UL 508A Applies Here?

From UL's standpoint, they don't care, they will take your money from you if you ask. The requirements for having a label from an NRTL (Nationally Recognized Testing Lab) such as UL vary by state, it is not part of the NEC. Some states do not require it at all. If you are being told your installation must have it, you would need to look at the State Electrical Code to see what it says specifically about where the requirement applies.

That said, most State codes have some sort of a "limited energy" clause stating, in one way or another, mainly to accommodate Building Management Systems such as HVAC controls and security alarm systems. That will state that if everything in a box is "low voltage" (usually defined as 50V or less), and can be classified as Class 2 (meaning 100VA or less) then it does not need further approval. That by the way is why you see a lot of power supplies that are 4A 24VDC; 4A x 24V = 96VA

So, what happens if you don't inspect it? It does not sound like an "industrial control panel" to me.

Do you want say it is UL listed? You'll have to pay them to test it first.

Is there more to this story?

Customer has a spec that says panels are inspected to UL 508A. (majority of their panels have VFD's, relays, switches, etc.) I don't think this one falls into that standard since it is by my reckoning not an industrial control panel per the UL definition and therefore does not even need to be seen by a UL inspector. I think this is low energy circuitry. (if you read first response by JRaef, no, the state does not require this to be inspected)

I did read JRaef"s response. I agree.

Your second post explained your motivation for asking the first question. That's what wasn't clear to me.

Oops, just read my own post, I have a cut-and-paste error in there, sorry.

If the customer has a spec that clearly states "panels" are to be inspected to UL 508A and this is contract work, it does not matter what we think or what UL 508A description/clarification state, you need to provide what is spec'd per the contract.

EXCEPT

If you can convince the customer and customer's engineer (if there is one) that this is not needed and he/she/they will sign off on this exception.

Most likely you or your company's monthly draw and/or final retention will be on the line so remember hand shakes and he said/she said will not hold up if a dispute arises later - get the change authorization signed before you deviate from the spec.

Final outcome - no inspection required by customer. Their spec did not require it. And, they had other reasons as noted below.

The panel was not really up to 508A standards, even if it was considered a control panel, which I contend it is not without any control apparti. The customer did not want a way to turn off the 24VDC to the instruments on the tank to prevent tampering - with no chance of hazard or injury from a few 4-20ma transmitters, a 24VDC sensor circuit (rupture disc) and a 50W 24VDC light, that control will remain in the control room. The real hazard would have been the powering down of the rupture disc sensor circuit. Indicator lights not lit in the control room - disc must be intact - right? Meanwhile the tank is vomiting $500000 of medicinal brew all over the floor. So, without the lockable disconnect switch on the panel, it was not going to be to 508A standards. Would have failed inspection miserably. Furthermore, I have no idea how we were going to figure the 508A required SCCR on a Class 1 (<30VDC/1000VA) low energy source. It would be a bit futile to even consider this rating, but you can bet it would have been required for an inspection.