATS 200 amp does not change anything. If anything it will complicate things as your conductors may be to small.

 

[Coppersmith]

To install as you describe, the ATSs would have to be service rated to comply with the NEC

Can someone quote the section number? I haven't found the term service rated anywhere in the NEC.

 

[jumper]

Can someone quote the section number? I haven't found the term service rated anywhere in the NEC.

Prolly written as Suitable for Use as Service Equipment. SUSE

 

[Coppersmith]

Prolly written as Suitable for Use as Service Equipment. SUSE

I found a dozen places where that phrase exists none of which referring to ATS's

 

[wwhitney]

I found a dozen places where that phrase exists none of which referring to ATS's

How about this:

230.82 lists the equipment that is allowed to be installed on the supply side of the service disconnect. Transfer switches aren't listed. So if the a transfer switch is to be installed right after the meter, the transfer switch has to incorporate the service disconnect. 230.70 says the service disconnect has to be "suitable for use".

Cheers, Wayne

 

[Coppersmith]

Ok, I may have found an applicable section:

230.82 Equipment Connected to the Supply Side of Service
Disconnect. Only the following equipment shall be
permitted to be connected to the supply side of the service
disconnecting means...

Since the main breaker is in the panel and I want to put the non-service rated ATS ahead of the MB I think 230.82 applies and says I can't. Can somebody confirm?

ETA: Thanks Wayne, I posted at the same time as you

 

[texie]

I found a dozen places where that phrase exists none of which referring to ATS's

Take a look at the UL Product Spec for transfer switches here: http://productspec.ul.com/document.php?id=WPTZ.GuideInfo
See if this helps you to better understand.

 

[Coppersmith]

Take a look at the UL Product Spec for transfer switches here: http://productspec.ul.com/document.php?id=WPTZ.GuideInfo
See if this helps you to better understand.

Interesting thanks.

"Transfer switches are intended for use with copper conductors unless marked to indicate which terminals are suitable for use with aluminum conductors. Such marking is independent of any marking on terminal connectors and is indicated on a wiring diagram or other readily visible location."