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Discussion Starter · #1 · (Edited)
I recently purchased a Firman T07571 Tri-fuel 7500/9400 watt generator from Costco.

I also installed a Square D by Schneider Electric QO1DM10030TRBR 30-Amp Generator Main Breaker Outdoor Manual Transfer Switch.

I intend to use the generator strictly as a back-up power supply for my home and will not use it like a construction site generator.

The Square D generator transfer switch panel uses the main service panel neutral.

The owner's manual for the Firman generator states that the neutral is bonded to the frame.

I understand that the neutral cannot be grounded in two places and that I need to disconnect the neutral from the generator's frame.

My question is: What is the procedure for disconnecting the neutral from the frame for this Firman generator?

I contacted Firman with this question, but they have not yet responded.

Thanks for all replies.
 

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Over the last several years, I have seen many questions about doing this, and it is inevitable a while later many of these same folks are asking if there is a quick way to reconnect the bonding for another application.

I was faced with this same problem a few years ago when I purchased my Yamaha YG2800i inverter generator.

There were instances where I wanted it to be a floating neutral, and times I wanted it to be a bonded neutral.

What to do? Well, the quickest and easiest way for me was to make up a short extension cord, one that was only about a foot long, but it was only a two conductor cord.

There was not a wire connected to the ground lug of the male plug.

Simply, plug your long extension cord into the short extension cord, plug the short extension cord into the generator and you are in business.

In effect, this does the same thing as disconnecting the bond in the generator but the plus is you are not modifying the generator and not voiding it's warranty.

If I needed the generator to be in the bonded neutral configuration, I just did not use the new short extension cord.
 

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Discussion Starter · #3 ·
Thanks for your info.

I think your suggested procedure is more for using a power cord plugged in to the generator for like running a saw. My application is attaching the generator through a transfer switch to certain house circuits. Here is the transfer switch. Square D by Schneider Electric QO1DM10030TRBR 30-Amp Generator Main Breaker Outdoor Manual Transfer Switch with 30-Amp Twist-lock Receptacle - Electrical Equipment - Amazon.com

If I can figure out how to disconnect the neutral from the frame, I would never reattach it. The only use I have for a generator is back-up power for my home.

I have searched for days exactly how to do this. I wish Firman would have the procedure on their website or FAQ's like Champion does.
 

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Ok, I need to revise my reply above, I mistakenly took for granted that your Firman generator was 120 volts only.

Foolish mistake on my part.

But, my reply is still valid, only needs a slight modification. You could make up a short, one foot extension cord, with three conductors, L1, L2 and neutral, but, do not connect a wire to the ground lug.

This will accomplish the same thing.

No, I was not referencing using the generator to run a saw, for that you would need a bonded neutral and for that application you would not use the new short extension cord that you just made up.
 

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Most generators I've seen have the neutral and ground jumpered in the generator head so the two wire extension still allows the generator frame to tie to neutral which is a good thing for safety. I'd feel better if the ground were in place.

IMHO, if ground and neutral are tied that's OK, if it's not that's also OK. Much confusion about two grounds, generators, ad nauseum. In point of fact you only have one ground at your service entrance feeding the load center (breaker box) probably a driven ground rod. You "theoretically or potentially" could get into trouble if you drove a second ground rod and terminated it at the generator-now you would have TWO grounds. Admittedly, I'm glossing over some things, but for temporary use in an outage you'll be fine.

If you're determined to disconnect the ground and neutral, get the wiring diagram for your generator and it will show where the connection is. It will probably require opening the generator head and removing a wire, if you're not comfortable doing that you'll have to get someone to do it.

If you haven't already installed the Square D unit, consider a generator disconnect, much cheaper to install. Here's a link to what they are.

 

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My question is: What is the procedure for disconnecting the neutral from the frame for this Firman generator?
Look in your Owner's Manual at the wiring diagram (page 37, I believe). Near the AVR there is a jumper that's tying the Neutral to the Ground. Remove it and you've floated the neutral. I've circled the jumper in red below.
9811

It probably looks something like this:
9812
 

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Discussion Starter · #8 ·
@tabora Ah, yes. Thank you sir! That is much appreciated! I found the diagram in my owner's manual on page 37, so I should be good to go for disconnecting the neutral. Your photos are also very helpful.
:) :) :) :) :)
 

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@tabora Ah, yes. Thank you sir! That is much appreciated! I found the diagram in my owner's manual on page 37, so I should be good to go for disconnecting the neutral. Your photos are also very helpful.
:) :) :) :) :)
@GenHappy Thanks in advance for all the info! Did it work for you to disconnect the neutral from the ground? When I tried, the “Bridge Rectifier” started to overhead and smoke??
 

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@GenHappy Thanks in advance for all the info! Did it work for you to disconnect the neutral from the ground? When I tried, the “Bridge Rectifier” started to overhead and smoke??
I too am looking into this, did you solve your rectifier issue? anyone able to do it? I am looking at a generlink and waiting for them to get back to me on why my generator is not listed T08072 and i suspect it is because it is bonded...
 

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I too am looking into this, did you solve your rectifier issue? anyone able to do it? I am looking at a generlink and waiting for them to get back to me on why my generator is not listed T08072 and i suspect it is because it is bonded...
I contacted Firman and spoke to a very knowledgeable technician there. They sent me a new rectifier, but told me there is NO way to remove the bond on my generator (T07571). They said it will burn out every time.
 

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@GenHappy Thanks in advance for all the info! Did it work for you to disconnect the neutral from the ground? When I tried, the “Bridge Rectifier” started to overhead and smoke??
The Bridge Rectifier (blue box) should have nothing to do with the neutral bond... It's just used to convert the battery charging current.
Schematic Rectangle Font Parallel Engineering
 
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it certainly looks that way, wonder why DL41 had a problem with his..
I’m definitely not an electrician, but I thought the same thing. So, I added the neutral ground bond wire back in, and the rectifier didn’t heat up and smoke. I removed the bond again, and it smoked and melted the rectifier. When I called Firman, both the tech and the parts guy said that is exactly what will happen because the wiring is more complex in that machine. What that all means, I don’t know. But I did test it, and re-test and have Firman confirm. If anybody has any additional insight, or can see something I screwed up on, I’d be happy for the feedback.

Attached is a picture of the jumper wire I removed and a picture of the rectifier before it melted
 

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Attached is a picture of the jumper wire I removed
That is the correct jumper to remove to break the N-G bond.

I don't see any way for the rectifier to get fried by disconnecting the N-G bond, but apparently you have shown that to be the situation. Maybe there is something they are not showing on the schematic.

What if you disconnect the plug from the "intelligent" rectifier? Will the gen still operate normally? If it does, then I think another battery charger could be used to charge the battery.
 

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I don't see any way for the rectifier to get fried by disconnecting the N-G bond, but apparently you have shown that to be the situation. Maybe there is something they are not showing on the schematic.
It would be interesting to see where the G/Y ground wire goes to from the 4-pin connector at the Bridge Rectifier. If it connects to a neutral rather than ground, that might do it...
What if you disconnect the plug from the "intelligent" rectifier? Will the gen still operate normally? If it does, then I think another battery charger could be used to charge the battery.
I agree, although it looks like that 12V supply is used for the fuel cut solenoids, too...
 
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@tabora Well, I think I have changed my mind about disconnecting the rectifier. I think the gen should still start and run with it disconnected because the battery would supply the power to fuel solenoid and other electronics. Right?
 
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