ATS Will Not Transfer Back To Utility

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Sam Moore

Member
Location
SC
Ok, I'm at wits end with an ATS that I'm trouble shooting...

-Briggs and Stratton 200 Amp ATS with Service Disconnect and AC Control Module
connected to a 12 kw B & S Generator

- Utility power fails and switchs to gen and all is well, problem is Utility returns and ATS will not switch back to Utility. Control board LEDs indicate that both utility and gen power is present. Once Utility is restored the only way it will transfer back is shut Gen breaker of and it will switch back to Utility, other wise it will run Gen until fuel runs out

History- I got involved after a surge hit ATS and this started...I replaced control board and transfering mechanism (solenoids and all) due to obvious burn marks on both...only parts left were fuses and breakers and ct's...generator and 240 volt sensing circuit check out fine
I also installed a surge suppressor to help prevent future attacks from mother nature and the poco

What am I missing???
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Is this a change in the behavior of the ATS? Did the same system work differently after some earlier loss of utility event? Is this the first time this ATS was ever called upon to switch to the alternate source due to a real loss of utility (as opposed to a routine test)?

My question is essentially this: Why are you expecting the ATS to automatically transfer back to its normal source?

An ATS can be designed (or programmed, depending on its control system) to be either "normal seeking" or "power seeking." The former will transfer back to normal as soon as it sees the power available, perhaps with a short time delay built it to allow it to be certain that the normal source is back to stay. The later will remain on whatever power source it is presently using, as long as that source remains available, regardless of whether another source is also available.
 

Sam Moore

Member
Location
SC
Is this a change in the behavior of the ATS? Did the same system work differently after some earlier loss of utility event? Is this the first time this ATS was ever called upon to switch to the alternate source due to a real loss of utility (as opposed to a routine test)?

My question is essentially this: Why are you expecting the ATS to automatically transfer back to its normal source?

An ATS can be designed (or programmed, depending on its control system) to be either "normal seeking" or "power seeking." The former will transfer back to normal as soon as it sees the power available, perhaps with a short time delay built it to allow it to be certain that the normal source is back to stay. The later will remain on whatever power source it is presently using, as long as that source remains available, regardless of whether another source is also available.

Yes this is a change in the behavior from what the home owner and the rep I talked too said...wished rep was more helpful but he was dumber than me...
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Without seeing the schematic for the controller, I can't give you an answer. But I will make an observation. Part of the ATS control system has the ability to recognize that normal power is available, as evidenced by the power available lights. But another part of the control system does not have the ability to recognize that normal power is available, as evidenced by its failure to transfer. Those are two different tasks that are performed by the control system. What your symptoms tell me is that something within the control system has failed. It could be as simple as a loose wire, or as complex as a control card.

But here is another observation. If you manually trip the generator, the ATS does return to normal. This seems to contradict my first observation. If something were loose or were to have failed, then why should we expect it to work properly, after you take away the alternate source?

The only explanation that makes sense to me is that the characteristic of "Normal seeking" as opposed to "Power seeking" is a user-selectable option. I would look for a toggle switch or a software command that tells the ATS to behave one way or to behave the other way.
 

Sam Moore

Member
Location
SC
Owner's manual states that it will transfer back to utility after utility voltage reaches 80% nominal voltage and holds for 10 seconds and generator will run in cool down mode for 60 sec after retransfer...
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I would lean more towards a limit switch problem, if they were not re-installed properly or bent after the coils were replaced, they may prevent a re-transfer until power is removed from the generator output. I don't think the CT's will have anything to do with it, as they just monitor load.
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
Inphase Monitor Feature

Inphase Monitor Feature

Ok, I'm at wits end with an ATS that I'm trouble shooting...

-Briggs and Stratton 200 Amp ATS with Service Disconnect and AC Control Module
connected to a 12 kw B & S Generator

- Utility power fails and switchs to gen and all is well, problem is Utility returns and ATS will not switch back to Utility. Control board LEDs indicate that both utility and gen power is present. Once Utility is restored the only way it will transfer back is shut Gen breaker of and it will switch back to Utility, other wise it will run Gen until fuel runs out

History- I got involved after a surge hit ATS and this started...I replaced control board and transfering mechanism (solenoids and all) due to obvious burn marks on both...only parts left were fuses and breakers and ct's...generator and 240 volt sensing circuit check out fine
I also installed a surge suppressor to help prevent future attacks from mother nature and the poco

What am I missing???

If the ATS is a 2 position switch (no neutral position) then chances are it has the inphase monitor feature (sync check) . It onlly allows transfer during hot-bus, hot bus transfer when both sources are within approx 10 elec. degrees. Check freq
of generator. If gen is set too close to 60.00hz then sync time wil be too long.
Adjust gen freq to 60.2 hz to get faster sweep time to allow transfer to normal.
If you do the test by operating the test switch HB, HB then it may not transfer to gen. If you are testing by opening normal breaker (dead bus-hot-bus) then the sync feature is not in circuit & it will transfer. Retransfer to normal is always hot-bus, hot-bus until you open gen breaker. That's why it transferred back.
Just adjust gen freq to 60.2 hz and test it.
This is a real common problem that the gen techs don't understand:roll:

Tony
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Tony,
Isn't an issue only with "closed transition" transfer switches? The ones that actually parallel the utility and generator for a cycle or two on re-transfer to utility. This ATS does not appear to be a "closed transition" device.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
The OP did not say, but judging from it being a 12 kw B&S generator, I would venture a guess that this is a single phase unit, and the t-switch would not have the in-phase monitor option. I think the switch is not fully transfering, maybe binding thus not opening the emergency side coil, but far enough to keep the normal coil locked out, then when the generator is switched off, it drops power to the emergency side coil, allowing it to move enough to have the limit switch make and go back to normal. This is assuming the new control board is wired and working properly. If it is the Generac style of switch, they are notorious at jamming again if all of the coil residue is not cleaned off the plunger.
 

Sam Moore

Member
Location
SC
I would lean more towards a limit switch problem, if they were not re-installed properly or bent after the coils were replaced, they may prevent a re-transfer until power is removed from the generator output. I don't think the CT's will have anything to do with it, as they just monitor load.

coils and limit switched were factory installed and tested... The switching mechanism was sold to me as a complete unit, all I did was attach bus to main disco breaker, leads to generator disco breaker and control wires...
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Tony,
Isn't an issue only with "closed transition" transfer switches? The ones that actually parallel the utility and generator for a cycle or two on re-transfer to utility. This ATS does not appear to be a "closed transition" device.

Don:

The ASCO series switches (300 and 7000 series) have the phase monitoring on open transition switches. It gives less of a jolt to motors during the transfer, and it is only active when a hot source to hot source transfer occurs (i.e. during testing or when the load transfers back to normal power.)

The ATS does have to have a pretty fast transfer though (the ASCO's are pretty fast). Otherwise, the phase alignment between the source and the decaying motor voltages might change during transfer.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
coils and limit switched were factory installed and tested... The switching mechanism was sold to me as a complete unit, all I did was attach bus to main disco breaker, leads to generator disco breaker and control wires...

And you also said you replaced the contol board? Can you post a factory control wiring diagram? Or maybe a model #?
 

Sam Moore

Member
Location
SC
And you also said you replaced the contol board? Can you post a factory control wiring diagram? Or maybe a model #?

Here's a link to a pdf of installation manual with diagrams, model # 71046 and yes control board has been replaced

http://www.norwall.com/product_pdfs/495_071025_0_om_Domestic.pdf

Thanks to everyone's input even if it doesnt directly help me with the problem at hand, I'm still picking up other knowledge... Eventhough I dont post very often on here, I read and learn something new or see a better way of doing something almost daily... when I worked for Mr. Big I learned from the more experienced guys that I worked with, since I've been working for myself this forum has replaced it plus I get the point of view from other owners/contractors
 
Last edited:

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Don:

The ASCO series switches (300 and 7000 series) have the phase monitoring on open transition switches. It gives less of a jolt to motors during the transfer, and it is only active when a hot source to hot source transfer occurs (i.e. during testing or when the load transfers back to normal power.)

The ATS does have to have a pretty fast transfer though (the ASCO's are pretty fast). Otherwise, the phase alignment between the source and the decaying motor voltages might change during transfer.
Thanks, I was aware of the fast re-transfer issue with larger motor loads, but I did not know that some open transition devices looks at the sync between the utility and generator on transfer when both sources.
There are cases where motors over 50 hp had their shafts broken on out of sync open transition transfer. The other way to deal with this problem it to put a delay between opening the connection to one source and closing the connection to the other source.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
Here's a link to a pdf of installation manual with diagrams, model # 71046 and yes control board has been replaced

http://www.norwall.com/product_pdfs/495_071025_0_om_Domestic.pdf

Thanks to everyone's input even if it doesnt directly help me with the problem at hand, I'm still picking up other knowledge... Eventhough I dont post very often on here, I read and learn something new or see a better way of doing something almost daily... when I worked for Mr. Big I learned from the more experienced guys that I worked with, since I've been working for myself this forum has replaced it plus I get the point of view from other owners/contractors

Sam
I am trying to understand the schematic in your link. Where do the other sides of F1 and F2 connect where it says gen/utility ? Do they go to the ATS output terminals T1 & T2 ?
Tks

Tony
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Here's a link to a pdf of installation manual with diagrams, model # 71046 and yes control board has been replaced

http://www.norwall.com/product_pdfs/495_071025_0_om_Domestic.pdf

Thanks to everyone's input even if it doesnt directly help me with the problem at hand, I'm still picking up other knowledge... Eventhough I dont post very often on here, I read and learn something new or see a better way of doing something almost daily... when I worked for Mr. Big I learned from the more experienced guys that I worked with, since I've been working for myself this forum has replaced it plus I get the point of view from other owners/contractors

I don't know how this post got in front of mine, because it wasn't there when I did my last post, but anyhoo, yes its basically the same switch as in my link, but its a much clearer diagram. I do believe it is the two wires got swapped accidentally. This would cause the switch to work on utility fail, but once transfered, it can't switch back because the other hot is open. I would check those connections first. If it's not there, check for voltage output on J1 to ground. Should be 120 volts at that point if the controller is calling for the transfer back to normal. The CT's are just for load shed purposes, so they should have nothing to do with the transfer.
 
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