# Back feeding house neutral



## Crawlfish

I've connected a 30 amp generator outlet to the line in of my hvac fuse box outside of my home. The problem is I didn't have a neutral to connect to. An electrical engineer friend said I didn't have to use it and to just cap it.

Another friend, wanting to see my test run brought his uncle along, another ee. He said I must tie the neutral to the panel.

After reading up on bonded and unbounded connections, I'm more confused than ever. The generator is a HF 450cc 8750/7000w item 68530. The manual says it should be locally grounded. The Main is open/off /locked out when generator is connected, of course.

My question is what is the point of landing to the panel neutral when the last four power outages broke the neutral connection when my service line was downed? 

Also, when back feeding, I already am using the house panel ground. Code says only one,right? HF manual ground is only necessary for use with portable tools only not for backfeeding applications?


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## aandpdan

Hi Crawlfish,

Are you using an interlock or transfer switch? By outlet, you actually mean an "inlet" right?

You need a neutral. Your electrical engineer friend is mistaken. There should be 2 hots, a neutral and a ground. Between both hots is 240 volts. Between EITHER hot and neutral is 120 volts. 

The neutral and ground are to be ONLY bonded at the main disconnect or panel. 

If you are running a 4 wire cord from your generator to the inlet as you should be you don't need a ground rod. The ground wire will be connected to your house grounding electrode system - as it should.


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## Crawlfish

*30 amp 10 gage*



aandpdan said:


> Hi Crawlfish,
> 
> Are you using an interlock or transfer switch? By outlet, you actually mean an "inlet" right?
> 
> You need a neutral. Your electrical engineer friend is mistaken. There should be 2 hots, a neutral and a ground. Between both hots is 240 volts. Between EITHER hot and neutral is 120 volts.
> 
> The neutral and ground are to be ONLY bonded at the main disconnect or panel.
> 
> If you are running a 4 wire cord from your generator to the inlet as you should be you don't need a ground rod. The ground wire will be connected to your house grounding electrode system - as it should.


Yes, sorry. I'm connecting a 10 gage 4 prong twist lock from the 30 amp outlet of the generator to the generator inlet receptacle I installed on the exterior wall of my house. Since One of the prongs is a neutral, I figured it should be landed. However, if it is critical to safe function, then what happens to the system when the service line is down and the neutral path is therefore broken? In the case of a downed power line, there is no neutral so what is the white doing for me then? Sorry, just trying to understand since both my friends are exp. engineers but have conflicting opinions.


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## aandpdan

Tell your electrical engineer friends to think "center tapped transformer" when it comes to utility power in the US - at least for the 120 volt portion. 240 volt loads do not use a neutral. Most stoves or dryers are 120/240 volts and use 120 volts for the controls/lights.

A neutral is critical. A broken/loose neutral to your house is a serious hazard. Power will flow from one hot leg through any shared neutral to the other hot leg. It can lead to imbalances in voltage, as one leg could have 230 volts and the other 10 or anything in between. Electronics can be seriously damaged and fires can result. If you had a problem with your neutral the power company would be out ASAP. It is that serious.


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## Crawlfish

*Neutral*

Yes it is serious. Limbs hit my service line twice separating the neutral leads. I opened my main after seeing the lights fluctuating. Power company said that was right thing to do. Fortunately, no equipment damage. The next two outages came from the big ice storm here in the southeast... That left us without power for four days. My question is that when a power line is down completely, as happened already, the neutral is lost as well as hot leads. So when I open the main and backfeeding what serves as a neutral path then?


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## aandpdan

The neutral from the generator is the neutral path.

A neutral/ground bond does not eliminate the neutral. 4 wires are required for a 120/240 volt service, 2 hots, 1 neutral, and a ground. 

There should not be any current flowing on the ground during normal operation. It is for "fault current" only.

The ground primarily serves as lightning protection. The impedance of the earth is too high to serve as a "fault path."

The power company in most cases only uses 3 wires. In that case the neutral and ground are bonded - they have different codes that they must meet.

Until the '08 National Electric Code you could run a 3 wire service from your main panel to a detached structure with the neutral and ground shared - no longer. 4 wires with a separate neutral and ground are now required.

3 wires also used to be allowed by Code for your stove or dryer, not anymore. 4 wires with a separate neutral and ground are now required.


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## Crawlfish

Thanks for the discussion aandpan. The n.e.c., treats separately derived systems differently from the permanent installations (utilizing an APS). I understand the APS setup opens the main AND neutral. Local hardware stores sell simple interlocks that prevent the main from being closed/on at the same time the generator panel breaker is closed/on. These manual interlocks purportedly meet code requirements and prevent hazards to lineman from idiots who forget to open the main before connecting the generator. 

My question is that unlike the APS setup, the neutral path isn't isolated by this alternative method. So with gen running, the utility neutral remains intact and I can see hooking up the gen inlet receptacle to the panel neutral bus. That,s what engineer 2 said as well. However if the line is knocked down, there is no neutral path as in first case. Does this change things? So does this mean I can't power safely with a generator? To complicate things, downed or crossed lines might energize the neutral and even with the main open could harm the generator.through an energized neutral. So does this mean the only safe way to backfeeding is with main open AND neutral open? Most of my coworkers backfeed without a manual or automatic transfer switch. Also many folks don't give as much thought into it or have opportunity to get advice from ee's ...


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## aandpdan

Whether or not it is a separately derived system depends upon your transfer switch. If the neutral is switched it is a separately derived system and the neutral is bonded at the generator. The problem with a bonded neutral generator is that you need to disconnect the neutral because Code does not allow you to have more than one neutral/ground bond - hence switch the neutral. 

Losing the POCO neutral is irrelevant. The generator neutral is still bonded to the grounding electrode system in the house at the main panel or first disconnect. Your generator will function correctly and safely.

Crossed lines on the POCO will trip their circuit breakers. POCO also grounds their neutrals. The neutral to your home from the POCO is grounded at the main service panel or disconnect as well.

The interlocks and small transfer panels you see are designed for "floating neutral" generators. In these generators the neutral and ground are ONLY bonded at the main panel - a non-separately derived system. Again, by Code there is only to be a single point of bonding.


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## Crawlfish

Again, great discussion aandpan. This is finally making sense. So, I need to determine whether my particular generator has a floating neutral vs bonded? Are HF gen sets known to be one or other?
Happy New Year!

×


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## aandpdan

It depends upon the genset if it is bonded or not. Many bonded neutral generators can be converted to floating neutral just by removing a jumper, usually at one of the receptacles. If you have standard outlet tester, the one with 3 lights, plug it into the receptacle and if it shows "open ground" then you have a floating neutral. 

Happy New Years too!


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## Crawlfish

Does it matter which receptacle on the gen set? If one receptacle is floating neutral they all are? I plan on using the 30 amp 4 wire twist lock outlet from the generator....so my tester won't work.


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## Crawlfish

Does it matter what generator receptacle I test? If one is floating neutral then all are? I plan on using the 30 amp 4 wire outlet on the generator and the standard 3 prong plug in tester won't work for that.


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## aandpdan

It doesn't matter. If one is bonded neutral to ground they all are.

You can also use a meter. Just check between neutral and ground on any receptacle.


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## Crawlfish

Ok, great. So, I know, if using my meter between ground and neutral I'm doing a continuity check? Set at 1k ohms expecting 0.

Thanks so much!


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## aandpdan

Yup. It shouldn't have any continuity.


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## Crawlfish

Ok, then tomorrow I test the genset and hope I find a floating neutral. I'm dreading crawling under the house to run a neutral too but I want it right!


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## Meadowlandselectrician

The Neutral is derived from the source at the transformer on the pole. The Neutral is the return path for the Hots. The Neutral in the Generator is also derived from the Generator. Ground is for faults, which is Hot not going to Neutral as it is designed. If you leave the power company's Neutral in place it actually creates a ground loop. So your allowing a path to ground through the Neutral that is bonded in the panel and the GFCI's on your Generator trip. The building ground, the wire attached to the ground rod outside and the building steel if it is such a structure, need to remain in place and be bonded to the new power source, your generator in this case. Lift the power company's Neutral. It is convenient to do it with a proper ATS or MTS but you can just temporarily disconnect the Utilities Neutral to test this.
The panel must be bonded to ground at the origination of power. That means the first panel you hit must have the Neutral and Ground bonded together in that panel. That stops any potential difference on the two conductors. It's to make sure you don't grab a water pipe and touch Neural and get zapped. Any Circuit or sub panel must keep the Neutral separated from the Ground. This prevents ground loops that could cause Potential differences on the Ground and Neutral conductors.


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## Crawlfish

Sorry for the delay... I didn't get notified and just checked back again after finishing my load test. 

It failed. So, I've run 10 gage wire from panel to the generator receptacle, two hots, neutral and ground. I opened the main and all panel breakers, unplugged loads to all receptacles, started the generator, connected the L14-30 twist lock to generator and gen inlet, closed the first inlet receptacle 30 amp breaker, with no problem. 

Upon closing the second 30 amp generator inlet breaker I heard a disconcerting hum. Had 110 but not 220. Went outside found the 30 amp generator breaker tripped. Reset it and repeated the test, this time closing the other breaker first with success. 

Upon closing the breaker for the other leg, I again got the disconcerting hum and sizzle. Generator breaker tripped again. So, I can get one leg closed using either breaker for 110 but not both at same time for 220. 

I'm told this setup is supposed to work. Is the reason it doesn't because of the intact utility neutral? Is it working for others Because they're hooking it up when power is out and lines down with neutral therefore disabled?


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## aandpdan

What do you mean 2nd 30 amp inlet breaker? You should be using a 30 amp, double pole, breaker. This occupies 2 slots in the panel - next to each other. Don't confuse it with a duplex breaker, occupies 1 slot.

It is not a neutral issue from your description. More likely you have both hot legs on the same bus.

Can you post a picture of your panel, cover off?

Do you have an interlock on this?

Just to add, when I exercise my generator I power the house through the inlet. Utility power is still available however.


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## Crawlfish

*Oh oh*

No interlock but I will get one.

Iam using two slimline breakers side by side. These were spares. See bottom panel on right. Bottom left two 20 amps are spares. 

So, it's been awhile... But these two 30 amps at bottom right are on same bus, drawing off the same bus instead of each leg on a different bus? 

Oh oh... But that an easy fix then...The double pole traverses both buses... Good grief me thinks the old timer' disease has got me .

See pics


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## aandpdan

Yes, I guess you've found the problem.


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## Crawlfish

Me? Haha! You know, you are quite kind and or subtle either way I appreciate it. Wish you were my neighbor friend. 

Had to rearrange things but I got the two pole in. That about takes all available space. Many of the circuits are dedicate to appliances or have just a few loads drawing on them so I think I'm good there.



Thanks again for finding my goof!


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## Crawlfish

Success! Pull started (first try) my new HF 13 hp, 7000/8750 watt generator. After isolating all breakers and main, I flipped my new double pole breaker (thanks ).

So glad to hear No hum or hiss! Systematically closed, in sequence, my gas pack heater under demand so it'd kick in and blow, then refrigerator, followed by the water heater and some lights. 

This China genset is doing all that I hoped it would.

Without the expert help I wouldn't have gotten this done. I appreciate all the replies very much


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## aandpdan

Great.

Now, not to keep bugging you about it but PUT IN AN INTERLOCK or something so you can't backfeed the POCO.


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## Crawlfish

Ok,I knew you promote the right way...I'm listening too... I already had a near miss And don't wanna put anyone else in harms way... Not to mention myself... It's just too easy to make a mistake I found.

I'm going to buy a dummy interlock... They made them specifically for me...so one is forced to disconnect the main when closing the gen circuit. The MTS is expensive at $200 but I may go that route later since it really is the better option.


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