8kw propane powered Onan generator set question.

[roadrunnertex]

Folk's
I am posting this question for a friend in Tulsa,OK.
He is looking to buy a 8KW propane powered generator set for stand by power in his home.
The last ice storm was tough on him so his question is what is the fuel (propane powered) burn rate under load?
Could he run it very long on a 20 pound type propane cylinder?
I told him to look for a 8KW Onan 1800 rpm 2 cylinder air cooled generator set.
Any idea's or input would be welcome.
Thanks,jlv

[belfert]

A fully loaded 8KW propane generator is going to consume 1.5 gallons per hour of propane.  Full load would mean a bit over 2 hours on a 20# propane cylinder.  I don't know how long a power outage your friend is designing this for, but consider that it might be difficult to get propane in a wide spread outage if the suppliers don't have power to fill the cylinder.

I have a natural gas 8KW automatic standyby generater at home and it burns a lot of natural gas when it does run.  I think I figured it could be upwards of $2 an hour in fuel, but a small price to not have froze pipes and such.

[DavidInWilmNC]

From my understanding of propane, he may have issues with enough propane vaporizing at 'ice storm' temperatures.  20lb cylinders are 'vapor discharge' and require the propane to vaporize (boil) to be used.  The vaporizing of liquid propane causes a pressure drop, which causes even more lowering of temp.  This will also cause the cylinder to have less usable propane.  From what I've read, he'll want a 100lb tank minimum (also generally vapor discharge) and possibly even a liquid discharge setup.  Some of this info may only apply to larger (12-20 kw) generators, but it would be worth your friend investigating.

From what I've seen, old Onan 6.5 kw RV generators (gas and LP) are pretty common and fairly inexpensive.  I have an old gas model that I'll probably use for home stand-by duty when I eventually replace it with a diesel generator. 

David

[HB of CJ]

Toos many variables to calculate goodly, soosss, best guess (educated) about 2, maybe 3 hrs.  Variables include mixure control, (like a carb) tune of mill, actual average load (low plus peak divided by hours) fullnessess of propane bottle, etc., etc., blah, blah blah.

Thank you DavidInWilmNC... I plum forgot your small propane bottle MAY NOT work with a gen set A ALL since gen sets, like some propane hog applications, require liguid fuel to the mixer and not just gasous gas.  Might work at light loads, but then again, may not work at all.

Your friend would need a dedicated propane tank that has the proper valving sooss the propane gen set gets the proper kind and amount of propane.  Other than that, fine.  Propane stores for years and as the $price$ skyrockets, will be a good $investment$.