We are attempting to make our UL component listing as generic as possible so that in the future we can source other vendors without updating our listing.

Say we had a generic PLC listed as a part of our control box that said something like "Programmable Logic Controller - Listed (XXXX), rated input: 100-240 VAC, 50-60 Hz, 120 VA."

Now say we found a vendor that supplied a similar PLC for half the price that had a rated input of: 100-240 VAC, 50-60 Hz, 60 VA (and is also listed under the same UL category code).  Are we safe to begin using the cheaper PLC without fear of a variation notice during an inspection?

My thinking is that the new, cheaper PLC uses half the power at the same voltage as the old PLC, making it safer, therefore requiring no action in UL's eyes.

Thanks in advance for the help.

Dave,

In your UL file will be a list of "critical components" that cannot be substituted without prior evaluation.

If the PLC is on the list, you can't substitute without permission.

If not on the list, it's best to go ahead and notify UL anyway.  Variance notices after you've produced a bunch of product can be expensive!

Good on ya,

Goober Dave

Dave,

The fact that UL accepted (or made) the entry in your UL file whereby the PLC manufacturer name/model number was not required is a very good sign.
In my experience with these generic file entries, UL tends to put the headline electrical ratings and sometimes a particular parameter in this case VA, is not safety critical to the end product. In my opinion you would be ok with your alternate PLC of the same UL CCN (category control number). Like with conditions of acceptability for recognized components, check any UL markings issued by the manufacturer that form part of their UL listing and ensure you comply with those.

John

He said attempting...not approved..
But IMO my answer would be NO as 60VA is not equivalent or larger than 120VA.

But if you put in a "Programable logic controller with a rated input of 100-240VAC, 60VA minimum" and you prove that the 60VA model passes then you can use a 120VA model or the 60VA model.

I'm not familiar with PLC ratings...
My response above was based on my assumption that the VA rating is related to the what's attached at the output connections and that a lower rating means less devices can be attached before it is overloaded. I'm thinking my assumption was incorrect.