Ok, I'm sure you have all dove into this topic before but I want to get it straight before hooking something up.

Using a portable Generator, Generac 5500, to back up a residential home, I need to have a three pole Transfer switch to isolate the neutral as well, right?

Then my question is, Is the bonding jumper in the generator suffcient to serve for the new bonding conductor? As far as I am aware the only jumper in this Generator is a #12 or #14 between the neutral and ground on the back of one of the receptcles? Which to me sounds like it is not sized appropriately, should be #6 ?

Your Feedback is appreciated...

Based on the information you've provided, the # 12 probably is adequate. I say this based on the fact that you probably are using the 120/240 part of the generator. I wonder if you are using a "Gentran" type connection where you selectively connect loads. As a rule the inspector has no control of a portable generator and whether or not the neutral is bonded to the frame of the generator. If the neutral and the frame are bonded together, you are doing the right thing by using a 3 pole switch to eliminate the bonding in two places problem. Now for the real world: We have an emergency, the utility has failed, we have a portable generator that has the neutral bonded to the frame, - I'm using it for power and the size of the bonding conductor that came with the generator is appropiate based on the factory specs.
One side note, Honda generators will trip the GFCI if the bonding jumper is not removed and you try to use them as a back-up for a utility and the Neutral is also at the utility.

How do you figure a #14 or #12 jumper is big enough? Doesn't the bonding jumper need to be #6 minimum for a 120-240V 60a system?

Sizing of bonding conductors for Service is covered in 250.102. (C) covers Supply side of Service and (D) covers Load side of Service. I don't know that this is the proper place to look because a generator is not Service. But it appears that in some cases even for Service Load size the bond can be as small as #14 AWG. The Bond that you mentioned that was on the generator is probably sized per manufacturer's specs. If there is any labeling, UL, CSA, etc I'm sure you don't have to worry about the bond being sized properly. Now you had indicated that it was a 120/240v. 5500 va generator so the capacity of the generator is 23a. on 240v. or if your are running it straight 120v. you might, I stress might, get 43a, I question if you could even do that at all. So 60a. is not what you can expect from this unit.

Don't most small transfer switches simply switch the phases? If you don't switch the neutral you float it in the generator. (the way it is usually shipped)

But George... if you are supplying the circuits soley from the generator... it IS a seperately derived service by definition and would need a service rated bonding jumper.

Gfretwell, if you REMOVE the bonding jumper in the generator it is no longer safe to use as a seperate unit for just the 120v receptacles at another time!? Right? Should I make up a jumper to fix that and instruct some ignorant homeowner to use this thing everytime you want to use your generator for the receptacles only... That's NOT safe either!!

Finally, I have yet to find online, and havn't checked at wholesale house yet, a Trasnfer switch made for switching the neutral. In these units are the individual circuit neutrals brought to a isolated bar in the transfer switch and then a pole of the switch transfers which neutral feeds it? (all while keeping it isolated from the transfer switch can since it has to go back to gen for bonding)

A few facts are in order:

1. Just because a 2 pole or a 3 pole double throw switch is being used to transfer a load from utility to generator does not make it a "Transfer Switch" Needs to be Listed as a transfer switch to be called a transfer switch.

2. If you are going to use the generator as a separately derived system you must break the grounded as well as the ungrounded conductors when using it in conjunction with a utility Service.

3. A Generator is not a "Separately Derived Service".

4. Kohler ship all of their generators from the factory with the common conductor bonded to the frame.

5. Generac and Onan and probably more, float the common conductor from the frame and their systems are shipped knowing they will be using them as backup for a utility.

6. Most portable generators say <7KW are shipped with the common conductors bonded to the frame and it is almost impossible to change them. Just put your ohm meter between the neutral terminal of an outlet on the generator and the frame and you see what I mean.

7. Most small generators are portable and the inspector has little to say about what homeowners do with them. Its the permanent installations that get inspected and these bonding issues are addressed.

8. If your going to use a ligit transfer swith your going to spend some serious cabbage. You'd be better off installing what they call a generator panel that has the interlock built in.

According to the code a generator CAN be a seperately derived system...

Another Electrician has steered me to a Siemans model of transfer switch that is three pole to switch the neutral.
SIE-EQG660D
Here is a link: http://hillsupplies.com/cgi-bin/search/subproducts.pl?qs=5803&sb=commodit&d=00&ft=1

This discussion is only referring to small portable generators used for Home back-up... Most gen's have the neutral bond to use with the recep. but HONDA is now putting them out without a bonded neutral, probably for the home back-up reasons, but isn't that electricaly unsafe? for use as the stand alone 120v recep's go?

Darryl- That was my point earlier, a generator is not a Service but a System. Hence the bonding jumper talked about in 250 for services is not applicable to generators. I'm not quite sure how youn size it. I'd have to research it. I've never had to size the bonding jumper for a generator but it's probably based on 12.5 % of the phase conductors. The Seimens panel looks like a good choice and I guess as long as your not ending up bonding the common conductor in two places your approved

"George Little
Member posted 01-16-2005 07:02 PM
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Darryl- That was my point earlier, a generator is not a Service but a System. Hence the bonding jumper talked about in 250 for services is not applicable to generators. I'm not quite sure how youn size it. I'd have to research it. I've never had to size the bonding jumper for a generator but it's probably based on 12.5 % of the phase conductors. "


I THINK YOU MEANT 125% OF THE PHASE CONDUCTORS IS WHAT THE BONDING JUMPER SHOULD BE SIZED AT? SO THE #14 OR #12 JUMPER WOULD NOT SUFFICE, WHICH WAS MY ORIGINAL POINT... AND WHAT ABOUT THE FACT THAT SOME GEN'S ARE BEING SOLD WITH ISOLATED NEUTRALS... IF THAT IS A CODE VIOLATION AS WE SEEM TO AGREE, HOW ARE THEY GETTING AWAY WITH IT... I KNOW THE NEC ISN'T APPROVING THEIR PRODUCT BUT CERTAINLY THE U.L. SHOULD BE CONSIDERING THE SAME SAFETY PROBLEMS IF THEY ARE MONITORING AND APPROVING PRODUCTS????

The last time I went through this exercise I looked at a few sites for portable generators (Honda etc) and they all said the ground and neutral were NOT bonded?
If this is a generator sitting out in the woods, supplying cord and plug connected loads, how does bonding the neutral give you any protection? In fact it is better to not have the neutral grounded. This is essentually the same principle as using an isolation transformer.

gfretwell wrote: "The last time I went through this exercise I looked at a few sites for portable generators (Honda etc) and they all said the ground and neutral were NOT bonded?
If this is a generator sitting out in the woods, supplying cord and plug connected loads, how does bonding the neutral give you any protection? In fact it is better to not have the neutral grounded. This is essentually the same principle as using an isolation transformer."

I WOULD BELIEVE THAT THE WAY YOU COULD GET HURT WITHOUT THE BOND IS BY GETTING HOOKED UP BETWEEN THE HOT AND NEUTRAL ON THE PORTABLE GEN... WITHOUT THE BOND, YOU ARE THE GROUND. IF YOU THINK THERE IS NO HARM FROM THE ISOLATED NEUTRAL ON HONDA PRODUCTS THEN WHY DOES EVERY OTHER GEN COMPANY BOND THEIR NEUTRAL AT THE GEN???? ARE THEY WRONG???

I'M TRYING TO SEE SOME CONSISTENCY OF OPINION AND FACT HERE AND I DON'T SEE ANY!!

[This message has been edited by Darryl (edited 01-17-2005).]

http://members.aol.com/gfretwell/honda.jpg

From the Honda EN3500 owner's manual

BTW if you get "hooked up" between the hot and neutral you are not "the ground", you are the "load".
The safety in isolation is because you do not complete a path if you are grounded and touch EITHER of the current carrying conductors.

G,
You're right, not between the Neutral and ground but between the neutral and gen frame you would complete a path that would not be dangerous if the neutral was bonded... In the Honda case with the neutral isolated, you would get a shock between neutral and ground or frame of gen...

If the frame is not bonded to either current carrying conductor what is the path for current?

Perhaps you should go to article 250 and look at the reason we bond a service.

"gfretwell If the frame is not bonded to either current carrying conductor what is the path for current?
Perhaps you should go to article 250 and look at the reason we bond a service."

the path is hot to load to neutral to you to frame or ground... In your line of thinking why is ANY generator bonded???

George,
Look at 250.30(A)(1).
Don

Thanks Don, missed that one. Interesting enough though, the size is very close to 12.5%. In fact I've heard it stated from the podium that T. 250.66 is based on 12.5%. When you do the math it's pretty close. That's what I like about this forum, what one of us misses the other one catches.
George

"The path is hot to load to neutral to you to frame or ground... In your line of thinking why is ANY generator bonded???"

How does ground or frame get in the fault path if the windings are not tied to either?

The reason we ground things on a utility service is because the utility grounds their end and provides that path.
There is no reason to ground one side of the winding on a portable generator. In fact you make it more dangerous when you do.
Do you understand the concept of an isolation transformer?
A portable generator is the same deal. If the output of the generator is not grounded you can safely touch either leg and not have a path to ground. (bird on a wire)

There is a code reason to bond the generator neutral to the frame. 250.20(B), 250.26 and 250.34(C).
Don

The most important part of the code is understanding when an article applies.
We are talking about PORTABLE generators not premises wiring.

250.20(B) Alternating-Current Systems of 50 Volts to 1000 Volts. Alternating-current systems of 50 volts to 1000 volts that supply premises wiring and premises wiring systems shall be grounded

NOPE

250.26 Conductor to Be Grounded — Alternating-Current Systems.
For ac premises wiring systems, the conductor to be grounded shall be as specified in the following...

NOPE

250.34(C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26...

NOPE

All of these refer to "premises" wiring.
When you connect a generator to a building it does require grounding the neutral but if you simply switch the phases with the transfer equipment and bring the neutral and ground straight in you use the system main bonding jumper to accomplish that.
In fact if you use a transfer switch like that you create a violation if you do have the generator grounding the neutral.

Greg- your right. Most portable generators hooked up via cord and plug attachment, create a code violation because the neutral and ground are bonded together on the generator in addition to the Service neutral and ground being bonded together. Unplug the generator and the violation goes away. As an Inspector it's impossible to police. George

OK if you guys agree that an isolated neutral Generator is both safe and the proper way to be for connecting to a service, then WHY do most of them bond the neutral to ground????

No body has answered that!

OK, some feel that a isolated system is ok for stand alone use, read the reasoning below (against that thinking)...

On a "stand-alone" (portable) generator serving cord-connected loads only, the frame is permitted to serve as the grounding electrode.

The neutral-to-frame bonding connection serves the same functions as the Grounding Electrode Conductor and Main Bonding Jumper do in a premises wiring system.
Without it, the equipment bonding conductor (EGC) in the load cords will not perform it's intended function.

Check this alert, http://labreq.lanl.gov/labreq/labreq.nsf/LookupDocNum/Alert0005/$File/alert0005.pdf
in particular the last paragraph regarding some Honda generators.

I can only tell you what the folks at Kohler told me- It's an application issue. Depending on how you are using the generator, as a stand alone system or as part of a backup for the utility. You may or may not want the neutral conductor bonded to the frame. If they didn't include the bonding conductor then you'd have to come up with it for a Separately Derived System. By the way, you can leave the bonding in place if your going to switch the neutral.

You are correct George about switching the neutral, but there are a great deal more transfer switches out there that do not switch the neutral. I don't even know how hard to get that one will be as it is from a canadian web site, and their code deals with this topic unlike in the U.S.

I am just trying to sort things out in my head so as friends ask me to install these, I can truthfully know I am steering them in the safest direction.

As an electrician, I back feed my whole panel from an outlet and have to manually shut off my main before doing it. I have the gen recep. locked off with the procedure hanging on it... (for my wife and myself) BUT I would NEVER hook up or recommend any other homeowner do that.

Right now my Generac 5500 Wheelhouse has the neutral bond in place. So yes I have effectively two paths back to the generator on two #8's (ground and Neutral) (Generator recep is in garage)and I bond the frame to a ground rod where I hook it up. I do not believe it provides a safety hazard it it's operating state, but I know what is there and what I am facing... Frankly, I feel that the potential is the same with the double bond and don't rightly see the hazard? Actually your service is double bonded, at your house and at the Power Co. Transformer... But again I would never suggest a friend do their's that way as it goes against the perceived standard.

I was trying to determine in my mind if leaving the bonding jumper off a Generator would be safe for stand alone use, as this would be cheaper to get a 2P transfer switch.

The bottom line is there seems to be no clear cut determination and in fact no current regulation in the USA, so I will recommend leaving the bonding jumper... (as that is factory installed) and that they pay extra for the 3P switch.

(But I still would like to hear a consensus on the gen bond for stand alone use... some say it's safe, some not... I can't place the theorey in my head on that one)

gfretwell,
In my opinion a portable generator is "premises wiring" per Article 100.

"resqcapt19
Moderator posted 01-17-2005 07:17 AM
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George,

quote:
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Hence the bonding jumper talked about in 250 for services is not applicable to generators. I'm not quite sure how youn size it.
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Look at 250.30(A)(1).
Don
IP: Logged

George Little
Member posted 01-17-2005 08:58 AM
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Thanks Don, missed that one. Interesting enough though, the size is very close to 12.5%. In fact I've heard it stated from the podium that T. 250.66 is based on 12.5%. When you do the math it's pretty close. That's what I like about this forum, what one of us misses the other one catches.
George"

YOU ARE MISSING SOMETHING HERE... 250.30 A LEADS YOU BACK TO 250.28 (D) WHICH SAYS THE MAIN BONDING JUMPER SHALL NOT BE SMALLER THAN THE SIZES SHOWN IN TABLE 250.66 (# 8 MINIMUM) THEN IT GOES ON TO ADD THAT IF PHASE CONDUCTORS ARE 1100 KCMIL OR GREATER YOU USE THE 12.5% THING YOU ARE STATING... THE MINIMUM SIZE FOR THE BONDING JUMPER IS # 8 ACCORDING TO CODE SO THE GENERATOR BONDING JUMPER OF # 12 OR # 14 IS NOT ADIQUETE!

It is clear you do not understand the concept of an isolation transformer and safety. I quit.

"gfretwell
Member posted 01-18-2005 12:05 PM
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It is clear you do not understand the concept of an isolation transformer and safety. I quit.
"

Don't leave yet... let's sort this out!

According to your opinion, the gen bond is the only acceptable bond for the neutral, Right?

That said, the code sizes the Main bonding jumper according to Table 250-66 which allows for a # 8 minimum which none of these gen's have... so are they all illegal as well? Do you recommend installing a new bonding jumper? And according to you all of these isolated neutral gens are wrong as well?

gfretwell,
Whom are you directing this statement to and can you expand on your statement?
Don

I know that what I am about to tell you can be dismissed as anecdotal but I have personal experience with getting a shock from a generator. While operating at a pier fire in San Francisco as a member of that cities Fire Reserves I was assigned to deploy a Circle D flood light down the side of the pier shed. As I was maneuvering around an obstruction at the edge of the pier deck I received a shock that prevented me from letting go of the flood light. I still had control of my other hand so I was able to hold on to the obstruction and avoid falling into the harbor. Once I had stumbled or fallen back to level pier deck I used my free hand to unplug the cord from the Circle D light. I don't want to think about what would have happened to me if I had fallen into the harbor with my left hand locked to the handle of a faulted flood light. The generator set was quite large as it was the departments special light and power unit. The neutral was bonded to the frame. The cord was two wire with no Equipment Grounding Conductor. The generator frame was not deliberately earthed but it may have been bonded to the truck frame. One possibility was that the other equipment deployed from the unit may have been the other side of the circuit but wouldn't that have meant that there were two complimentary faults in two different items. If one of the other loads had an Equipment Grounding Conductor that might explain the return path. Both the fireboat Frank White and the Fire Boat Phoenix were pouring thousands of gallons of salt water onto the pier. We had been operating for over six hours at that time and I was soaked to the skin. The conclusion I drew from that experience was that if the neutral is to be bonded then the equipment should have an EGC. Conversely if the neutral was not to be bonded then it should supply double insulated portable equipment only in order to insure complete isolation under real world conditions.
--
Tom H

Don surly you are following this same thread at Mike's?

I am curious to why you would apply the NEC to a UL listed piece of equipment?

Darryl SHOUTING (using all capitols) is not necessary, it does not prove your point and it is generally considered bad forum etiquette.

Bob

If you ground the generator nutral to the frame then you must ground the frame and treat the generator as a separatly derived source and switch the nutral at the transfer switch. However if the nutral is separate from the frame then they are bonded at the main disconnect and are treated as a non-separetly derived system. Then you do not switch the nuteral at the transfer switch. Both are according to the code.

Bob,
Just because a product is listed doesn't mean that is in compliance with the NEC. In my opinion, any connection to the generator, either hard wired or cord and plug connected, is premises wiring and this wiring must originate from a grounded system. If there is no internal bonding jumper, it is not a grounded system and you can't use the power from that system and be in compliance with the NEC.
That being said, I think that in most cases, an unbonded generator is safer than a bonded one.
Don

Using your definition, the generator on my bicycle and the wires to a light on the front of it would be covered by the NEC. My bicycle is not grounded nor does it have listed CL2 cabling. If a generator, battery, or similar is not really portable (i.e. it weighs over 200 lbs and doesn't have wheels or it is hard wired into building wiring) then I could believe your interpretation of premesis wiring.

Mark the discussion was mainly about PORTABLE generators... (with wheels)

The discrepincies are, with a two pole transfer switch everyone seems to concur that you need to remove the neutral bond in the Gen. If that is done is the Gen still safe for stand alone use without the neutral bond that was factory installed and UL approved.

In the USA most if not all transfer switches are sold as only two pole units... (Canada sells 3-Pole, as is really needed)
The hesitation was in changeing factory wiring on a Gen and it's then safety factor... (and the Bonding jumper size was a side point)

That was my point, although I went a little far with the bicycle analogy. Don seems to think that anything plugged into a portable generator, when used in the portable mode without any transfer switch, is required to be grounded because just about everything is premises wiring. Certainly if you connect it to your house wiring via a transfer switch, then it must be grounded and I don't question that.

Either a 2 pole or 3 pole tranfer switch is fine as long as you've used the correct one based on bonding jumpers and grounding. The issue seems to be if you've removed your bonding jumper do you have an unsafe or nocompliant generator when you unplug it from your transfer switch. I would say it is safe. Whether it is compliant is being debated.

[This message has been edited by resqcapt19 (edited 01-22-2005).]

Yup he is right, that bike generator is a premises.

Next time I see someone dragging one of those little generators back to a campsite in the woods I will be sure they drive 2 rods or show me a grounding survey (<25 ohms). ;-)
Better be doing that with their flashlights too.

Seriously, when you ground one of those legs you make the other one 120v above everything else in the environment. If you float both, sitting in the dirt does not give you a return path. The power supply on a lab bench is the same way. They run it through am isolation transformer and do not ground either leg. That way there is not a fault path to the bench.

I'm not saying that the bonding makes a safer system, because it doesn't, I'm just saying that when you combine the definition of "premises wiring" with the rule in 250.20(B) that the winding must be bonded to a grounding electrode, in this case the generator frame.
Don