Yes, if you have components that say they need a Class 2 power source, that means their UL listing is dependent upon that, so using them without one would void your ability to list the panel.
Offhand, I know Phoenix Contact makes at least one certified Class 2 UPS.
Really? I've never seen one and a review of their catalog says nothing about it.
As I understand it, the problem is the batteries. You can have a Class 2 listed
power supply, which limits the output power to 100W max. (5A at 24VDC). You can also put a DC UPS on most power supplies. But as soon as you add the DC UPS to a Class 2 listed power supply, you void the Class 2 listing of the power supply because it's based on it's INHERENT power limiting capability but you have no ability to limit the power coming out of the battery, because it's on the LOAD side of the power supply. In other words if there is a short on the DC side, all of the battery stored energy will feed that short, nothing will limit it to 100W. I don't know of anyone that has come up with a power limited battery system that would meet Class 2 circuit standards.
The acceptable method I know of for this is to have a line or control voltage (i.e. 120V) fed UPS unit with the proper A-Hr rating for the task, FEEDING a Class 2 listed power supply that takes your line voltage to 24VDC, 100W limited.
One issue with that is finding / using a UL listed UPS unit. UPS units are (if at all) listed under UL 1778, not UL 508. The UL 508a rules for assembling control panels states that all components must be listed under UL 508, or
on a specific short list of "other approved UL standards". The glitch is, UL 1778 is NOT on that list in the UL 508a procedure documents, yet if you look at the UL documents for UL 1778, it specifically states that they CAN be used in UL 508a control panels! This state of confusion has existed now for over 10 years and for some unknown reason, UL never fixes it. 9 out of 10 UL inspectors that work on the 508a panel shop program are aware of this glitch and understand, once in a while you run across a real jerk who says "NO! It's not specifically in the UL 508a documents!" It's a very frustrating thing when that happens...
