UL Listed Pad Mounted Transformer For US Market

[KS20]

Can soomeone tell me for a Pad Mounted Transformer to be UL listed (In USA) as a whole, whether all the Material, Parts, Fittings and Accessories need to be UL listed individually. or whether there are some particular components and Fittings which need to be UL listed only for a Pad mounted transformer to be UL listed a whole.
Below are the some parts
Silicon steel CRGO Laminations for Core
Aluminum or Copper Foil/Strip conductor for Making Winding
Thermally upgraded paper Insulation for Conductor covering on windings
High Density Pressboard Cylinders, Blocks, Key spacers, Rectangular and dovetailed sticks.
Copper/Aluminum Cables/Bus bars for internal connection in Windings
Carbon Steel/Mild Steel for Tank, Bracket for structural parts and Enclosures of Transformer
Mineral/Envirotemp FR3 Oil for Cooling of Transformer.
Bay-O-Net Fuses
Current Limiting Fuses
Pressure Vacuum Guage
Liquid Level Guage
Liquid Temperature Guage
Pressure Release Device.
Radiators and Radiator Valves
Drain, Sampling, Filter and Shrader Valves
LV and HV Bushings and Bushing spades for external connections
Load Break switch
Off Load Tap Changer in HV
Stainless Steel Name Plate
HV Bushing Parking Stand
LV Bushing Support (FRP material)
SS Ground Pads
Control Box
Drip Shield

 

[Gr8blu]

UL generally certifies either parts or assemblies. This means that if the intent is to certify the transformer and all its accessories as a unit, it would have to be manufactured and tested with all the applicable subcomponents from the list above. It would ALSO mean that absolutely no substitutions would be allowed - so if the certification was with pressure gauge X, it can only use pressure gauge X.

Alternatively, the manufacturer can define the "basic assembly" to be just the transformer itself - in which case, every add-on accessory (such as a pressure gauge) would ALSO require certification as a discrete assembly. From the list above, I would probably look at the valves, gauges, pressure relief device(s), fuses, and switch as "external" accessories. Lump everything - except oil - together as the "basic transformer assembly".

Note that the cooling medium (oil in this case) is NOT going to UL certified. The transformer could be certified such that it requires a specific grade/viscosity of oil, but that's about it.


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