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An Onan JB Performance Question


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  #21  
Old 08-06-2017, 12:16:52 PM
len k len k is offline
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Default Re: A JB Performance Question

I was thinking about engine sputter ( not firing / missing ) when cold starting. Possibly water (steam) in exhaust condenses on cold spark plug and shorts it out (no spark). Then when next charge(s) of air comes in it drys it out and it sparks again. After engine and plug are hot no more condensation. Just a theory

We have an old spark plug tester that applies high voltage (model T buzz box), can vary pressure ( 150 psi), and has a window to see spark. On old slightly carboned plugs spark is intermittent or non-existent at higher pressures. Condensation on plug should mimic carbon as far as conductivity.

---------------

Leon .......my comments about purging demand reg and hose to carb were to be done with engine off.

Just for test purposes to eliminate that variable, Not a bad idea to purge your whole gas line from house to gen if gen has not been used for ~ 6 months. I know so much air will diffuse into a valve closed off nat gas line in ~ 6-12 months, that the vapor will not ignite, not so sure about a 100 ft line open to gas supply at the house

Last edited by len k; 08-06-2017 at 01:11:39 PM.
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  #22  
Old 08-06-2017, 12:36:41 PM
JohnnyC JohnnyC is online now
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Default Re: A JB Performance Question

Quote:
Originally Posted by MBB View Post
Leon even the Transfer switches have a time delay for the motor to warm up. See attached.
That is true, sort of..... The LT II series transfer switches have optional time delay relays for:

Transfer - allows the generator set stabilize before application of load
Retransfer - allows the utility to stabilize before retransfer of the load
Stop - maintains availability of the generator for immediate reconnection in the event that the utility fails shortly after retransfer. Allows gradual generator set cool down by running unloaded.

My LT II switch has only the Retransfer and Stop time delay relays. All the other relays in the switch are regular non-timed relays and react instantaneously - or at least that is what it seems like. If there is any fixed delay, then it is only a second or two and that is not long enough for a transfer function under heavy load with a genset cold started especially on gasoline.

I attached a picture below with the relays marked. I hope to get a time delay relay for the Transfer function.

The LT III ATS by default have a fixed 3 second delayed Start, 3 second delayed Transfer, 5 minute Stop, and 5 minute Retransfer under their "Package A Control". Package B Control offers adjustable time delays.

JohnnyC
New Jersey
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  #23  
Old 08-06-2017, 12:54:26 PM
JohnnyC JohnnyC is online now
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Default Re: A JB Performance Question

Leon and everyone, I ran the tests mentioned earlier and have it on video on my cell phone. To recap the tests - 1) Cold start with load 2) Warmed up JB and cycling about 6 kw on and off while focusing on amps, and hz as well as sound of the JB running. Testing work well. At the moment the video is in raw files on my cell. I got to run to Home Depot for paint to finish my house painting a.s.a.p. Rain coming late this evening. I will process the videos later today, post to YouTube and provide a link. Leon, once you view the videos I'm sure you will be surprised.

JohnnyC
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  #24  
Old 08-06-2017, 12:59:04 PM
len k len k is offline
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Default Re: A JB Performance Question

Leon..... I'ld open up starter and do some maintenance. My 7NHM will sometimes not engage and just spin. Does it more in cold weather than warm. Plastic stater gear assembly
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  #25  
Old 08-06-2017, 12:59:11 PM
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Jim McIntyre Jim McIntyre is offline
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Default Re: A JB Performance Question

Quote:
Originally Posted by armandh View Post
problem overview

cold air is more dense than warm air
thus the start up mix is lean
So, I've been thinking about that. It's hands-down the case for a gasoline carb.

But it's a different situation with a gaseous carb. Simply put, when the ambient air is cold and dense, so is the fuel gas. Both the fuel gas and the air follow the basic fundamental gas laws in pretty much the same way. I think this is why gaseous carbs don't need a choke.
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  #26  
Old 08-06-2017, 12:59:15 PM
MBB MBB is offline
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Default Re: A JB Performance Question

My point is that motors cars, etc. Should be warmed up first before applying loads as more wear occurs. Newer choke assemblies fuel injection make choking less noticeable however older vehicles specifically when these units were built were not as sophisticated and cars required more of a warm up time. This I would say also applies to generator motors. Probably less so with natural gas but I still would be hesitant about loading to full load without the motor being warmed up.
Just my opinion.
Mike
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  #27  
Old 08-06-2017, 01:12:32 PM
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Default Re: A JB Performance Question

Quote:
Originally Posted by Leon N. View Post
...I would be willing to bet there are not many operational JB's out there today that meet this requirement, especially if operating of natural gas which has a much lower heat content than either propane or gasoline. Onan says to derate 20% on NG...
Could be, but mine does. Keep in mind that 'Full Load' as defined by Onan, on a nat gas-fueled JB is 6500W. This was covered in post 28 here:

https://www.smokstak.com/forum/showthread.php?t=145667

My set absolutely recovers in 2s or less at 6500 W.

NL 61 Hz, 233V
6.5 kW 57 Hz, 225V
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  #28  
Old 08-06-2017, 02:21:27 PM
Leon N. Leon N. is online now
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Default Re: A JB Performance Question

The Onan certified performance was demonstrated I am sure with a warmed up engine and running on either gasoline or propane, not NG for sure.

Bottom line, do it any way you want but document the results. My set gets used monthly. The gas line is 120 feet of 1 inch black iron pipe. If I had to do it over again I would use inch and 0ne-half piping. But once again, the set works fine once it has been running for a few minutes. That carb popping is random and does not always occur. Maybe another hint that points to the regulator is even if warmed up and operating within spec, dropping a 4Kw load abruptly does sometimes briefly introduce some carb popping until it settles down. My governor maybe a bit too sensitive, but why is the performance somewhat ragged during the warm-up and not after it has been running for awhile? Has anyone else seen this type of behavior?
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  #29  
Old 08-06-2017, 02:49:09 PM
len k len k is offline
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Default Re: A JB Performance Question

If diaphragm has a crack in it then it may randomly allow air to enter for a leaner mix.
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  #30  
Old 08-06-2017, 04:21:22 PM
JohnnyC JohnnyC is online now
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Default Re: A JB Performance Question

Leon, here is a video of today's tests as discussed earlier.

https://www.youtube.com/watch?v=UKFm...ature=youtu.be

JohnnyC
New Jersey
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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 online now
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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

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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  #37  
Old 08-06-2017, 08:06:54 PM
Leon N. Leon N. is online now
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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 online now
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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
JohnnyC JohnnyC is online now
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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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