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How to disconnect neutral from the frame of Firman T07571 Tri-fuel purchased at Costco

38K views 138 replies 31 participants last post by  DL41 
#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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#2 ·
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.
 
#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.
 
#4 ·
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.
 
#5 ·
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.

 
#7 · (Edited)
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
 
#16 ·
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.
 
#17 · (Edited)
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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#20 ·
@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?
 
#23 ·
Maybe? Easy to try it if you have the generator as @DL41 does. I'd need to spend some time deciphering the function of the Dual Fuel module SM1-SM4 switches as shown in the diagram's switching chart.
 
#21 ·
So on systems where neutral is not disconnected from grid, interconnect switch, you are suppose to not have the ground bonded to the neutral at the generator.
Why do I care? If my neutral and ground wire are same gauge, length, and terminations. I just don’t see it as a problem.
 
#22 · (Edited)
So on systems where neutral is not disconnected from grid, interconnect switch, you are suppose to not have the ground bonded to the neutral at the generator.
Correct. That is known as Not a Separately Derived System. It looks something like this. Notice that the N-G bond at the generator is not there. The N-G system bond is at the far left.
Rectangle Font Parallel Engineering Diagram

Why do I care? If my neutral and ground wire are same gauge, length, and terminations. I just don’t see it as a problem.
The codes state that only one N-G bond be made in an electrical system. Its all about safety. The codes have been developed over many decades and, unfortunately, revisions made after someone has died or been severely injured due to the way a system was wired. Running the system with the N-G bond in two places puts the wires in parallel. The neutral and the ground will share the current flow. This is known as objectionable current.

We can't tell you what to do...we can only point to the proper way by code.
 
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#32 ·
And another thought about that...

His insurance company may deny his claim should he have a fire even if it had nothing to do with the gen-house wiring. They always look for a way out of paying a claim.
 
#33 ·
I have 2 generators.
13000 kw propane / natural gas Mecc Alte alternator. I’ve sent Mecc Alte an email to see if they can provide the details for removing the GN bond.

I also have a pulsar 12kw tri fuel ( converted ) generator. Similarly - I’ve reached out to them to see if they can provide details if removing the GN bond.
Given the option I’m going to see if I can get a floating neutral that will sort all of this bonded neutral in my panel.
Will update if I hear back from either of them.
Regards

mac.
 
#35 ·
The Pulsar looks like a typical bonding wire. Check for continuity between ground and neutral before and after disconnecting the bond wire. Gen should not be running of course.

Look on the Northstar for a similar type bonding wire. Sometimes they are on the panel if not on the alternator.
 
#38 ·
On the Northstar, look here...
View attachment 12083
Again, check before and after for continuity between neutral and ground at the front panel plugs.
My Northstar is a little different. It has a Mecc Alte 14kva alternator.
I have a pic attached below.
There are 4 posts on the terminal block.
The 2 right posts connect the hots from the alternator through to the panel.

The two posts on the right are connected to 2 different neutrals from the alternator. Odd I know but there are 2 neutral wires running from the terminal block back to the alternator. Both of these terminals are tied together with a bonding strap. Each post is also bonded back to ground with 2 bond straps. Then there is 1 neutral running to the panel.

Prior to removing GN bonds I did verify that there was continuity between G and N on my 30 amp plug.
After removing both GN bond wires I confirmed that there was NOT continuity between G and N.


Neither Mecc Alte nor Northstar would provide info on removing the GN bond. Mecc Alte said to refer to the final generator builder ( Northstar ) and NorthStar said they couldn’t comment due to it being a liability for them to instruct anyone on modifying equipment.

So. General questions

I connect to my service panel with a 4 wire gen cable. It has an 8 gauge ground ( 6 gauge hot and neutral ). My service panel does have a GN bond.

Technically speaking. Even if I remove the GN bond at the generator the system still has a GN bond through the cable and service panel….Yes? I’m trying to think about any potential issues this might create. Service or safety wise.

i rarely if ever use this generator unless it’s plugged into the house. I’m assuming the house ground at the service panel should be sufficient for a system ground vs grounding at the gen itself. Appreciate some thoughts.

lastly. I appreciate that if ever running stand alone I won’t have a GN bond and from what I’ve read this is a safety risk. Makes sense to make a 120v 3 prong male plug and jump the ground to neutral and just plug it in one of the 120 outlets. Yes?
Appreciate any thoughts.
Regards
Light Hood Automotive tire Motor vehicle Rim
Kitchen utensil Electrical wiring Gesture Circuit component Audio equipment

Mac.
 
#42 ·
I’m interested in this topic as well. I have a Firman h07553, and I confirmed it’s bonded at the engine by using a voltage meter (tested with the neutral attached and detached with generator off). My only concern is the issue mentioned regarding the bridge rectifier melting. Does anyone have more information on this?

I did reach out to support at Firman and they stated the mod isn’t supported based on warranty, NOT on the technical side. I also examined the schematic and it’s very similar as ones posted in this thread.

I also want to state, for clarity and not as a recommendation (or in regard to safety), that my setup with a ProTrans 2 into my main panel does work even though the generator has a bonded neutral, AND the main panel is bonded. There’s no issues with breakers flipping (this was a short test and only mentioned for completeness - do not take this as a recommendation for setup with considering local code).

I’d like to also state there is a lot of conflicting information online from Reliance, DYIers, electricians and everything in-between. Ranging from:
  • Bonded vs. floating is only an issue with GFCIs tripping.
  • Bonded vs. floating is a code and safety issue (being shocked or worst).
  • Bonded vs. floating is a non-issue because power is off at utility and it will prefer the path of least resistance.
A lot of this, I’m sure, is related to local code differences, interpretation differences, and just plain “it works for me, so it must be fine”.

I should also mention, with bias, that Reliance seemingly downplays any safety concerns and only mentions tripping breakers being a concern. Their “go to” solution is to simply disconnect the neutral at the generator and be done with it.
 
#44 ·
I have a background in electrical engineering and I even find it daunting to get to a real practical answer.

Neither of my generators have a GFCI on the generator itself and I’ve never had a problem with Tripping GFCIs in the house so I was ignorantly bliss to the issue until I read the concern on a post here

Yes. Having only one GN bond in the system is code. But that code was changed so at some point it was acceptable to have more than one. From what I can see is at some point there must have been enough instances of people getting harmed that they changed the code. And for my money….I want to be code compliant so I’ve been searching for the right solution.

There are really 4 types of info im seeing from manufacturers.
1. Champion as an example. They post pics of how to float the neutral on specific generators they s
2 Others like pulsar will answer the question when asked and provide instructions
3 others refer you to a licensed electrician but I’m not certain how an electrician would
Answer a question like will removing the GN bond cause any alternator damage.
4 Others like Northstar who simply say they can not provide any detail.

I think I’m going to remove the bond on the Northstar and just run it in anger. Ultimately I’m more concerned about safety than damaging the unit and with no intel from the manufacturer it’s going to have to be a trial. And seeing as the bond is still in the system ( at the panel ) I’m thinking it’s a reasonable safe bet it works just fine. But will be making a jumper so if even run stand alone I can plug the jumper into an outlet on the generator and provide the GN bond through the panel.
Cheers
Mac
 
#43 ·
Not sure if anyone has asked firman but worth the email.
I have 2 generators. A Northstar 13k and a pulsar 12k. Northstar wouldn’t provide any info on the alternator performance with the GN bond removed where as Pulsar quickly answered my email
And provided pics on which wire to remove. Worth seeing if you can find their contact info.
cheers.
 
#46 ·
I am going to attempt to reach out to Firman again, perhaps I'll reach someone else and get a better answer regarding lifting the neutral and how it affects the rectifier. I am going to also try to get a specific part number of the rectifier, and perhaps find more information about it online (being "intelligent" as GenKnot mentions vs. a diode bridge).

I am also curious now based on macdenewf's comment of when and why the code was changed, but I agree safety first.
 
#49 ·
I am also curious now based on macdenewf's comment of when and why the code was changed
He is possibly referring to the change made in NEC 2008 pertaining to the acceptable grounding methods at buildings or structures supplied by a feeder or branch circuits from a grounded service located at another building or structure supplied from a common service. A subpanel is an example...you do not make a N-G bond there so as to avoid objectionable current on the ground wire.
 
#48 ·
This is interesting. Based on the comments from the author of the video he had no issues with his bridge rectifier and it’s the same model referenced earlier in this thread. I wonder what the difference is?

My Firman h07553 looks exactly the same on the generator motor (also of note, the white short cable can be removed entirely if desired).
 
#53 ·
I'm willing to bet that "intelligent" bridge rectifier is just a fancy name for a voltage regulator. It basically charges the battery and supplies power to the fuel cut solenoid (when triggered), as well as the generator control box/module.

I can't imagine a scenario wherein removing the N-G bond could have an effect on this regulator, much less destroy it. The DC ground path should still work in this case, regardless of whether or not it's tied in to the Neutral circuit. The only reason it can burn up is if a voltage differential is introduced as a result of removing the bond. But again, I don't see how that's possible.
 
#55 ·
With the risk of destroying the generator and voiding my warranty being too much, I've decided to look into an Inverter Generator that will provide sufficient power (to avoid THD issues) along with allowing the neutral to be floating. For those of you who may find this thread in the future this is what I am considering at the moment:


Champion has support with videos for lifting the neutral bond (very simple), the THD is low, run-time is decent, it has a 50A hookup (which I need), it's quieter and price point isn't too much more.
 
#56 ·
👆 Sounds like a good plan to me.

I have an older Champion (2008 model) non-inverter that has served me well. I recently bought a WEN GN625i that is an inverter unit. The waveforms on it are better looking than my grid power...I'm very happy with it. I had to change to the WEN because my old Champion had too much THD to run my new gas furnace blower. The Champion inverter should have a comparable high-quality sinewave too.
 
#57 ·
I'm monitoring this thread regarding the issue of converting a Firman generator, T08072 in my case, from bonded to floating neutral. My setup is a manual interlock switch on my panel, and a 50amp plug for connection to the generator.
Initial testing works well on natural gas, which I plan to use for partial home backup. I like the option of a manual transfer switch and I pick which circuits/devices I want.
I would like to have the safest setup possible, so a single bonded connection in the main panel and a floating neutral at the generator is the setup as I understand it.
My son-in-law, an electrician, installed my 50amp setup and confirmed there should be only one neutral ground point, and should be at the main panel. He really could not comment on the Firman generator changing to floating neutral causing any damage in the generator.
Hearing from a few users that they have made the change to the Firman generator with no damage to the regulator would be welcome.
 
#58 ·
Hearing from a few users that they have made the change to the Firman generator with no damage to the regulator would be welcome.
Yes, it would be good to hear that the N-G bond can be disconnected without frying the voltage regulator on the unit. Unfortunately, no one has said that is the case. So, the jury is still out!
 
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