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Onan DEH-30 glitch


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Old 09-10-2017, 02:32:32 PM
turbo15479 turbo15479 is offline
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Default Onan DEH-30 glitch

I have an Onan DEH-30 converted to single phase that has been in use by me for three years. It is running through an Asco automatic transfer switch. It has had a glitch since I have been using it. Gere goes, as long as the outdoor temperature is sixty degrees or above the generator starts and transfers electric flawlessly. When it is below sixty degrees ( there is a little wiggle room here as I don't know the exact temperature) the generator does not make electricityy. If I snap the exciter breaker on and off it immediately makes electricity. Any ideas what it could be? Once I do this I can shut it down and if restarted immediately it makes electric. I wanted to try a different exciter breaker but I don't think it is available anymore ( at least I cannot find one ) and it is only one amp. This unit has the Lehman Ford diesel which would not be a part of the problem as so far the engine is running well. Any ideas on what is wrong would be greatly appreciated as in colder weather if I am not at home I lose the luxury of automatic power transfer. Oh, when it does happen the engine is running normally but no electric is show on the meter nor does it trip the transfer switch unless I cycle the exciter breaker off and on. I know it is temperature related but how does this tie in with the exciter breaker? Thanks in advance for any replies. If anyone knows where to buy this one amp breaker please let me know. Bruce
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Old 09-10-2017, 04:42:09 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan DEH-30 glitch

The only thing I could think of. Would be the breaker sticking contacts dirty. I have had them start at 10 degrees just fine
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Old 09-10-2017, 05:38:29 PM
turbo15479 turbo15479 is offline
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Default Re: Onan DEH-30 glitch

Yes the engine starts right up but the generator does not make electric in cold weather until I turn the exciter breaker on and off. We had numerous power outtages this summer and it worked flawlessly. This morning the outside temperature was 41 degrees and when it started up to exercise the engine started fine but the generator made no power until I flipped the exciter breaker off and on. In the winter months I have an oil pan heater on and three heat lamps hanging over the unit but it must not be warm enough to make electric but starts fine. I would like to change the breaker if I can find one because it has to be that or the surge when I turn it off and on. Bruce
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Old 09-10-2017, 06:21:15 PM
Wayne 440 Wayne 440 is online now
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Default Re: Onan DEH-30 glitch

Please read this disclaimer before going further- I claim NO expertise, there is NO warranty expressed or implied. You are welcome to take my advice at your own risk, but don't whine and complain about the results afterwards.

IF it were mine, I would temporarily put a 1 amp slow blow fuse in place of the breaker. Then try it when it gets cold - if you get power, suspect the breaker; if not the trouble is likely elsewhere.
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Old 09-10-2017, 06:51:40 PM
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Default Re: Onan DEH-30 glitch

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Originally Posted by turbo15479 View Post
Yes the engine starts right up but the generator does not make electric in cold weather until I turn the exciter breaker on and off. We had numerous power outtages this summer and it worked flawlessly. This morning the outside temperature was 41 degrees and when it started up to exercise the engine started fine but the generator made no power until I flipped the exciter breaker off and on. In the winter months I have an oil pan heater on and three heat lamps hanging over the unit but it must not be warm enough to make electric but starts fine. I would like to change the breaker if I can find one because it has to be that or the surge when I turn it off and on. Bruce
I understand that. I ment the whole system came up just fine. You might try ebay or try Allied Electronics out of Ft Worth Texas
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Old 09-12-2017, 08:04:26 AM
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Default Re: Onan DEH-30 glitch

turbo15479
I think we have the same unit. I cannot offer you useful information, but want to learn about same equipment.
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Lehman Ford 2712E Diesel Engine
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Old 09-12-2017, 09:30:22 AM
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Default Re: Onan DEH-30 glitch

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Originally Posted by turbo15479 View Post
...Once I do this I can shut it down and if restarted immediately it makes electric....
This may be your hint.

For the excitor breaker, leave it closed while the unit has been sitting/not being used for a while, and before the first start of the day, gently open the control panel doors, and on the terminal strip on the left side of the panel box interior, temporarily unhook wire 62 (black wire going to excitor breaker), and use an digital ohm meter across the excitor breaker terminals. Should get a very low reading (less than one ohm). Then open/close breaker several times, and observe reading every time. Should be fairly consistent. (ie; should be less than one ohm every time, not 5-ohms, 0.3, 7, 1.2, 4, etc..)

Wait until you think its likely to start and not make AC voltage right away. Have a good quality digital voltmeter handy, and carefully access the load lines (at the breaker or ATS) and measure what voltage level you see. Your symptoms sounds as if your residual voltage goes flat after sitting unused. I would think you should see around 3-5 volts AC. If it appears to be a 1 volt or less, the regulator may not be building up its voltage loop at the first start of the day. Snapping the breaker on/off after its running at rated speed is opening the AC power to the regulator, and residual may have built up enough at steady rated speed that opening and re-closing it provides just enough voltage to allow build up.

I would suggest to use a helper for the first-start test, so you can be in a position to monitor the voltage during engine cranking and during up to rated speed. If the residual voltage doesn't seem to appear until rated speed is hit, then it may indicate weak residual voltage in the alternator. After you've tested for this, then open/re-close your excitor breaker, and verify you now have voltage. Shut the unit off, open the excitor breaker (leave it off), and have your helper restart the genset while you monitor for the residual voltage again, and confirm if the value is higher the second time, compared to your first readings. This would indicate a weakness in the system holding residual voltage if the readings are very different. Readings that are very close to the original readings may point to other issues, but try these tests first.
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Old 09-12-2017, 10:47:27 AM
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Default Re: Onan DEH-30 glitch

Eric. I recall a first start problem from several years ago. Onan published a fix for it. Just can't remember what it was and I am leaving for the doc. I can look it up later.
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