Standby generator stalls

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jazzman

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Hello,
I have a 15KW Generac generator with an automatic transfer switch that will start in the event of a power failure. The switch will transfer to generator power and the generator will run and carry the load for about 15 minutes. Then it stalls. The transfer switch will remain in the generator position. I can restart the generator by flipping the switch to manual and it will continue to carry the load. Any ideas as to what is going on? Thanks.
 
The generator will run just fine while in manual mode therefore I do not believe that there is a problem with the fuel delivery. It must be a problem with an electrical component in either the transfer switch or the generator.
 
The generator will run just fine while in manual mode therefore I do not believe that there is a problem with the fuel delivery. It must be a problem with an electrical component in either the transfer switch or the generator.
I agree. If it is one of those components you won't get much help from Generac. You'll have to find one of their illustrious trained dealers to help you out unless a forum member has that knowledge and is willing to provide you with it and sell even you the parts.
 
Since it only "stalls" when being controlled by the transfer switch, and yet the transfer switch remains in the generator position, I would look for a lost engine running signal from the generator to the switch or a failure of the run command line from switch to generator.
Knowing that does not necessarily help nail down the problem, but it could localize it to either the generator or the generator start circuitry in the switch.
 
Just curious, is it stalling Like there's a gas pressure problem or is it shutting down ?

I agree, what do you mean by "stalls"? Does it just quit for no reason or does it seem to run out of gas or quit when a large load (HVAC) is dropped on it?
When you exercise it under load does it transfer back to utility when it stops or stay in emergency?
 
Not knowing the age of the generator, I can only give you general tips. First off, the transfer switch itself is "dumb." It just contains the switch that is controlled by a relay in the switch. The switch provides both phases of utility power to the generator controller in the gen itself (terminals n1 & n2). Controller in the gen controls the starting, running, shutdown and transferring of loads. Control of transfer is controlled by the controller via providing ground to the relay in the transfer switch.
On the newer ones, just having it running in manual will not make it transfer. It will transfer only if utility power is lost on n1 and/or n2. If you have it running in manual and it is powering the loads and utility power returns, it will go ahead and transfer the loads back to utility after the delay elapses.

Therefor, the problem is with the gen. Could be a controller going bad, or could be something else. If it's not showing any alarms or error lights when it shuts down, it's probably the board. If it is showing an alarm or an error light, look in the direction it's pointing you, but I don't know why those conditions would only be present during auto operation and not manual.

p.s. I've seen ants get in the gen controller area and make them do some wacky things, could be something to check.
 
Brilliant speculation! Transfer switch output is driving the "test" input of the generator controller rather than the "run" input?

Agreed. If the genny runs fine under load and at the correct voltage and frequency, then cuts out at 15 minutes, especially if that failure can be reproduced more or less identically repeated times, that pretty much rules out fuel and mechanical issues.
 
Not knowing the age of the generator, I can only give you general tips. First off, the transfer switch itself is "dumb." It just contains the switch that is controlled by a relay in the switch. The switch provides both phases of utility power to the generator controller in the gen itself (terminals n1 & n2). Controller in the gen controls the starting, running, shutdown and transferring of loads. Control of transfer is controlled by the controller via providing ground to the relay in the transfer switch.
On the newer ones, just having it running in manual will not make it transfer. It will transfer only if utility power is lost on n1 and/or n2. If you have it running in manual and it is powering the loads and utility power returns, it will go ahead and transfer the loads back to utility after the delay elapses.

Therefor, the problem is with the gen. Could be a controller going bad, or could be something else. If it's not showing any alarms or error lights when it shuts down, it's probably the board. If it is showing an alarm or an error light, look in the direction it's pointing you, but I don't know why those conditions would only be present during auto operation and not manual.

p.s. I've seen ants get in the gen controller area and make them do some wacky things, could be something to check.

These last few posts have been very helpful. I will be doing some troubleshooting today and will post my findings if there are any. Thanks folks.
 
First of all an ATS is not dumb. It is the brains of any emer backup system. It contains both sources volt and frequency sensing, engine start signal, time delays and engine cooldown features. The genset is the dumb guy in the system in that all it knows it to start and run when the signal is there and shut down when the signal is gone. All ATSs are designed to immediately retransfer to normal if the genset shuts down IF THE NORMAL POWER IS PRESENT. If the genset shuts down after 15 min and the ATS does not transfer back to normal then the problem is probably in the controller for the ATS. I am not that familar with residential ATS units but the logic (controller) for the commercial and industrial units is a motherboard. I would check the board out to make sure there is no dirt, moisture, spiderwebs, or ants like the other guy mentioned. Send us the model# of the unit so we can take a look at what you got.
 
First of all an ATS is not dumb. It is the brains of any emer backup system. It contains both sources volt and frequency sensing, engine start signal, time delays and engine cooldown features. The genset is the dumb guy in the system in that all it knows it to start and run when the signal is there and shut down when the signal is gone. All ATSs are designed to immediately retransfer to normal if the genset shuts down IF THE NORMAL POWER IS PRESENT. If the genset shuts down after 15 min and the ATS does not transfer back to normal then the problem is probably in the controller for the ATS. I am not that familar with residential ATS units but the logic (controller) for the commercial and industrial units is a motherboard. I would check the board out to make sure there is no dirt, moisture, spiderwebs, or ants like the other guy mentioned. Send us the model# of the unit so we can take a look at what you got.

That may be true for the ats's you work with, but not the residential Generacs. Volt and freq sensing, engine starting, time delays and cool downs are all handled by the controller in the generator itself. Some service entrance rated Generac resi ats's contain a load shed module that monitors freq for its own purposes, but otherwise has no bearing on generator running/ats transfers.
 
That may be true for the ats's you work with, but not the residential Generacs. Volt and freq sensing, engine starting, time delays and cool downs are all handled by the controller in the generator itself. Some service entrance rated Generac resi ats's contain a load shed module that monitors freq for its own purposes, but otherwise has no bearing on generator running/ats transfers.

Ok so regardless of "where" this controlle resides it appears that is where the problem is.
 
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