ECN Forum Forums Code Related Discussion NEC & other Code issues Using not Listed Equipment at 24VDC

Hello,

We (a german company)want to build up an inspection machine, based on 24VDC.
As a power supply we use a listed power supply 3x400VAC In -> 24VDC Out.
At the 24VDC output there are connected a UPS and a 24VDC power-supply for a PC.

Whats about the components on the secondary 24VDC side. Must they be UL-listet?

I have heard that component on secondary circuits must not be listed.
Are there exceptions?