Selecting the correct backup generator

RoySalisbury · February 2011

I'm looking to expand my solar power generation with a backup generator. Currently I have two generators. A small 2kw pull start, and a larger 8kw Ridgid with remote electronic start. Unfortunatly for me, while the Ridgid has an electronic start, it still requires manual choke. I've looked for an after market "upgrade" that would allow me to use an AGS on the Outback inverters but have had no luck so far.

Anyway, I'll probable end up sellling both and getting the correct model and required bits, but need to know what that is. I want to hook it up to an Outback VFX3524 inverter/charger. At most I'm thinking the max output does not need to go over 3kw (since the inverter won't, and the highest draw I would have would only be about a 1.5kw draw (2.5 kw surge) for the AC unit).

So, what might will I need? I see the Honda 3000i series get good marks and is very quiet .. What about the parts to hook into the inverter (AGS switch, relays, ect).

Thanks for you help!

Roy

BB. · February 2011

Re: Selecting the correct backup generator

The problem I have seen is there are few (if any) small (<3-5 kW) gensets that are setup for automatic start. The Honda's all need to use the choke to start when cold (as I understand)...

I think a eu2000i with auto-start capabilities would be a really nice unit. 1,600 watts is a nice size for a cabin or small off grid home (or even emergency power).

How about anybody here that has done a propane conversion on the Honda eu3000i? Do they start in cold weather without a choke?

Otherwise, what about electric start Onan gensets for RV's... Do they have/need automatic chokes? Can they be setup for auto-start?

Sorry, more questions than answers here.

-Bill

dagr51 · February 2011

Re: Selecting the correct backup generator

I have an Onan 5.0 CCK that starts remotely. On gasoline it had an automatic thermo choke, but I removed the choke and the carb butterfly when I converted it to propane as you cannot use a choke on propane - at least with this unit.

RoySalisbury · February 2011

Re: Selecting the correct backup generator

I think I found a possible solution on the Ridgid Generator forum:

http://www.ridgidforum.com/forum/showpost.php?p=314307&postcount=7

Going to see if he still has the plans or is selling the modification. If so, then my current generator should work if I can get a 2/3 wire relay hooked up to it and the AGS on the Outback.

Its a bit of a gas hog, but its better than nothing for an emergency charge when not around.

Roy

oil pan 4 · March 2011

Re: Selecting the correct backup generator

If you want a quiet generator that isnt a gas hog find a diesel generator with a 4 pole alternator.
They are quiet and fuel efficient because they only run at 1800rpms.
I don't care what any one says, there is no such thing as a quiet 3600rpm gas generator.
On of the smallest generators I work on is a little liquid cooled 5kw diesel kubota with a kohler generator. When running at a 2kw load they can go 3 nights dusk till dawn on 14-15 gallons of diesel.

icarus · March 2011

Re: Selecting the correct backup generator

~36 hours of 2kw load on 15-16 gallons of fuel seems like no bargain!

A honda Eu 2000 will use ~ 1/2 gallon every 6 hours if memory serves. I don't know what a Eu 3000 will burn at 2 kw load.

My ancient Lister 5 kw SL 2 will pump out 5 kw forever on ~ 1/4 gallon of fuel per hour.

Tony

techntrek · March 2011

Re: Selecting the correct backup generator

Only problem with diesel gensets is they need to be constantly loaded to a minimum % to prevent "wet stacking" (lots of info via Google). Suddenly the genset is dead from deposits.

That is usually not a problem in a commercial setting where loads are fairly constant day-to-day... the usual lights, computers, HVAC and industrial equipment. A typical home might need 500 watts 24/7 if they aren't too energy efficient; of course an energy efficient home will need far less. Then an A/C compressor will kick on and the home will need an additional 4000 watts for 20 minutes (even more to get through the startup surge). If you size a genset to handle the peak loads it will run most of the time at >10% of its capacity most of the time. Not an issue for a gas, NG, or LPG genset, but a big issue for diesel.

oil pan 4 · March 2011

Re: Selecting the correct backup generator

The diesel generators seem to run fine for many thousands of hours running at less than a half load.
Diesel generators that wet stack do so from being run at light load or almost no load, throw in worn piston rings and bad valve guide seals and that makes it worse.
If you were real creative you could always run propane or natural gas fumigation.

russ · March 2011

Re: Selecting the correct backup generator

oil pan 4 wrote: »

If you were real creative you could always run propane or natural gas fumigation.

What in the world is that?

techntrek · March 2011

Re: Selecting the correct backup generator

oil pan 4 wrote: »

The diesel generators seem to run fine for many thousands of hours running at less than a half load.

Many of them can go down to 40% load without wet stacking, I didn't say you had to stay above 50%, only that there was a minimum %. Even at 40% they usually aren't a good idea for a backup generator because a home's loads are well below that minimum % most of the time.

Far different situation if you are living off grid and you need to bulk charge your batteries in the morning after several cloudy days, or need it to run a heavy load every day like a water pump. Then your load is a known steady load and you can size a diesel genset accordingly.

techntrek · March 2011

Re: Selecting the correct backup generator

russ wrote: »

What in the world is that?

+1, I'd love to know too.

Cariboocoot · March 2011

Re: Selecting the correct backup generator

Fumigatin' diesels! The process of feeding them some natural gas or propane to increase combustion temperatures and reduce deposit build-up. They make kits for diesel trucks for this (Bullydog) because it also boost HP & torque. It also shortens engine life, especially if you get it wrong. On the tractor pulling circuit they feed them ether. Very impressive power output; very shortened lifespan. (It is standard practice to use a shot of ether to start some diesel engines.)

In any case, matching the gen size to the application is key. There's no sense running a 20kW unit where only a 2kW is needed, no matter what the fuel.

mike95490 · March 2011

Re: Selecting the correct backup generator

If you were real creative you could always run propane or natural gas fumigation.

What in the world is that?

Where vapor fuel is added to the intake air, and can replace up to 80% of the diesel. Some diesel fuel needed to provide the ignition. Supposed to help clean out carbon deposits from the engine too.

The poor mans way is to use a unlit propane torch spraying fuel into the intake. When it explodes, you are poor.

oil pan 4 · March 2011

Re: Selecting the correct backup generator

I have experemented with propane fumigation.
It works really well as long as you dont over do it.
Diesel truck/tractor sled pulling would be a good example of over doing it.
Or you could get 2 smaller generators, fire them both up as needed and phase sync them so they can work together on one load.

techntrek · March 2011

Re: Selecting the correct backup generator

Cariboocoot wrote: »

Fumigatin' diesels! The process of feeding them some natural gas or propane to increase combustion temperatures and reduce deposit build-up. They make kits for diesel trucks for this (Bullydog) because it also boost HP & torque.

Ah, thanks. I had heard of using LPG for power boost, just hadn't heard that term and didn't know it also helped with deposits.

oil pan 4 · March 2011

Re: Selecting the correct backup generator

I was wrong about that 5kw 4-pole kubota I work on. Friday I filled one up and it holds just over 11gal, not 14 or 15. I was thinking of another type of unit.
I don't work on the tiny ones as much these days.
So 3 nights around 36hr for less than 12 gallons of diesel.
I have had these engines completely apart before and they dont wet stack or soot up or any thing running a 40% load for thousands of hours.
The only generators I have that wet stack are the big ones that normally get run at like 2% or 3% load continiously.

The way you un-wet stack them is run them at as much load they hold for a few minutes to 20min until the smoke lets up.

What I did for years until I got a generator was I bought a stand alone inverter and hooked it up to a vehicle battery to run the small loads when the power went out. You can use your vehicle as a little generator for short peroids.

Propane and natural gas fumigation when done right can help the engine last longer, the engines run cleaner, less soot gets in the oil, the oil stays cleaner longer, the flameable gas aids the diesel in completely buring up.
Any flameable gas or easy to vaporize liquid can be used. Something having a high "octane" rating helps avoid pre-ignition. Methanol, ethanol, propane and methane all have "octane" ratings near or well above 110.
Fumigation with Ethanol or methanol is called a "hot shot".
Water Methanol mixes are used to cool EGT's and boost fuel mpg.
When I ran propane funimation I had an EGT gauge and the temp read no different unless I had it floored.

BB. · March 2011

Re: Selecting the correct backup generator

It would be neat to see auto start 2kW diesel or propane gensets... Guess that market is just too small now.

I would suggest to people that they put some sort of Watt*Hour meter on their genset and do a kWH per Gallon (lb, liter, etc.) measurement and see what their "mileage" really is.

I have seen people's whose numbers for diesel work out to 7kWH per gallon (or even more).

A typical "noisy" 3.5-5kW genset probably gets around 6kWH per gallon at full power. If we assume that these gensets run about 1/2 fuel flow on 0-50% output loading, running 400 watts on a 5kW genset would be (these are just rough guesses and assuming a fridge, few lights, radio will average 400 watt draw):

0.5 * 5 kWH / 6kWH per Gallon = 0.42 gallons per hour
0.4 kWatts * 1 Hour / 0.42 gallons per hour = 0.95 kWH / gallon

A Honda eu2000i is spec'ed at 1,600 watts * 4 hours @ 1.1 gallons or 400 watts @ 9.6 hours on 1.1 gallons of fuel:

1.6kW * 4 hours / 1.1 gallons = 5.8 kWH per gallon
0.4kW * 9.6 hours / 1.1 gallons = 3.5 kWH per gallon

Assuming (just to get some numbers for an example here) that Oil Pan 4 was running his 5kW diesel at 40% load, 11 gallons for 36 hours:

5kW * 36 hours * 0.40 / 11 gallons of diesel = 6.5 kWH per gallon

Which would be pretty fuel efficient.

If you needed ~2kW or more of electric power during an outage, that 5kW diesel would be the way to go... If you needed ~400 watts or so to run "your home" during an outage, then I would humbly suggest a smaller genset as it would only use:

36 hours / 9.6 hours per gallon = 3.75 gallons of fuel

Or about 1/3rd the gallons of fuel (price of diesel/gasoline, transportation, storage, also are part of the decision process) for the same time frame.

A standard 5kW "noise maker" genset powering a 400 watt load would run about 0.42 gallons per hour or:

0.42 gallons * 36 hours = 15.1 gallons of gasoline

Even more fuel that the 5kW diesel supplying a 2kW load (vs 400-2.5kW for the gasoline genset).

Again, power usage/needs are a very personal choice... Just suggesting ways to help you make your own decisions about what will work well for your setup.

Please note, the numbers above for the diesel genset are just guess work on my part--Oil Pan 4 may be able to tell us what his loads actually where and we can work out the real fuel flow equations.

-Bill

oil pan 4 · March 2011

Re: Selecting the correct backup generator

These generators run two 1000w halide lamps.
I would say fuel consumption isn't bad, right around 2lb/hr for a 2kw load.
If this were my personal generator I know I could get better fuel economy, I would mod it by tossing the belt driven battery charge alternator and running a charger off 115VAC power. Install a larger radiator so the fan wouldn't be needed that often and ditch the belt driven fan for an temp switch controled electric one, powered by AC. Lastly make the generator speed switchable between 50 and 60Hz, That way I can run low power loads (if I have to) on 50Hz and save some fuel. It would be 300 less RPMs.

I have a lot of crap to run and I would want to be able to make my equipment mobile.

As of 2010 the density of petroleum diesel is about 0.832 kg/l (6.943 lb/US gal), about 12% more than ethanol free petrol (gasoline), which has a density of about 0.745 kg/l (6.217 lb/US gal).
E10 gas weighs in at about 6.12 lb/gal.

Selecting the correct backup generator

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