Generac Generator damaged by Transfer switch

[killahog]

Hello, I have a Generac brand Generator that was running when the main breaker from the house was closed and power was backfed into the generator and fried it. I guess fried was not the best description there was no fire it just bogged down while running and I did actually smell the odor of burnt insulation or wires. I am looking for advice or suggestions into what damage was likely caused and where would be a place to start in determining if the unit is salvageable. The unit was purchased around 2006 and the badge on the inside of the box has the following Information .

Thanks .

 

[grounded-b]

Your post title suggests that you had an automatic transfer switch. Or do you have a sliding "interlock" on your breakers, which you may have over-ridden?

There is no way power could "back-feed" the generator, with an automatic transfer switch, unless the blade mechanism is damaged

More info please

 

[Neggy]

what transfer switch were you using, if properly wired to code it is near impossible to do what you are describing.

 

[Norcal]

deleted.

 

[Neggy]

That unit has a control panel that disconnects it from the utility power, I'm trying to figure out how it was wired that the generator bypassed the control panel, the main breaker at the panel is never touched, that is why Generac generators are "automatic"

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[killahog]

I bought the house with this installed, I called an certified electrician to come out and set it up to automatically start when the power went out because it was not doing so. The electrician said all I had to do was read the manual for the generator and follow the instructions to auto start. I did that and then pulled the main breaker in my house and the Generator started. When I closed the main that’s when the Generator started bogging down and I ran outside and shut it off. I am assuming the transfer switch was not set up properly.

 

[BillK]

I think it would be well worth the cost of a service call from a Generac tech. They should be able to tell you what was damaged and what is wrong with the automatic transfer switch.

 

[Lassen Forge]

Sounds like an out of phase condition to me...

If your transfer switch internally shorted, it could have stayed connected to your genset when the "shore power" came back on line and stayed hooked up, throwing whatever amps the pole transformer could feed into the generator rectifier or control panel... you can probably go after the manufacturer of the transfer switch. Contact Generac to find out what may have been damaged, they'll probably recommend a tech to check out your generator and repair whatever got fried.

If you're doing a self-imposed lockout instead of an automatic switch (we did that for a number of years), ANY time you do a manual change (Line to Generator, Generator to Line) you NEED to have a "Zero Condition" between powering up the "live" side... Everything OFF, then power up the generator with shore power off, then everything off, and power up the shore power with the generator disconnected... otherwise you can get into the (destructive) issue of being out of phase which WILL cook things tout suite...

When I was on the bridges, there was a 20 second interrupt before the generators in our power house (GE Turbine units) kicked over to supply our facility... time to wind up, make sure the generators were in sync, then connected to a proven dead incoming line... and then when shore power was restored, the contactors killed everything for a 10 second time span before shore powere was connected to our facility, so there wouldn't be a conflict between the phase of our plant and that of the power company. Since the power was stepped up and down from 12KV, it would have been some pretty impressive fireworks otherwise.

 

[theoldwizard1]

When I was on the bridges, there was a 20 second interrupt before the generators in our power house (GE Turbine units) kicked over to supply our facility... time to wind up, make sure the generators were in sync ...

50 years ago, I had a friend that worked for a big time share computer company. Their backup power was 16 cylinder diesel engines. They were "exercised" once a month. It took 15 MINUTES of operation before they were considered stable enough to accept the load.

 

[theoldwizard1]

When I first started my professional career over 45 years ago, the place I first worked haa computer from the 60s. Back then the best way to make a large amount of 5V DC power was with an MG set. Motor-Generator. Probably a 10-20 HP motor connected to a big *** DC generator. I wonder how long the brushes lasted ?

 

[rlitman]

Sounds like an out of phase condition to me...

If your transfer switch internally shorted, it could have stayed connected to your genset when the "shore power" came back on line and stayed hooked up, throwing whatever amps the pole transformer could feed into the generator rectifier or control panel... you can probably go after the manufacturer of the transfer switch. Contact Generac to find out what may have been damaged, they'll probably recommend a tech to check out your generator and repair whatever got fried.

If you're doing a self-imposed lockout instead of an automatic switch (we did that for a number of years), ANY time you do a manual change (Line to Generator, Generator to Line) you NEED to have a "Zero Condition" between powering up the "live" side... Everything OFF, then power up the generator with shore power off, then everything off, and power up the shore power with the generator disconnected... otherwise you can get into the (destructive) issue of being out of phase which WILL cook things tout suite...

When I was on the bridges, there was a 20 second interrupt before the generators in our power house (GE Turbine units) kicked over to supply our facility... time to wind up, make sure the generators were in sync, then connected to a proven dead incoming line... and then when shore power was restored, the contactors killed everything for a 10 second time span before shore powere was connected to our facility, so there wouldn't be a conflict between the phase of our plant and that of the power company. Since the power was stepped up and down from 12KV, it would have been some pretty impressive fireworks otherwise.

I've seen several types of transfer switches. The type we use at work has mechanical interlocking where it is not possible to close both sets of contacts simultaneously (even if the contacts weld; the same cannot be said about breaker panel interlocks). A "static switch" made by APC we once dealt with used software based interlocking, where the logic would control which contactor closed. One "exciting" day a contactor welded shut creating a phase-phase bolted short when the other one closed.

Many ATS will have a fast return feature that watches on an internal synchroscope and flips back at the zero crossing, but I'm not remotely suggesting DIY use of a synchroscope, so yes, you'll need a neutral position with everything to be open for a few seconds between closing connections with either source.

50 years ago, I had a friend that worked for a big time share computer company. Their backup power was 16 cylinder diesel engines. They were "exercised" once a month. It took 15 MINUTES of operation before they were considered stable enough to accept the load.

Yeah, that was then. Each old fashioned diesel engine would be hunting in RPMs just enough that the synchroscope would be moving too quickly to safely transfer until everything is sufficiently warmed up and calmed down.

The pair of diesels at my work parallel in under 12 seconds from start up. Modern common rail EFI diesel (and bi-fuel) engines have incredibly stable revs, plus we use block heaters 24/7/365.25, so all starts are warm. Also, the CANBUS based controller can communicate directly with both engines, assisting with the stability for synchronization purposes.

 

[wyliesdiesels]

I bought the house with this installed, I called an certified electrician to come out and set it up to automatically start when the power went out because it was not doing so. The electrician said all I had to do was read the manual for the generator and follow the instructions to auto start. I did that and then pulled the main breaker in my house and the Generator started. When I closed the main that’s when the Generator started bogging down and I ran outside and shut it off. I am assuming the transfer switch was not set up properly.

Is there a model number on this ATS?

something doesnt make sense here.

If its a true ATS with a double throw switch, there would be no way for utility power to feed to the generator.

Can you take pics of the inside of the transfer switch (with the cover off) and post them here?

 

[Neggy]

the ATS is in the Generac housing.

something is broken or seriously FUBAR'd /Moused for it not to have switched from generator to utility the minute it saw line voltage

The contactor is designed to be on one power source or the other, because if it isn't it will feed back thru the meter socket to the street and thru the transformer, frying some Lineman on the pole

As someone said above, get Generac out there

 

[avistar23]

The top section of that is the ATS, its a generac style contactor similar to asco and kohler etc. just with generac control logic, no way for that to back feed when properly hooked up, ive never ever seen that happen.

 

[killahog]

I will take a picture Saturday I am out of town.

 

[James-W]

I am in the camp of having a Generac tech come and check it out. They may have seen similar problems in the past and if so, they likely will have an idea as to how extensive the damage is.

 

[killahog]

That’s sounds like very sound advice.

 

[Chilliwack Murray]

Just to take a few things out of the mix:

This would not be an out of phase condition switching from one source to another, that is only relevant on a 3 phase system where spinning 3 phase motors act as generators for a short time and maintain line voltage, if the sources are not in sync there can be massive current flow to bring them into sync. To avoid this, either an inphase monitor (or internal synchroscope mentioned in a previous post is used to transfer when the sources come into sync or there is a delay between sources - usually 3-4 seconds to allow residual voltage to decay. Single phase systems can be transferred with only 50-100ms between live sources.

Any residential ATS will be open transition ATS should be built with a physical interlock to prevent both contactors being closed at the same time. Closed transition switches mentioned in previous posts are used in 3 phase systems and utilize a similar sync check system as above. They close onto a new source (when sync conditions are met) then open the previous source 80-100mS later so they don't have the physical interlock between sources however closed transition switches do not exist for this application. That said, it is possible on some brands of contactor (generac buys contactors, they don't make their own) to weld shut and partially connect two sources. This is considered the worst kind of bad. In a world of 'you get what you pay for', generac are the cheapest and that has been their business model from day one.

The generator needs to be looked at by a qualified generator tech as does the installation . On a brush type unit there are no components on the rotor to be damaged but there would have been a large spike induced into the rotor which may have damaged the voltage regulator (likely part of the control on that size unit). The breaker on the unit should have tripped quick enough to have saved the stator windings from damage so if your lucky, just a controller and maybe brushes on the generator.

The most common cause for what you describe is someone getting the utility input and the load output mixed up on the transfer switch. Everything will appear normal as long as utility is available however when the ATS transfers to generator it would connect the generator to the utility. If this were the case, you should not have had any power to the loads with the utility breaker open and the generator running prior to the failure.

 

[killahog]

Just to take a few things out of the mix:

This would not be an out of phase condition switching from one source to another, that is only relevant on a 3 phase system where spinning 3 phase motors act as generators for a short time and maintain line voltage, if the sources are not in sync there can be massive current flow to bring them into sync. To avoid this, either an inphase monitor (or internal synchroscope mentioned in a previous post is used to transfer when the sources come into sync or there is a delay between sources - usually 3-4 seconds to allow residual voltage to decay. Single phase systems can be transferred with only 50-100ms between live sources.

Any residential ATS will be open transition ATS should be built with a physical interlock to prevent both contactors being closed at the same time. Closed transition switches mentioned in previous posts are used in 3 phase systems and utilize a similar sync check system as above. They close onto a new source (when sync conditions are met) then open the previous source 80-100mS later so they don't have the physical interlock between sources however closed transition switches do not exist for this application. That said, it is possible on some brands of contactor (generac buys contactors, they don't make their own) to weld shut and partially connect two sources. This is considered the worst kind of bad. In a world of 'you get what you pay for', generac are the cheapest and that has been their business model from day one.

The generator needs to be looked at by a qualified generator tech as does the installation . On a brush type unit there are no components on the rotor to be damaged but there would have been a large spike induced into the rotor which may have damaged the voltage regulator (likely part of the control on that size unit). The breaker on the unit should have tripped quick enough to have saved the stator windings from damage so if your lucky, just a controller and maybe brushes on the generator.

The most common cause for what you describe is someone getting the utility input and the load output mixed up on the transfer switch. Everything will appear normal as long as utility is available however when the ATS transfers to generator it would connect the generator to the utility. If this were the case, you should not have had any power to the loads with the utility breaker open and the generator running prior to the failure.

Thank you for taking the time to explain that. I will take the cover off the transfer switch and post a few pictures and get in contact with generator tech.

 

[killahog]

Pictures from inside transfer switch cabinet.

 

[killahog]

Update photos

 

[wyliesdiesels]

WOw looks like a hack job.

Whats with the doubled up #12 or #10 on the breakers at the bottom?

Is that the main breaker for your main service panel?

Where does the feed from the generator come in at?

 

[Chilliwack Murray]

It does look like a hack job and probably doesn’t meet code anywhere but I don’t see anything wrong from a functional point of view. The Generac transfer switch output feeds the Generac panel and is also jumped over to the Westinghouse panel where they’ve added a second breaker before the existing main for some reason.

Both panels are fed from whatever source the transfer switch is connected to. I would assume the intent is to open the main on the Westinghouse panel when running on generator to reduce load. Once retransferred to utility the Westinghouse main breaker could be reclosed and everything powered by utility.

My guess is that the OP closed the Westinghouse main breaker while the transfer switch was still on generator supply overloading the generator.

If that’s the case, it’s unlikely there was any damage to the generator - very likely there is a breaker right on the generator that has tripped and needs to be reset.

 

[killahog]

I am assuming the feed from the Generator is coming thru the conduit at the top of the transfer box. I don’t know why those wires are doubled up . Westinghouse panel is feed from this main box that is in another room. When the generator was running I closed the switch on box listed as A and that’s when the generator started bogging down.

 

[Chilliwack Murray]

It looks like the output of the transfer switch is feeding the Generac panel breakers as well as the Westinghouse panel based on the wire colours. Can you confirm the details on the photo?

If the Westinghouse is fed as shown in this photo it should have no other utility connection. If so, turning the main breaker back on should not have caused a back feed and should only have overloaded the generator which would cause it to bog down and possibly trip a breaker and cause a shutdown fault on the controller that would need to be reset.

 

[Badgerstate]

Hello, I have a Generac brand Generator that was running when the main breaker from the house was closed and power was backfed into the generator and fried it. I guess fried was not the best description there was no fire it just bogged down while running and I did actually smell the odor of burnt insulation or wires. I am looking for advice or suggestions into what damage was likely caused and where would be a place to start in determining if the unit is salvageable. The unit was purchased around 2006 and the badge on the inside of the box has the following Information .

Thanks .

So, former Generac tech here and Ive worked on those 16Kws many times. So, if you smelt burning wire insulation, its difficult to tell just how much of it is fried.
It could be OK as-is and it could be trash. I mean, you could be looking at the entire rotor or stator being trash at this point in time.
Youre really never going to know until you tear into it and see what youve got.

 

[killahog]

The Westinghouse is fed thru the top.

 

[wyliesdiesels]

It does look like a hack job and probably doesn’t meet code anywhere but I don’t see anything wrong from a functional point of view. The Generac transfer switch output feeds the Generac panel and is also jumped over to the Westinghouse panel where they’ve added a second breaker before the existing main for some reason.

Both panels are fed from whatever source the transfer switch is connected to. I would assume the intent is to open the main on the Westinghouse panel when running on generator to reduce load. Once retransferred to utility the Westinghouse main breaker could be reclosed and everything powered by utility.

My guess is that the OP closed the Westinghouse main breaker while the transfer switch was still on generator supply overloading the generator.

If that’s the case, it’s unlikely there was any damage to the generator - very likely there is a breaker right on the generator that has tripped and needs to be reset.

Look again. the westinghouse panel breaker has 3 wires total on each lug. theres 2 larger wires- 1 brown, 1 black, that are connected behind the smaller doubled up wires on the breaker. This could be from the main disconnect in the other room

there should only be one feed to that westinghouse breaker, which would be from the ATS. but that doesnt look to be the case.

I am assuming the feed from the Generator is coming thru the conduit at the top of the transfer box. I don’t know why those wires are doubled up. Westinghouse panel is feed from this main box that is in another room. When the generator was running I closed the switch on box listed as A and that’s when the generator started bogging down.

where do the brown and black wires coming out of the bottom of the westinghouse breaker go to? looks like they go up into the SEU cable coming in thru the top center conduit- brown on left black on right.

 

[killahog]

I assume they go out to my shop.

 

[wyliesdiesels]

...deleted

 

[wyliesdiesels]

I assume they go out to my shop.

the shop feed should be on a branch breaker not coming out of the line side of the main breaker

 

[wyliesdiesels]

open up panel A, that black disconnect and the panel in your shop and take some pictures. post them here.

im wondering why you have 2 disconnects.

Also, since there is a main disconnect and transfer switch, this westinghouse panel should be setup as a subpanel w/ isolated neutral NOT as a main service panel

how does the PoCo feed come in? Meter--> black disconnect--> transfer switch or???

 

[Bert_]

Cut the zip ties is your Westinghouse panel. A bunch of those wires aren't hooked up.

 

[killahog]

Panel A on the right, when I opened the lever all the power to the house went out.

 

[wyliesdiesels]

Woa WTF is going on here. it just keeps getting worse...

the wire jumpers are not kosher. also the neutral bond to the frame is no bueno

ok we need to backup here. Where does the feed from the meter come in at? Panel A?

You really need to gut all this and start over.... what a mess

 

[Neggy]

STOP
DO NOT DO ANYTHING ELSE

GET A LICENSED ELECTRICIAN OUT THERE AND GO OVER THE WHOLE ELECTRICAL SYSTEM TOP TO BOTTOM

THERE IS SO MUCH WRONG/DANGEROUS THERE I WON'T EVEN COMMENT ON IT.

 

[killahog]

The main power comes into the back of box (A) from there the power goes out and into Into a large black box below A&B and then into box (B) the one with the copper and aluminum wires. In that lower box the wire branches off to feed the newer sub panel that feeds the GEO Thermal and electric water heater and then it goes into box (B) where it is fused with a 100 amp fuse. The power runs from B to another breaker box that is pictured with the door open and references Water heater, oddly the power comes into the top of this box and then goes out to a large switch box it is the one with the 4 pole switch. The wires are connected to this large switch and then go right back out the top and back into the box that references (Water Heater),Additionally there is another heavy set of wires that leave the WH box and go on the feed box that is to the left of the Guardian transfer switch. So from what I can tell the generator is powered from the westinghouse house box. I programed the generator to start when no power was present and pulled the breaker on box (A) and it started up. I let it run for about 3 minutes and when I closed breaker (A) the generator bogged down and I ran out and knocked the breaker down outside and could smell burnt insulation . Nothing inside the house or anywhere visible on the generator appears to be burnt. I will try to post the next set of pictures in the order in which the power is routed.

 

[PCustoms]

Holy **** man, how long you been in this house? Was there an inspection done when you bought it?

Looks like it was wired with leftovers from Frankenstein's lab. There's seriously so much wrong with this place you need to call an electrician Monday and be prepared to open the wallet.....

 

[wyliesdiesels]

Wow that is a serious mess.

Id rip it all out and start over. There are some serious issues here

Is that transfer switch service rated? If so then it should be directly behind the meter, in place of disconnect A. Everything after it should be setup as a subpanel.

you shouldn't have 2 disconnects especially one with a bonded neutral running through a disconnect.... the neutral bond should only be in the first disconnect

that 4 pole knife switch with triple tapped lugs is definitely something out of Frankenstein's lab lol

get an electrician in there to clean all that up

 

[killahog]

I was mistaken about the feed that goes to my shop, the shop is powered

Holy **** man, how long you been in this house? Was there an inspection done when you bought it?

Looks like it was wired with leftovers from Frankenstein's lab. There's seriously so much wrong with this place you need to call an electrician Monday and be prepared to open the wallet.....

I have been here 10 years but the generator is the only thing I have had trouble with. I don't think there ever was an inspection done before I bought the place.