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Onan 12.5JC-18R/30634AB. All the info you got!


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Old 09-11-2017, 10:16:42 AM
MESS MESS is offline
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Default Onan 12.5JC-18R/30634AB. All the info you got!

Onanparts hooked me up with the info on my Generator, for all you gearheads give me all the info, you know about this specific JC. Is it good, any limitations I should know about? Nothingbutdarts gave me some info already. I will say that it was able to power everything in my house During Hurricane IRMA without out an issue, my biggest question is what is my actual fuel flow I had 50 in the tank and was able to ration it out 6 days after running it for 8 hours the first day... The Onan was our only lifeline and she did not fail me. They don't make them like this anymore. I was thinking when I first bought the house of replacing it, but after seeing what it can do and the reliability, I think she is going to get a refurbishing overhaul very soon...
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Old 09-11-2017, 10:35:24 AM
Ray Lynch Ray Lynch is online now
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Default Re: 12.5JC-18R/30634AB. All the info you got

Average gasoline consumption at rated load is 2.1 GPH.
Ray
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Old 09-11-2017, 10:52:33 AM
len k len k is offline
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Default Re: 12.5JC-18R/30634AB. All the info you got

Gasoline
~ 1 gal/hr no load
~ 2.2 full load
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Old 09-11-2017, 12:05:34 PM
MESS MESS is offline
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Default Re: 12.5JC-18R/30634AB. All the info you got

Quote:
Originally Posted by len k View Post
Gasoline
~ 1 gal/hr no load
~ 2.2 full load
I am guessing that diesel and propane are the same burn rate? I was figuring it was somewhere around 1-3 depending on the load. Going to be looking at buying a 500 Gallon tank rather then the 100 Gallon, as a result of this storm... Going to cost me 1499.00, just for the tank not counting fuel Things are so expensive here.
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Old 09-11-2017, 12:17:08 PM
nothingbutdarts nothingbutdarts is online now
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Default Re: 12.5JC-18R/30634AB. All the info you got

Fullload LP fuel consumption for a 15.0JC is 110 Cubic Foot per hour.
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Old 09-11-2017, 12:29:18 PM
len k len k is offline
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Default Re: 12.5JC-18R/30634AB. All the info you got

Don't think your going to see 3 gal/hr gasoline , 15kwJC is only ~ 2.4 at full load. Just ratioing 2.4 x( 12.5/15) = 2.2

They say propane is ~ 10-15 % higher burn rate than gasoline, (check manual).
Diesel is ~ 1/2 of gasoline
Manual should have specs on nat gas, I'm not that familiar with NG, but I estimate it at ~ 240k BTU/hr at full load. (Just ratioing: 15JC is ~ 290k so 290k x12.5/15 = 240k)

Last edited by len k; 09-11-2017 at 06:10:44 PM.
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Old 09-11-2017, 06:00:36 PM
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Default Re: 12.5JC-18R/30634AB. All the info you got

Good to know that you made it through IRMA. The Onan J series is built to last and run continuous so you made a good choice there. The two cylinder versions are similarly reliable and have half the fuel consumption so if you don't need that much power they are something to think about. Ideally a generator that is just big enough to supply your basic needs is optimum when looking at long term outages. If you are sharing power with your neighbors then the JC is great. The diesel DJCs are fairly economical and diesel usually has good availability and long term storage characteristics , better than gas. Cheers Dan
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Old 09-11-2017, 06:08:26 PM
len k len k is offline
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Default Re: 12.5JC-18R/30634AB. All the info you got

7.5JB = 7.5 kw
~.6 gal/hr gasoline no-load
~ 1.2 full load
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Old 09-12-2017, 06:21:54 AM
Kevin K Kevin K is offline
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Default Re: 12.5JC-18R/30634AB. All the info you got

Quote:
Originally Posted by MESS View Post
Going to be looking at buying a 500 Gallon tank rather then the 100 Gallon, as a result of this storm... Going to cost me 1499.00, just for the tank not counting fuel Things are so expensive here.
That's not a bad price for the tank. The last time I checked, the 500 gallon tank and two regulators would cost me over $2,000 plus sales tax. Of course, I live in New York State, home of fees, surcharges, and one of the highest tax rates in the country. That sad and sorry fact is reflected in the price of just about everything I buy locally. Unfortunately, I can't get a 500 gallon propane tank with free shipping from Amazon Prime or Ali Express.

Propane is a great fuel, but unfortunately you can't carry it in a bucket. It requires an expensive tank that may be difficult to get filled during an extended power outage as the local propane dealers have "priority customers" that get the first shot at any remaining supply. The result is that the only fuel you can count on during a widespread power outage is the fuel in your own tank.

Diesel 138,500 BTU/gallon
Gasoline 117,000 BTU/gallon
Propane 93,000 BTU/gallon

Diesel gives the best fuel economy, but diesel generators are quite a bit more expensive than gasoline or propane models. Then there is the cold weather starting issue, an important consideration here in the Northeast where winter temperatures are routinely down to zero degrees Fahrenheit in the winter.
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Old 09-12-2017, 02:59:13 PM
len k len k is offline
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Default Re: 12.5JC-18R/30634AB. All the info you got

2 cylinder 7.5JB is 7.5 kw rating, 4 cylinder 12.5JC and, 15 JC are 12.5kw and 15kw respectively. (12.5 and 15 are same engine, different genhead)

Diesel has less power: 2 cylinder 6DJB is 6kw ,and 4 cylinder 12DJC is 12 kw

Of course to burn diesel you'll need a diesel engine, DJB or DJC (not a JB or JB)

D before the J means diesel, R would mean radiator (water cooled), M would mean marine (water cooled)

Last edited by len k; 09-12-2017 at 03:20:59 PM.
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