Re: UL listing requirement for added control
It is not an NEC issue,
it is a UL issue. They tested and listed everything as a complete unit. If you have changed the configuration and added parts, it has to be retested unless it was designed for the added component or modification.
For instance, you install a panelboard and then install circuit breakers that were listed with that panelboard, you have no problem. However, if you install a panelboard and then install circuit breakers that
were not listed for use with that panelboard, you have a big problem.
The same would apply if you modified the bus to accept one-half size circuit breakers; the equipment was not tested for use in that manner.
Bottom line, is the box listed for use with the stop button? A call to UL may be in order.