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42 comments
Guru
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Back Feeding A Power Panel

12/21/2007 7:29 AM

The recent power outage here in Oklahoma had several people using generators to run their houses.

I am by no means a "qualified electrician" however I do have extensive knowledge about it. (I repair all the equipment here mech and elec)

Several people asked me if it was OK to simply hook their generators into one of the large 230v breakers in their homes and and simply power up the whole house.

Now barring the lecture of turning off the main so as not to back-feed the lines and thus shocking or perhaps killing the linemen working to get your power restored. (I told several people this very thing and they had no idea)

I felt like this was a bad idea and responded with just hook up the things you want to use directly and do not use the breaker panel for this.(most generators have OL protection) I always thought that running reverse current through a breaker was a bad thing.

Several people said that some of the linemen hooked up their houses in this manner.

My questions are as follows: (I know FINALLY!)

Is it or is it not a bad thing to back feed a breaker in a panel to power up the buss-bar?

Does this affect how the breaker being fed operates?

what damage (if any) could this cause to the household circuitry?

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#1

Re: Back feeding a power panel.

12/21/2007 8:06 AM

All I can tell you is that some years ago I was helping a friend rewire an old store front and was working on a secondary panel. I threw the breaker leading to the circuit I was pulling out and cut the wire next to the breaker. A nice pair of Klein diagonals protected the defective circuit breaker as well as the feed breaker and the mains breaker. I've since seen other breakers fail closed, particularly older ones that have been as switches.

If it was me, I'd want to be able to see a physical opening of the circuit between my generator and the mains.

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Guru
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#2

Re: Back Feeding A Power Panel

12/21/2007 9:35 AM

Barring the safety concerns, As long as you said the mains are disconnected and the breaker can hold the current provided, there is no problem electrically. The definition of Alternating Current is that current normally flows in both directions.

As far as safety goes when the system must be off the grid to hook or disconnect a power generator. This not only protects the linesmen, but if it were on the grid, it would be a fire hazard if the primary generation comes back on line out of phase. Basically everything hooked up would be fed with double the voltage (lots of sparks and flames!).

The proper way is to have a three pole two throw switch before the mains input to the panel.

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#7
In reply to #2

Re: Back Feeding A Power Panel

12/21/2007 10:43 PM

You would not need a three pole switch as you would not be permitted to switch the neutral. Under the Canadian Electrical Code the neutrals must be bolted together.

Rick...

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Anonymous Poster
#42
In reply to #7

Re: Back Feeding A Power Panel

03/29/2010 1:56 PM

actually the neutral does have to be switched. I'm a licensed electrician in canada and have done a number of generator installs. what i normally do is install a genny panel to run what needs to be run when the powers out. In the main interlock in a genny panel the neutral gets tacked onto the mains with the hots so that it's switched from gen neutral to street neutral with the power. The reason for this is because even though your "off the grid" the neutral can still backfeed out to the pole and seriously injure someone working on it. It's a bit of a grey area but to "my interpretation" :) of the rules in the code book i think you can backfeed a panel if it's a temporary service but ONLY if the neutral isn't still hooked up street side.

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#3

Re: Back Feeding A Power Panel

12/21/2007 9:46 AM

It is common practice to back-feed panels through a power cord (in construction).

You can also find sub panels that have the bus bars fed in the same manner that you have described at you local big box hardware store.

Electricity will flow and be interrupted by the breaker regardless of which direction it is flowing. The exceptions to that would be AFCI & GFCI breakers. Those breakers operate with a specific load path.

Regardless of whether you are using this as a temporary means, I would posts signs all over the panel box to ensure that whomever has access to the box can instantly figure out where the panel is being fed from.

As far as what the NEC allows, I do not believe that it is specifically prohibited. I will verify that, and get back to this post if I find out that I am wrong (about what the NEC allows).

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#5
In reply to #3

Re: Back Feeding A Power Panel

12/21/2007 10:58 AM

Regarding the first sentence (to my original post): It is common practice (in construction) at this point of construction when you see this being done...there are no feeders landed at the main or the Meter has NOT been installed.

Please VERIFY what you intend to do with your local utility company first. A locking mechanism for the breaker (available at most electrical supply houses), should be installed at the breaker, but there are MANY other possible dangers in what you have proposed.

I would by no means recommend hooking up 2 sources to the same panel without a ATS that was designed and installed by professionals.

My response was to your question as to could it be done, not should it.

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#4

Re: Back Feeding A Power Panel

12/21/2007 9:47 AM

There are automated systems for this, that isolate the house from the grid, start the gen set, and then when it senses that the grid is back, drops off the gen set and repowers the house from the grid.

Pretty expensive, but worth it in areas where you loose electricity a lot. I certainly would not suggest rigging up something, and what they seem to be proposing would likely violate the local electrical codes.

I am with you, just plug in what you need to the generator, and leave the house wiring as is.

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#6

Re: Back Feeding A Power Panel

12/21/2007 2:03 PM

Thank you for all your replies.

Please let me reiterate though that I am not doing this. I had people where I work that were doing this, or having it done and as I said I thought this was an unsafe practice and ill advised and tried to convince them not to do this.

My advice to them from the beginning was not to do this and just directly hook things into the generator.

Please do not take that wrong.

My main concern now that this has all passed and everyone has now had their powered restored is that no hidden damage has been done to their respective household systems having done this.

Again I thank you all for your comments and welcome any additional information on this and possible causes and effects from having done so.

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Anonymous Poster
#20
In reply to #6

Re: Back Feeding A Power Panel

12/22/2007 1:34 PM

I lived for many years in an area where power was interrupted fairly often. I had a licensed electrician install a system to allow a portable generator to feed the entire house. There were two parts: a switch to prevent 'back feeding' of the grid (and also to prevent power from comming into the house when power was restored), and a three prong (220 V) socket to connect my generator to the main power panel. My understanding is that the three prongs in this socket were connected directly to the input side of the main breaker, with one prong to the 'negative' 110v line (black), one to the neutral line (white), and one to the 'positive' 110v line (red).

While working in construction I have seen other setups, and while they work, I believe that in this case the by-the-building-code method is almost certainly safer. If powering the box through an individual pair of breakers was ok I think someone would be selling power cords with various breaker shaped connectors on one end just for this purpose.

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#8

Re: Back Feeding A Power Panel

12/22/2007 5:57 AM

Maybe I am barking up the wrong tree here, which would show that I do not understand this matter at all, but here in the UK they are talking often about generating your own (green) power and when you do not need it yourself, to feed it back to the power grid so your electric meter runs backwards and deducts what you generate from the mains bill.

Not knowing how this is done I can only state having heard about it but apparently they do sell automatic switches that do this without the power companies complaining about it.

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#9

Re: Back Feeding A Power Panel

12/22/2007 8:21 AM

You need to follow the rules for where you live, generally you must have either a completely automatic switch over, or a mechanical one that removes the connection to the utility supplier, before connecting to your private generator....just back feeding into a socket is really really dangerous for all concerned. Insurance would not cover injuries or fires caused in this manner as it is totally illegal to do in any country....

YOU MUST MAKE SURE THAT YOU NEVER BACK FEED OUT OF YOUR HOUSE!!!!

It could injure a lineman.....I have not heard of that because usually they work only on the high voltage side of the transformer and one would expect the breakers to be off there....but if power returns and your have the unfortunate result of the generator running and mains comes in, the generator could do a nasty "back flip" if not in phase with the mains......it would probably at least burn out or get damaged......

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Anonymous Poster
#39
In reply to #9

Re: Back Feeding A Power Panel

11/20/2008 7:32 AM

just learn all you can about backfeeding and do it, it just feels so right and good backfeeding into the dryer outlet, yep alot of people will try to scare you but like i said just read everything you can about doing it safely first, that includes learning about floating neterals and grounded neterauls, i love backfeeding but if your not very smart about the safty of electricity don't do it, end of story

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#40
In reply to #39

Re: Back Feeding A Power Panel

11/20/2008 7:57 AM
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#10

Re: Back Feeding A Power Panel

12/22/2007 9:06 AM

I have often thought that an electric motor phase-reversing breaker pair used to change the direction of a 3-phase electric motor would make a good safety switch between the line and a standby generator set feeding a breaker panel.

It provides all the electrical isolation and more then enough contacts and there is usually a mechanical bar between the breakers to make sure only one breaker can be closed at any time. The breaker switching could be wired to be automatic or manual.

This would only be applicable for as stated places prone to power loss, and would operate like this:

1. when power is lost the utility breaker drops out and a contact on the alternate power breaker starts the standby generator.

2. when power returns the main breaker reenergizes and the power comes from the utility, in the same instant in time the alternate breaker is de-energized and the contact drops out stoping the standby generator, or initiating shutdown/cool down cycle. There is no overlap of power source, the gen drops out before the utility connects and vice-versa.

The problem could be if you have large heavily loaded motors, when this switches back to utility it could be so fast that the out-of sync condition could cause shafts or shaft keys to snap and or a sudden momentary jerk in a load. Pure resistive loads such as electrical heating or lighting wouldn't notice any change. If there is a surge arrestor installed at the power distribution panel it will help to dampen switching.

Most standby generators take 10 seconds or thereabouts to start and pick up the load, so there would be a "pause during the period of darkness" but going to utility would be accomplished instantaneously.

------------

Yes while working as an electrician I was in the basement of a golf course shop in summer heat and was replacing breakers for some reason and came across one that when switched open was still energized, for some reason that day I checked it with a meter before grabbing into things.

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#11

Re: Back Feeding A Power Panel

12/22/2007 9:31 AM

I know what I have heard about and read about and I also know what is being said here about NOT BACK FEEDING the grid but.....

Bergey Windpower is one of the world's leading suppliers of small wind turbines. With 30 years experience, installations in all 50 U.S. States and more than 100 countries, and an international network of 500 dealers, we have the products and experience to put the wind to work for you.

At Bergey Windpower, we take pride in offering advanced-technology products that let homeowners and businesses generate their own clean power and even spin their utility meter backwards. Our turbines are also used for off-grid homes, for rural electrification, and to boost the performance of solar electric systems.

It clearly states here that you can back feed the grid with these systems and have your meter run backwards as a result. Now these systems are freely available and no energy company to date has made them ilegal for use.

Read the full story here but there are numerous other websites, also in the UK, stating the same thing.

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#12
In reply to #11

Re: Back Feeding A Power Panel

12/22/2007 9:56 AM

That is not quite the same thing.....firstly, you have to have a contract with the normal power provider......firstly to allow the backward connection and also they do not pay the same to you per unit as you pay them....usually around 25% of their charge, you get back.....eg 4 units back to pay for one unit used......or thereabouts.....

Secondly, when a whole district goes down, you cannot hope that your windmill will keep a 100 houses in electricity.......so I guess when the mains goes off, you go off the mains with your windmill as well......

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#14
In reply to #12

Re: Back Feeding A Power Panel

12/22/2007 10:07 AM

I don't know about contract but if your meter runs backwards, does it not count the same rate per time unit so the pay is negative but in the same, inverted rate?

Secondly, the system is first and foremost to supply yourself with green power. The advantage you can feed the grid when you don't need it, or produce more than you use yourself, is just the bonus. You will never be able to feed enough to replace the power supplier in order to feed the houses around you.

I would expect that, once you have invested in this system, you would want optimum performance. That to me means that you want the returns wherever possible so in case the system goes down, you don't just feed the grid for nothing. I think it will switch automatically so you only supply yourself in that case.

With regards to electrocuting the line workers, should that not be their problem? If there is a chance of the lines being live, they should check, isolate and check again. We have had this discussion over and over again here so that we should at least agree on.

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#15
In reply to #14

Re: Back Feeding A Power Panel

12/22/2007 10:19 AM

The real dangers (generally) is when people back feed via a socket and a cable from an emergency generator and when the power comes back on, the generator flips or catches fire or something........

Connecting a generator to a dead house must be made only once the normal mains have been isolated, but year after year the same mistakes are made again and again!!

Again its a safety issue, that must be repeated so long as electricity is used.......

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#22
In reply to #15

Re: Back Feeding A Power Panel

12/22/2007 2:05 PM

You are 100% right! The ONLY safe way is to use a transfer switch. That way power can feed the panel from one source only: generator or power company or whatever, but only one source at a time.

Transfer switches come in all varieties, from fully automatic to manual switchover.

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#38
In reply to #14

Re: Back Feeding A Power Panel

01/07/2008 1:05 PM

I was under the impression (not from any article you have poited out) that there was a second meter installed in situations like this to measure what you gave back to the grid. Hence your meter does not really run backward.

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#13

Re: Back Feeding A Power Panel

12/22/2007 10:05 AM

In our place, you MUST Galvanically disconnect yourself, all phases and neutral as well from the incoming power lines in case you are generating your own power.

It is not only dangerous, it is stupid. Why would you want to deliver free power, and kill you gen set in the process?

Wangito.

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#19
In reply to #13

Re: Back Feeding A Power Panel

12/22/2007 12:27 PM

"Ganvanically"...I don't think I've ever heard that word in the US. What does it mean in your part of the world?

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#23
In reply to #19

Re: Back Feeding A Power Panel

12/22/2007 2:08 PM

Means:

physical Solid contact, solder, nut and bolt or switch wafer, or what have you as long as it is solid, between two similar or different metals, which have the least interaction between them.

Well I used slang here (which I shouldn't have). You should read :"Galvanic connection" Google "Galvanic series connection" if you care to...

Wangito

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#24
In reply to #19

Re: Back Feeding A Power Panel

12/22/2007 2:35 PM

Try "Galvanically", it works better, if you understand electrics anyway....

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#16

Re: Back Feeding A Power Panel

12/22/2007 10:38 AM

Co-Generation is not an Emergency Standby Generator, please do not confuse the question. I am deadly serious in the following information.

Co-Generation requires a contract with the electric utility to buy and sell or net at the facility power meter. It also requires the cogeneration plant owner to have protection relays and a generator that the breaker opens when the utility voltage is lost. This should happen instantly when the utility drops voltage or goes "out of bounds" on volts, amps, phase relationship, etc. Having put over 15 generating or co-generating plants on the grid I can speak about this. The utility will certify the co-generation plant as suitable to connect to the grid. You do not have a right to connect anything to the grid!

Standby generation, is exactly that it is not meant to put power on the grid. It is isolated from all other power sources and from the grid. Even nuclear power plants have standby generators to keep the lights and heat on when the grid goes down!

The grid normally demands so much power that if large generators are lost the voltage drops and a cascade follows.

If your local distribution line becomes seperated from the grid there should be no power on it from anywhere until the utility restores power!

Alternate utility power supply to feed the in-plant bus is also done, boiler rooms in hospitals and other critical applications will often have multiple utility feeds to the switchgear from different utility power lines, these may automatically switch if the primary source is lost.

You don't want to be on the distribution line supplying power because:

1. it is life threatening to utility linemen and your neighbors,

2. you are responsible for what you connect to the utility under normal or emergency or any other definition of circumstances

3. when the utility restores power it will no doubt be out of sync with your little generator and you may want to be in the next county to watch the fireworks as it electricly and mechanicly becomes many pieces, and if your lucky your house doesn't burn down too.

4. Even when the power is off to the distribution line, the utility can restore it at any time, and anyone in contact with the line will experience an enlightening experience seldom repeated!

Understood?

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#17
In reply to #16

Re: Back Feeding A Power Panel

12/22/2007 11:11 AM

Correctly, Brilliantly and exotically put! It drew a smile from me after others had done the opposite.

Many thanks CoronaCameraMan (I hate to think where or how you earned that Nickname......!)

For the rest of you Erks, please read and understand particularly our Mr Head-Case!!!and anyone else out there thinking of doing the same somewhere sometime!!!!!

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#21
In reply to #17

Re: Back Feeding A Power Panel

12/22/2007 1:49 PM

Maybe I had you wrong too.

Nice to find out who your friends are!

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#25
In reply to #21

Re: Back Feeding A Power Panel

12/22/2007 2:38 PM

Don't get upset, we always say "If the cap fits, wear it!!"

Have a great Christmas in spite of me!!!

I just want to extend your command of the English language in many different ways, (is my other excuse!!)

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#18

Re: Back Feeding A Power Panel

12/22/2007 11:23 AM

The nickname was easy, I chose it, see my websites

www.specialcamera.com

www.corona-technology-course.com

The rest was life experience, now that was expensive.

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#26

Re: Back Feeding A Power Panel

12/22/2007 4:38 PM

Corona Man,

Your ratio of good answers to posts (37 to 1. which is excellent) is clearly reflected here. Great response! 39 to 2?

Thanks!

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#27
In reply to #26

Re: Back Feeding A Power Panel

12/22/2007 5:20 PM

I would have thought so, maybe the hall monitor hasn't checked in yet?

Chuckle, please

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#28
In reply to #27

Re: Back Feeding A Power Panel

12/22/2007 6:21 PM

Love to chuckle with you, explain please?

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#29

Re: Back Feeding A Power Panel

12/22/2007 10:45 PM

I have read most of the posts on this thread and boy are some folks over thinking things.No you don't want to back feed the grid for obvious safety reasons. Yes there are switches available for this purpose but they are generally expensive. Here in rural Colorado we just pull the meter, hook up to the connectors beneath the meter that service the house and run the gen set. 5KW will run most households in the area, including the well pump. Almost no one uses electric room heat. When the power outage is over the, electric co. comes out, retags the meter and we're done. No muss no fuss no injuries.

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#30
In reply to #29

Re: Back Feeding A Power Panel

12/22/2007 11:07 PM

It's refreshing to hear that one last bastion of the "Wild West" is alive and well.

Please folks... lets not take this gent's method of connecting a generator as "industry standard".

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#32
In reply to #29

Re: Back Feeding A Power Panel

12/23/2007 12:55 AM

I suspect -shart4legged- are on the distribution lines of an electric co-op.

You may wish to consider the cost of having the lineman come out (maybe 40 miles each way) to plug the meter back in. The co-op could probably buy and furnish non-load break transfer switches with an outlet and plug for the cost of one trip of the lineman to replace the meter. If the co-op furnished the parts and said they will not be back to replace meters.

Just a thought as we all know we taxpayers help to fund the electric co-ops (and other utilities and oil companies, etc everybody except small business).

If one person were killed doing the "meter pull" (do you want to volunteer?) we could probably get a bill thru Congress to fund these transfer switches, maybe we need more then one fatality...

I've probably lost my good answer point already too...

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#31

Re: Back Feeding A Power Panel

12/23/2007 12:01 AM

And if the power came back on as he was "popping the meter out", it might pop the rancher out! with the potential explosion. No utility will authorize anyone to "pull the meter" there are too many hazards with both the utility feeder and the house line exposed in the meter socket. If I were the utility I wouldn't be back to put the meter in for a very long time.

But I have been told of bankers who licked there fingers and put them against the outlet to find out if the power was on. I also knew an electrician who plugged in an electric rotary saw and it killed him and another electrician who bought the business then wired the outlet and the plant electrician wired the plug, when the electrician plugged it in he fried his hand.

If this is routine why doesn't the rancher have a transfer switch (at zero current flow with the load breaker shut off) and a socket to plug the standby generator into? It is so simple and inexpensive to do...

5kW is probably not 3 phase so he shouldn't have to synchronize if phases are rolled so all the motors aren't running backwards.

Years ago and probably still today there are tractor PTO mounted generators, you'd get a real kick from that.

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Anonymous Poster
#33

Re: Back Feeding A Power Panel

12/26/2007 11:21 AM

The best and safest method is to install a ATS (auotmatic transfer switch ) inline prior to your main panel.When utility power drops out your ats drops out and switches over to your secondary source of power.When utility is re energize the switch transfers the power back to utility and drops out the secondary source .you can pic these switches up almost every where .

yours Blackfoot

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#34

Re: Back Feeding A Power Panel

12/31/2007 7:18 AM

I appreciate all the feed back on this post. I wish to thank all of you for opinions and input.

I have been on vacation for the last week so I am sorry for not replying for so long but rest assured i am back and ready to go at it again.

At the beginning of the post I was meerly concerned for the thousands of people out here working to restore power that were trying to help but after reading some of the posts I feel like others may have been at risk as well.

Power is fully restored to all the homes and businesses that were out now and I am not sure if there were any related injuries reported. At the peak of it there were over 250,000 customers without power as was reported in the news. there is still a lot of debris laying around from all the ice damage to trees and such but all in all I think we will recover.

Thank you again for all the fine posts. If any other posters have suggestions for the common goon feel free to keep things rolling.

Wishing you all the best of the holidays and a safe new year.

Jeff

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#35
In reply to #34

Re: Back Feeding A Power Panel

12/31/2007 10:18 PM

I have a question for anyone that would like to respond.

I have a 5500 w gasoline generator that I use whenever I have a power outage. I use a manual transfer switch to disconnect furnace, regfrig, etc. from mains and over to gen.

Question: Do I need to drive a grounding rod into the ground and attach the generator frame (ground) to it?

Seems like when contractors use such a generator on a job site there's no earth ground so should I use the generator as if it were just a job site power source?

Just something I've been wondering about.

-John

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#36
In reply to #35

Re: Back Feeding A Power Panel

01/02/2008 11:01 AM

I do the same John. But it will not hurt to put in a separate ground as the neutral in created within the generator.

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#37
In reply to #36

Re: Back Feeding A Power Panel

01/02/2008 11:32 AM

Thanks!

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Anonymous Poster
#41
In reply to #36

Re: Back Feeding A Power Panel

11/20/2008 8:00 AM

it sure could hurt you, from what i read there should only be one ground and that shout be at panel, again only one grounded netraul and that should be at the panel other wise you can meake a gound fault circut

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