# Portable generator install



## jwjrw (Jan 14, 2010)

Customer installed a 30 amp receptacle to plug a generator into. I always thought you would have to disconnect the neutral to keep from back feeding the poco lines. Am i thinking correctly? Also I'm not sure if this would be legal even on a portable without some type of transfer switch.

I appears if you shut the main off no back feed will happen but still I dont think this would be legal?


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## raider1 (Jan 22, 2007)

You must use a transfer switch or other type of trasfer device to connect a portable generator. You can't backfeed a receptacle.

Checkout 702.5.

Chris


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## jwjrw (Jan 14, 2010)

raider1 said:


> You must use a transfer switch or other type of trasfer device to connect a portable generator. You can't backfeed a receptacle.
> 
> Checkout 702.5.
> 
> Chris



Chris if this customer did this and shut main off it would not be a legal install but would it be safe?


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## farlsincharge (Dec 31, 2010)

In theory it would be safe, however two points come to mind.

I have seen breakers fail closed before, even when the handle is moved to open.

People get excited in an emergency type situation and tend to forget things. Like shutting off the main breaker for example.

There are interlock kits available for some panels. SQ D actually makes them and there are aftermarket companies as well.

Transfer switches and sub panels with built in interlocks are also available.

Up here, the neutral does not have to be switched. The neutral must be unbonded from ground inside the generator though.

The amount of hack generator setups, and peoples attitude towards them scares me a great deal.


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## backstay (Feb 3, 2011)

jwjrw said:


> Chris if this customer did this and shut main off it would not be a legal install but would it be safe?


 
If you don't interlock the main with the generator feed or use a transfer switch, you run the risk of backfeeding. Not safe.


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## Jlarson (Jun 28, 2009)

jwjrw said:


> Chris if this customer did this and shut main off it would not be a legal install but would it be safe?


It would be safe. I do it but then again I'm trained to do stuff like that and have the gear to confirm the main is open and such. Now whether or not joe homeowner can do it safely is up in the air.


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## Rockyd (Apr 22, 2007)

jwjrw said:


> Customer installed a 30 amp receptacle to plug a generator into. I always thought you would have to disconnect the neutral to keep from back feeding the poco lines. Am i thinking correctly? Also I'm not sure if this would be legal even on a portable without some type of transfer switch.
> 
> I appears if you shut the main off no back feed will happen but still I dont think this would be legal?


The connection should be taken off the side of the house with a baseball bat if they refuse to get a transfer switch!  Needlessly killing lineman, because of DIY efforts is no way to go through life. That said, a professional can leave the neutral connected so that it is not SDS.

Not safe for reasons Farl goes into...like plane crashes - most caused by "human error".


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## jwjrw (Jan 14, 2010)

It appears if the main functioned properly and disconnected no back feed could happen. I advised it was a bad idea because there is an IF involved. I'm trying to up sell a genny package but he is up north and was wanting the house electricians building his house to pre wire for future gen. They have no clue and I told him what I thought it would be but without seeing it I couldn't say. He doesn't want to hurt anyone so I think he will go the safe way.


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## farlsincharge (Dec 31, 2010)

jwjrw said:


> It appears if the main functioned properly and disconnected no back feed could happen. I advised it was a bad idea because there is an IF involved. I'm trying to up sell a genny package but he is up north and was wanting the house electricians building his house to pre wire for future gen. They have no clue and I told him what I thought it would be but without seeing it I couldn't say. He doesn't want to hurt anyone so I think he will go the safe way.


If it is still an option at this point, tell him to put in a QO main panel that has an interlock kit designed for it.
This would be the cheapest option and also give him control over his entire loadcentre with standby power, rather than a few select loads in a sub panel.


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## micromind (Aug 11, 2007)

The majority of transfer switches I install have a common neutral. All neutrals connect to a common point. Only the hots are transferred. 

The neutral only carried current from the utility to the load or from the gen to the load. It cannot carry current from the gen to the utility, because there is no return path. It's just one wire.

There are instances where the neutral is transferred as well as the hots (hospitals come to mind), but it isn't necessary in most applications. 

If all neutrals are connected to a common point, do not bond the neutral to ground at the gen. The bond at the utility service is enough; there can be only one. 

If the neutral is transferred along with the hots, then the gen neutral needs to be bonded as well as the utility service. 

In the application you described, having the gen neutral connected to the utility neutral is ok.


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## nrp3 (Jan 24, 2009)

I don't like the idea of modifying someones generator. What if they use it away from the house and the frame isn't bonded?


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## Shawn23 (Jan 5, 2011)

raider1 said:


> You must use a transfer switch or other type of trasfer device to connect a portable generator. You can't backfeed a receptacle.
> 
> Checkout 702.5.
> 
> Chris


 
702.5 , Where does it say that you cant back feed a receptacle? I see in 702.5 #1 Manual Transfer Equipment, back feeding a recepticle seems like a manual transfer to me and the load selection shall be the users option.

I have done it both ways in the heat of battle but when not being pressed by a hurricane in a couple of hours I prefer the auto transfer

More important to me in this discussion is...... would this be considered and "optional standby system article 702" or "generators article 445" or both?


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## Dennis Alwon (May 9, 2009)

jwjrw said:


> Chris if this customer did this and shut main off it would not be a legal install but would it be safe?


I consider myself pretty knowledgeable about the safety of generators. I had a generator that I backfed a breaker in the panel during hurricane Fran. I am smart enough to shut off the main but in my haste I forgot to after refueling the generator. Fortunately it was only on for a minute before I said---OOOPs. So----- it is not safe at all. It is very easy to forget that main.


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## doubleoh7 (Dec 5, 2009)

Shawn23 said:


> 702.5 , Where does it say that you cant back feed a receptacle? I see in 702.5 #1 Manual Transfer Equipment, back feeding a recepticle seems like a manual transfer to me and the load selection shall be the users option.
> 
> I have done it both ways in the heat of battle but when not being pressed by a hurricane in a couple of hours I prefer the auto transfer
> 
> More important to me in this discussion is...... would this be considered and "optional standby system article 702" or "generators article 445" or both?


 
Where does it say you can have a cord with two male ends.


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## Dennis Alwon (May 9, 2009)

Shawn23 said:


> 702.5 , Where does it say that you cant back feed a receptacle? I see in 702.5 #1 Manual Transfer Equipment, back feeding a recepticle seems like a manual transfer to me and the load selection shall be the users option.


Back feeding a receptacle is not the same as a manual transfer switch. A transfer switch connects to one set of contacts while simultaneously disconnecting the other. Big difference- no human error involved with a transfer switch.


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## Dennis Alwon (May 9, 2009)

doubleoh7 said:


> Where does it say you can have a cord with two male ends.


That's exactly correct. Normally one would have a receptacle on the wall that is a male while the cord from the genny has a female cord cap. The transfer switch will guarantee the male receptacle would only be energized when the cord is plugged in from the generator.


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## B4T (Feb 10, 2009)

A transfer switch works same as a 3-way toggle switch.. 

The house panel is load.. POCO feed is traveler #1... generator feed is traveler #2..

But in a (2) pole version..


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## don_resqcapt19 (Jul 18, 2010)

nrp3 said:


> I don't like the idea of modifying someones generator. What if they use it away from the house and the frame isn't bonded?


 Many portable generators for cord and plug connected equipment do not have a neutral to frame bond.


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## garfield (Jul 30, 2009)

An electrician friend of mine backfed a panel through the dryer receptacle. The Homeowner promised they would call him when power came on. They didn't. They turned on the main with the generator connected. Fried the generator. My friend felt bad...I thought it was funny and served them right.


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## doubleoh7 (Dec 5, 2009)

Dennis Alwon said:


> That's exactly correct. Normally one would have a receptacle on the wall that is a male while the cord from the genny has a female cord cap. The transfer switch will guarantee the male receptacle would only be energized when the cord is plugged in from the generator.


 


Plus, who would like to get a call that the custom 2 male ended cord they made up electrocuted someone's kid when they grabbed ahold of it.


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## B4T (Feb 10, 2009)

garfield said:


> An electrician friend of mine backfed a panel through the dryer receptacle. The Homeowner promised they would call him when power came on. They didn't. They turned on the main with the generator connected. Fried the generator. My friend felt bad...I thought it was funny and served them right.


There have been stories of linemen getting electrocuted because guys plug the generator into the dryer outlet and leaving the main closed..


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## doubleoh7 (Dec 5, 2009)

garfield said:


> An electrician friend of mine backfed a panel through the dryer receptacle. The Homeowner promised they would call him when power came on. They didn't. They turned on the main with the generator connected. Fried the generator. My friend felt bad...I thought it was funny and served them right.


 
Your friend is a moron who could have killed someone.


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## kbsparky (Sep 20, 2007)

Shawn23 said:


> 702.5 , Where does it say that you cant back feed a receptacle? ...


Try looking in 406.6(B): ".... no receptacle shall be installed so as to require the insertion of an energized attachment plug as its source of supply"

You should consider using a _flanged inlet_ for generator feeds. That keeps this section of the _Code_ in compliance.


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## Salvatoreg02 (Feb 26, 2011)

Dennis Alwon said:


> That's exactly correct. Normally one would have a receptacle on the wall that is a male while the cord from the genny has a female cord cap. The transfer switch will guarantee the male receptacle would only be energized when the cord is plugged in from the generator.


You can have two female ends, plugged into two male recessed receptacles with no exposed engerized parts.

Sent from my iPhone using ET Forum


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## kaboler (Dec 1, 2010)

Will I learn about all this in school before I become a journeyman?


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## cabletie (Feb 12, 2011)

The whole idea of using a ul listed portable generator instead of a ul listed emergency back up generator is just wrong! I am afraid of charging a screw gun battery off of a portable generator because I have burned them up before. Also fried a customer’s furnace being a nice guy and giving them use of the generator over night until the power company could get there. It was connected directly to the furnace with permanent wiring removed. And that was with a different generator. My boss had to take off the amount of the repair from his bill. Tell your customer to use his gen for drop lights and skill saws.


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## nrp3 (Jan 24, 2009)

I think it depends on the generators you use and what you connect them to. There are furnaces/boilers that are very electronic dependant that don't do well with a generator. I can't remember the brands but at least one of them was covered under warranty and they replaced the control board with a new one. I wouldn't hook up any flat screens to them or my computer, but have good luck with basic heating and lighting. Microwaves seem to survive. I use the portable on my house and have good luck with it.


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## Dennis Alwon (May 9, 2009)

Salvatoreg02 said:


> You can have two female ends, plugged into two male recessed receptacles with no exposed engerized parts.
> 
> Sent from my iPhone using ET Forum


Tell me how-- the generator certainly doesn't have a male end since it would be energized when started and a safety hazard-- so how would you have 2 female end?


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## kbsparky (Sep 20, 2007)

Salvatoreg02 said:


> You can have two female ends, plugged into two male recessed receptacles with no exposed engerized parts.


Not likely. If such a scenario were possible, the exposed prongs of the "male recessed receptacle" on the supply end would be hot. "Exposed energized parts" as you say. Someone poking their finger in there would get zapped.

That is why the generators have female receptacles, and you install a flanged inlet at the other end.


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## Shawn23 (Jan 5, 2011)

kbsparky said:


> Try looking in 406.6(B): ".... no receptacle shall be installed so as to require the insertion of an energized attachment plug as its source of supply"
> 
> You should consider using a _flanged inlet_ for generator feeds. That keeps this section of the _Code_ in compliance.


 
Thanks for that code reference. I knew it was not in 702 so i was wondering where he came to that conclusion.

I use the recessed male below the panel so that the genny cord has the female end thus leaving no live parts exposed.

Its one thing to know the code, its another things to understand why or how they came up with that code. This discussion has brought out many different opinions and code references that have helped me greatly.


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## 2001fltri (Apr 28, 2010)

plain and simple, I am probably wrong ..but,I use a three phase manual disconnect simply because when the PoCo's primary falls on to the secondary neutral, I don't want it to have a chance to enter my house. so I simply use the transfer switch to disconnect everything coming from the utility when I'm, in emergency power. but then again this is only at home on the farm. I use to climb poles for humungus electric here in pa. and have seen a few things happen.:whistling2:


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## electricmanscott (Feb 11, 2010)

2001fltri said:


> plain and simple, I am probably wrong ..but,I use a three phase manual disconnect simply because when the PoCo's primary falls on to the secondary neutral, I don't want it to have a chance to enter my house. so I simply use the transfer switch to disconnect everything coming from the utility when I'm, in emergency power. but then again this is only at home on the farm. I use to climb poles for humungus electric here in pa. and have seen a few things happen.:whistling2:


So do you disconnect the house from the grid too.


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## RePhase277 (Feb 5, 2008)

I think the idea that backfeeding kills linemen may be grounded in reality but is over blown. When I worked for the POCO (briefly) we grounded lines religiously. It wasn't dead until it was grounded.

In most cases, I think all of your neighbors tied to the line would quickly overload the generator and trip the breaker.

At any rate, backfeeding without some kind of transfer or disconnect is pretty stupid.


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## cabletie (Feb 12, 2011)

2001fltri said:


> plain and simple, I am probably wrong ..but,I use a three phase manual disconnect simply because when the PoCo's primary falls on to the secondary neutral, I don't want it to have a chance to enter my house. so I simply use the transfer switch to disconnect everything coming from the utility when I'm, in emergency power. but then again this is only at home on the farm. I use to climb poles for humungus electric here in pa. and have seen a few things happen.:whistling2:


 
That is probably a very good idea, but opens up another can of worms. Does that make it a transfer switch? Is the transfer switch rated for use as service equipment? Is the grounding electrode system brought to the transfer switch (first system disconnect)? Now the generator is a separately derived system and a service and needs a grounding electrode system. How is that going to be done with a portable generator? The list could go on and make for a good debate.


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