I work for an electric cooperative in Ohio and we recently had a severe ice storm. As in every long power outage many generators were running. (Most not hooked up properly.) One question that we received was that several people damaged their generators by hooking them up to a 240 volt breaker. When they returned the generator the place that sold them said that the new generators could not run that way so they gave them a previous year's model and they hooked it up the same way and it functioned properly. Does anyone know how the generators have changed?
Generator Connections
- Thread starter dyanchik
- Start date
- Status
Re: Generator Connections
bump
I too would like to know if there's any difference.
By the way, what is your policy towards homeowners who backfeed their panels instead of using a transfer switch? What happens to their generators if they are backfeeding your lines when you turn your lines back on?
~Peter
bump
I too would like to know if there's any difference.
By the way, what is your policy towards homeowners who backfeed their panels instead of using a transfer switch? What happens to their generators if they are backfeeding your lines when you turn your lines back on?
~Peter
Re: Generator Connections
dyanchik,
You left a lot of information out of you question.
You mention
If so, what liability does the generator manufacturer had if the generator is not applied per their instructions and violate code requirements?
As is common with electrical and electrical equipment failures it is most difficult to determine a cause of failure as most often the even that caused the failure has long passed.
If the homeowner was back feeding and either didn't know enough to open the main breaker or simply forgot to do so, the utility power came back on and now the homeowner doesn't want to assume the cost of his lack of knowledge of carelessness. The vendor doesn't know from adam anyway and the customer is complaining so the replace the generator as defective and not address the issue that the product was misapplied.
dyanchik,
You left a lot of information out of you question.
You mention
Are we to assume that is a 2p branch breaker that is being back feed?
If so, what liability does the generator manufacturer had if the generator is not applied per their instructions and violate code requirements?
As is common with electrical and electrical equipment failures it is most difficult to determine a cause of failure as most often the even that caused the failure has long passed.
If the homeowner was back feeding and either didn't know enough to open the main breaker or simply forgot to do so, the utility power came back on and now the homeowner doesn't want to assume the cost of his lack of knowledge of carelessness. The vendor doesn't know from adam anyway and the customer is complaining so the replace the generator as defective and not address the issue that the product was misapplied.
Re: Generator Connections
Say the power goes out. The home owner doesn't bother to open the main, starts her generator and closes the gen main. What happens? Well this 5kW gen is trying to power all of the houses on its transformer, light up the HV line back through the utility transformer, and power all of the houses on the block through their transformers all the way back the open utility cutout. I'd say that qualifies as a 0 ohm impedance. I'd say the gen CB trips immediately or the gen burns up shortly after immediately. Shouldn't be any concern about the utility coming back on. The gen would never stay on line driving into the utility.
Sure sounds like we are missing a lot of the story.
carl
Practically speaking you can't with any gen that the homeowner would have.
Say the power goes out. The home owner doesn't bother to open the main, starts her generator and closes the gen main. What happens? Well this 5kW gen is trying to power all of the houses on its transformer, light up the HV line back through the utility transformer, and power all of the houses on the block through their transformers all the way back the open utility cutout. I'd say that qualifies as a 0 ohm impedance. I'd say the gen CB trips immediately or the gen burns up shortly after immediately. Shouldn't be any concern about the utility coming back on. The gen would never stay on line driving into the utility.
There would have to be a major changes in the Laws of Physics and Engineering to get the previous year's model (or any model) to drive into a dead short. The utility, with the power off and all of the houses hooked up, look like a dead short - that's the definition of 0 volts.
Sure sounds like we are missing a lot of the story.
carl
- Location
- Massachusetts
Re: Generator Connections
Lets say the customer is on their own transformer and the reason the power is out is that a primary fell to the ground with one end still tied to that transformer.
Now you have a live line waiting for a victim.
We never know what the scenario will be for any outage, but a back feed can kill power company employees trying to restore power.
It is imperative to use a transfer device, the NEC requires it and so do many utilities as a condition of service.
[ January 14, 2005, 06:30 PM: Message edited by: iwire ]
Carl IMO you are making some dangerous assumptions.
Lets say the customer is on their own transformer and the reason the power is out is that a primary fell to the ground with one end still tied to that transformer.
Now you have a live line waiting for a victim.
We never know what the scenario will be for any outage, but a back feed can kill power company employees trying to restore power.
It is imperative to use a transfer device, the NEC requires it and so do many utilities as a condition of service.
[ January 14, 2005, 06:30 PM: Message edited by: iwire ]
Re: Generator Connections
I have spent a lot of years, far enough out, that the extra gen you keep at your house is not an emergency genset. If the power goes out four or five times a year, always in the winter, then preparing for it is called normal, not an emergency. So I've seen a lot of ways to do this.
One I saw consisted of a 50A feed from the main panel to a little SQD QO subpanel. The first two CBs were a 2 pole 50A, and a 2 pole 30A. installed side by side with an interlock device between them (about $6 from SQD). The 50A was fed from the main panel. The 30a was backfed using a #10 SO cord with 4 prong male plug to fit a 5kW gen. The cord was long enough to reach outside to the gen location.
From the sub panel, he had the oil fired boiler, a couple of light circuits, and an outside outlet for the truck heater.
Safe, no back feed to a dead buss, cheap, no 200A transfer switch - code compliant?, don't know, I carefully didn't look it up.
carl
Just an aside about transfer switches and generators: Mind you, I would never advocate this, just something I have heard about and have seen a time or two.
I have spent a lot of years, far enough out, that the extra gen you keep at your house is not an emergency genset. If the power goes out four or five times a year, always in the winter, then preparing for it is called normal, not an emergency. So I've seen a lot of ways to do this.
One I saw consisted of a 50A feed from the main panel to a little SQD QO subpanel. The first two CBs were a 2 pole 50A, and a 2 pole 30A. installed side by side with an interlock device between them (about $6 from SQD). The 50A was fed from the main panel. The 30a was backfed using a #10 SO cord with 4 prong male plug to fit a 5kW gen. The cord was long enough to reach outside to the gen location.
From the sub panel, he had the oil fired boiler, a couple of light circuits, and an outside outlet for the truck heater.
Safe, no back feed to a dead buss, cheap, no 200A transfer switch - code compliant?, don't know, I carefully didn't look it up.
carl
Re: Generator Connections
Bob,
This primary traveled a quarter mile to the break, so if I had backfed my transformer, I could have energized this quater mile of conductor with a relatively small generator.
Carl, a lineman was killed in Young Harris, Georgia this past summer from this same case scenario.
Roger
Bob,
you are right. You know the setting my house is in and your scenario has actually happened to me.
This primary traveled a quarter mile to the break, so if I had backfed my transformer, I could have energized this quater mile of conductor with a relatively small generator.
Carl, a lineman was killed in Young Harris, Georgia this past summer from this same case scenario.
Roger
Re: Generator Connections
Now, how about rereading the post. This time pay attention to the physics and the science. And please, respond concerning my reasoning of what would happen if one did try to drive into a closed main to the utility.
**************************
Now separate subject - as far as killing utility people from home owner back feeding, I'll let our utilities guys be the authority, but I'll bet it ain't gonna happen. For one thing, I've never seen any utility crew working on a dead line that they didn't have a spider hooked on it. And second, I can't imagine any utility is going to let 5 bazillion jack and jill home owners be in charge of their safety. They are going to mitigate the risk somehow.
I want to be perfectly clear. I'm not saying it is okay to backfeed. I'm saying I suspect there is little risk to utilities workers because they know it can happen, there are way too many daffy home owners out there and the utilities crews guard against it.
carl
Come on Bob - give me a break :roll: The conversation was about what could be the difference between two models of generator - one that could drive into a closed main and one that could not. My response was not about if a transfer switch is needed - of course it is.
Now, how about rereading the post. This time pay attention to the physics and the science. And please, respond concerning my reasoning of what would happen if one did try to drive into a closed main to the utility.
**************************
Now separate subject - as far as killing utility people from home owner back feeding, I'll let our utilities guys be the authority, but I'll bet it ain't gonna happen. For one thing, I've never seen any utility crew working on a dead line that they didn't have a spider hooked on it. And second, I can't imagine any utility is going to let 5 bazillion jack and jill home owners be in charge of their safety. They are going to mitigate the risk somehow.
I want to be perfectly clear. I'm not saying it is okay to backfeed. I'm saying I suspect there is little risk to utilities workers because they know it can happen, there are way too many daffy home owners out there and the utilities crews guard against it.
carl
Re: Generator Connections
Carl,
Roger
Carl,
it has already been addressed and in my post it shows that a primary (at any voltage} can be refed and kill.
iT HAS HAPPENED AND UNFOURTUNATELY IT WILL HAPPEN AGAIN Soory to bring this to your attention. :roll:
Roger
Re: Generator Connections
I guess that was a little abrupt.
You want to talk about dead linemen. Well okay with me, but I don't want you to feel sorry about it.
I joined the topic cause it was about generators and how could different model years feed differently into a utility. That is the physics and science I was talking about.
You don't want to. That's okay with me. I just won't be joining you.
You have a good day
carl
I guess that was a little abrupt.
You want to talk about dead linemen. Well okay with me, but I don't want you to feel sorry about it.
I joined the topic cause it was about generators and how could different model years feed differently into a utility. That is the physics and science I was talking about.
You don't want to. That's okay with me. I just won't be joining you.
You have a good day
carl
- Location
- Massachusetts
Re: Generator Connections
IMO you are looking at "the physics and the science" of this with only one mode of utility failure in mind.
No, I do not believe my 5KW portable generator will light up my town if the problem is miles away from me.
However we can never know what or where the failure will be and in my opinion your post seemed to say a back feed can not happen.
I am fully away a home generator is not an 'emergency' generator it is an optional standby by unit, it makes no difference you still need to prevent a back feed.
Physics and science not withstanding I think it is dangerous to lead anyone that reads this forum to believe that a small home generator allowed to back feed the utility is safe simply because it will likely be overloaded and fail.
Sure the power company guys should be watching out for themselves, that does not relive us from following the rules even for a rare outage.
Bob
[ January 15, 2005, 06:42 AM: Message edited by: iwire ]
Carl, I am sorry you feel you need a 'break' I take this issue of back feeds very seriously.
IMO you are looking at "the physics and the science" of this with only one mode of utility failure in mind.
No, I do not believe my 5KW portable generator will light up my town if the problem is miles away from me.
However we can never know what or where the failure will be and in my opinion your post seemed to say a back feed can not happen.
It all depends on how far 'into the utility' we are talking about.
I am fully away a home generator is not an 'emergency' generator it is an optional standby by unit, it makes no difference you still need to prevent a back feed.
If you read my post I used the term transfer device not transfer switch as I am also aware that there other ways to prevent a back feed than a true transfer switch.
Physics and science not withstanding I think it is dangerous to lead anyone that reads this forum to believe that a small home generator allowed to back feed the utility is safe simply because it will likely be overloaded and fail.
Sure the power company guys should be watching out for themselves, that does not relive us from following the rules even for a rare outage.
Bob
[ January 15, 2005, 06:42 AM: Message edited by: iwire ]
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: Generator Connections
Simple: "Mr. Homeowner, you need to install a transfer switch to protect your generator and to prevent the electrocution of utility workers from your honest mistake. Given the seriousness of this problem, I'll give you a break in the price if you would like me to hook it up for you."
I think my threeway switch transfer switch should be legal, I just can't figure out how to make a 4-gang with threeway switches scream and shout the way it's required in 702.7.
This little question causing all this ruckus?
Simple: "Mr. Homeowner, you need to install a transfer switch to protect your generator and to prevent the electrocution of utility workers from your honest mistake. Given the seriousness of this problem, I'll give you a break in the price if you would like me to hook it up for you."
I think my threeway switch transfer switch should be legal, I just can't figure out how to make a 4-gang with threeway switches scream and shout the way it's required in 702.7.
Re: Generator Connections
Bob, roger -
Sigh, I thought I was out of this.
roger - just an aside: When you are trying to make a point, and don't think you are getting through, restating the same ideas in a louder voice doesn't help. Let me give you an example.
RESTATING THE SAME IDEAS IN A LOUDER VOICE DOESN'T HELP.
See what I mean?
I have been yelled at. It has been suggested that my understanding of electricity is deficient and that I have little concern for the safety of linemen. Well, I likely don't agree, and certainly have not improved my understanding by being yelled at. Regardless, I absolutely defer to you two. You certainly have been here far longer than I and are obviously far more knowledgeable that I in this matter.
When I read the first two posts, I thought the conversation was about why some models of generator would drive into a shorted utility buss and some would not. You two seem far more interested is throwing rocks than in discussing the physics of what is happening at the generator. As I said, I am okay with that, it's your decision, not mine. But, I would rather not be part of this.
Now if someone wanted to discuss impedances, short circuit currents, open circuit voltages, reverse power relay schemes for small gensets, code required equipment (yes Bob, "transfer device" required - I heard you) I'm interested.
Other than that, may I please be excused from this topic now?
carl
Bob, roger -
Sigh, I thought I was out of this.
Well guys, looking from my side, I think you two are looking at this with only one special case mode of failure - a very narrow limited view. However, I bow to your (both of you) superior knowledge and judgement, and I absolutely admit to my short sightedness in this issue.
Bob - I got that. Gee, I may have even understood that before you told me. Driving into a high impedance, open buss with a small generator will (can?) cause primary voltage voltages the be at similar levels as the utility supplied HV. These high levels of voltage on the broken primary line induce additional risk to utility repair personnel. I promise, I clearly had both of these concepts under control before the discussion.
roger, Bob - I certainly appreciate you two reminding me of this again, and again, and again, and again. Let's see if I got it. Improper back feeding of open (high impedance) utility lines will (can?) cause additional risk to utility personnel.
Bob, roger - I am glad to see you both clearly understand this. It really improves your credibility and makes it a lot easier for me to accept your clearly superior judgement in this case.
Bob - I changed my mind on this issue. I'm okay here, you go ahead and keep the "break". Who knows? Maybe you will need it one of these days.
roger - just an aside: When you are trying to make a point, and don't think you are getting through, restating the same ideas in a louder voice doesn't help. Let me give you an example.
RESTATING THE SAME IDEAS IN A LOUDER VOICE DOESN'T HELP.
See what I mean?
I have been yelled at. It has been suggested that my understanding of electricity is deficient and that I have little concern for the safety of linemen. Well, I likely don't agree, and certainly have not improved my understanding by being yelled at. Regardless, I absolutely defer to you two. You certainly have been here far longer than I and are obviously far more knowledgeable that I in this matter.
When I read the first two posts, I thought the conversation was about why some models of generator would drive into a shorted utility buss and some would not. You two seem far more interested is throwing rocks than in discussing the physics of what is happening at the generator. As I said, I am okay with that, it's your decision, not mine. But, I would rather not be part of this.
Now if someone wanted to discuss impedances, short circuit currents, open circuit voltages, reverse power relay schemes for small gensets, code required equipment (yes Bob, "transfer device" required - I heard you) I'm interested.
Other than that, may I please be excused from this topic now?
carl
Re: Generator Connections
Carl stated "Just an aside about transfer switches and generators: Mind you, I would never advocate this,
One I saw consisted of a 50A feed from the main panel to a little SQD QO subpanel. The first two CBs were a 2 pole 50A, and a 2 pole 30A. installed side by side with an interlock device between them (about $6 from SQD). The 50A was fed from the main panel. The 30a was backfed using a #10 SO cord with 4 prong male plug to fit a 5kW gen. The cord was long enough to reach outside to the gen location.
From the sub panel, he had the oil fired boiler, a couple of light circuits, and an outside outlet for the truck heater.
Safe, no back feed to a dead buss, cheap, no 200A transfer switch - code compliant?, don't know, I carefully didn't look it up."
carl
CARL, THIS IS ONLY A SAFE INSTALLATION IF THE NEUTRAL ON THE GENERATOR IS FLOATING OR NOT BONDED TO THE GROUND AT THE GENERATOR AS MOST STORE BOUGHT PORTABLES ARE! IF THE BOND IS STILL IN PLACE THE NEUTRAL NEEDS TO BE BROKE AT THE PANEL WITH THE CIRCUIT CONDUCTORS...
-DEREK
Carl stated "Just an aside about transfer switches and generators: Mind you, I would never advocate this,
One I saw consisted of a 50A feed from the main panel to a little SQD QO subpanel. The first two CBs were a 2 pole 50A, and a 2 pole 30A. installed side by side with an interlock device between them (about $6 from SQD). The 50A was fed from the main panel. The 30a was backfed using a #10 SO cord with 4 prong male plug to fit a 5kW gen. The cord was long enough to reach outside to the gen location.
From the sub panel, he had the oil fired boiler, a couple of light circuits, and an outside outlet for the truck heater.
Safe, no back feed to a dead buss, cheap, no 200A transfer switch - code compliant?, don't know, I carefully didn't look it up."
carl
CARL, THIS IS ONLY A SAFE INSTALLATION IF THE NEUTRAL ON THE GENERATOR IS FLOATING OR NOT BONDED TO THE GROUND AT THE GENERATOR AS MOST STORE BOUGHT PORTABLES ARE! IF THE BOND IS STILL IN PLACE THE NEUTRAL NEEDS TO BE BROKE AT THE PANEL WITH THE CIRCUIT CONDUCTORS...
-DEREK
Re: Generator Connections
I'm not so sure about the unsafe part, especially if one is using an equipment grounding conductor, not just the raceway. Yes, the neutral current is shared over the parts of the grounding conductor that is in parallel.
However, consider stove and dryer installations in the US for the last 60+ years. Apparently, it was not unsafe to to this. I'm not sure I see the difference safety wise. But, I'm definitely listening to learn.
carl
[ January 15, 2005, 08:30 PM: Message edited by: coulter ]
You're right, the code says that. As you said, one would have to use neutral switching breakers or remove the bond at the gen.
I'm not so sure about the unsafe part, especially if one is using an equipment grounding conductor, not just the raceway. Yes, the neutral current is shared over the parts of the grounding conductor that is in parallel.
However, consider stove and dryer installations in the US for the last 60+ years. Apparently, it was not unsafe to to this. I'm not sure I see the difference safety wise. But, I'm definitely listening to learn.
carl
[ January 15, 2005, 08:30 PM: Message edited by: coulter ]
Re: Generator Connections
I was going to ask at some point anyway, how does any transfer switch comply with 702.7? I'm thinking the simple residential panel with interlocked mains for example.
George, how would the transfer switch otherwise be legal? Never heard of a 2-pole threeway switch. Just curious;Originally posted by georgestolz:
I think my threeway switch transfer switch should be legal, I just can't figure out how to make a 4-gang with threeway switches scream and shout the way it's required in 702.7.
I was going to ask at some point anyway, how does any transfer switch comply with 702.7? I'm thinking the simple residential panel with interlocked mains for example.
- Location
- Illinois
- Occupation
- retired electrician
Re: Generator Connections
Paul,
Don
Paul,
Everything complies...if you don't have or don't want to provide the signals, it wasn't practicable.
Don
- Status