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Fuel consumption - don’t have a problem- need to understand usage

Posted: Sun Sep 13, 2020 7:54 pm
by Caipira
I recently installed a 22KW water cooled generac with the 2.4 liter Mitsubishi engine.
I read all the specs on fuel consumption. I’m running on LP gas.
I was expecting 40-50 gallons per day.

I got exactly the opposite .
I have 2300 sq ft heated plus pool. The most I have ever seen on my meter is 9.5 kw under normal conditions. Of course that doesn’t include the large draws for motors and or compressors starting up. Without a/c running it’s about 6 kw.
I’m all electric with 2 big fridges and 2 small. 2 water heaters, pool pump dryer etc. Typical all electric house.
During Hurricane Laure I even ran a 100 ft cord next door to the neighbors house.
In 48 hrs I only used about 25 gallons of propane. I don’t understand it.

Could it be because it’s the water cooled unit running at only 1800 rpm? Could it be that most of the time I was running at 25-35% load.
I have a lot of people asking me questions and fuel consumption always comes up.
I’m the only one that is reporting excellent economy.
I want to answer their questions as best I can.

So the whole point of this post is to find out if anyone else has experienced the same results.

Appreciate any comments.

Re: Fuel consumption - don’t have a problem- need to understand usage

Posted: Sun Sep 13, 2020 9:56 pm
by Chris
Even at 25% load, the 2.4L 22kW only uses 1.1 gal per hour (right on with your findings). At lower electrical demand, the fuel consumption would go down obviously. At 50% load it requires 2.1 gal, then 2.8 gal at 75% and 3.4 gal at 100% load (which most people will never sustain longer than a few seconds).

Your 6kW is roughly 24% of the max output, so you're right at that 1 gal mark. 24 hours, 24 gallons.

I'd say you're right on par with what you'd expect from a unit like this!

Re: Fuel consumption - don’t have a problem- need to understand usage

Posted: Sun Sep 13, 2020 10:53 pm
by Caipira
Thanks for the quick reply. I guess I’m on track except for one thing.
It was about 25 gallons in 48 hrs. About 1/2 gallons per hour.
Then again I’m sure I’m off a little bit because I’m going by the gauge on my tank.
Not by far though because I fill my small bottles during the winter to heat my shop.
Last winter I kept track of usage and tank level using the per cent gauge so I feel confident that I’m close.
Kind of I think I know what I’m looking at but I don’t know/ believe what I’m seeing.
Anyway you’ve given me enough info to answer questions about my system.
There’s a lot of interest in the area in Generacs right now especially since there’s a lot of houses that still don’t have power and may not for another month or so.

Thanks again

Re: Fuel consumption - don’t have a problem- need to understand usage

Posted: Mon Sep 14, 2020 6:47 am
by murphy
Propane tanks can only be filled to 80% maximum.
The gauge is % of a full tank.
I'll use a 120 gallon tank as an example.
When full of propane it is at 80% which is 96 gallons.
When the gauge reads 50% that is 60 gallons. (1/2 of 120).
A 40% reading is 48 gallons which means half of the initial fill has been used.
The gauge is not very accurate. It is marked in 5% increments.

Re: Fuel consumption - don’t have a problem- need to understand usage

Posted: Mon Sep 14, 2020 8:07 am
by Caipira
I understand the filling to 80% and of course they’re not that accurate. But with your help we’ve nailed this down to a gallon or less at the load I’m running.
I had mine filled at the end of winter. When summer got here it expanded to 85%.
It’s a 330 gallon tank (250 usable) and now it’s on about 77%.
There’s no way to pin it down other than to assume it’s in the 1 gallon range.
Everybody is talking generators wherever you go after the latest hurricane and with another heading to Louisiana this week you can only imagine the conversations.
I’ve heard horror stories about fuel consumption and I know most are true.
I just want to tell my experience and try to give some reasonable explanation.
Get one big enough to not stay heavily loaded and go water cooled if budget allows.
Any other info you care to share is welcome.
I want to be as a accurate as possible.

Re: Fuel consumption - don’t have a problem- need to understand usage

Posted: Mon Sep 14, 2020 10:17 pm
by Chris
Honestly, fuel consumption is really just a math equation (don't ask me for the math on it haha). Basically X amount of kW = Y amount of fuel needed to generate the HP required to spin the rotor. That being said, there would be a skew if you had a massively overpowered gen and were only using a small amount of it. For example: a 150kW gen only being used for 10kW is going to draw a LOT more fuel than a 16kW being used for 10kW.

Hopefully that makes some sense!