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An Onan JB Performance Question


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  #31  
Old 08-06-2017, 04:28:26 PM
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Default Re: A JB Performance Question

She sounds and runs as good as it looks Johnny.. Great Job!
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  #32  
Old 08-06-2017, 05:02:14 PM
Leon N. Leon N. is offline
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Default Re: A JB Performance Question

Johnny I just saw your video. WOW. My JB no way operates like that! When I dump a 4 KW load on the JB the frequency drops to about 50 Hz and then slowly creeps back up to an in spec reading. When the machine is warmed up it does the same but with in just about 2 seconds. So I wonder why yours is so different. For one thing, I think the fact that I am using natural gas could make a difference. Strange because the only reading that falls out of spec is the recovery time. I also suspect since you have a different back end, maybe that says something. Also is your freq meter damped? Your JB does not sound at all like mine. I need another data point. Hello Jim?
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  #33  
Old 08-06-2017, 06:24:43 PM
Vanman Vanman is offline
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Default Re: A JB Performance Question

JohnnyC's JB performs just as I would expect any set to perform under similar circumstances, with resistive load.

All my sets (the ones that run ) perform similarly, once dialed in. Mine are all gasoline fueled, so far.

Here's my big Kohler taking a single 5 kW tungsten lamp, across the line. Tungsten resistance is ~1/6 of normal when cold, so this starts out as a radical overload... This is before I replaced the makeshift governor spring that it came with too. Voltage and frequency regulation are now much better.

https://m.youtube.com/watch?v=7-pcwto-ofI
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  #34  
Old 08-06-2017, 06:55:41 PM
JohnnyC JohnnyC is online now
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Default Re: A JB Performance Question

Quote:
Originally Posted by Leon N. View Post
Johnny I just saw your video. WOW. My JB no way operates like that! When I dump a 4 KW load on the JB the frequency drops to about 50 Hz and then slowly creeps back up to an in spec reading. When the machine is warmed up it does the same but with in just about 2 seconds. So I wonder why yours is so different. For one thing, I think the fact that I am using natural gas could make a difference. Strange because the only reading that falls out of spec is the recovery time. I also suspect since you have a different back end, maybe that says something. Also is your freq meter damped? Your JB does not sound at all like mine. I need another data point. Hello Jim?
Leon, someday after I disconnect all those wires between the JB and the ATS and the controller I will roll the JB to the house and hook it up to NG for a test. I suspect it will behave the same, but will not achieve more than 7kw which is expected. In the past I exhaustively tested my 6.5NH and the 4.0 BFA as well as my ex 15.0 JC and my ex- 5.0 CCK on NG. The results were a derated top end which was expected. Otherwise all my gensets reacted as they should under load.

You ask why my JB is so different? All I can say is my JB was recently rebuilt with the exception of it being bored since it only had 216 hours on it and the cylinder bore cross hatching looked new. Other than that just about every nut and bolt was touched. The carburetor was completely gone through and all settings were done to spec, tested and retested and then tested again.

You had a concern about my frequency meter - The analog meters on the JB are almost 30 years old. The frequency meter may need to be dampened if it was designed to be because it does jump a little. The digital frequency meters (Gencon II Pro and the JohnnyC kilowatt meter) are all stable.

Anyway, it was a pleasure as always to run these tests. I think I am about to run out of propane soon and I got lots more work to do with the controller.

JohnnyC
New Jersey
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  #35  
Old 08-06-2017, 06:59:58 PM
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Default Re: A JB Performance Question

Its been shown on the Stak before, but has some relevance to this thread, so here it is again. A few years old now. This is one of my 6.0 JBs on propane with 5640 Watts of 120v heater load on it (2820 X 2). Did not think to try switching all on and off at once to see reaction. Hunts a little with no load, but meter shows only varying a minimal amount - and still within normal acceptable range.
https://www.youtube.com/watch?v=XU-Dc7Gz3GU
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Last edited by John Newman, Jr.; 08-06-2017 at 07:32:41 PM.
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  #36  
Old 08-06-2017, 07:28:14 PM
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Default Re: A JB Performance Question

Quote:
Originally Posted by Leon N. View Post
I need another data point. Hello Jim?
Did you see my video?

As I did a year ago, I repeated my frequency vs. time measurement. This time I started with a load of 3.2 kW. Then about every 5 seconds, I switched to 6.6 kW, then no load. The JB is natural gas fueled.

Please take a minute to study the attached diagram, and let me know what conclusion you draw, or what questions you have.



My conclusion is this measurement clearly shows the frequency of the set is 60 Hz at half load, jumps up to 61.5 Hz at no load, and drops to 57 Hz at 6.6 kW load. I didn't record the voltage, but with the YD sets it's not too interesting - it just stays at 230V the whole time, give or take a volt or two.
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Old 08-06-2017, 08:06:54 PM
Leon N. Leon N. is offline
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Default Re: A JB Performance Question

Jim I am sorry, but for some reason I do see the data I was asking you folks to determine so that I can compare JB performance of a supposedly good running 7.5 JB to my JB. In your illustration, post # 36 it looks like the transition from NL to 6.6 KW is instantaneous? Please explain.

Can you explain how the chart you illustrate in your post # 36 satisfies or meets the requirement stated by Onan which states: "---Recovers to steady-state operation in less than 2 seconds on application or removal of rated load in one step".
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  #38  
Old 08-06-2017, 08:21:09 PM
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Default Re: A JB Performance Question

Yes, I instantaneously changed the load between no load and 6.6 kW, and the frequency always stayed within 61.5 and 57 Hz. That's 4.5 Hz of droop, so not quite in line with Onan's 5% governor spec.

My data shows certainly it stabilizes within 2 seconds - looks more like 1 second to me, but again my set doesn't meet the 5% droop spec at this load. Basically, I see 7.5% droop.

On gasoline or LP, I'm pretty sure it would meet spec, but I don't feel like measuring it...

I would add that if you're really MEASURING 50 Hz at 4 kW, something is seriously out-of-whack. And I don't know how slow you mean when you say it recovers slowly, but mine recovers, as I said, within a second or so.
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  #39  
Old 08-06-2017, 08:56:32 PM
Leon N. Leon N. is offline
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Default Re: A JB Performance Question

Jim we are not on the same wave length so to speak. If I understand you, your machine stays at 57 Hz? Yes that is out of spec. My JB does not stay at 57 Hz but recovers a bit slower to end up within the 5% tolerance. Yes my JB frequency briefly drops to about 50 -55 HZ but always recovers to the in spec value, that is the specified 5% window.

As far as I can tell, Onan does not put a figure on how far the frequency can fall or droop, but indicates recovery should be within 2 seconds. That 2 second figure is my concern when the machine is COLD, not when warmed up.

Do you mean to tell me your YD equipped JB does not show any appreciable frequency dip and recovery time lag? Guess Onan must have improved on something?

I still would like to figure out why my JB cold performance is different than when hot even at a 4 KW load.
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  #40  
Old 08-06-2017, 09:54:07 PM
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Default Re: A JB Performance Question

Leon, I think we need someone with a mag end to run the tests. Regardless, it is hard to believe a droop down to 50 or 55 Hz no matter how brief under normal loads would be considered normal. Who here has a mag JB?

JohnnyC
New Jersey
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