I am very sorry for the delays.
I have been on vacation for a week, and when I returned, I found that almost no generator questions had been responded to.
I am trying to work on a backlog of about 200 questions, and am doing the best I can.
I work 2 day jobs, and normally help on Just Answer in the evenings - and I still don't even have everything unpacked and cleaned up from my trip.
I am hoping to be back on my normal schedule after this weekend - but hopefully we will have yours done well before that.
There is only 1 thing that tells the genset that utility is back on - and that is a 240V feed to the genset from utility.
If the genset is in AUTO, and has the READY light lit while the power is on, it is getting a 240V signal from utility. If it weren't, it would be running all the time in AUTO.
The reason I asked about this being a new install, or if any work has been done recently, is because if the utility sensing wires are connected in the wrong place inside the transfer switch, what can happen is that the leads are sensing utility - but when utility fails, and the genset starts, it can actually read the output from the genset, instead of utility. It would think that it is seeing utility power, when it was really seeing genset power.
Lets start there.
Open the cover of the transfer switch, and remove the inside panel. Be careful, as there is 240V present in there.
In the bottom left corner of the TS, there is a 5-screw terminal strip with 4 wires attached to it. The left 2 wires are labeled N1 and N2, and lead to a fuse block with 2 fuses in it. These fuses are labeled F1 and F2. From the fuses up, the wires are labeled N1A and N2A.
From the fuses, the wires N1A and N2A need to go to the utility contactor.
There are 2 contactors, one right above the other. The top contactor is the utility contactor, and has 2 lugs on it.
The bottom contactor is the standby contactor, and has 4 lugs on it.
Check to make sure the N1A and N2A wires go to the top contactor - if they do not, they are in the wrong place.
Let me know what you find.