Just started up my Generac Natural Gas generator for the first time
Transfer switch automatically switched over to generator power as
expected however, when I turned utility power back on the switch did
not transfer back to utility.
I had to open the switch and manually transfer back to the utility
This happened both times I tested.
Any input as to what would prevent the switch from switching back to
How did you test, by turning off the main utility breaker? How long did
you wait after turning utility power back on? Most transfer switches
have timers and won't transfer back to utility for about 10 minutes
after it comes back to insure it is stable.
That's the way the big units work, transfer switch transfers 10-15
minutes after commercial power is restored, then has about a 3-5 min
generator run without power for a "cooldown" before final shutdown.
From page 18 of the Owner and Installation Mnaual, it looks like 15 seconds
is the delay after utility power is restored until the automatic transfer
switch is restored to the utility position. See Step E below - retransfer:
A. Utility Voltage Dropout Sensor
. This sensor monitors utility source voltage.
. If utility source voltage drops below about 65
percent of the nominal supply voltage, the sensor
energizes a 10 second timer.
. Once the timer has expired, the engine will crank
and start if utility is still low.
B. Engine Warm-up Time Delay
. This mechanism lets the engine warm up for
about five (5) seconds before the load is trans-
ferred to the standby source.
C. Standby Voltage Sensor
. This sensor monitors generator AC output volt-
age. When the voltage has reached 50 percent of
the nominal rated voltage, transfer to standby
D. Utility Voltage Pickup Sensor
. This sensor monitors utility power supply volt-
age. When that voltage is restored above 75 per-
cent of the nominal source voltage, a retransfer
time delay starts timing.
E. Retransfer Time Delay
. This timer runs for about 15 seconds.
. At end of a 15-second delay, circuit board action
de-energizes transfer relay in the transfer switch
if utility is still present.
. Retransfer to utility power source then occurs.
F. Engine Cool-down Timer
. When the load is transferred back to utility power
source, the engine cool-down timer starts tim-
. The timer will run for about one minute, and the
generator will then shut down.
The diagnostics and repair manual is at:
It is a 151 page very technical document, and I (as a graduate electrical
engineer) can read it with some difficulty. Page 67 has the specific fault
you are trying to correct.
I would suggest you get a local Generac person to trouble shoot it. It is
under warranty and the problem looks like it could be the logic board, coil,
etc. Since the unit is brand new, let them fix it !!
Tested two ways...turning off the 70 amp breaker that powers the
transfer switch and the second time turning off the main breaker.
What I observed (before opening the transfer case and seeing the
switch still in the generator mode) was that the unit was running in
cool down mode, observed that the basement circuits seemed to be
getting some sort of "trickle" power (lights were dimmed, battery back
up sump pump was running but the two AC pumps also seemed to be
running (but dry, not moving any water).
We were told the switch should go back to utility within 30 seconds
once utility power is detected again. It doesn't make sense if it
takes 10 or more minutes then our lights/appliances are not going to
have any power until the transfer switch pops back to utility mode.
If you have any sort of "half powered" condition like this it indicates
a serious problem. Get it checked by a competent person ASAP or sooner.
With a properly wired and functioning transfer switch all circuits only
have three possible states, powered properly from utility, powered
properly from the generator or unpowered if the selected source is not
Someone else posted info from the manual indicating a 15 second utility
stabilization delay followed by a one minute generator cool down delay.
The big transfer switches typically have longer delays like the 10 min
retransfer I mentioned and longer generator cool down.
The switch did not move back to utility even after the cool down was
over and the generator shut down.....waited another 5 minutes and
still no switch. In the meantime, the sump pumps were without
power....definitely does not seem correct.
The manual I sent handles Generac models up to 16KW. I assume you are
referring to huge models when you refer to such long transfer times. The
longer delay times are intended to prevent intermittent utility power to
cause the generator to toggle / transfer the load back and forth
I think Pete has it right -- from Generac site on spec's for one of
their automatic transfer switches -- I suspect if you look carefully,
the unit you have will describe how it is set up or how to modify it.
Although I suppose w/ a package unit they could have set it up w/ a
fixed time delay to avoid user interference.
0.1-10 Sec. (Adj.)
5-30 Min. (Adj.)
5 Sec.-3 Min. (Adj.)
1-30 Min. (Adj.)
Michael, I'm glad to see that you didn't need / use the Generac maintenance
manual link I sent previously to you. Also glad your problem is solved. Good
luck with your new Generac. Mine works beautifully and I hope yours does as
replying to mikegold, Mark14103 wrote:
I bought a 10 kw whole house transfer switch and with utility power on. The
generator won't shut done it says no power detected. Checked wiring and
everything is properly done any suggestions?
On Friday, April 22, 2016 at 8:44:05 PM UTC-4, Mark14103 wrote:
Two choices. If you have the skills, get a schematic and start diagnosing.
If not, call a pro. For what it's worth, from what I saw with a neighbor's
system and from reading reviews on Amazon, I wouldn't put any money into
a Generac home system.
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