[RE-wrenches] generator suggestions

Wed Jan 30 12:44:40 PST 2013

Jay, 

In addition to what Dan has said, 1 gallon of propane has about 35% less BTU's compared to 1 gallon of gasoline. So the propane derating must be added to the altitude derate to determine generator output.

Larry Crutcher
Starlight Solar Power Systems

On Jan 30, 2013, at 1:32 PM, Dan Fink wrote:

Jay;
The "standard" seems to be 2-3% derate for every 1000 feet above sea level for gasoline, diesel or LP gas generators, and supposedly more like 5% for natural gas. (in general we don't work in areas that have natural gas service, we only do off-grid). So the propane de-rate for altitude is no worse than the diesel or gasoline de-rate, it's just added on top of it. In practice, we are not seeing that big a hit, but it is hard to really judge. Also, air-cooled generators don't cool as well at high altitudes and tend to run hot.

A fairly common troubleshooting call we've seen in the past is clients who have purchased cheap portable generators from Home Depot, Harbor Freight etc. and then find that they can't tune them for anything above 6000 feet -- the carb adjustment screws don't go that far, and the fine print in the warranty actually says 6000 ft max. Ouch! They run so poorly that very few modern inverter/chargers will even look at their input. I've been a local firefighter for 14 years now, even worse problem with chainsaws (2-stroke). We've learned how to bust out the plastic "EPA stops" on the carb adjust screws, with the of course unofficial instructions to throw the saw into the fire if the EPA shows up......

Never had the slightest high-altitude issues with the Honda x000i series running OK, and I have no idea why. The de-rate factor is certainly still there, but no issues idling or running, no matter what the draw. My Honda 3000i issues are from a different cause I think; there is an extensive thread on that in the archives here that I started in July 2011 I think.

DAN FINK

On Wed, Jan 30, 2013 at 1:12 PM, Jay Peltz <jay at asis.com> wrote:
Hi Dan

So true. But never had it explained to me why propane is different than gasoline or diesel at altitude. 

Thx

Jay
Peltz power

Sent from my iPhone

On Jan 30, 2013, at 11:42 AM, Dan Fink <danbob88 at gmail.com> wrote:

> And because of our Colorado location here, we are always dealing with altitude de-rate factors. We are usually installing at 7000 - 10000 feet elevation, which is a big hit. Propane de-rates gennys even further.
> -- 
> Dan Fink,
> Executive Director;
> Otherpower
> Buckville Energy Consulting
> Buckville Publications LLC
> NABCEP / IREC accredited Continuing Education Providers
> 970.672.4342 (voicemail)
> 
> 
> On Wed, Jan 30, 2013 at 12:38 PM, Jay Peltz <jay at asis.com> wrote:
> > Hi all
> 
> I've found through hard experience that all generators except diesels seem to be smaller than name plate rating.
> 
> And while the charging maybe reduced if I am conservative in telling the inverter how large the genny is I rarely get the genny to trip its breaker.
> 
> 
> Jay
> 
> Peltz power
> 
> 
> 
> 
>  
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-- 
Dan Fink,
Executive Director;
Otherpower
Buckville Energy Consulting
Buckville Publications LLC
NABCEP / IREC accredited Continuing Education Providers
970.672.4342 (voicemail)

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