What type of interlock device? Who makes it?

 

This one: http://www.interlockkit.com/InstrK8210GENewDsn.pdf

 

You would use an ordinary breaker for backfeed purposes.

The best way to arrange ground and neutral for a backfed generator is to unbond the neutral from the generator's frame and ground connection inside the generator. Occasionally this cannot be done easily in which case I would be tempted to leave the green wire unhooked somewhere in the wiring between panel and generator. I would not mutilate a generator to get its neutral and ground unbonded.

 

Connect the neutral and the ground wires from the generator to the load center. DO NOT tamper with the generator.

 

If you cannot remove the N-G bond at the generator, then you must switch the grounded connector at the transfer switch.

 

What do you think would be the consequences? It works fine on my personal home and others I have done.

 

Its a code violation, plain and simple. And just because it works, doesn't make it correct.

 

A generator is not considered a permanent part of the electrical system. Removing the bond in the generator voids the warranty. Also if the generator is used for anything other than back feeding the house it could be potentially dangerous with the bond removed.

Oddly enough this is one of the reason a genny panel switches out the neutral that you argued so much about not needing.

brric, what's you've in essence done is run a ground and a neutral in parallel with each other, in theory they can both carry some of the current.

 

A generator is not considered a permanent part of the electrical system. Removing the bond in the generator voids the warranty. Also if the generator is used for anything other than back feeding the house it could be potentially dangerous with the bond removed.

Oddly enough this is one of the reason a genny panel switches out the neutral that you argued so much about not needing.

brric, what's you've in essence done is run a ground and a neutral in parallel with each other, in theory they can both carry some of the current.

That is correct. It is a temporary plug and cord connection. It is not intended to be permanent. Also, removing the bond would create a possible generator fault clearing issue.

 

i should have clarified, only the last bit of that post was directed at you brric, the first was for stickboy.

never thought of the fault issue, good point.

 

i should have clarified, only the last bit of that post was directed at you brric, the first was for stickboy.

I know.

 

My research leads me to respectfully disagree.

 

So where in the NEC do you believe you can have two separate N-G connections? You can always just purchase a generator with a floating neutral, or install a 3 pole transfer switch, the option is yours.

 

Is a portable generator a separately derived system or non-separately derived system?

 

Thats not what determines it, the transfer switch does.

IF you have a solidly connected grounded (neutral) connection, then you do not have a SDS, if you break the grounded (neutral) connection then yes, you do have a SDS, and the generator then requires ground rods.


With that said, you MUST know if the generator you are wiring has a N-G connection before you can make the correct transfer switch selection.


This may help you digest some of the info I posted...http://www.imsasafety.org/journal/ma03/ma5.htm

 

How would you use a 3 pole transfer switch for the OP'S installation?

 

The only way you can use a interlock kit legally is if his generator has a floating neutral. Otherwise, he would need a manual 3 pole transfer switch.

 

Simpliest thing to do is to wire it up as is and see if the gfci trip on the generator, if it does then the simplest way to get it working is to float the ground coming from the generator inside the panel. Legalities of it can be argued for days. Keep in mind that the code only contains info on how to wire it up to the electrical system. the actual internal generator wiring is a UL standard that has to be followed by the manufacturer.

In all honesty there's a bunch of ways to wire them, if you look in the genny manual it will most likely tell you that you need either a 3 pole or 4 pole transfer switch if it has a bonded neutral inside. If it has a floating neutral then it will recommend a 2 pole transfer switch.

Safest and most expensive way is to leave the generator as is as to not void your warranty and actually spend the money on the recommended transfer switch for your particular unit.

 

Hi! I'm planning on using an interlock kit (code approved model) when connecting my generator to my home's main power panel, as follows (drawing attached):

7500W generator (Generac GP7500E) with L14-30 generator cable connecting generator's 240V 30A outlet to an L14-30 inlet box (on house), then connect the inlet box to 30A dual-pole backfeed breakers in the primary power panel using 10/4 wire.

Backfeed breakers and main panel input breaker will be mutually exclusive using interlock (only one can be on at any given time).

My question is do I run both the neutral and ground wires from the inlet box to the neutral bus bar in this primary power panel, or just the neutral wire? If just the neutral wire, what's done with the ground feed? Anything?

One other secondary question: Are backfeed breakers unique from standard breakers? Do I need to find specifically backfeed breakers, or will your standard 30A dual-pole breakers work for this application?

Thanks for your help!

This would not be a separately derived system since your interlock does not open the neutral connection to the utility grounded conductor which has earth grounding both at the service equipment and utiltiy transformer.
Being a non separately derived system the the NEC would require that no neutral to ground bonds exist load side of the service equipment. You would technically, in order to be code compliant, need to determine if the neutral and ground are separated at the generator. In the event you do not isolate then your equipment grounding conductor will be energized due to the connected neutral of the utiltiy at the service equipment of the home with the generator neutral.
Bottom line is portable generators were designed to serve as power sources for job sites and cord and plug equipment not standby power for a home and therefore have neutral and ground bonded in acccordance with 250.30 while considering 250.34(A). Think of them as service equipment.

Now having said that I would venture to say 80% of portable generators powering homes with transfer switches or interlocks that do not switch the neutral do not have their neutrals isolated from ground. NOT because it isn't required but because they simply are not familiar with that rather confusing part of the NEC.

It would be advantageous to all of us to start a new thread about grounding of generators and in particular portable ones and when and when not to requrie ground rods at the generator. I would bet it will generate some eye opening. If we all tie in the NEC articles to back up the discussion I actually think we could reach a professional consensus on the code compliance requirements for grounding portable generators.

I would suggest providing graphics/drawings as well as Nec articles and subsections to make your points would be great. I'll start it and we can see where it goes... It would be better IMO if we do not link to other written articles and provide our own explanations to which others can add.

 

This one: http://www.interlockkit.com/InstrK8210GENewDsn.pdf

Unfortunately installation of this kit is a violation of 110.3b. Wyle Labs lost its listing capabilities and it is not listed by any other recognized listing labs. Sorry.

 

It was my understanding that anything previously listed by Wyle is still in force and legal. Those listings were not revoked.

They are no longer able to list any new products by the recent action of losing their certification.

 

deleted.

 

First, thanks to everyone for their thoughtful responses! I hadn't imagined that my query would garner such a lengthy discussion.

Frankly, I was hoping to use the interlock solution in order to make use of all of the circuits in the house during an outage, as you probably have guessed. Having over 20 individual circuits in the house, I didn't want to be limited to powering 10. Not that I'd power all 20-some-odd circuits at once with a 7500W generator, but it would be nice to have the flexibility to pick and choose from all 20 at any given time.

The differing opinions about how or if to connect the ground line in my proposed application leaves me feeling a bit sketchy about using the interlock solution, but I'm not sure that a transfer switch solution looks much different when it comes to the N and G connections.

This video (http://www.youtube.com/watch?v=5dKfVgVvEt8&feature=youtube_gdata_player) shows the neutral and ground wires being used for the Reliance transfer switch solution. In part 1 of this video series (http://www.youtube.com/watch?v=7--oK3BXN5U&feature=youtube_gdata_player), connecting the transfer switch to the power panel is shown, and both the ground and the neutral wires are used and connected to the neutral bar in the main panel. Once the transfer switches are put in the generator position, how does this differ from my interlock solution in regard to the NG connections? There is no mention in the videos about whether the N and G are bonded at the generator or not.

Sounds like a thread on grounding generators would be in order, and I'd like to know if anyone starts one, but I'd still like to know how to handle my situation.

 

First, thanks to everyone for their thoughtful responses! I hadn't imagined that my query would garner such a lengthy discussion.

Frankly, I was hoping to use the interlock solution in order to make use of all of the circuits in the house during an outage, as you probably have guessed. Having over 20 individual circuits in the house, I didn't want to be limited to powering 10. Not that I'd power all 20-some-odd circuits at once with a 7500W generator, but it would be nice to have the flexibility to pick and choose from all 20 at any given time.

The differing opinions about how or if to connect the ground line in my proposed application leaves me feeling a bit sketchy about using the interlock solution, but I'm not sure that a transfer switch solution looks much different when it comes to the N and G connections.

This video (http://www.youtube.com/watch?v=5dKfVgVvEt8&feature=youtube_gdata_player) shows the neutral and ground wires being used for the Reliance transfer switch solution. In part 1 of this video series (http://www.youtube.com/watch?v=7--oK3BXN5U&feature=youtube_gdata_player), connecting the transfer switch to the power panel is shown, and both the ground and the neutral wires are used and connected to the neutral bar in the main panel. Once the transfer switches are put in the generator position, how does this differ from my interlock solution in regard to the NG connections? There is no mention in the videos about whether the N and G are bonded at the generator or not.

Sounds like a thread on grounding generators would be in order, and I'd like to know if anyone starts one, but I'd still like to know how to handle

I know i stirred the pot on the issue, but the reality of it is, everyday generators are installed incorrectly by licensed contractors, and the like... Most people don't feel it is a real issue with the multiple N-G connection in a portable generator installation, well, because it still works in the end, and most likely will never be an issue. but still a violation none the less, and under the right circumstances could create a serious issue. Its one of those items that just gets installed either by lack of knowledge, or just the way we do it mentality...

 

If you use an ungrounded extension cord (or unhook the green wire from the male receptacle on the side of the house) you eliminate the duplicate return path from the house panel via the ground wire and permanently bonded neutral and ground in the generator and thus prevent the generator GFCI from tripping under otherwise normal operation.

The generator GFCI will still protect persons from electrocution from generator power because the generator neutral is the ultimate return destination and the generator hot and neutral are monitored by the GFCI.

With an interlock transfer (any kind) set for utility power, there is no current flowing on the generator line to the house so there would not be a voltage drop on the neutral. In turn there could not be a floating above zero volts of the generator body still bonded to that neutral. (Zero volts relative to the other end of the generator neutral which is at the neutral bus and connection to the grounding electrode conductor.)

 

Yes, I see that. I was somewhat confused by the term "extension cord." I was picturing an extension cord like you might use to use a drill away from an outlet in your house.

I'll be using the 240V 30A NEMA L14-30 outlet on the generator, and, therefore, a heavy, 4-conductor cable (L14-30P - L14-30 R) from the generator to a L14-30P inlet box, then wire the inlet box to either a transfer switch or to two 30A backfeed breakers in the main panel (if I opt to use an interlock on the panel).

In either event, I won't connect the ground line from the generator to the transfer switch or the main panel... just let it float.

So, again, my remaining question: Should I physically ground the generator (to a grounding rod or some such) as specified in the owner's manual? I'm assuming that I should.

Thanks again!

 

Hi!

I'm going through the same exact thing as tjnoff is. I have a Champion 7000/9000w generator and I bought a "generator inlet" box that I mounted outside. I have that wired to my main panel and have a 30 amp 2 pole breaker. On the generator, I purchased a 240v L14-30 4 conductor cable that I plug into the generator and then into the inlet. From what I read, it's a white, ground, and two hots on the inlet and outlet on generator. Nothing else is connected to the generator. No ground, nothing for the 120v outlets, nada.

I assumed everything is grounded through the panel and sent to the generator via the ground in the cable. I want to do it the right way and that's why I'm asking.


Thanks!

 

There was a further discussion of this here: http://www.diychatroom.com/f18/disc...m/f18/discussion-proper-grounding-portable-generators-148672/index3/#post957825

The consensus was that the best solution for wiring a portable generator to your main power panel (where neutral and ground are bonded together) was to run all four conductors (both hots, neutral and ground) from the generator through the inlet box to the power panel, and connect both neutral and ground to the panel's bus bar, but only if ground and neutral are UNbonded on the generator. This is probably a couple of wires in the actual generator part of your portable generator.

Also, were you ever to use your generator stand-alone, to power tools in the field, for instance, you MUST rebond neutral and ground on the generator.

 

Thanks for the shortened version. I didn't check the link, but in a short and sweet answer, what could happen if you don't unbound the neutral and ground on the generator?

Also, what happens in situations where the ground is to the EMT conduit? It doesn't get grounded to the bus bar through a cable, however, the neutral is grounded, as far as I know. So, essentially, the ground goes to the EMT which is grounded to the neutral....

Confusing stuff.

Thanks again for the short and sweet version!

 

your ground could potentially carry some current.

 

Being that it's the same size, it will carry half the current.

 

It is my belief that nothing bad will happen if the generator cannot easily have neutral and ground unbonded (and that step/process/instruction/mandate was therefore omitted/skipped/neglected) and also the panel was not revamped to separate grounds and neutrals, whether or not the ground connection (equipment grounding conductor) between the generator and panel is a metal conduit or a wire.

It would be a good idea to check the link to that other thread on proper grounding and reading the entirety thereof.

 

Thanks!

Thanks for the information. I will definitely check out the other thread and read up.

Thanks!

 

You definatly want the inlet box to be grounded! There are several ways to do this. You could just bring the ground wire from the main panel and terminate it on the ground screw along with the one going to the inlet. Another way would be to bring the ground wire from the panel and use a wirenut to join it with one wire going to the ground screw and another to the inlet itself. If you used metal conduit to connect the box to the panel, I dont believe a ground wire is required at all because the conduit serves as the ground conductor.

P.S. The inlet is only rated for one wire per connector. Puting two wires in the G slot would be "double lugging" and is a big no-no.

 

... bring the ground wire from the panel and use a wirenut to join it with one short length of wire going to the ground screw and another to the inlet itself...

Do it this way if two wires want to go under one screw or if one wire wants to go under two screws.

 

Bonds

Well I like that idea but if i use square d homeline interlock breaker and back feed I would be bonded on both ends The other thought that I have come up with is a sub panel move only breakers i need and take neutrals and grounds that go with those circuits in the sub panel they would be a separate ground bar the feed for the sub would be 50 amp inlet male plug. main panel feed for sub would be 50 amp female plug if I wanted to use generator the plug would be unplugged from main to sub and plug there to the feed the sub from generator that plug would be my transfer switch when using gen I could stay bonded and totally of main. If I use the back feed method with interlock and stayed bonded in main and at generator what are my potentional dangers that way thank you

 

If I use the back feed method with interlock and stayed bonded in main and at generator then what are my potentional dangers that way thank you

Now I believe there are none.

If you can get an interlock compatible for back feeding the panel via a breaker set then you might not want to go through the trouble of installing a subpanel and rearranging into a group the circuits that will receive generator power.

 

I am very interested here but still don't quite understand. It seems several electricians have differing opinions on the neutral/ground in this thread. Or maybe you don't and it's I that don't follow.


I too am using an interlock kit on a 1983 SquareD QO Panel and am installing a standard 2 pole 30 amp breaker to serve as the backfeed breaker.


1) Is a standard breaker is sufficient as long as it is secured by the bracket provided by the kit?


2) My panel seems to have one neutarl/gound bar and both the bare wires and neutrals are connected there. Must I also connect both the ground and neutral from the 10-3 wire that runs from the outside inlet box to the backfeed breaker to that bar?


3) Should I unbond the ground in the generator or leave the green wire disconnected as stated above somewhere between the generator and the panel?


Thanks
Mike

 

I am very interested here but still don't quite understand. It seems several electricians have differing opinions on the neutral/ground in this thread. Or maybe you don't and it's I that don't follow.

No, you're right, there are differing opinions on bonding/unbonding N-G at the generator in this thread.

I too am using an interlock kit on a 1983 SquareD QO Panel and am installing a standard 2 pole 30 amp breaker to serve as the backfeed breaker.


1) Is a standard breaker is sufficient as long as it is secured by the bracket provided by the kit?

Yes, that's what I used and it tested fine.

2) My panel seems to have one neutarl/gound bar and both the bare wires and neutrals are connected there. Must I also connect both the ground and neutral from the 10-3 wire that runs from the outside inlet box to the backfeed breaker to that bar?

I did, but I know this is a point of discussion here (see my next answer). But, again, I tested the system and ran the fridge, lights, TV, etc. All ran fine.

3) Should I unbond the ground in the generator or leave the green wire disconnected as stated above somewhere between the generator and the panel?

Based on all of the very good input I got here on both sides of the discussion, I had the generator's N-G unbonded and the neutral and ground lines connected from the generator all the way through the inlet connection to the neutral bus bar in the power panel when I went to test this setup, but nothing in the house was getting power. I reconnected the N-G bond in the generator, left the neutral and ground lines connected between the generator and the bus bar, and everything in the house that I tested powered up.

I know there is still the open point about possible current on the ground line with neutral and ground bonded at two points, so I can't say it's 100% without risk, but others here have claimed to do it this way without issue. You'll just have to weigh the pros and cons for yourself as I did.

 

Thanks TJ,

For confirming it's an issue still under debate. I will then connect the neutral and ground from the generator to the neutral bar in my panel. Course I've read enuff that somethings definitely work but remain with a potential for a problem even if the odds of a problem are negligible.

Can I double up the connects to the bar as ther are no open slots and I see that some slots are doubled up while some have only a single white or bare wire in a slot.

And thanks for confirming the standard 30 amp breaker is fine cuz I read only once in a forum that a standard breaker will trip or overload (or something to that effect). I think the only difference between the std and the special generator B/F Breaker is the special breaker has screws to secure it instead of the retaining clip one would use for the standard breaker.

Going to call Champion's hotline on their opinion and warranty. I noticed they have technical bulletins about unbonding at the generator.

I don't know alot about electricity but seems odd that the gen would not power your circuits with the ground unbonded.

Thanks again
Mike

 

As long as your leads have good physical contact when secured to the bus bar, it should be fine doubled up, although mine had space for extra connections, so I had no need to double any up.

My interlock kit came with a zip tie to physically secure the feedback breaker to the adjacent breaker in the other row. Other than that, it's just a standard dual-pole 30A breaker.

Not sure why I didn't get power with the N-G unbonded at the generator, but as soon as I bonded it, I had power.

 

N-G unbonded at the generator, but as soon as I rebonded it, I had power.

Was unbonding neutral and ground in the generator as you did it according to the generator instructions?

Maybe you were not supposed to unbond N-G in the generator, and the generator center taps and other neutral related conductors were fundamentally connected to the frame with the neutral conductor to the receptacles also connected to the frame.