PS = Power supply which is what determines class as per 725.
Generac uses 4 or 5 control wires, two which monitor the utility lines N1 and N2 are 120 volts to ground or 240 volts between them and are protected by 5 amp fuses in the ATS, the other 3 are 23 (12 volt negative transfer signal) 194/15 (12 volt positive reference) and 0 ( 12 volt negative reference) 0 is not use anymore since they have moved the charger to the control board in the newer Nexus systems, and even many older units didn't use it unless you installed the charger in the ATS, so only three of the 5 conductors have to be kept separate from the line voltage circuits, but even Generac ran them in the same flex on the smaller combo ATS panels with circuit breakers, and their wiring diagrams stated up to 30 feet was allowed.
Even though the control wire (23) is part of the 12 vdc system it controls an ice cube relay that controls the transfer switch coils which are 120 volts each, if there were no signal on wire 23 then the transfer switch uses the 120 volts from the utility (N1) to transfer back to normal, also if there is no 120/240 output from the generator the ATS will not transfer from utility since the ATS coils use the 120 volts from the generator to transfer and a set of limit switches to turn off the 120 volts once it has transfered.
On some models there are a set of wire for manually starting the generator when a manual transfer switch is used these are 183 and 178, I have only seen them on their commercial lines of generators or one ordered with a manual TS.
In all of Generac's wiring diagrams the utility sense wires (N1 and N2) are shown run in the same conduit as the 12 volt control wiring but I have run these with the power conductors so I could just run a 3 wire cable for the others.
