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Old 02-10-2009, 09:53 AM   #1
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2008 30' Classic S/O
Dearborn , Michigan
Join Date: Aug 2006
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LP-fueled generator power fallacy

I decided to conduct a little experiment, with my YAMAHA 2400, to find if there is an actual loss-in-power while fueling with LP.

For those who haven’t come across the various threads on this- it’s a debate that’s come about because of the disparity between gasoline and LP’s BTU/gallon ratings.

According to the DOE: LP=91,330 BTU/gallon, while GAS(summer average)=114,500 BTU/gallon (gasoline blends/additives depending on season, can vary BTU rating)

I realize I should establish a ‘control’ or baseline first, by quantifying the numbers based on gasoline fuel-- but heck, I never claimed to be a scientist. I’m gonna start with LP, and compare them to the YAMAHA published numbers for peak/continuous amp output.

So, ‘Part 1’ will be LP. If anybody’s interested I’ll put up ‘Part 2’, which will be same generator/loads running on gasoline.

At some point, I’d like to factor in a ‘fuel-consumption’ number (which is probably what the real variable is here)- I have no idea how I might do that- so feel free to chime in...

here’s the equipment:
(1) YAMAHA EF2400IS. Tri-Fuel converted carburetor by USCarb. Published SPEC’s by YAMAHA running gasoline: 17A(20A MAX), 2000W (2400W MAX).

Measuring instrumentation:
(1) RadioShack Analog clamp-on ammeter
(1) HD modified extension cord
(1) APC switched/fused 7-outlet power strip

I’ll generate load with these:
(2) Craftsman halogen shop lamps: 3.5A low/7.0A high (ea.)
(1) RIGID 4GAL/5.0HP shop vacuum: 10.0A (probably has a startup spike, but ammeter doesn’t give me ‘rush’ feedback)


24A load:
both halogens on high, shop-vac running. Genset ran/powered items for ~10sec at 4380 RPM, then tripped to ‘overload’.

20.5A load:
one halogen on high, one on low, shop-vac running. Genset ran/powered items at 3220 RPM for 10 minutes.

So, what I’m finding is the 2400 is capable of significantly higher output than what YAMAHA publishes. It’s probably safe to assume the start-up under the 24A load had a significantly higher ‘spike’ that it was supplying also.

The test I’m real interested in, however, is starting my 13.5k BTU A/C unit, on a nice hot and humid summer day.

You can find a picture narrative of the above, here:

Picasa Web Albums - JOSEPH - YAMAHA EF2400...

A family of eight, blogging all things camping from our Airstream
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Old 03-31-2011, 11:21 AM   #2
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Summersville , West Virginia
Join Date: Aug 2010
Posts: 3
No Yamaha power loss even on natural gas

We install hybrid systems (tri-fuel) on the full line of Yamaha generators from the EF1000i all the way up to the EF12000DEC. When we test the units prior to crating and shipping, each one is tested under full rated load and only on natural gas. We have never had a unit that would not produce the full Yamaha rated wattage.

I mention this because we design systems for other brands and there have been units (mainly the Honda copies made in china that we affectionately termed CHonda's) that seem to run fine on gasoline and propane, but will not even fire on natural gas. So years ago we stopped doing both the NG and LP testing since determining that any unit that runs successfully under full load with NG will, without a doubt, do so on propane.
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Old 03-31-2011, 04:35 PM   #3
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2012 30' International
Walkerton , Virginia
Join Date: Dec 2003
Posts: 2,552
Thanks for posting, US_Carb - I had wondered about whether I lose much by running on propane and am glad to see that I don't. It is nice and clean, nice not to have to mess with carrying gasoline.

Somebody, please, point me to the road.

AIR 3987
WBCCI 4596
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