generators, bonded neutrals, and transfer switches

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jlp16au

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I have read all of the generator threads that I could find but I still have some questions.

I am building a house and wanted a transfer switch for my portable generator. My generator is a Honda generator. Looking at the manual Honda says:

"Honda portable generators have a system ground that connects generator frame components to the ground terminals in the AC output receptacles. The system ground is not connected to the AC neutral wire. If the generator is tested by a recptacle tester, it will not show the same ground circuit condition as for a home receptacle."

Is this a bonded neutral or not?

Will a transfer switch that just switches the two hot wires be ok or should I switch the neutral also?

If I can use a two pole transfer switch, Do I need to connect the generator frame to an earth ground (i.e. ground rod by the generator)?

Sorry for the long post

Thanks,
Josh
 
Re: generators, bonded neutrals, and transfer switches

Q. Is this a bonded neutral or not?

A. No, according to your quote from the manual, the frame is not bonded to the neutral.

Q. Will a transfer switch that just switches the two hot wires be ok or should I switch the neutral also?

A. The two-pole transfer switch is the correct one.

Q. If I can use a two pole transfer switch, Do I need to connect the generator frame to an earth ground (i.e. ground rod by the generator)?

A. No, but ensure that the generator cord or cable contains an equipment bonding conductor (green in sketch), and keep the runs as short as possible.

Ed


Gen4.gif


[ January 13, 2005, 12:36 AM: Message edited by: Ed MacLaren ]
 
Re: generators, bonded neutrals, and transfer switches

In my opinion, that generator is not in compliance with 250.20(B).
Don
 
Re: generators, bonded neutrals, and transfer switches

Originally posted by don_resqcapt19:
In my opinion, that generator is not in compliance with 250.20(B).
Don
Click to expand...
I was wondering about that myself.

[ January 13, 2005, 07:42 AM: Message edited by: petersonra ]
 
Re: generators, bonded neutrals, and transfer switches

I will bite also,in following the above post, and in referance to FPN in 250.20(d) in the discription of a separately derived,and if 250.66 is observed for bonding jumper,then you'll need to educate me further..

[ January 13, 2005, 09:14 AM: Message edited by: dillon3c ]
 
Re: generators, bonded neutrals, and transfer switches

Jim,
How is it a grounded system if the neutral is not connected to a grounding electrode? The information posted said that the neutral is not connected to the generator frame which is the grounding electrode for portable generators per 250.24(A). And before anyone asks, the generator output is "premises wiring" per Article 100.
Don
 
Re: generators, bonded neutrals, and transfer switches

I am seeing that the generator neutral is grounded by the connection to the existing grounding system at the house service. Also, the generator in this application is NOT considered as a separately derived system.

This is perfectly legal and feasibile and desirable. In my opinion.
 
Re: generators, bonded neutrals, and transfer switches

on the other hand, if the transfer switch also disconnected the generator neutral and the utility neutral, then the generator WOULD be a seperately derived system and would require a main bonding jumper (system bonding jumper) and a grounding electrode system.
 
Re: generators, bonded neutrals, and transfer switches

Your going the same route I took crossman,FPN in 250.34
 
Re: generators, bonded neutrals, and transfer switches

crossman,
I am seeing that the generator neutral is grounded by the connection to the existing grounding system at the house service. Also, the generator in this application is NOT considered as a separately derived system.
This is perfectly legal and feasibile and desirable. In my opinion.
Click to expand...
I agree that if you connect it that way it would be code compliant. My problem is that this is a portable generator that does not have a grounded conductor as required by 250.20(B).
Don
 
Re: generators, bonded neutrals, and transfer switches

I would say that as soon as you connect the portable generator to the system as shown in the diagram in this thread, then it does have a grounded conductor... through the MBJ at the utility service.

You definitely bring up an interesting point though. I think that bonding the neutral at the generator is going to create some of those multiple paths that we talk about as being bad.
 
Re: generators, bonded neutrals, and transfer switches

crossman,
This is a portable generator and it is not intended to be connected to a building wiring system. In my opinion, the neutral must be bonded to the frame when used with cord and plug connected equipment.
Don
 
Re: generators, bonded neutrals, and transfer switches

Very interesting indeed. Sometimes you have to be a lawyer to decipher the NEC!

Okay, 2005 Code, 250.34(C) requires the neutral of the portable generator to be bonded to the frame... but only if it is a separetly derived system... which in this case is a question mark at this point.

Now, the FPN in 250.34(C) refers us to 250.20(D) for portable generators supplying fixed wiring systems:

The FPN in 250.20(D) reminds us that an alternate AC power source is not a seperately derived system if the neutral is solidly interconnected to a service-supplied system neutral.

So, what is the definition of solidly interconnected?

I assume this generator will be connected by cord and plug to the transfer switch... and is a cord and plug connection considered as "solidly interconnected"?

Very interesting...
 
Re: generators, bonded neutrals, and transfer switches

I'm not talking about the use of this generator when connected to a transfer switch. I'm talking about its intended use as a portable generator. The fact that the neutral is not bonded to the frame makes it easier for a code compliant connection to a transfer switch, but it does not meet the requirement of 250.20(B) when used to supply portable equipment.
Don

[ January 13, 2005, 03:57 PM: Message edited by: don_resqcapt19 ]
 
Re: generators, bonded neutrals, and transfer switches

Okay, I understand your point now. You are saying that the generator itself is in violation of 250.34(C) the day it was bought from the Honda shop and transported into an area in which the AHJ has deemed the NEC to be the governing rules?

So this particular generator is in compliance with the Code ONLY when attached to a fixed wiring system with a solid connection from the generator neutral to the fixed wiring grounded conductor.

If you use the generator only for cord and plug connected appliances, it is in violation.

Sounds to me like the AHJs need to raid the Honda shops and redtag these things! :)
 
Re: generators, bonded neutrals, and transfer switches

Correct me if I am wrong but a portable generators are not listed for use as a standby generator. So Honda is wrong by floating the neutral on there portable generators? If that is the case then all portable generators netural should be bonded to there frame.
 
Re: generators, bonded neutrals, and transfer switches

fc,
If that is the case then all portable generators netural should be bonded to there frame.
Click to expand...
It is my opinion that this bonding is required by 250.20(B).
Don
 
Re: generators, bonded neutrals, and transfer switches

but the FPN in 250.34(C) talks about portable generators connected to fixed premises wiring. So this implies that it is okay, or else why the FPN? (yes, I know that the FPN is just explanatory and note an actual part of the code)

Do the UL listings say that the generator is not for use with fixed premises wiring? Possibly, if not probably...

I do know that some of the big portable generators are EXPRESSLY designed for attachment to fixed premises wiring for use in emergencies like down here when the Houston medical Center was flooded out a couple of years ago.
 
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