Generac Transfer Switch

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MSU_Electrician

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Mississippi
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Electrician
I’ve got a 200 amp generac transfer switch that functions fine every time I’m called out. The customer tells me that every time the power goes off the generator takes over and everything functions as it should. When the power is restored the generator transfers back and all 240v appliances are non functioning and random rooms have no power. I haven’t been able to recreate the issue but it sounds like they are loosing a phase. If anyone is a generac expert I would appreciate the advice.


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Then that's where the problem lies: the internal transfer switch itself, or a terminal or conductor on it is loose.

I'm guessing you mean manually cycle it with the metal handle, and not with the service breaker in the ATS.
 
LarryFine said:
Then that's where the problem lies: the internal transfer switch itself, or a terminal or conductor on it is loose.

I'm guessing you mean manually cycle it with the metal handle, and not with the service breaker in the ATS.
Click to expand...

No he is cycling the service breaker. The gen kicks into warm up then goes into cool down and power is returned to normal.


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MSU_Electrician said:
No he is cycling the service breaker. The gen kicks into warm up then goes into cool down and power is returned to normal.
Click to expand...
In that case, I would have the customer flip the transfer switch manually next time it happens, not the breaker.

By tripping the service breaker, two different parts are being cycled, so we're not sure which one is the cause.

Troubleshooting is a process of elimination. We need to see whether the switch or the breaker is the culprit.

By the way, he could just reset the breaker immediately without having to wait for the generator to start and run.
 
With the 80kW Generac I care for, the ATS got confused - only once so far. The ATS dropped from Gen to the neutral position instead of completing the cycle to Line. I locked out the gen, opened the main, set the ATS to Line with the metal handle, and closed the main. No problems since, but I'm unsure if gen power has been called for since then.

With the OP's symptoms, it almost sounds like only one pole of the ATS is closing to the line side when it acts up.
 
Can you get a list of areas without power when it happens, and see which leg it is on?

On my 20kw Kohler system, there is no neutral position on the ATS, it clicks over very solidly from one to the other.
 
Barbqranch said:
Can you get a list of areas without power when it happens, and see which leg it is on?

On my 20kw Kohler system, there is no neutral position on the ATS, it clicks over very solidly from one to the other.
Click to expand...

Problem is it only happens with a true power loss so it’s hard to say


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We have been on outages and restored power and the transfer part was only supplying 120V. They have 240 below the generac main, it just doesn’t make contact through the actual transfer switch.
We usually bypass them if we don’t have many out just to help until they get their electrician
 
Based on the the OP info it sounds like what he thinks is happening is correct. On retransfer back to utility power, one of the phases is not connecting causing single phasing to the loads. And whether the operator is MANUALLY transferring the ATS back to utility or opening the utility breaker ( cycle test ) has no bearing on the problem. Sounds typical of a lack of maintenance and the switching mechanism needs to be cleaned and re-lubed to correct the problem. This is what keeps my co in business. Dried grease and dirt in the switching mechanism is the culprit, My Friend, and Music To My Ears!
 
ATSman said:
And whether the operator is MANUALLY transferring the ATS back to utility or opening the utility breaker ( cycle test ) has no bearing on the problem.
Click to expand...
I meant to differentiate between the two. But, now that you mention it, if the problem was the breaker, it wouldn't occur during automatic operation.

So, the manual switch operation should clear it also. It's got to be the actual transfer switch mechanism in the ATS itself.
 
ATSman said:
Based on the the OP info it sounds like what he thinks is happening is correct. On retransfer back to utility power, one of the phases is not connecting causing single phasing to the loads. And whether the operator is MANUALLY transferring the ATS back to utility or opening the utility breaker ( cycle test ) has no bearing on the problem. Sounds typical of a lack of maintenance and the switching mechanism needs to be cleaned and re-lubed to correct the problem. This is what keeps my co in business. Dried grease and dirt in the switching mechanism is the culprit, My Friend, and Music To My Ears!
Click to expand...
With Genercraps it could be a misadjusted clearing contact too, dropping power to the coil before the switch is totally closed. I have replaced those that have failed before.
 
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