UL 508a components

[Nick DiBernarod]

I'm recently new to the UL 508a MTR control building. All of our motors operate off of 24VDC. I'm sourcing our a job for a Canadian customer. The one problem I've run into and cannot find an answer is the bridge rectifier. We have 220VAC coming into a step down transformer to 24VAC, then goes to a bridge rectifier to convert to 24VDC. The problem is that I cannot find a UL recognized component for Canada for the rectifier. Since this is a 24-volt control circuit does it matter?
Is UL only concerned with the circuit before the step-down transformer?

 

[Jraef]

I think you have missed some elements of your MTR exam…

If you are building a panel for Canada, your UL 508A license but have a “cUL” endorsement. It’s been a while for me, but back when I did it, UL charged extra for that, so if you didn’t take that extra step, your UL 508A was not going to be good in Canada.

But also, you will not find a UR (UL Recognized) component with anything other than that in it, because the nature of using a Recognized Component means you must add it to your procedure in accordance with whatever other components that device is Recognized to be used with, then the ENTIRE PANEL becomes UL listed by you, the 508A shop. So IF, as per above, you are already certified to do cUL 508A, and you used the UR component correctly and properly add it to your UL 508A procedure, the component itself would not need to be any different. In other words, there is no “cUR” because UR devices don’t stand alone, ever. By definition, they can ONLY be used as part of a larger listed assembly.

 

[Nick DiBernarod]

Thanks, I think there's a few questions I have that the field engineer needs to answer when he does his first site visit

 

[petersonra]

If you cannot find a suitable bridge rectifier use four diodes.