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


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  #21  
Old 02-08-2018, 04:09:25 PM
Topman Topman is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Thanks Dan,
Okay so if I want to connect a wire to this generator, I would have a black/red wire to each side of the existing on board breaker and the white wire would connect to the pin which connects T2 and T3. Then the bare wire to ground.

But if this generator would be used as back up power for the house I would need to unbond the ground and neutral at the generator. Would I then remove T2 and T3 from the pin that they are connected to?
Thanks, Iver.
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Old 02-08-2018, 09:11:23 PM
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Unbond t2 and t3 then check continuity from each wire to frame and that should give you your ground. Without it running
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  #23  
Old 02-11-2018, 11:52:41 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, thanks KPack.

I removed and separated T-2 and T-3 from the ground post.
I set one side of my meter to frame and the other side to each of T-2 and T-3 one at a time.

At first I didn't get a continuity reading until I set my meter to 20M.
Then I got a reading of @5.60 on T-2 and NO reading on T-3.

So that should make my T-2 the ground and my T-3 should be the neutral.
Thanks, Iver.
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  #24  
Old 02-12-2018, 05:27:51 PM
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

If you are wiring this to a 120/240V circuit T2 and T3 together are the Neutral you can't separate them . If the generator is used as a "portable" generator not connected to the house then it is OK to have the neutral and ground bonded together. It is my understanding that if the generator is connected to the house wiring then you would unbond the neutral and ground so that the neutral would carry through to the house wiring and the ground would not. The house will have it's own ground which will not change. I believe there is considerable written about this in the electrical code so that would be your final source of correct information. Lots of other guys have brought forward information on this and they have a better understanding than I do. However incomplete my explanation is you definitely do not separate T2 and T3 and use one as ground and the other as neutral as that is what I understood you to be saying. Cheers Dan
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Old 02-12-2018, 06:12:23 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?

I just have to cut in here to clarify a couple of things.

The author said the following: I didn't get a continuity reading until I set my meter to 20M.

If I am not mistaken he set his ohm meter to the 20 meg ohm range. That will give him erroneous readings because the two stator windings are relatively of low resistance. By do that all he is measuring is the basic insulation level of the windings. He should use a very low resistance range to check for circuit continuity. That is between T1 & T2 then between T3 & T4.

Please note the Onan gen lead marking configuration in Fig 1-11 attached. There are two stator windings.
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Old 02-12-2018, 11:27:17 PM
Topman Topman is offline
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Thanks for the responses.

First of all I can't verify the quality of my multi-tester(low battery?) but the only difference I could find between T-2 and T-3 was that I did get continuity between the frame ground and T-2. I did not get any reading on the meter between T-3 and the frame ground.

As the generator sits now, the T-2 and T-3 are both connected to the ground bolt in the enclosure. When running the generator output is 230v between T-1 and T-4. And 115v between either T-1 and (T-2/T-3) or T-4 and (T-2/T-3).
Just as indicated in Fig. 1-11 of the drawing.

I understand regulations stipulate there can only be one place where the neutral and ground are bonded in a system.
So if I was going to connect this generator to a house system I need to unbond the neutral and ground.

So, does this mean that T-3 is the neutral??
Thanks but still confused.
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Old 02-12-2018, 11:47:21 PM
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

T2 and T3 together are the neutral , not one or the other. If this is carried through to the house and connected to the neutral in your main panel there will be a connection with the main ground in the panel where the existing neutral and ground are bonded. I presume you are going to use an transfer switch. I really wish one of the fellows who is more knowledgeable than me on the ins and outs of ground/neutral bonding would pipe up , I don't want to steer you wrong. Cheers Dan
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Old 02-13-2018, 12:06:45 AM
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

Thanks Dan,
Like you, I was hoping that someone who has done this before would chime in with some information.
In my old Wisconsin generator, the neutral is separated from the ground and used as the white wire and then the bare copper wire goes to the frame.
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Old 02-13-2018, 12:21:04 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?

"Ground" is the generator frame. "Neutral" is T2 and T3, which are always joined together in that set for 120/240 volt service.
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Old 02-13-2018, 12:49:07 AM
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Default Re: Onan MDJE - How can you tell what is T1, T2, T3 or T4?

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.
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