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Onan MDJE - How can you tell what is T1, T2, T3 or T4?


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  #31  
Old 02-13-2018, 08:16:16 AM
Leon N. Leon N. is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

No NO Please! What Wayne and BigBlockChev said is correct. You have to ground T2& T3 to the generator frame, period. They constitute the neutral. The neutral is electrically tied to the white wire and the so called green wire when they are connected to your house panel.

It is or can be very dangerous to not to tie T2 & T3 to the generator chassis., if you want 120/240 service. For example, what if there is an insulation failure in the generator? The generator frame could become alive and you touch the machine and get a shock. Please with all due respect, do not do that.
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  #32  
Old 02-13-2018, 08:21:39 AM
Wayne 440 Wayne 440 is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

And here we go...
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  #33  
Old 02-13-2018, 09:01:27 AM
KPack KPack is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

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Originally Posted by Topman View Post
Okay, Wayne 440. Thank you very much.

So if I understand you correctly, and as BigBlockChev says:
T-2 and T-3 together are the neutral.

I would need to remove both T-2 and T-3 from the ground post to un-bond the generator.
Keeping them together on an insulated terminal, they would be the (white) Neutral.
Bare wire goes to the frame.
Hopefully, that's it?
Thanks, Iver.
Are you going hook your generator to your house panel or are going to use the generator by its self?
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  #34  
Old 02-13-2018, 10:29:41 AM
Leon N. Leon N. is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

There is nothing mysterious about this. The owner should refer to the Onan operators manual for the kind of information I attached in my previous post.
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  #35  
Old 02-13-2018, 02:22:05 PM
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

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Originally Posted by Leon N. View Post
There is nothing mysterious about this. The owner should refer to the Onan operators manual for the kind of information I attached in my previous post.
Just that it can be bonded in two different places. But a lot of people do it and don’t have trouble.
On a welding forum I read they hook there welders to there house panel but don’t unbond t2 and t3 at the welder.
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  #36  
Old 02-13-2018, 03:03:39 PM
Topman Topman is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Okay, just when I thought it was resolved.......
This generator was originally designed to operate in a boat. The manual describes the wiring with T-2 and T-3 bonded to the frame which is how it should operate in that environment.
And if it was to operate on land as a stand-alone power source that also would be the case.
However, my plan is to use this generator as a back up power source for our house. Now from all I have read and from what I understand is that the residential electrical system requires neutral bonding ONLY once. Generally at the service entrance power panel.
So, if I want to be in compliance I need to unbond the generator or unbond the service entrance panel.

If the generator is combined with the house system, and the house system neutral is bonded at source, does that not protect the system?

I am open to any suggestions as to what to do.
Thanks , Iver.
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Old 02-13-2018, 03:49:37 PM
Leon N. Leon N. is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

OK you are getting there. May I address your comments because I have successfully installed my JB into our home electrical system.

Okay, just when I thought it was resolved.......
This generator was originally designed to operate in a boat. The manual describes the wiring with T-2 and T-3 bonded to the frame which is how it should operate in that environment.
And if it was to operate on land as a stand-alone power source that also would be the case. [ YES that is correct]

However, my plan is to use this generator as a back up power source for our house.

[This is exactly what I have done now some 48 years ago and it continues to work very nicely]


Now from all I have read and from what I understand is that the residential electrical system requires neutral bonding ONLY once. Generally at the service entrance power panel.

[ Yes. When you say "neutral bonding" what that means to me is that the neutral is bonded to earth ground at one and only one point in the electrical system. It means the utility neutral inside your entrance panel has a relatively heavy wire running from the neutral ground bus inside your panel to a water pipe or a single earth ground point. This is where all the white and green Romex wires are connected]

So, if I want to be in compliance I need to unbond the generator or unbond the service entrance panel.

[No! The generator frame like any electrical motor or device need to electrically grounded, that is tied to the neutral (t2/T3) and hard wired to the neutral in your house power panel I just described. You should never unbound the service entrance panel. I assume you mean disconnect the utility neutral from that earth ground/water pipe.]

If the generator is combined with the house system, and the house system neutral is bonded at source, does that not protect the system?

[Yes, however,when you say " combined with the house system" what you should mean the generator neutral should not be switched but solidly connected to the house neutral. By using the term " combined" I hope you mean disconnecting the utility hot leads analogous to the generators T1 & T4 and switching the house loads over to the generator by using, for example a double pole double throw circuit breaker type contactor inside your house panel.]

[In my installation, my generators output leads are configured as previously shown in my attached Figure 1-11. T2 & T3 are hard wired not only to the generator chassis but run to and hard wired to the house panel /utility neutral bus which in turn is earth grounded to the house water pipe. I employ a two-pole interlock type circuit breaker mounted inside the house panel along with the branch circuit breakers. This allows me to select either utility or gen power but obviously not both at the same time. I do not employ an automatic transfer switch.]
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Old 02-13-2018, 04:12:11 PM
Wayne 440 Wayne 440 is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

.........
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  #39  
Old 02-13-2018, 09:59:42 PM
Leon N. Leon N. is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Oh come on Wayne, it isn't that bad. Seriously, what I said is what I have done and I have never had a connectivity problem. If you have any questions I would be happy to explain.
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Old 02-13-2018, 10:16:37 PM
Wayne 440 Wayne 440 is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Leon, I understand what you have done. And at the time, that was (as far as I know) a commonly accepted method. But today, (again as far as I know) it is generally not. My understanding is that N-G should be connected at either the generator set or the service panel, not in both places.

I am going to do myself and possibly others a favor and no longer discuss N-G bonding on this board. It is a dead horse that deserves no further beating from yours truly.
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