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Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - off grid solar


I just bought two 7.5 JB units and need some help to get them running and setup. #1 7.5...

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  #1  
Old 12-08-2010, 04:14 PM
whitestrabbit whitestrabbit is offline
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Default Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - off grid solar

I just bought two 7.5 JB units and need some help to get them running and setup.
#1 7.5 JB-3CR/8388T, Serial# 0372347152
#2 7.5JB FL, spec 30634D, Serial# E920467725, wiring diagram 612-6070-02, 1PH 120/240, 1800RPM

Is this correct based on above? (I decoded from Onan FAQ on smokstak)
#1 – 1972, J Series, 2 cyl, 120/240VAC, remote electric start, magniciter?
#2 – 1992, J Series, 2 cyl – what is FL ?, 1PH 120/240, 1800RPM

Anything else useful or interesting to know from the numbers ?

They came in a steel frame one stacked above the other. I purchased from a liquidator who got them from a liquidated business so they were run in a commercial environment and hopefully maintained well. They were kept inside a building and appear to be in great shape cosmetically. The seller indicated the 1992 unit was a backup never used except exercising and the paint still looks new. There was only a single hour meter which indicates 855 hours. The ATS’swere not included. I paid $1,350 total. Is this a decent price? I purchased to use with an off grid solar system to be run around 200-400 hours per year. I debated buying a newer 3600RPM generator (like Kohler 8.5RES=$4,000). After reading on this forum and on off grid solar forums that recommended 1,800 RPM Onans I decided to go for it. My wife thinks I am insane buying these old things, and I am hoping she is not correct considering I just noticed Smokstak is an “antique” generator forum!

I was not able to test them but the seller (a local ebay seller with 99.9% rating) wrote a receipt such that I could get full refund if they don’t operate properly. Based on the fact that it took 8 hours for 4 guys to inch/wrestle these things up a muddy hill (not tractor accessible) on sheets of plywood I really don’t want to have to make a return so I need to get these things running and tested! Holy cow they are heavy!

Manuals:
I found this YD Service Manual with Google.
http://igor.chudov.com/manuals/onan/...end-Manual.pdf
Is my 1972 model a magniciter? So this YD manual does not apply to that unit?
Does anyone have an owner’s manual or other manuals for these units?
wrabbit@gmail.com

Startup:
I plan to get new plugs, new fuel filters, clean air filter. They appear to have been run on gasoline. The 1992 model has gelled gas that smells like turpentine and the 1972 model has liquid gas that smells like turpentine in the inspection bowls. What should I use to clean the fuel system? Carb cleaner? Do I need to totally disassemble the carb and clean floats, needle valves, etc? Will I need a rebuild kit? Anything to be careful of? It looks like the fuel line goes into/through an LP regulator. Do I need to clean this? Anything else unique to these engines I need to get these running?

Propane Setup:
I would like to run them on propane. Is this setup covered in an owner’s manual somewhere? If so does anyone have a copy? I have a 1,000 LP tank with a 10 psi regulator. I see what looks like an LP regulator on the engines that the gas line appears to pass through. Do I need another regulator ? Anything I need to know to get them running on propane?

Auto Start:
I plan to use for an off grid solar system with a Xantrex XW6048 solar inverter (accepts 240VAC generator input to charge solar battery bank and acts as transfer switch (ATS) for grid power if available which we don't have currently) and a Xantrex automatic generator start (AGS) module. The AGS provides a start signal to the generator, then looks for a run signal from the generator. I currently have the AGS wired and working with a little Honda 3kW generator through a Honda remote start switch and it works great. Hopefully I don't need the Onan ATS. The inverter auto generator start supplies a start signal (can be custom programmed to be held for any time period and programmed for restart intervals, etc) and then looks for a run signal after a few seconds and then needs to see 240VAC. Anyone have a wiring diagram or advice if and how to wire this auto start up for the 7.5JBs?

Thanks!

---------- Post added at 01:14 PM ---------- Previous post was at 01:06 PM ----------

One more question. Anyone have fuel consumption numbers for the 7.5 JB?
Gasoline vs Propane?
Couldn't find in FAQ section.
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Old 12-08-2010, 04:33 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Any pictures so we can see what your talking about. I dont think they have lp regulators if they smell of gas. unit #1 maybe a trifuel unit as it has the same T in the model number as mine..
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Old 12-08-2010, 04:50 PM
Old Style Old Style is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Those were a good buy! Those were on CL list? Post some pics.

Hope you only tried to take one up the hill at a time

$1,350 was a great price. Run one on LP the other on gasoline gives you choice. Remote start will be easy.
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Old 12-08-2010, 05:03 PM
Isaac-1 Isaac-1 is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Ok, let me start of saying it sounds like you did good on the price, given that they sound like well maintained machines. The late model YD series unit is the more desirable of the two based on parts avalaiblity, etc. This pair was likely installed as a redundent backup, so if one stopped for any reason they second could take over, also perhaps to provide constant reliable power in case of extended power outage (one can run while the other is offline for oil change and other maintenance) It is very unlikely that these were configured for parallel operaiton as the cost of a reliable sycrhonization system likely costs more than these generators sold for when new.

Now down to some random tidbits,

You are not the only one that would like to find magniciter documention, there seems to be very little out there, most as accumlated knowledge on this board, see the magniciter sticky at the top of the Onan section.

These JB's are built better than anything you can buy today, 1800 rpm is certainly better than 3600 for lots of reasons. The Kohler 8.5 RES is not a bad unit (one of the better residential backups on the market) , but a J series Onan is on a whole other level. (explain to your wife that the Kohler is designed for standby use, the J series Onan is built to run day in and day out for years, then be rebuilt and run for years more) To put this in perspective the U.S. Army still uses Onan J series engines in their MEP-002a 5KW (and MEP-003a 10KW) generators (although they are in the process or retiring them), the MEP-002a was introduced during the Vietnam war, they run them for 5,000 hours between rebuilds and issue them back out into the field over and over again, then they still sell in the $800+ range when they show up on the surplus market.

You will need a 2 wire to 3 wire start converter to use with modern transfer switches, Onan made these, but they tend to sell for steep prices these days ($300+ on ebay), or you could build your own, somone posted a how to build one with common off the shelf parts for $20-30 a while back, The skill needed to build it is on part with typical homework assignements (maybe semester projects) for most introductory electronics classes taught in trade schools or for technical majors in colleges. Could probably be built in an hour or two by someone with the right skills.

If it were mine I would probably use the YD as the main unit and and magniciter as a backup.
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Old 12-08-2010, 06:12 PM
Leon N. Leon N. is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Provide me your email address and I will share with you my 40+ years of experience with the Onan 705 JB plant and I will pdf to you the Onan Electric Generating Plant Operators Manual and Parts Catalog as well as The Onan Major Service Manual which includes wiring diagrams, all exclusively for the Magneciter version.

Leon
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Old 12-08-2010, 06:51 PM
whitestrabbit whitestrabbit is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Quote:
bobbyz72 Any pictures so we can see what your talking about. I dont think they have lp regulators if they smell of gas. unit #1 maybe a trifuel unit as it has the same T in the model number as mine..
Here's some photos. I'll post more. I need to take a picture of the thing that looks like a regulator to me as I don't have one - it's raining right now, so have to do that later. It may not be a regulator. The gas line goes into it, so maybe not.

Leon my email is wrabbit@gmail.com - thanks! Really appreciate it.

Quote:
@Old Style Those were a good buy! Those were on CL list? Post some pics.

Hope you only tried to take one up the hill at a time

$1,350 was a great price. Run one on LP the other on gasoline gives you choice. Remote start will be easy.
Yes, found on Craigslist listed for $1599. They were also listed on ebay I think for $1999 Buy It Now. Yes, we took them out of the frame and inched them seperately. Broke the glass in one ammmeters but otherwise looks like they survived ok. I'll have to take and post some pics of the location. It was a bit crazy. The top one sits on the top of the frame which is probably 3.5' off the ground, so we used ATV ramps on the uphill side onto the frame.

Quote:
@Isaac-1 the U.S. Army still uses Onan J series engines in their MEP-002a 5KW
Wow. Good to know. That makes me feel much better about the purchase!

Quote:
@Isaac-1 You will need a 2 wire to 3 wire start converter to use with modern transfer switches,
I don't need to use a modern transfer switch. I just need to be able to give the generator a start signal and get a running signal back. Can I do that without buying the start converter?

Quote:
@@Isaac-1 If it were mine I would probably use the YD as the main unit and and magniciter as a backup.
Is there a difference in the quality of power generated between the two? Why do you recommend using the YD unit as main?

thanks all!
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Old 12-08-2010, 06:57 PM
whitestrabbit whitestrabbit is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

here's a few more pics - all the pics so far are taken in the sellers warehouse. I have it sitting on a concrete pad and plan to build a shed enclosure around it. Any recommendations on how to pipe exhaust and do I need to do anything with the Vacuflow output?

I will take and post some more pics closer up later on of the front showing the thing I thought might be an LP regulator.
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Old 12-08-2010, 07:26 PM
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Quote:
Originally Posted by whitestrabbit View Post
#1 – 1972, J Series, 2 cyl, 120/240VAC, remote electric start, magniciter?
#2 – 1992, J Series, 2 cyl – what is FL ?, 1PH 120/240, 1800RPM
Anything else useful or interesting to know from the numbers ?
The first unit is fitted with a Magniciter Genend, for sure.
The (T) in the first units Model Number is the Spec Code, but it does NOT necessarily denote anything about if the unit was given Dual or Tri-Fuel capabilities. That information is coded in the Option Codes between the (/) and the (T).

The second unit is fitted with a Brushless YD Genend, with an AVR and the (F) stands for Stationary Service, Electric Start, and remote start capable. The (L) designates a 12 Wire Stator, which makes it totally Re-connectable, in both Single, and Three Phase. From looking at the posted DataPlate on this unit, it would seem that the Genend is ALSO an Extended Stack unit, which means there is NO DIFFERENCE in Rated Load, between the Single and 3 Phase, ratings. A VERY GOOD Thing....

Yes, You got a GOOD DEAL, at that price.

When designing the Mounting of these you should look at putting them up on a heavy Bench maybe 24" off the floor. Makes things a LOT easier to work on, and LubeOil changes can all be done by gravity flow, which will be a BLESSING, down the road. I would pull the Exhaust piping that is there, at the flange and have a fabricator, redo that by putting a 90 1 1/5" Elbow right at the flange and then a short nipple, directly to a 1 1/2" NPT Union. then put the chunk of flex tubing on the other side of the Union, and then on out of the building thru a Medical Grade Silencer. All this would be supported externally to the genset. The Flex is important, to decouple the engine vibrations, from the Exhaust System, and will save you a lot of money by not having to hire a fabricator to repair a broke Exhaust Manifold. the Union will allow you to disconnect the Genset from the Exhaust System, with just a Pipe Wrench, for any MAJOR service it may require in the future. A little Never-Sez on the Union is always a good thing. Since this is for Off-Grid, it means energy is expensive, so since you paid for all those cooling BTU's, when you bought the fuel, you might as well get something out of them, instead of heating the whole outdoors. I liked a system that I saw a neighbors place. He build a Drying Shed on the outside of his PowerHouse, and vented the Cooling Air thru the shed and used the shed as a place to hang wet raingear and other things that needed drying out, and let those BTU's do that rather than bring all that moisture into the Cabins living area, and boosting the humidity in there. Just a thought...
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Old 12-08-2010, 07:47 PM
Isaac-1 Isaac-1 is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Quote:
Originally Posted by whitestrabbit View Post
Is there a difference in the quality of power generated between the two? Why do you recommend using the YD unit as main?

thanks all!
The short answer is the YD unit is a brushless design where the Magniciter has brushes. As a general rule you will get cleaner power from a brushless generator, in addition you don't have all those stuck / sticking brush concerns and brush wear. As to the voltage regulation itself there are differences between the response of the Magniciter and the VR-21 electronic AVR in the YD series unit the advantages and disadvantages depend on what you will be doing with the generators (type of loads).

Ike
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Old 12-08-2010, 09:12 PM
whitestrabbit whitestrabbit is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

more pics of generator
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Old 12-08-2010, 09:16 PM
whitestrabbit whitestrabbit is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

more pics of generators and hill we drug them up !
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Old 12-08-2010, 09:20 PM
whitestrabbit whitestrabbit is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Pictures of the hill.
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Old 12-08-2010, 09:59 PM
Max Thompson Max Thompson is offline
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Default Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

I am going to try to attach the index from a magniciter service manual I have. I do not have the cover page so I do not know what the number of the manual is. Is this manual not in everyone’s library? It is about a 28 meg. PDF but I have it broken into 3 pieces that I think I have e-mailed out before.
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Old 12-08-2010, 11:25 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Looks like... the clean one... has a propane/natural gas line comming off the carb also. I think the things you are calling regulators and actully fuel pumps.
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Old 12-09-2010, 08:33 AM
Ted_Cool Ted_Cool is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

I thought it might be a gas line, too, for a moment - but I'm pretty sure it's the crankcase breather tube.

That fuel bowl looks nasty. I doubt it's been run recently. SeaFoam to the rescue?
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Old 12-09-2010, 08:42 AM
K D Redd K D Redd is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

NO BIG Onan expert here BUT I see no evidence of the needed equipment gaseous fuel operation. It can be added in several ways.

Kent
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Old 12-09-2010, 09:01 AM
bobbyz72 bobbyz72 is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Oh come on guys, My 7.5 has the gas line in the same place, and the brether is at the bottom. This is a gas line.....
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Old 12-09-2010, 01:04 PM
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

I think you might be right about that. It would explain the nasty fuel bowls.

Maybe you could ask the seller to give you the rest of the gas parts.
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Old 12-09-2010, 01:30 PM
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - off grid sola

Whitesrtabbit,

Looks like a very good find!

I'm "off-grid" and have a bit of experience now with a propane JC with Magneciter; along with two Kohlers, one older one with transformer regulation, and a "newer" one with solid-state AVR.

I've experienced a few issues with all three: The Magneciter "let-the-smoke-out" of one of it's reactor coils - which I re-built (see one of the "Magneciter" sticky postings); the older Kohler had a plugged radiator; and the newer Kohler is having an occasional issue with the AVR.

Of the three, the Onan JC with Magneciter is my favorite for holding voltage regulation, the older kohler is my next favorite, and the solid-state AVR is my least favorite, though that whole unit is now my best one.

From this board, I've learned that some of the Onan AVR's are very gooe, and some not so good; and, that "Flight Systems" is highly recommended for AVR replacement parts, if found necessary.

Should you need specific help with the Magneciter, I'm more than willing to share what knowledge I have.

Regards and good luck with the off-grid!

JLB
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Old 12-10-2010, 01:55 AM
whitestrabbit whitestrabbit is offline
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Default Re: Onan 7.5 JB - need help to startup 2 units, setup LP & auto start - offgrid solar

Quote:
Originally Posted by bobbyz72 View Post
Oh come on guys, My 7.5 has the gas line in the same place, and the brether is at the bottom. This is a gas line.....
When you say gas line, you mean propane or gasoline? I assume propane.
The gas line you outlined is rubber. Propane can run in a rubber ?

Quote:
Originally Posted by ted_cool View Post
I think you might be right about that. It would explain the nasty fuel bowls.

Maybe you could ask the seller to give you the rest of the gas parts.
How does this explain the nasty fuel bowls?

What gas parts am I missing? When you say gas you mean propane?
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