Looking into some educational information on UL listings. As a generator technician I am sometimes tasked with making modifications to the Transfer Switch. Some of these modifications may be minor but others intrusive such as contactor and controller change. I am curious how does this change the UL listing and if it does what can this impact?
Automatic Transfer Switch UL Listing
- Thread starter jbrown013
- Start date
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Any non-OEM direct equipment change would affect the listing IMHO. UL has a field inspection option (expensive) to update the listing on site.
Unfortunately, in my experience the code leaves it up to the AHJ to determine if the field modification is in line with the product application from the factory.
Another thing to think about is if the field modification would void a warranty. While code compliant, you could get into trouble with your ownership if they aren't able to warranty it.
Another thing to think about is if the field modification would void a warranty. While code compliant, you could get into trouble with your ownership if they aren't able to warranty it.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Also liability in this litigious society.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
- Occupation
- Electrician
Correct. I always say there is really no such thing as "voiding a listing". Its really up to the AHJ per 110.2. personally im a fan of dont ask dont tell here
Many states have requirements that all electrical equipment be NRTL listed. UL isn't your only option, and we have Field Evaluation Bodies that can approve things on site. Not cheap, and in WA the state maintains a list of approved field evaluation bodies if you need to use one.
As others have said its mainly liability,if your going by the letter of the NEC depending on what code cycle your on and your other state laws around electrical products an ATS might not even be required to be listed. At one time we worked thru a factory dealer for one particular residential brand and that allowed us to make factory approved alterations, I never considered if we voided the listing nor had a AHJ ask.
The one thing that has really changed recently in the 2023 NEC 702.4(A)(2)(b) is the UL listing requirements for the load shed, a UL listed NEC article 750 'energy management system' is not what most load shedding modules are. So while a load shed may be ul listed its not guaranteed an AHJ allow it under 702.4(A)(2)(b)
The large hospital / research center that I retired from had over 75 ATS'S. Most of the newer ones were expensive 600 to1200 amp models with closed transition and ability to place them in bypass to perform yearly PM'S, cleaning & testing. For what its worth cannot remember ever seeing a UL or other approved testing agency label on any of them. Same with million dollar equipment made outside of the USA .The one or two times they had a contact wired in on ATS'S to signal a remote alarm the ASCO tech did the work.