Backfeeding your panel with a portable generator

themcfarland · Oct 14, 2010

the inverter type generators are very nice and I wish I had one, but until then I will run my elcheapo 6500 chinese clone .. it isnt as good but I did run it with nice surge protectors..

Now another thing of note, is to be sure to never let the generator run out of gas while under load, and to be sure to throw the breaker before powering down or up..

drumz2129 · Oct 14, 2010

I can see where this could be a problem if you are grounding your generator on its own rod, or if it is sitting on the ground and grounding its self. My generator is on wheels and has rubber isolation feet up front, it connects with with a twist-lok plug and connects to my house's ground through it, which all goes back to one grounding point.

Any time you add an extra connection, either another fuse box or a generator, it all needs to bond back to the one grounding rod, it should not have its own grounding rod. If it does, you can get a ground loop and develop stray voltage. If everything is bonded back to one central point which should be the grounding lug on your main panel or grounding rod, there should be no problem.

I have personally seen ground loops carry as much as 45VAC, this was an extreme case where the building was also improperly bonded and it would light you up if you touched the door knob on a humid day. Say the ground loop was carrying 20V, your TV is used to seeing 120V, now it is seeing 100V since it is connected to one hot leg and to the neutral, (0V-120V=120V VS 120V-20V=100V) things like light bulbs (incessant) can work on this, they just wont be as bright. Your TV may or may not work on this, if it does it will most likely run much hotter due to the lower voltage.

The OP is good information and anyone who plans to back feed should have their plans checked out by a certified licensed electrician.

El Rubio · Oct 14, 2010

nickatnite said:
So the Honda and yamaha brand of generators that are also branded "inverters" are not really generators? And with that, you are saying that the Honda Eu6500i inverter/generator that is sitting in my garage that will run my entire house MINUS the a/c is not really a generator? If so, then power that this generator produces is no different than a regular 6,000 watt generator with a Briggs and Stratton motor? As in clean power.

*** I am not an electrician, don't play one on TV, nor have I slept at Holiday Inn recently***

I'm not saying that at all. A generator and an inverter are two different things. Your generators generate AC electricity that is converted to DC and then back to AC by the inverter ckt. The idea is exactly like you said, it gives a cleaner sine wave with less noise or spikes on it and more accurate frequency. My original post is about backfeeding a house panel with a portable generator. There is an inherent issue with the practice ( not withstanding the whole backfeeding concept) used by many and described in the pages of this forum.

My advice is the same whether you backfeed the dryer ckt or a dedicated outlet through a transfer switch. It's one basic warning. Most portable generators, including your inverter type, are wired with a ground to neutral bond. This is an OSHA requirement for portable use. That bond should be removed if powering a house panel since most transfer switches don't transfer the neutral. If any electricians want to chime in, I think they would agree that you never want to have more than one neutral to ground bond.

CAJUNLAWYER · Oct 15, 2010

I have a generator with three plugs and tree extension cords.
One goes to my ice box
one goes to my freezer
and one goes to the 7,000 btu window unit I keep for emergencies and pop in my bedroom window. Worked for Andrew, Worked for Lili , worked for Rita and worked for Gustave. :rolleyes:

El Rubio · Oct 18, 2010

CAJUNLAWYER said:
I have a generator with three plugs and tree extension cords.
One goes to my ice box
one goes to my freezer
and one goes to the 7,000 btu window unit I keep for emergencies and pop in my bedroom window. Worked for Andrew, Worked for Lili , worked for Rita and worked for Gustave.

That's fine as long as the bond is still in place and the extension cords aren't really long and thin. Ideally you would ground to a suitable earth ground.

Suburbazine · Oct 18, 2010

Suitable earth ground being a 8 foot long 0.5 inch thick copper bar hammered into the ground until only the top 6 inches or so sticks out.

Most people just take a 6' section of rebar and hammer it in.

oldman45 · Oct 19, 2010

I have a genset that puts out 8500 watts. It remains in my garage until needed which in this area is more often than I would like.

It has ran as long as four days and never been connected to the electrical panel.

With four main heavy gauge extension cords of 25 feet in length, I can power everything in this 3,000 ft home other than the ac. I run a cord to the kitchen for the fridge and a light. I run one to the master bedroom for a stand alone ac unit or a 1500 watt heater (depending on the season), Another goes to my office for the tv, computer, fax and lights. Another goes to the den for tv, oxygen machine for the wife, lights and a spin off cord to one of the bathrooms for light.

I turn on a ceiling light so when power comes back on, I can turn my genset off. It takes me less than 15 minutes to get everything in place. Each cord is labeled and is in the box beside the genset in garage.

At night when the power is off, I run the security lights off the genset.

The reason for all this is I do not want it wired into the panel. Too much expense for no more often than it is needed for long periods.

I admit a large whole house genset would be nice but then there is either propane or diesel to worry with but there is also about $10,000 expense.

El Rubio · Oct 20, 2010

oldman45 said:
I have a genset that puts out 8500 watts. It remains in my garage until needed which in this area is more often than I would like.

It has ran as long as four days and never been connected to the electrical panel.

With four main heavy gauge extension cords of 25 feet in length, I can power everything in this 3,000 ft home other than the ac. I run a cord to the kitchen for the fridge and a light. I run one to the master bedroom for a stand alone ac unit or a 1500 watt heater (depending on the season), Another goes to my office for the tv, computer, fax and lights. Another goes to the den for tv, oxygen machine for the wife, lights and a spin off cord to one of the bathrooms for light.

I turn on a ceiling light so when power comes back on, I can turn my genset off. It takes me less than 15 minutes to get everything in place. Each cord is labeled and is in the box beside the genset in garage.

At night when the power is off, I run the security lights off the genset.

The reason for all this is I do not want it wired into the panel. Too much expense for no more often than it is needed for long periods.

I admit a large whole house genset would be nice but then there is either propane or diesel to worry with but there is also about $10,000 expense.

Whatever works for you is fine. Many people do use portables through their house electrical system and there's an inherent flaw with that. It's simple to remedy and that's what I describe.
Backfeeding your panel can be done safely even with a smaller portable generator. It doesn't have to cost a fortune either. I run a 7Kw for the convenience of being able to turn on any lights and ceiling fans, refrigerator, window unit AC's, etc without extension cords. It will handle my entire house except for central air but does require some consideration. I may have described this before but after that ice storm a couple of years ago, I decided to get a whole house standby generator. It looked like it was going to cost around $5-7k with me doing some of the installation. My brilliant wife suggested I compare using a smaller portable with a couple of window units. We had done this after Gustav for a couple of days with a borrowed generator. A 7Kw generator was around $1100. I figured that a 6-6.5Kw would handle most of my needs. I didn't want to have to keep several gasoline cans around and maintain the fuel so I added natural gas conversion. It had to be safely operated and hooked up without tools. The whole setup including natural gas hookup was around $1700. The difference was $3-5k just to run my central air for the most part. It runs great on natural gas too. 1 ccf of nat gas will run approximately as long as 1 gallon of gasoline in this setup. 1 ccf of ng costs about 70 cents in this area compared to whatever gasoline goes for. So far, I'm very happy with the results - obviously

Barney88PDC · Oct 20, 2010

I am trying to understand the "risk" with multiple grounds. I have a larger Diesel Gen Set with a terminal on the generator with 4 terminals. 2 Hots, Neutral, and a ground lug. I use a 2/4 SO cord to go from the Gen to my house's main panel. I also run a 6AWG wire from the gound lug on the gen set to a 8' ground rod I drove specifically for the generator it self.

My hook up in the panel is as follows. I turn off the main, and pull the neutral off the bus from the road. The 2 hots hook up on a 100amp 2 pole breaker. The Neutral goes where the neutal from the road was. And the gound goes on the ground bar. So I am grounded in the main panel on the ground bus which is obviously connected the the main panels ground bar in the slab. And one of the 4 conductors (the green) runs back to the generator to the gound terminal where it meets the 6AWG running to the gound bar at the generator.

My question is would my setup be of any concern and if so why.

I would think if you had say 100 circuts you could put 100 different gound bars in the gound and run each circut in there own independant ground and it would not make any difference electrically than them all going to a common ground? Is my understanding flawed?

drumz2129 · Oct 20, 2010

Barney88pdc said:
I am trying to understand the "risk" with multiple grounds. I have a larger Diesel Gen Set with a terminal on the generator with 4 terminals. 2 Hots, Neutral, and a ground lug. I use a 2/4 SO cord to go from the Gen to my house's main panel. I also run a 6AWG wire from the gound lug on the gen set to a 8' ground rod I drove specifically for the generator it self.

My hook up in the panel is as follows. I turn off the main, and pull the neutral off the bus from the road. The 2 hots hook up on a 100amp 2 pole breaker. The Neutral goes where the neutal from the road was. And the gound goes on the ground bar. So I am grounded in the main panel on the ground bus which is obviously connected the the main panels ground bar in the slab. And one of the 4 conductors (the green) runs back to the generator to the gound terminal where it meets the 6AWG running to the gound bar at the generator.

My question is would my setup be of any concern and if so why.

I would think if you had say 100 circuts you could put 100 different gound bars in the gound and run each circut in there own independant ground and it would not make any difference electrically than them all going to a common ground? Is my understanding flawed?

Your set up is perfectly fine. The problem would be if you did not have a ground wire from your generator to the panel. From what I understand OP points out a problem if you were to ground your generator then hook up the two hots and a neutral to your main panel. Everything connected to the panel would be getting a ground through the panel's ground rod and you would have a floating ground between the generator and all your devices. This could cause issues if the 'ground system' begins to carry stray current.

rborison · Oct 23, 2010

Good Info!

Interesting discussion. Thanks

Yrdawg · Oct 23, 2010

One ground for entire system...if a ground were to open...not likely...AND some one grabbed the break on either side it would make them a conductor IF there were fault or imbalance current on the line......

It's typical municipality knee jerk IMHO

Mine is connected thru a 50 amp dbl pole breaker ...when I need the generator I turn off the feed @ the main...turn on the gen to the busses by the 50 amp...all on one ground

The 4 wire hookup is what comes from the utility anyway..just continue their ground to your system ...ground is called common for a reason...it's COMMON...it always ends up in the dirt

So far I am not on my utility's most wanted list

El Rubio · Oct 24, 2010

Yrdawg said:
One ground for entire system...if a ground were to open...not likely...AND some one grabbed the break on either side it would make them a conductor IF there were fault or imbalance current on the line......

It's typical municipality knee jerk IMHO

Mine is connected thru a 50 amp dbl pole breaker ...when I need the generator I turn off the feed @ the main...turn on the gen to the busses by the 50 amp...all on one ground

The 4 wire hookup is what comes from the utility anyway..just continue their ground to your system ...ground is called common for a reason...it's COMMON...it always ends up in the dirt

So far I am not on my utility's most wanted list

It's not 'one ground for the entire system', it's all grounds at the same potential. More ground rods, the better-as long as they are bonded to each other. The earth doesn't have the same conductive characteristics everywhere so it isn't "common" in that sense. Common in the sense you are referring is an electrical common that is most effective and safest when all are at the same potential. It's not knee jerk at all but really is proven to be the most effective method. Multiple unbonded grounds are asking for stray voltages and surge damage.

Yrdawg · Oct 24, 2010

El Rubio said:
It's not 'one ground for the entire system', it's all grounds at the same potential. More ground rods, the better-as long as they are bonded to each other. The earth doesn't have the same conductive characteristics everywhere so it isn't "common" in that sense. Common in the sense you are referring is an electrical common that is most effective and safest when all are at the same potential. It's not knee jerk at all but really is proven to be the most effective method. Multiple unbonded grounds are asking for stray voltages and surge damage.

OK...the bonded word got by me...I agree..so the common is only common by mechanical bonding...not thru earth ...I did not consider the differences in earth conductivity, here it's so wet at 6 or 8 ft I wouldn't expect much differential

my-rifle · Jul 20, 2012

This is an interesting thread. Can't say I understand everything in it, and I'm not going to pay another electrician $1000 to look at my generator setup, but the power went out about two hours ago, and I've been running on my 5kw Briggs and Stratton generator all that time. The central A/C is disconnected, but everything else in the house is enabled. Two refrigerators, about four fans, three computers behind UPS's, and a bunch of compact fluorescent light bulbs are running fine. I'll let you all know if anything blows up.

drumz2129 · Jul 20, 2012

my-rifle said:
This is an interesting thread. Can't say I understand everything in it, and I'm not going to pay another electrician $1000 to look at my generator setup, but the power went out about two hours ago, and I've been running on my 5kw Briggs and Stratton generator all that time. The central A/C is disconnected, but everything else in the house is enabled. Two refrigerators, about four fans, three computers behind UPS's, and a bunch of compact fluorescent light bulbs are running fine. I'll let you all know if anything blows up.

You do have your main breaker (should be a 200A at the top of your box or by the meter) off, correct?

my-rifle · Jul 20, 2012

drumz2129 said:
You do have your main breaker (should be a 200A at the top of your box or by the meter) off, correct?

In my very old house the main breaker is backed up by a main fuse which I pulled and set on top of my generator so I could see it before I started the generator. Thanks for the reminder though.

Yrdawg · Jul 20, 2012

my-rifle said:
In my very old house the main breaker is backed up by a main fuse which I pulled and set on top of my generator so I could see it before I started the generator. Thanks for the reminder though.

Me too...used a cord and plug off the 230v receptacle and put in the panel thru a dbl pole breaker

Double safety

Our utility looked it over a couple months ago in an outage. They just locked my base up and re sealed it.

We are rural...IDK about city

Isaac-1 · Jul 23, 2012

The problem with backfeeding is there are story after story out there of "responsible" people backfeeding who seem to know what they are doing only to be away from the house and have a family member do something like flipping the main breaker back on to see if the power is working without first stopping the generator, or flip the breaker on while the generator is stopped for refueling to check for power and not flipping it back before restarting. What a lot of people don't realize is backfeeding that 120V from a small generators can backeed through a closed main breaker to the pole top transformer where that 120V will be stepped up to several thousand volts and momentarily can supply a high voltage surge potentially miles down the line where a lineman may be working on the line that was tested as dead moments earlier. If your not going to invest in a real transfer switch / panel, at least get a breaker interlock kit like the ones sold at http://www.interlockkit.com/ they are not as safe as a real transfer switch, but certainly beat backfeeding, if not just stick with using extension cords and your generator, your conveinence flipping a light switch to get light instead of using a floor lamp plugged into an extension cord is not worth the life of the people that go out in the storms to try to restore your power.

Ike

Backfeeding your panel with a portable generator

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