Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Electric Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

An Onan JB Performance Question


this thread has 424 replies and has been viewed 9669 times

Reply
 
Thread Tools Display Modes
  #1  
Old 08-05-2017, 06:10:26 PM
Leon N. Leon N. is offline
Registered-III
 
Join Date: Oct 2009
Location: N. Chelmsford, MA, USA
Posts: 3,504
Thanks: 643
Thanked 2,004 Times in 1,204 Posts
Default An Onan JB Performance Question

I have been wondering for some time why my JB will not meet the 2 second response time until it is thoroughly warmed up? My JB has the tri-fuel carburetor but I alway burn the utility supplied 1000 BTU natural gas. From a cold start once up to speed dumping even with just a 4KW load on it all at once can take up two 4 seconds to return to a stable RPM. However, when fully warmed up by running for 10 minutes it will return to stable operation in less than 2 seconds applying the same 4 KW load in one step. All other specified parameters, voltage and frequency remain in the specified tolerances be it NL or with a FL of 32 amperes.

Has anyone else observed such behavior? Could this droop be due to the fuel and or that old Garretson regulator which I continue to use? I also note there is noticeable, hunting and occassional popping back through the carburetor until the unit warms up. Once fully warmed up, it behaves like a charm and the issue I describe here goes away.

To me it is no big deal, just curious if others have seen this and what if anything they did about it.
Reply With Quote
Sponsored Links
  #2  
Old 08-05-2017, 07:50:53 PM
Handyhiker1 Handyhiker1 is offline
Registered-II
 
Join Date: Jul 2014
Location: Akron, Ohio
Posts: 551
Thanks: 323
Thanked 254 Times in 126 Posts
Default Re: A JB Performance Question

Just as a general engine acting like this, it sounds like it is a little lean on the fuel.
Reply With Quote
  #3  
Old 08-05-2017, 07:56:56 PM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 14,735
Thanks: 390
Thanked 5,331 Times in 3,882 Posts
Default Re: A JB Performance Question

Common for engines. Never gave it much thought why they run rough when cold.

On gasoline engines I would have guessed gasoline needed a warm engine to help evaporate the liquid, but your nat gas fueled so that theory is out the window. Would expect the propane to flow fast enough to quickly purge any air that back diffused into demand reg.

Guess that leaves oil wanting to warm up and thin out, less drag. Could be heat expands clearances and makes less drag too.

Last edited by len k; 08-05-2017 at 08:17:54 PM.
Reply With Quote
The Following 2 Users Say Thank You to len k For This Post:
  #4  
Old 08-05-2017, 08:22:40 PM
dracer dracer is offline
Registered
 
Join Date: Apr 2017
Location: Klamath River, California
Posts: 38
Thanks: 0
Thanked 5 Times in 5 Posts
Default Re: A JB Performance Question

popping back threw the carb means it is running lean
Reply With Quote
  #5  
Old 08-05-2017, 08:38:08 PM
Leon N. Leon N. is offline
Registered-III
 
Join Date: Oct 2009
Location: N. Chelmsford, MA, USA
Posts: 3,504
Thanks: 643
Thanked 2,004 Times in 1,204 Posts
Default Re: A JB Performance Question

Yes, it appears to be running lean when first started up. I can stop the popping by riching it up a bit. BUt, then once it has warmed up, it does not meet the Onan performance spec unless I lean it out a tad. So what is the likely hood it is the Garretson regulator?

Where are all the JB users tonight? Could they share their experience? I guess in order to comment one has to know what the Onan JB spec says. There has been lots of discussions in the past about performance in terms of frequency and voltage but little discussion about the Onan JB 2 second recovery requirement except to hear comments like my machine grunts a little bit but recovers. To me meeting this 2 second requirement is important WRT starting motor loads, like a central AC system which could be damaged, not to mention other connected loads.
Reply With Quote
  #6  
Old 08-05-2017, 08:55:11 PM
MBB MBB is offline
Registered-III
 
Join Date: Apr 2009
Location: Elk Grove Village IL USA
Posts: 3,073
Thanks: 1,323
Thanked 2,367 Times in 1,276 Posts
Default Re: A JB Performance Question

Better to leave it run a little lean. Natural gas better to run lean than rich can burn valves and pistons if too rich. My JC does the same for about 2 minutes. It too runs on natural gas. I have yet to do a tuneup on it though since I bought it.

Last edited by MBB; 08-05-2017 at 09:31:00 PM.
Reply With Quote
  #7  
Old 08-05-2017, 10:52:35 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,924
Thanks: 1,116
Thanked 1,790 Times in 1,063 Posts
Default Re: A JB Performance Question

Quote:
Originally Posted by Leon N. View Post
Yes, it appears to be running lean when first started up. I can stop the popping by riching it up a bit. BUt, then once it has warmed up, it does not meet the Onan performance spec unless I lean it out a tad. So what is the likely hood it is the Garretson regulator?

Where are all the JB users tonight?
I be here.... Just so happens I was "playing" in my garage with my JB, ATS and controller. I had a 2kw load going through the ATS to the Utility. I simulated a power outage by cutting the utility breaker inside the garage panel. The ATS kicked and started a cold JB (75 degrees outside) and immediately transferred the 2 kw load to the JB after the JB started (3 seconds of cranking and within 2 seconds once the JB kicked over and up to speed). There was no issues, no bogging, no abnormalities. I am running on propane and the JB was NOT started or warmed up prior to my test. If you want, I can redo the test with a 4 kw load, but I know the results will be the same.

Below are two pictures showing the specs I was running this evening on each of the 2 legs (A and B) single phase.

JohnnyC
New Jersey
Attached Thumbnails
Click image for larger version

Name:	001.jpg
Views:	61
Size:	124.6 KB
ID:	288029   Click image for larger version

Name:	002.jpg
Views:	59
Size:	123.3 KB
ID:	288030  
Reply With Quote
  #8  
Old 08-05-2017, 11:26:19 PM
Leon N. Leon N. is offline
Registered-III
 
Join Date: Oct 2009
Location: N. Chelmsford, MA, USA
Posts: 3,504
Thanks: 643
Thanked 2,004 Times in 1,204 Posts
Default Re: A JB Performance Question

Johnny does the ATS wait to see that the JB NL parameters, frequency and voltage are in spec before applying the load? Try your test running on 1000 BTU/CF instead of that hotter stuff they call propane.

I am beginning to think my problem is fuel related or could it be a sluggish governor? If so, but why is everything OK when hot? Oh well, I am the same way when I get up.

Yes, where are our JB user friends? Guess they all have retired knowing they have one fine running machine.
Reply With Quote
  #9  
Old 08-05-2017, 11:37:13 PM
Wayne 440 Wayne 440 is offline
Registered-III
 
Join Date: Nov 2004
Location: Kentucky
Posts: 5,186
Thanks: 310
Thanked 4,248 Times in 2,034 Posts
Default Re: A JB Performance Question

I think it is reasonable to assume that the Onan specification was based on the set's abilities at normal operating temperature, i.e, after it is "warmed up". IF it were my set, I would be satisfied with the stated performance.
Reply With Quote
The Following 2 Users Say Thank You to Wayne 440 For This Post:
  #10  
Old 08-05-2017, 11:41:22 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,924
Thanks: 1,116
Thanked 1,790 Times in 1,063 Posts
Default Re: A JB Performance Question

Quote:
Originally Posted by Leon N. View Post
Johnny does the ATS wait to see that the JB NL parameters, frequency and voltage are in spec before applying the load? Try your test running on 1000 BTU/CF instead of that hotter stuff they call propane.

I am beginning to think my problem is fuel related or could it be a sluggish governor? If so, but why is everything OK when hot? Oh well, I am the same way when I get up.

Yes, where are our JB user friends? Guess they all have retired knowing they have one fine running machine.
Leon, I guess you want me to run the JB on NG.. That test will have to wait for now. I got a bazillion wires connected between the JB, ATS and the controller and at the moment will be extremely time consuming to separate the components in order to roll the JB from my garage to the house for a NG hookup. I don't have NG in my garage which sits about 160 feet from the house.

As for the question about the ATS, I don't have an answer without reviewing the manual for that particular operation. There is an optional time delay relay that is user adjustable to allow the generator to start and stabilize before transferring power, but I don't have that optional time delay relay. Everything happens so fast from the moment the utility goes down and the generator goes online with the load transferred.

JohnnyC
New Jersey
Reply With Quote
  #11  
Old 08-06-2017, 12:02:11 AM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 3,870
Thanks: 632
Thanked 2,065 Times in 1,207 Posts
Default Re: A JB Performance Question

Doesn't seem right, Leon.

Here' how mine behaves. I had run the set for about 60 seconds before this video, so it was't really warmed up.

https://youtu.be/0vERaGEr6ac
Reply With Quote
The Following 3 Users Say Thank You to Jim McIntyre For This Post:
  #12  
Old 08-06-2017, 01:28:38 AM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 14,735
Thanks: 390
Thanked 5,331 Times in 3,882 Posts
Default Re: A JB Performance Question

Leon........ here's a test you can do to check demand reg, to eliminate variable of air diffused into nat gas in it. Energize nat gas solenoid and blow into vent of demand reg for 5-10 sec. That way propane flow will purge demand reg of all air. Then start engine and do your transient response load test.
Reply With Quote
  #13  
Old 08-06-2017, 09:06:09 AM
Leon N. Leon N. is offline
Registered-III
 
Join Date: Oct 2009
Location: N. Chelmsford, MA, USA
Posts: 3,504
Thanks: 643
Thanked 2,004 Times in 1,204 Posts
Default Re: A JB Performance Question

Jim I like the way you shut down your JB. However, not sure what else I got from your brief video. I would like to see how your JB responds (recovers) when dumping a FL on it. Could not tell from your video.

lenK yes, by forcing more full into the carburetor, my JB will start quicker. If I try this while running "it don't like that". Not practical to blow into the Garretson when load is applied. Surely you did not mean that. Nothing is perfect.

I think my problem may be pointing to the old, lazy Garretson regulator. The problem seems worse in the Winter. I do have Garretson repair kit.

I agree with Wayne, and will probably leave well enough alone- and that probably goes for the starter as well. But these little things still irk me.

There must be some JB users out there who have seen theses problems. Oh well.
Reply With Quote
  #14  
Old 08-06-2017, 09:19:48 AM
armandh armandh is offline
Sponsor
 
Join Date: Aug 2006
Location: Suburban St. Louis, Missouri
Posts: 2,657
Thanks: 169
Thanked 638 Times in 511 Posts
Default Re: A JB Performance Question

problem overview

cold air is more dense than warm air
thus the start up mix is lean

[gasoline] this sort of cold to warm engine variation not corrected by the automatic choke was covered by a slightly rich mix

now days it is the mass air sensors that help control the mix [tighter control but more stuff to have issues]

gen-sets that had to provide full output at start usually had heaters 24/7 or were kept "indoors"

so if you can't wait for warm up, keep it warm, which can be costly.

Last edited by armandh; 08-06-2017 at 09:36:09 AM.
Reply With Quote
The Following User Says Thank You to armandh For This Post:
  #15  
Old 08-06-2017, 09:21:41 AM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,924
Thanks: 1,116
Thanked 1,790 Times in 1,063 Posts
Default Re: A JB Performance Question

Leon, do you want to see what happens when a full load (7.5 kw) or when 4 kw is dumped immediately on a JB when started cold? I think dumping a full load on a cold anything is not wise. I would think 4 kw dump on a 7.5kw JB when started cold is realistic and reasonable. Time permitting today (Sunday) I will do that test and put it on video. First, I have a few time consuming chores to do such as some maintenance house painting and reconfigure my father's desktop PC. Also, this will be done on propane. Way too much to disconnect in order to roll the JB to the NG fuel source at the house.

***Let me know if you want me to run the test.

*** UPDATE: I just watched Jim's video (Jim, you got a nice and healthy sounding JB).... What I plan to do is start my JB with a 4kw load on it at start up. It may sound crazy, but in reality if a circuit was already loaded and running from the Utility then suddenly a power failure hit, my ATS would immediately signal the generator to start and transfer the load in a blink of the eye. SOOOOoooooo, this is how I will run my test which is different than Jim's demonstration. Is that what you are looking for Leon??

JohnnyC
New Jersey
Reply With Quote
  #16  
Old 08-06-2017, 09:49:53 AM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 3,870
Thanks: 632
Thanked 2,065 Times in 1,207 Posts
Default Re: A JB Performance Question

Quote:
Originally Posted by Leon N. View Post
Jim I like the way you shut down your JB. However, not sure what else I got from your brief video. I would like to see how your JB responds (recovers) when dumping a FL on it. Could not tell from your video.
At time 00:30, I switch on a full load. You can tell from the sound of the engine. You can also tell the governor responds instantly, doesn't drop much in speed, and is not unstable. Isn't that what you asked about, Leon?

Leon - what happens when you open the mixture screw on your carb a quarter or half turn? Does it get better or worse?
Reply With Quote
  #17  
Old 08-06-2017, 09:54:25 AM
Leon N. Leon N. is offline
Registered-III
 
Join Date: Oct 2009
Location: N. Chelmsford, MA, USA
Posts: 3,504
Thanks: 643
Thanked 2,004 Times in 1,204 Posts
Default Re: A JB Performance Question

These are al good valid comments from you guys. I agree, I would not dump a full load on my JB from a cold start. Same goes for my cars, I do not drive at 65 MPH from a cold Winter start. That being said, my real concern is in the Summer time starting that 3 ton AC from a cold start. I would never do that but I have been playing around with a 4 Kw resistive load bank and I notice the JB responds differently when 4 Kw is dumped on the cold machine vs when it has been running for a few minutes. True, I am burning NG not propane or gasoline which is ~ 2.5 x more powerful.

Johnny I would be interested how your JB and other user's JBs react to the following 1966 Onan "Performance Certified" spec sheet which I have the original copy received from Onan back in 1970. It says the following and I quote:

UNIT PERFORMANCE: Frequency Regulation. " Droop governor - 5% (3 cycles) maximum, no load to rated load. Recovers to steady-state operation in less than 2 seconds on application or removal of rated load in one step".

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.

I suspect Onan subsequently dropped this requirement. My JB will meet this requirement @ 4Kw. Have not tried it at 7.5Kw or even 6 Kw because, I do not have such a load except for the central AC which draws about 88 amps on start up. But I worry from time to time because I also use rotating back emf motors to help the JB.

Are you guys aware of this JB recovery spec? I have not seen much discussion about it.

I would say this however, if your JB can meet the 2 second recovery spec, then it probably is a well tuned, well operating gem!

It would not be correct to run this test @ 7.5 Kw on NG due to the lower heat content of NG. However, try this test on propane or gasoline fueled JB and see what your stop watch says. Would be interesting to know.

One more thing, recovery to SS operation to me means the JB must be back within the 3% voltage and 5% frequency tolerances to be a valid test.
Reply With Quote
  #18  
Old 08-06-2017, 10:13:07 AM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,924
Thanks: 1,116
Thanked 1,790 Times in 1,063 Posts
Default Re: A JB Performance Question

Leon, my comments are in bold red below

Quote:
Originally Posted by Leon N. View Post
These are al good valid comments from you guys. I agree, I would not dump a full load on my JB from a cold start.

--- snip ---

Johnny I would be interested how your JB and other user's JBs react to the following 1966 Onan "Performance Certified" spec sheet which I have the original copy received from Onan back in 1970. It says the following and I quote:

UNIT PERFORMANCE: Frequency Regulation. " Droop governor - 5% (3 cycles) maximum, no load to rated load. Recovers to steady-state operation in less than 2 seconds on application or removal of rated load in one step".
I may have misunderstood what you originally wanted tested. From the Onan Performance Certified Statement it does not say anything about a cold start no load and immediately banging it at full load. Either way I can test since as already mentioned once the ATS starts the generator it will bang it at whatever load is present on the circuit, if any


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. True and it is silk screen printed on one of the tins too (at least with the 1991 models).

--- snip ---

Are you guys aware of this JB recovery spec? I have not seen much discussion about it. I never read the spec, but at times I only do selected reading

I would say this however, if your JB can meet the 2 second recovery spec, then it probably is a well tuned, well operating gem! A test will tell all and looking forward to doing it on video hopefully today

It would not be correct to run this test @ 7.5 Kw on NG due to the lower heat content of NG. However, try this test on propane or gasoline fueled JB and see what your stop watch says. Would be interesting to know. NG test will have to wait on my end. As already mentioned, I got way too many things hooked up to my JB at the moment and would be a p.i.t.a. to disconnect in order to roll the JB to the house for a NG hook up.

.
JohnnyC
New Jersey

Last edited by JohnnyC; 08-06-2017 at 11:09:43 AM.
Reply With Quote
  #19  
Old 08-06-2017, 10:15:44 AM
Motorhead's Avatar
Motorhead Motorhead is offline
Subscriber
 
Join Date: May 2007
Location: Central Coast, California
Posts: 3,335
Thanks: 1,475
Thanked 2,188 Times in 1,181 Posts
Default Re: A JB Performance Question

Quote from Onan unit performance: "UNIT PERFORMANCE: Frequency Regulation. " Droop governor - 5% (3 cycles) maximum, no load to rated load. Recovers to steady-state operation in less than 2 seconds on application or removal of rated load in one step".
"

As I read this, it doesn't say that the unit has just been started and is cold or at Operating temperature. Doesn't say what fuel either.
I have an option on my Garrettson which is a 12 volt solenoid primer. I have a momentary contact switch on my generator control panel. I energize it for 2-3 seconds and my set starts right up. I wait about 1 minute before loading just to let the engine warm and lubricate. I can then flip my transfer and it will start my 3 ton A/C and usually the refrigerator at the same time. I have a gas valve like Jim M has and often shut mine down the way he did on the video. My set is close to my gas meter with a 12 foot hose between the meter and generator.
Leon, How long of a gas pipe do you have between the gas meter or house supply and your generator shed? Could there be some problem where the line isn't all the way purged with all natural gas vapor after sitting?
Does the symptom change say if you fire up the JB, run it for 30 seconds, shut it down, restart it then try your test?
__________________
Back of 1958 5CCK
Contractors model
On trailer owned by
"Ma" Bell.
Reply With Quote
The Following User Says Thank You to Motorhead For This Post:
  #20  
Old 08-06-2017, 11:47:33 AM
MBB MBB is offline
Registered-III
 
Join Date: Apr 2009
Location: Elk Grove Village IL USA
Posts: 3,073
Thanks: 1,323
Thanked 2,367 Times in 1,276 Posts
Default Re: A JB Performance Question

Leon even the Transfer switches have a time delay for the motor to warm up. See attached.
Attached Files
File Type: pdf Time Delay.pdf (191.9 KB, 26 views)
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Farmall H Performance Help The motor kid pig guy Antique Farm Tractors 2 08-14-2015 12:19:40 AM
US Injector #4 Performance ChickenSoup Steam Stationary Engines, Traction Engines, Steam Boats 7 08-13-2014 10:42:03 PM
Onan J-Line Engine Performance Curves Leon N. Onan Generators 7 04-07-2010 09:42:07 PM
Battery Performance Nubian Onan Generators 12 03-04-2009 01:11:21 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 01:56:06 AM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277