Wiring a Generator to main panel

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Old 10-31-01, 05:37 PM
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Question

We just bought a generator for back up power for our house. It doesn't come on automatically, but I do want to wire it to certain circuits on my electrical panel. I've seen switches at the Sears Hardware store near my house that automatically switches the power back to the main supply when it comes back on (so the circuits don't try to get power from the power company, and the generator), but they are kind of expensive.

Does anybody know of a way to accomplish this inexpensively?

Thank you in advance for any suggestions.
 
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Old 11-01-01, 06:46 AM
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Consider a double-pole double-throw enclosed knife switch.The panel with the ememrgency ciruits connect to the common terminals of the DPDT.The top terminals connects,say, to the CB in the house panel-the bottom terminals connect to a 2-pole CB which connects to the un-grounded generator leads. The generator CB should be sized to limit the generator amps. to the rated value of the generator.
 
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Old 11-01-01, 08:14 AM
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Lightbulb Alternative to transfer switch.

You can connect the loads you want to be able to run from the generator to a small sub panel and supply that sub panel via a cord and plug tail that is plugged into either a receptacle fed from the main panel or a cord from the generator. Since the tail cannot be plugged into two places at once there is no way to cross connect the generator and the utility power. The receptacle from the main panel should be configured for the sub panel's full load. since this may be more than the generator can supply you may need an adapter which matches the cord from the generator in order to connect the supply tail to the generator cord.

Individual loads such as furnaces can also be converted to cord and plug connection so that you can run cords to each one from the generator. The use of cord and plug connection also replaces the disconnecting means that is required to be in sight of appliances that are fastened in place.
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Old 11-01-01, 10:29 AM
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Herm,
I usually start a homeowner/genny deal here;
http://www.gen-tran.com/
surf it up, ask us & we will respond
 
  #5  
Old 11-01-01, 02:22 PM
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Wgoodrich
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There are many different wiring designs meeting the NEC requirments of the NEC concerning generators. The least expesive that meets the NEC requirements that I know of is using a transfer clip used to straddle two 240 volt breakers installed in you main panel. Click on the following link. This is a drawing of that wiring method. Look on the left side for links to many more different drawings showing other methods of meeting the NEC requirements depending on location of generator and size.

After you have read and looked there maybe you will have enough info to want to ask some questions back here again.

http://homewiring.tripod.com/generator.html

Hope this helps

Wg
 
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Old 11-01-01, 11:35 PM
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Warren,
I am curious about this 'T-clip', Is it something that is made for all panels, or made by each panel maker? where can i go to learn more about it?
The only prob i have ( with a does-all T-switch) is that some will dump the entire dwelling onto a small genny...
 
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Old 11-02-01, 04:18 AM
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User mistakes are not always preventable.

Originally posted by wirenuts
Warren,
I am curious about this 'T-clip', Is it something that is made for all panels, or made by each panel maker? where can i go to learn more about it?
The only prob i have ( with a does-all T-switch) is that some will dump the entire dwelling onto a small genny...
Wirenuts

Your concern is well founded. The generators have built in overload protection so they will get several chances to figure it out.
I am an electrician and years ago I was vacationing in Maine. The camp next to us had built in electricity, but no utility service, while ours ran entirely on propane. I kept hearing a generator start, run hard, idle down, run hard, idle down, run hard, idle down, and stop. after three cycles I walked over and offered to help. I found the occupants trying to run excessive load on a small generator set. I turned off much of the load and the generator ran fine. Several of that party of campers were very disappointed that they could not run the whole camp on the generator they had brought with them. I found them a rental company in town that would rent them a larger set. On my advice they wrote down all of the loads they wanted to run before going to rent the other generator. I also provided them with the national park specification on day and night generator noise levels. When they returned they were towing a trailer mounted set that was quiet enough for use on a movie set and capable of powering a maxed out two hundred amp service.

I am also a volunteer fire fighter. Three years ago we had a fire that was caused by a tenant moving her ironing board over by the apartments distribution panel so she could hold the breaker, that her iron was tripping, closed. The fourplex apartment building was a total loss.

All most folks know about electricity is that they throw the switch and the light comes on!
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Old 11-02-01, 04:53 AM
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Matt Marsh
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T-clip

Wirenuts,

The only T-clip that I am familiar with is for the square D QO series panels. I believe that the intent is not to install it in the main panel. I don't see how it would work in a panel with a main breaker anyway. The intent is to install a small say a 12 circuit panel next to the main panel, feed it with the appropriately sized feeder to a back fed 2-pole breaker from the main panel. Another 2-pole breaker sized for the generator is installed adjacent to the first, and this T-clip merely acts as an interlock that prevents both breakers from being in the "on" position at the same time. All it really is, is a build-it-yourself manual transfer switch. Square D sells two packages necessary for this install. Package #1 includes the T-clip, and package #2 includes the brackets that clamp the backfed breakers to the bus. I have this system installed in my own home.

Matt
 
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Old 11-02-01, 06:13 AM
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resqcapt19
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Tom,
I am also a volunteer fire fighter. Three years ago we had a fire that was caused by a tenant moving her ironing board over by the apartments distribution panel so she could hold the breaker, that her iron was tripping, closed. The fourplex apartment building was a total loss.
Breakers do not work that way. You can not keep a breaker from tripping by holding the exterior handle. They have a "trip free" design that lets the contacts open even if the handle is locked on.
Don(resqcapt19)
 
  #10  
Old 11-02-01, 06:28 AM
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Wirenuts, this product showed in my juisdiction about 3 years ago. You have no idea how hard I questioned this product. Where it was allowe, if it was listed and labled, Ul approved, what brand panels can be used, etc. I even called the NFPA and Underwriters lab. The response was that it was listed as an accessory and most panels that have the same breaker design of ITE, GE, etc. Allowing the bracket to be installed on the breakers face in the emergency panel then held in place by the emergency panel cover was allowed to be used with this bracket. Cost factor is between $20 and 30 dollars. This bracket can be used on any branch circuit breaker allowing this bracket to fit to it as an accessory to that panel. After all the research I found it to be legal to use and within the NEC and UL requirments. Since then I have seen too many to count in this jurisdiction serving generator loads from 15 amp to 125 amps. The top breaker in the emergency panel mounted in place as a main breaker in the branch circuit line of breakers normally serves an emergency circuit sub panel from a breaker in the main panel serving that feeder to that emergency subpanel having lighting etc. in that sub panel served by the top breaker mounted in that emergency panel as the manufactured power feeder from that main panel. The next lower breaker is connected below that first breaker with that bracket mounted over both double pole breakers. The second breaker is feed from the output of the generator. With the bracket installed it has a swing arm that make one breaker turn off when the other breaker turn on and vise versus.

Matt discribed it well. Check with your local electrical supply house. If they can not find the source of this trasfer bracket the can call Kirby Risk of Shelbyville,Ind. and ask them where they are ordering it. This company is one of the suppliers in this area that has them in stock.

Very inexpensive method of providing an approved form of transfer switch protecting back feed from entering the Utility company's power grid.

You spoke of concerns of overloading the smaller generators. The NEC dictates the breaker sizes sized as per the NEC to protect that generator to a maximum of 125% to my memory. You may size the breakers in a mismatch using this bracket allowing a smaller breaker to serve the emergency power yet a larger breaker to serve that emergency panel with factory power. The link I provided above was an attempt to provide the information in design meeting the NEC requirements. Hope is was thorough enough to provide the help you needed.

Good Luck

Wg
 
  #11  
Old 11-02-01, 09:32 AM
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Originally posted by resqcapt19
Tom,
I am also a volunteer fire fighter. Three years ago we had a fire that was caused by a tenant moving her ironing board over by the apartments distribution panel so she could hold the breaker, that her iron was tripping, closed. The fourplex apartment building was a total loss.
Breakers do not work that way. You can not keep a breaker from tripping by holding the exterior handle. They have a "trip free" design that lets the contacts open even if the handle is locked on.
Don(resqcapt19)
Don

Did you perhaps mean to say that modern breakers do not work that way?
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  #12  
Old 11-02-01, 09:45 AM
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Hornetd, to my knowledge all breakers ever having been on the market has an internal trip mechinism that is independant as to whether the breaker handle is held in the on position or not. The breakers will trip internally, regardless how hard you hold the switch handle to the on position. This is also why you have to push the switch handle hard to the off position then back on. The internal release resets to the switch mechinism internally when you turn the external switch hard to the off then back to the on position. The internal release will separate from the external switch when a short or overload occurs.

Hope this helps

Wg
 
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Old 11-02-01, 10:32 AM
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Fire cause determination

I did not even look at the panel I just observed during the interview with the tenant. Perhaps she reclosed the breaker repeatedly. What she said was that she had held the breaker closed. There was the burned out building and that was what she said. Now I have to wonder what the actual cause of the ignition was.
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Old 11-02-01, 11:37 AM
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Tom;
We pulled an all-nighter as EMS ( re-hab)at a 10+-Acre brush fire the other night. One of the newbies wondered out loud if wires started it. I was mortified, we are so far out in the sticks here, and our trade STILL is suspect! Having done my time as a volley firefighter I must point out statistics attributing towards fires of electrical orgin are in part, an educated guess. The greater part, Darwinians with little regard for electricity.

Warren,
I'm sure if you've checked this little widget out it's kosher. You would not have it on your site otherwise. I would only further ( not trying to argue) that all that is 'listed' is not gold.
As a contractor, i am constantly questioning manufacturer's. Some of the feedback I get is a rather generic, thank you, roundfile, blow-off response.
The other side of the coin, obviously, is in meeting NEC minimum , which is the bid-winner.
Conflicting huh !
 
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Old 11-02-01, 01:23 PM
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Hornetd, I too have a sore spot about fires being blamed on electrical without having an electrical expert confirming that cause. I too have seen electrical blamed many times when it wasn't electrical. I have also seen electrical blamed when it was electrical. I will say this [probably inviting a massive rebuttal] I have yet in 30 years seen a fire truly caused by electrical that was not in some kind of disrepair, or not meeting the minimum safety standards, or not a flawed piece of manufactured electrical product. The experience that I have seen is that if that electrical truly met the minimum safety standards of the NEC, I have never seen that wiring meeting the requirments of the NEC to have caused the fire. I know we spend a lot of time turning up our noses at something hard for us to accept as allowed by the NEC, questioning or not liking the idea of that wiring style allowed by the NEC, yet I have not been in a situation after a fire thinking "wow and that met the NEC requirements". Seems to me that the NEC has a good track record even if it is minimum safety standards. Most people like to wire better than the NEC requirements. Yet those minimims of the NEC seem to work without mishap to my knowledge.

As for your breaker being held on by a broom handle. It is entirly possible. If a breaker has failed to the point that it won't click to the on position due to being a bad breaker or damaged breaker. Yet holding the breaker in the on position while still spring loaded to turn of if it weren't for that broom handle may have invited the breaker also not to have tripped due to being previously broken in the first place. Just a thought but may have happened. If the breaker was not right in the first place then possible the wires caused a meltdown without that bad breaker tripping. What do you think.



Wirenuts, after two years of track record with the thin piece of tin product used as the transfer switch mechanism tends to make me more compatible with it being used. NEC and UL doesn't seem to have a problem with it being used. I can't say that It failed at anytime to work. I have been monitoring this transfer and generator combo with the Power companies and they have reported no feed backs due to failure of the device no matter how cheap it looks. The two breakers if properly sized will meet the NEC requirments for overcurrent devices in this wiring design also. Looks cheap yet expensive is not always better either. We'll see as time goes by. So far they seem to be fine to use by track record.

Wg
 
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Old 11-03-01, 03:18 AM
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I believe one could fabricate one of these T-bar interlocks.
I wonder installing a home-faricated one would pass with
the NEC, or the common AHJ, since it does not carry current,
nor resides in the panel.
 
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Old 11-03-01, 05:12 AM
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Originally posted by Wgoodrich
Hornetd,

snip

As for your breaker being held on by a broom handle. It is entirly possible. If a breaker has failed to the point that it won't click to the on position due to being a bad breaker or damaged breaker. Yet holding the breaker in the on position while still spring loaded to turn of if it weren't for that broom handle may have invited the breaker also not to have tripped due to being previously broken in the first place. Just a thought but may have happened. If the breaker was not right in the first place then possible the wires caused a meltdown without that bad breaker tripping. What do you think.

Snip

Wg
If she had repeatedly reclosed the overheated breaker could she have caused it to fail or fuse internally so that it could be held closed? I don't know! From now on every fire I am on that gets called electrical I will write down the information about the equipment involved.

I will say that in the thirty years I have been a fire fighter I have seen some bizarre electrical fires. I have actually seen a fire caused by rodents chewing on the wires. When we traced the fire back to the point of origin we found the remains of the mouse with its jaw around the fixture wire at the point of origin. Since my apprenticeship instructor had said that that was a myth that never happened I removed the entire fixture, mouse and all, and took it to him. The mice had taken up residence in a fixture canopy underneath a low density cellulose ceiling tile assembly. Those of you who have been in the fire service awhile know how easy that stuff ignites.
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Old 11-03-01, 06:38 AM
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Gary, when researching this product I questioned the listing and labeling requirement of this product. It is my understanding after talking to UL that accessory products of a panel is not required to be listed or labled such as this bracket. I don't see a problem of making one if you AHJ approved its use. It is not the intent of the NEC to prohibit experimental wiring designs. I have seen in my jurisdiction a 20 hp 3 phase motor with 240 v single phase connected to it and a 3/4 hp motor as a drive motor to turn the 20 hp motor creating the third leg same as a roto-phase would use. I challenged its use. It was legally proven that if that home made roto-phase was used privately and not used for sale to others it was allowed to be used by the maker of the product. Don't know if that ruling was right or not.

Hornetd, I suspect it is possible to have a failed breaker that would not turn on and stay on. I have seen this condition in the field concerning a failed breaker. It is possible that the insides of that breaker was fused not allowing an overload trip to activate within that breaker. All this is assumption. No qualified electircal expert ever saw that product said to have caused that fire. That is where we need to approach a lot of work to correct. We need to know and not guess what the cause of fires are. We need an electrical expert to make the final ruling as to cause of an electrical fire. Few firemen have that extensive of training. In my opinion this declaring cause of fire is where we have a need for change. Hopefully this post may get some in the position of influence to rethink this subject and look for improvement on declaring cause of fires. I agree at times a rodent has caused a fire. Often times the rodent gets electricuted with the wires still separated and now fire occurred, then years later a fire does occurr and this rodent is found and that rodent was blamed. A pile of oily rags, wet hay, and many other conditions can cause spontaniouse combustion. Yet if that mouse caused the ungrounded and grounded conductors to touch very few sparks would occurr in a very short perioud of time limiting the chance of being a cause of fire due to the breaker tripping due to interupting rating of that overcurrent device. Now as of 2002 we have a new product on the market that has been mentioned in this forum that should when ran a while getting good quality control save a lot of house fires. This product is called an arc fault breaker. If there is sparking occur on a branch circuit protected by this arc fault breaker it is designed to trip due to the reading the sparking when it happens. I suspect when this product comes to be known as reliable with a track record we will start pushing all existing wiring to be arc fault protected. I can see a great improvement of safety from fire in using this new product especially in existing homes with buried junctions not even contained in a box buried within walls where no one knows they exist. This arc fault breaker will monitor that hidden connection for any loose connections or arcing. Sounds like a great new product. We will see as time goes by. Got to help can't hurt.

Hope this helps

Wg
 
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Old 11-03-01, 04:44 PM
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Thank you everybody for the great response to my thread. I will do more research, based on your responses, to try and acheive this inexpensively, and safely.
 
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