# Generac Whole House acting weird.



## Toller (Dec 27, 2015)

I have a Generac 8kw whole house generator; about 3 years old.
We had a power outage last month. The generator started up, but the circuits got no power. I opened the transfer switch up and found 123v at both wires, but the coil that sends power to the circuits didn't catch. I measured voltage between the wires and found 3v, rather than the 240v I expected. I presume that is why the coil didn't catch.
I called the company that services it. They said to manually turn it off and back on. It was fine then, with 240v between the wires. He didn't see that it needed any service.

I called Generac. The guy there said that he had never heard of anything like that before, but would ask around. In the meanwhile he said I should rely on my service man, who had their highest certification.

The service man suggested I try it every few weeks. (it exercises every week, but does not power anything). If it worked normally he didn't see there was anything to do. I have tried it twice since then and it has been normal.

Any idea why it would act up this way?
Anything that can be serviced?

Just because I got lucky once doesn't mean I will the next time.


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## KRE (Nov 29, 2011)

If you have a PDF of the wiring diagram post it and I'll take a look. Bottom line if, the certified service folks can't tell you what is going on or, fix it within 2 trips max, I'd suggest getting different service folks.


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## Toller (Dec 27, 2015)

Manual is at:
https://www.generator-parts.com/manuals/home-standby/0G9266.pdf
The wiring diagram is on page 163.

When it didn't work initially, he though the winding had to be flashed. After it did work twice he thought a circuit breaker had tripped and reset.
I don't know anything about windings, but it looks to me that if a circuit breaker had tripped I would have 120v on one wire and 0v on the other; not 120v on both that were the same leg. But if I knew anything, I wouldn't be asking here.

I guess the bottom line is that what happened isn't possible, so they don't know what to look at.


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## KRE (Nov 29, 2011)

First question I have is did you turn the gen-set circuit breaker off then back on, or did you just reset the auto/run switch and all was well w/o touching the gen-set circuit breaker? If you turned the breaker off first was it in the tripped position or was it in the normal on position, and do you know the difference? This answer is very important into what happened and what comes next.


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## Toller (Dec 27, 2015)

Okay, there is a compartment on the side of the generator with a 35a breaker in it and a status light. The manual calls that the main breaker. It was in the on position; he has me turn it off. Then he had me open the cover and switch the generator from automatic to off. After a 10 count I switched it back to automatic to start it, and turned the 35a breaker back on. It worked normally.

It is hard to be sure of something that happened a couple weeks ago, but I am pretty sure the breaker was solid on; I know it clicked when I turned it off. Both hots from the generator had voltage, so wouldn't it have had to be on? (they were just the same leg in stead of opposite...)


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## KRE (Nov 29, 2011)

Toller said:


> Okay, there is a compartment on the side of the generator with a 35a breaker in it and a status light. The manual calls that the main breaker. It was in the on position; he has me turn it off. Then he had me open the cover and switch the generator from automatic to off. After a 10 count I switched it back to automatic to start it, and turned the 35a breaker back on. It worked normally.
> 
> It is hard to be sure of something that happened a couple weeks ago, but I am pretty sure the breaker was solid on; I know it clicked when I turned it off. Both hots from the generator had voltage, so wouldn't it have had to be on? (they were just the same leg in stead of opposite...)


The breaker should have snapped, if it clicked it most likely was in the tripped position. Now based upon what you said I am leaning towards the conclusion that it was an out of phase trip when it last exercised and you did not notice the problem as the ATS would have re-transferred as soon as the breaker tripped. What causes a out of phase trip, well any ATS without a inphase monitor can transfer or retransfer when the voltage potential is anything between 0 and twice the RMS voltage do to the hertz difference between the two power sources. This means your normal 240Vac single phase home can be spiked with 480Vac if the phase voltage is 180* out of sink. To see this first person take a std Volt meter and place one meter lead on the normal power side and the other meter lead on the genset side with both leads on the same phase. With both power sources available (like when exercising) you will see the meter scrolling between 0 and the max voltage of both phases added together. Now add the max potential between both sources and you quickly arrive at 460-500Vac that can be induced into the home wiring, depending the ATS mechanical transfer times. The home voltage takes a few MS to 1 sec to decay to zero volts. Most all trips come from reactive currents and in a home this is the HVAC, Freg, freezer or most anything with a motor or transformers. A high load of CFL's will do this as well. Quality ATS systems have protective devices to reduce this issue but you don't see them on box store gensets. The breaker trip is all pure conjecture on my part but, unless you have connections or devices not shown on the diagram this is the best read I can give you from afar. If anything else arises or you remember something different let us know. Hope the helps, Kenneth -------------------- Edit to Add, remember as voltage goes up across a fixed resistance amperage goes up as well, so if you take a heating load of say 9.5 ohms and apply 240Vac you will draw 25.3 amps but that same 9.5 when say 440Vac is applied will draw 46.3 amps which would trip the breaker. This is why in-phase monitors or a switch that stops in neutral (no power either way) for a few seconds will stop this issue. Your unit may never do it again or may do it very often. If it happens often there are other ways/devices outside of the ATS that will stop the breaker from tripping but they are not cheap or w/o add issues.


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## Dan N. (Jul 23, 2015)

I believe it is also likely that a brown out could have caused this to happen. It is somewhat likely that low voltage could have confused or not been enough to trip the coil to operate for that particular time. Do you know if you have brown outs in your area or not and what controller do you have, nexus or evolution?


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