How to generator power pass through to inside the house.

[CobyRupert]

Lenny: That shouldn't happen.
The neutral, from the utility transformer, is bonded to ground (the earth, "0" volts, ground rods, etc.. ) at the first disconnect from the utility service point (usually by bonding neutral bus and ground bus in your main panel and connecting to ground rod). The neutral might also be grounded (with a ground rod) at the utility's transformer (especially if it's pad mounted). Only if your ground system and/or neutral bonding goes bad (neutral is "lifted") could neutral become energized.

The overwhelming majority of commercial residential transfer switches sold do not switch the neutral. When you plug the genny in, it uses the same ground and neutral system, and bonding point between the two, that your house does when on utility power.
(If you do have a rare transfer switch that switches the neutral your generator is now a "Separately derived system" and need ground rods, jumper bond at genny between neutral and ground, etc...etc..basically things get more complicated)

The reason why Fried's (-that's NOT a good name for someone doing electrical work!) method is "dangerous" (but often done) is because it relies on a human to remember the correct procedure when another human's safety depends on it, rather than a mechanical interlock. And that's not fair to the Lineman.

In reality if you try to energize the utility line:
- The lineman has probably grounded or shorted the lines he's working on so only smoke will come out of your genny (or breaker will hopefully trip)
- There's little chance your 10kW genny is going to backfeed through the ((say) pole mounted 13.2kv-120/240) transformer, power up the 13.2kv line and power all your neighbors on that line without instantly tripping out. - Though this depends on where the utility fault is and how many neighbors you're trying to power. Though I suppose theoretically, Lineman could still get a shock in that instant.
- When utility power comes back on and you (or someone else) messes up and turn on utility breaker into panel still supplied by active genny (or vice-versa)....you also may get some "magic smoke" escaping out of your genny.

 

[MAD777]

Thank you! I know what generator to shop for now! On 7200 watts, I should be able to limp through outages. Only my well pump is 220v and it's artesian, so it doesn't have to work hard. Otherwise, my priorities would be the controller on my Propane heat system and the refrigerator. Any left over would be to light up my gas stove and a couple lights. I can manually keep all breakers off that I don't need. Plus, I will disconnect at the meter, just so I sleep better.

 

[TheMan419]

Thank you! I know what generator to shop for now! On 7200 watts, I should be able to limp through outages. Only my well pump is 220v and it's artesian, so it doesn't have to work hard. Otherwise, my priorities would be the controller on my Propane heat system and the refrigerator. Any left over would be to light up my gas stove and a couple lights. I can manually keep all breakers off that I don't need. Plus, I will disconnect at the meter, just so I sleep better.

I have a similar set up to you. My gen is 6900 watt running with 8k watt surge. The electrician who set things up said plenty of power for well, fridge, pumps to run boiler and a few lights.

I tend to switch boiler off if I need water.

Also I have not completely converted to led yet

 

[CobyRupert]

Remember when on genny and flipping on breakers and tryng to squeeze out every Watt from genny:

Start motor loads first. Genny can better stay under it's "trip out rating" and handle the motor inrush currents if your not adding the inrush ON TOP OF other loads.
Add those other loads after in rush has past and your only adding them to the RUNNING load.
Of course, this is very hard when you have a well pump or something that cycles. ...but you can predict.

 

[lennyzx11]

Cody,
I’m going to disagree. Then I’m going to be quiet.
If that neutral line is opened or powered for any reason, there exists a possibility of a difference of potential between neutral and ground. You specifically don’t bind ground and neutral within auxiliary sub panels.

With multiple bonding points and between. There is a possibility to cause both the neutral and ground to carry current. This also energizes every metallic object touching the ground wire. No one will ever know the fault is there. Until grounded.

I’m not going in depth farther on this thread. But backfeeding a receptacle is a dangerous practice that leaves room for human error to unknowingly get someone hurt.

 

[Travelover]

Cody,
I’m going to disagree. Then I’m going to be quiet.
If that neutral line is opened or powered for any reason, there exists a possibility of a difference of potential between neutral and ground. You specifically don’t bind ground and neutral within auxiliary sub panels.

With multiple bonding points and between. There is a possibility to cause both the neutral and ground to carry current. This also energizes every metallic object touching the ground wire. No one will ever know the fault is there. Until grounded.

I’m not going in depth farther on this thread. But backfeeding a receptacle is a dangerous practice that leaves room for human error to unknowingly get someone hurt.

Does this mean that the generator interlocks that are sold by the electrical service box manufacturers are inherently dangerous? As cautious as they are, it seems like they'd not sell them nor would they be approved by codes or testing certification labs. Just asking..........

 

[LouNY]

Cody,
I’m going to disagree. Then I’m going to be quiet.
If that neutral line is opened or powered for any reason, there exists a possibility of a difference of potential between neutral and ground. You specifically don’t bind ground and neutral within auxiliary sub panels.

With multiple bonding points and between. There is a possibility to cause both the neutral and ground to carry current. This also energizes every metallic object touching the ground wire. No one will ever know the fault is there. Until grounded.

I’m not going in depth farther on this thread. But backfeeding a receptacle is a dangerous practice that leaves room for human error to unknowingly get someone hurt.

The two lines that I underlined are correct.

Sub panels do not have the neutral and ground bonded,
However your main panel does have them bonded and in all cases that I am aware of they also go to a ground rod,
On top of that your meter box neutral is bonded to a ground rod.
So you have at least two locations were the neutral is bonded to an earth ground.

Back feeding a receptacle is a dangerous practice, it is done even though it shouldn't be.
Very few home generators have the power to backfeed a transformer,
if they don't instantly go up in smoke they will stall from the inrush current demand.

 

[TractorGuy]

I did a lot of research on the subject of bonding the ground and neutral and the common answer was it should be bonded at the main panel only and not in any subsequent panels. I'm not going to pretend to understand how a second bonding can result in stray voltage but it was a common concern. With that said if you are back feeding a generator you want to make sure it doesn't have the ground and neutral bonded at the generator. I'm not sure if any portable generators do or not. You could check for that with the generator not running by connecting an ohm meter between ground and neutral. If it has continuity then it will have the ground and neutral bonded and those should be separated before back feeding into a house panel. Most or all will have a ground connection you should drive a ground rod for and connect to. My Military surplus diesel HAS a bonding strap I had to remove when connecting to my house.

You are not limited to a 30 amp load to back feed. If you have a larger generator they make back feed inlets in 50 amp. https://www.homedepot.com/p/Reliance-Controls-50-Amp-Non-Metallic-Power-Inlet-Box-PBN50/205337810

I used a breaker interlock with 50 amp wiring and connectors. My house is all electric and for the most part I can run all my 120V stuff and any two of my 240V circuits. Part of back feeding is understanding how much load your generator and circuit can handle and doing the load management required to prevent overloading the generator. My generator will run steady with a 13,500 watt resistive load applied. It will start and run my 3.5 ton AC and my 1.5HP well pump. It won't do either in conjunction with the hot water heater or stove in use so I leave those breakers off. If I need to heat water or cook I turn the AC breaker off and turn on the water heater or stove.

This is how the Square D interlock looks.

 

[aczlan]

I did a lot of research on the subject of bonding the ground and neutral and the common answer was it should be bonded at the main panel only and not in any subsequent panels. I'm not going to pretend to understand how a second bonding can result in stray voltage but it was a common concern.

As I understand it, the concern is that if the neutral to your sub panel gets disconnected (and the ground is bonded to the neutral in the sub panel as well as in the main panel), now anything connected to the sub panel has whatever voltage is supposed to be on the neutral on the ground which could energize the metal case of an appliance.
If they are not bonded in the sub panel, you may fry things because you could have voltage way too high on one side but not on the other (ie: 80v on one leg and 160v on the other vs 120v on both legs), but no one should be injured because the ground is still connected properly.

Aaron Z

 

[MF RED in MT]

And once you have your "outside generator plug" (male end) wired up to your "generator transfer switch panel", then you may want to add a "meter box" to balance each 110 volt leg of the generator to insure one 110 volt leg does not have the majority of the (Wattage) load used while the other 110 volt leg has very little (Wattage) load use.

KC