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Onan JC 15kw Natural Gas Question


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Old 04-16-2018, 07:41:13 PM
Mark82 Mark82 is offline
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Default Onan JC 15kw Natural Gas Question

New to this and I have a question on natural gas supply for a onan jc 15kw. Right now it's set up to run on propane but I would like to run it on natural gas supply for my house but I'm not shore if my house supplies enough gas to run the generator and my furnace 100,000 btu/hr and hot water heater 35500 btu/hr everything else is electric. My gas meter is a Rockwell 175. Can some one point me in the right direction. And if I was to keep it propane how long will it roughly rum on a full load on 100 lb tank ?
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Old 04-16-2018, 08:32:23 PM
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Default Re: Onan jc 15kw Natural Gas question

Most of your answers will be here:

https://www.dropbox.com/s/jqxlcyu5rr...Fuels.pdf?dl=0

I don't know about your gas meter, but if the '175' part means 175,000 BTU/hr, then it's too small.
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Old 04-16-2018, 08:51:18 PM
Leon N. Leon N. is offline
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Default Re: Onan jc 15kw Natural Gas question

Mark.

I run my JB on natural gas. The natural gas in this area is supplied to the home at 60 PSI. Since I installed my JB in1970 I was always concerned about the capacity of the gas regulator which lowers the incoming pressure to about 4 inches. All out home appliances use natural gas except the electric clothes dryer. Many years ago I determined the current gas regulator capacity was in the area of 300 CFH. My JB alone draws about 120-140 CFH at full load. So for many years I was always cognizant of what appliances were on when the JB was running.

Well this past Summer, the local utility changed out the gas regulator indicating it was too old, since it was installed in 1969. So I merely asked the guy who was changing the pressure regulator if he cold substitute a larger capacity regulator. No problem. He replaced the 300 with a 500 CFH regulator. Now do not worry about this concern any more. Perhaps you can do the same. You need a copy of the Onan tech bulletin, T-015 referred to above which lists the fuel requirement for your JC and answers your question.

Last edited by Leon N.; 04-16-2018 at 08:56:03 PM. Reason: Typos
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Old 04-16-2018, 09:32:05 PM
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Default Re: Onan jc 15kw Natural Gas question

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Originally Posted by Leon N. View Post
...You need a copy of the Onan tech bulletin, T-015 referred to above which lists the fuel requirement for your JC and answers your question...

...which I provided in the link above...
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Old 04-16-2018, 10:40:14 PM
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Default Re: Onan jc 15kw Natural Gas question

255 CFH for genset + 100 CFH furnace + 35.5 tank = 390.5 total CFH

390.5 / 175 = 2.2 factor of over spec.

Now know that meters will typically flow a lot more than spec, just drop a bit more pressure. If your gas is set at 7" like here and 4" is the minimum, then you have a long way to go before dropping below minimum.

Also, your generator is not likely to run at full load.

Me, I would figure out a way to hook it up and test it while watching pressure to see what really happens.

Also the R175 is a cheap junky meter, maybe the utility would replace it if you asked.
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Old 04-16-2018, 10:47:23 PM
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Default Re: Onan jc 15kw Natural Gas question

Quote:
Originally Posted by Birken Vogt View Post
255 CFH for genset + 100 CFH furnace + 35.5 tank = 390.5 total CFH

390.5 / 175 = 2.2 factor of over spec.

Now know that meters will typically flow a lot more than spec, just drop a bit more pressure. If your gas is set at 7" like here and 4" is the minimum, then you have a long way to go before dropping below minimum.

Also, your generator is not likely to run at full load.

Me, I would figure out a way to hook it up and test it while watching pressure to see what really happens.

Also the R175 is a cheap junky meter, maybe the utility would replace it if you asked.
I read the same thing about the Rockwell meter being junky . I went out and looked at my gas meter and it is good for 250 CFH. My JB at full load needs 126 CFH at full load. Unless I am running my 3 ton AC, I am only running 1/4 to 1/3 load.
I looked up and 1 cu.ft. is supposed to equal roughly 1000 BTU.
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Old 04-17-2018, 09:25:07 AM
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Default Re: Onan JC 15kw Natural Gas question

Ok thanks everyone for your information I called my gas company and they will up grade my meter for no charge

---------- Post added at 09:25:07 AM ---------- Previous post was at 09:17:29 AM ----------

I noticed people tap in at the meter to supply the generator but my meter is too far away to do that it is in the front of my property my question is can I tap it in at the garage where they line comes in and then to the generator the line coming in is an inch and a half pipe will that be sufficient? Probably going to be less than 15 feet from there. Technical bulletin says that I can use 1 inch pipe as long as it's 15 ft or under.
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Old 04-17-2018, 09:37:03 AM
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Default Re: Onan JC 15kw Natural Gas question

I would tell the gas company what you need. But as long as you have the correct pressure. At where you want to tap in you should be fine.
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Old 04-17-2018, 10:50:18 AM
Birken Vogt Birken Vogt is offline
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Default Re: Onan JC 15kw Natural Gas question

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Originally Posted by Mark82 View Post
I noticed people tap in at the meter to supply the generator but my meter is too far away to do that it is in the front of my property my question is can I tap it in at the garage where they line comes in and then to the generator the line coming in is an inch and a half pipe will that be sufficient? Probably going to be less than 15 feet from there. Technical bulletin says that I can use 1 inch pipe as long as it's 15 ft or under.
Add up the total flow for any given section of pipe such as your 1.5", generator, appliances, whatnot.

Figure the total run from the meter to the farthest appliance, including the branches of smaller pipe feeding that appliance.

Then use that length column from this chart: https://www.engineeringtoolbox.com/n...ing-d_826.html against the total in the 1.5" that you figured earlier.

This will tell you if the 1.5" pipe has excess capacity.

You also need to do the same calc with the generator branch line.

If you post the lengths of pipe we can do an example calc for you if you want.
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Old 04-17-2018, 11:26:29 AM
Mark82 Mark82 is offline
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Default Re: Onan JC 15kw Natural Gas question

[QUOTE=Birken Vogt;1479159]Add up the total flow for any given section of pipe such as your 1.5", generator, appliances, whatnot.

Figure the total run from the meter to the farthest appliance, including the branches of smaller pipe feeding that appliance.

Then use that length column from this chart: https://www.engineeringtoolbox.com/n...ing-d_826.html against the total in the 1.5" that you figured earlier.

This will tell you if the 1.5" pipe has excess capacity.

You also need to do the same calc with the generator branch line.

If you post the lengths of pipe we can do an example calc for you if you want.[/QUOT

Okay I will bust out the tape after work and get some measurements thanks
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