Generac Guardian transfer command failure

[ee8.scotts]

I'm chasing a problem with an older 15kW Generac Guardian where it didn't transfer power during the last outage.

Generator starts and runs perfectly when manually tested, putting out a solid 242V. The issue is the separate Generac ATS (0J9771) isn't engaging when utility power drops. The generator runs, but it's not sending the control signal to the transfer switch.

I've checked the low-voltage control wires between the unit and the ATS, and they look fine. Everything points to the generator itself.

Is there a known component or relay inside the generator's control panel that commonly fails and prevents it from sending the transfer command after it's already running? Before I swap the main control board, I'd appreciate any input on common failure modes for that transfer signal output.

Thanks for the help.

 

[Maya_Mahabala]

from what i know it’s usually the transfer relay on the control board. Generac used some weak relays on those older Guardians that get sticky after years of heat cycling. If it starts fine but won’t signal transfer, that relay or the control harness plug is your prime suspect.

 

[PGB1]

Maya_Mahabala is exactly correct, ee8.

When generators do their preventative maintenance test cycle, the contractor or relay which switches from utility to generator does not get called to move. Doing so would be a nuisance for the occupants. (The statement pertains to residential and normal commercial. Hospital and some other systems test are differently)

They get stuck, as Maya mentioned. And Generac has very poor history with the contractors. So my bet is that the contractor was stuck from lack of use and from being cheap of design.

If you are 100% certain that you can work safely with electricity and have all personal protective equipment, test this way:
A) Disconnect utility to the generator so that it calls to feed the house.
B) Firmly tap the contactor a few times. It probably will snap into action.
C) Get a replacement soon.

If the contractor does not snap into action, test voltage to the relay coil. Some are energized when utility is normal and some are the opposite, you have to check the wiring diagram. The problem could be the relay that feeds the contractor or the circuit board itself.

I wish that I could offer more help & advice to you.
My normal generator work is connecting and servicing industrial, emergency and temporary power generators from 208 volt up to 315,000 volts and in the multi-megawatt range, so the only thing I know about residential units are from a few small projects at work, family & friend freebie jobs and from others in the field.

Oddly, almost all of my family & friend freebie jobs are Generac and Guardian. After studying the components, I'm absolutely not a fan. (Unless they have improved significantly)

Generac Warranty Story:
I got called to a hospital for an emergency connection of a portable stand-by generator. They had utility power fail and the TWO redundant backup generators did not provide power. (Generac) Both were less than 1 month old. (Not installed by me)
One Generac's stator came out of the housing. The other had a piston fly out of the cylinder, through the cylinder head, through the armor guard fence and into the back window of a car parked in the lot across the alley.

It took Generac 29 months and two tort suits to fix the generators. The hospital had to pay for rental generators the whole time. (Thousands per week)

 

[VoltagexV]

I'm chasing a problem with an older 15kW Generac Guardian where it didn't transfer power during the last outage.

Generator starts and runs perfectly when manually tested, putting out a solid 242V. The issue is the separate Generac ATS (0J9771) isn't engaging when utility power drops. The generator runs, but it's not sending the control signal to the transfer switch.

I've checked the low-voltage control wires between the unit and the ATS, and they look fine. Everything points to the generator itself.

Is there a known component or relay inside the generator's control panel that commonly fails and prevents it from sending the transfer command after it's already running? Before I swap the main control board, I'd appreciate any input on common failure modes for that transfer signal output.

Thanks for the help.

@ee8.scotts, they bring up a good point about transfer switches not usually actuating during weekly self-tests, which can cause the ATS contactor to get sticky. However, since your generator is running but not sending the signal to the ATS coil, the issue is still likely on the generator's side, possibly that relay failing to close or having pitted contacts. Try to check the voltage on the transfer signal terminal inside the generator with the unit running during an outage simulation. If it's 0V, the transfer relay is the prime suspect. If you have the voltage, then the problem is the ATS contactor, and the tapping method mentioned could confirm it.