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70 KW Onan - How big of propane tank required


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  #1  
Old 04-24-2008, 11:57:59 AM
richard.bessey richard.bessey is offline
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Default 70 KW Onan - How big of propane tank required

All,
We have a newly aquired 70 KW Onan genset with a ford 460 on it, currently setup for propane, we plan to change it to Natural Gas eventually.
Anyway, as a temporary fix I was looking at getting a propane tank so we can get the genset up and running since its going to take us a bit before we have natural gas ready.

I know we have to used a good sized tank for this since the engine requires so much fuel, it will frost the tank if its not big enough.

How big of tank do we need? Will a 100 lb (20 gallon) be enough, or do we need to go bigger? Could I hook up a dozen 5 Gal tanks?

Regards,

Richard Besseh
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Old 04-24-2008, 02:10:27 PM
Jim Rankin Jim Rankin is offline
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Default Re: 70 KW Onan - How big of propane tank required

70kW will demand around a million BTU/hr or 400 cubic feet of 2500 BTU/Cu ft LPG/hr. I would get with the local LPG folks and see if they can supply a tank and size it and the regulator for that demand. The tank size will depend on above ground/in ground, lowest outdoor temperature etc. Line size will depend on the length of the run from tank to generator. Frequently a first stage regulator is used to bring the pressure down to maybe 10psi to get the vapor to the building through a smaller line than otherwise would be required if you have just the one regulator at the tank to drop the pressure to the normal use pressure.
I would guess around a 500 gallon would be the minimum and that wouldn't probably do in the winter.
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Old 04-24-2008, 07:53:20 PM
K D Redd K D Redd is offline
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Default Re: 70 KW Onan - How big of propane tank required

At 70 degrees F a full 100 lb/20 gallon tank can supply 300,000 BTU's per hour. Half Full 167,000 BTU's per hour. At 40 degrees F full will provide 214,000 BTU's/HR. Half full at 40 degrees F 125,000 BTU's/HR. If you are going to use it any length of time on LP I would set a MINIMUM 500 gallon tank, A 1000 gallon would be better.

Kent
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Old 04-24-2008, 10:01:09 PM
John A John A is offline
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Default Re: 70 KW Onan - How big of propane tank required

Up in your neck of the woods, I would not install anything less than a 1000 gallon tank.
Last 460 I connected used 2 - 1000 gallon tanks, and after 2 hours of operation had a frostline on both tanks.

John
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Old 04-25-2008, 12:14:47 PM
K D Redd K D Redd is offline
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Default Re: 70 KW Onan - How big of propane tank required

On a big engine like that if there is ANY way you can feed it with LIQUID LP, depending on the safety regulations, you would not need as much tankage.

Kent
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Old 04-25-2008, 11:53:09 PM
Jeffw5555 Jeffw5555 is offline
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Default Re: 70 KW Onan - How big of propane tank required

I agree; you should go with liquid feed. It's not hard to do; just really need an Impco Model E vaporizer/regulator.

Then you could run it on any sized tank. Keep in mind it will burn 4-8 gallons per hour depending on load.

I've got my 75.0 ENT running on liquid. I have a 500 gallon tank, but only because I want enough for a couple days operation.
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Old 04-28-2008, 11:48:09 AM
richard.bessey richard.bessey is offline
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Default Re: 70 KW Onan - How big of propane tank required

Thanks guys, not news I wanted to hear but that info is exactly what I was after.
Thanks again!
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