UL listing for replacing equipment in existing gear

[Mr. Pickle]

I have a scenario where the Client has a 30 or so year old switchgear lineup. Inside this lineup is an original ATS which recently has been having issues. Client would like to change out the ATS with a new one. Being the new ATS will have a UL listing, does the installation inside the switchgear need to be UL tested (meaning a UL sticker put on the switchgear cabinet where the old ATS is being removed and a new ATS is being mounted in) . If yes, this would need to be performed by a 3rd party certifier. Also if yes, why?

 

[petersonra]

does the installation inside the switchgear need to be UL tested (meaning a UL sticker put on the switchgear cabinet where the old ATS is being removed and a new ATS is being mounted in)

I doubt anyone here can answer that question.

You probably need to ask this question of the AHJ before you get a permit for this work.

It might be easier if the new ATS was installed outside the limits of the switchgear.

 

[yesterlectric]

This sounds like perhaps a main-tie-main, possibly medium voltage switch gear lineup with 240V control power and control power transformers on both sides. If that's so, can't you just get the original manufacturer to sell you replacement parts?

 

[tom baker]

Could you get just the guts of an ATS, ie mounted on a back panel with listing label and install that in existing enclosure? If a field inspection is needed then ETL is much less expensive than UL

 

[Jraef]

I’m going to assume this is a switchboard, not switchgear.

Unless the ATS is the same manufacturer as the switchboard, it was unlikely listed as part of the Switchboard assembly under UL 891, because if directly connected to the bus, that requires very expensive testing. So usually what they do is just put it in an enclosure that matches the switchboard and then cable connect it to the bus. Inside of that compartment, the ATS has its own UL 1008 listing label, which is really what AHJs look for. So doing what Tom suggested above would be the same thing.

If on the other hand the ATS is hard bus connected to the switchboard and listed as part of the UL 891 assembly, then you can only replace it with something the Switchboard mfr has listed in their equipment. Or, remove the hard bus connections, add lugs, and cable connect it.

 

[Todd0x1]

I’m going to assume this is a switchboard, not switchgear.

Unless the ATS is the same manufacturer as the switchboard, it was unlikely listed as part of the Switchboard assembly under UL 891, because if directly connected to the bus, that requires very expensive testing. So usually what they do is just put it in an enclosure that matches the switchboard and then cable connect it to the bus. Inside of that compartment, the ATS has its own UL 1008 listing label, which is really what AHJs look for. So doing what Tom suggested above would be the same thing.

If on the other hand the ATS is hard bus connected to the switchboard and listed as part of the UL 891 assembly, then you can only replace it with something the Switchboard mfr has listed in their equipment. Or, remove the hard bus connections, add lugs, and cable connect it.

Out of curiosity what is the difference between hard bus and cable connections to the ATS, practically speaking? Can cables to a replacement ATS get bolted to the bus where the old ATS used to be if bus connected or does the switchboard manufacturer need to get involved with that?

 

[Jraef]

Anything connected to bus must be tested under the switchboard standards when connected to the bus, especially for Short Circuit testing (bracing, separation etc) and heat rise. Not so with cable connected devices, so long as they are properly installed. It’s the same for MCCs (which were originally based on the same switchboard testing standards). You can’t connect anything to the bus unless it has been specifically tested. ATS are the thing that this applies to more than anything else.