Sizing a whole house generator for a 3 Ton Air Conditioner

Deveak

Solar Enthusiast
lol bounder can barely pull it, not legally. i think its about 6000lbs plus the steel trailer is probably another 1200-1500
Generator is for the farm mostly for irrigation well pumps. in a dry summer we can easily go thru 3000 gallons of diesel a month.
Farming gets expensive lol.
At that fuel cost have you considered building a solar trailer? What kind of peak and continuous output do you need? You could put a smaller Diesel engine with a 200-300 amp alternator for fuel savings and instant power if needed.
 

2009Bounder2020

Solar Enthusiast
At that fuel cost have you considered building a solar trailer? What kind of peak and continuous output do you need? You could put a smaller Diesel engine with a 200-300 amp alternator for fuel savings and instant power if needed.
Ya but its farming so hit or miss on the rain. Normally just a month or 2 a year, some years like last year we didnt need to irrigate most of the fields. I forgot we use same diesel for a couple small tractors we use to mow and pull trailers around the farm . We have off grid solar to run the main house , morton buildings , barns, with fixed propane and generator backups. We cut the utility power cord about 5 years ago, never have second thought it. The irrigation in the fields we move the generators around as they dont run 24/7we have 400 acres but its on 6 different properties within 100 miles of each other. We probably have about 40 well heads. We have 8-9 generators of various power/age most are old diesels, they dont really die if you maintain them. Im upper 40s and some were grandpas when he was young. I cant see some of the home depot versions lasting that long but what would i know about generators.

this generator is overkill but it can run 3-4 well pumps and only be at maybe30-40% is the largest load draw, but the pumps are not soft start so its good to have excess capacity. I was more saying to look for local used diesel generators, Ive seen what those generac small units prices go for and you can probably find used diesels easier than you think if you look around, wont be same brands as home depot.
 

Hedges

Photon Sorcerer
Which is why I was teasing you about it, questioning the wisdom of getting such an oversize generator (turns out it wasn't.)

3000 gallons, whether you pay $2 or $4, I'd think PV to reduce fuel consumption would have quick payback.
Depending on the curve of fuel consumption vs. load.

Next thing I'd consider is PV direct to VFD, let pump speed vary according to what sun produces.
 

2009Bounder2020

Solar Enthusiast
10-4 , i forget not everyone is a farmer lol. the red diesel (off highway) helps , and i didnt figure in the 10-20% probably goes in the lawn mower and bobcat and small tractor.

the caterpillars start off at around 20K which is probably the right size for a typical 3-4 bedroom suburban house with some headroom same size as the generacs but i would take a 20-40 year old Cat over a brand new generac any day, they dont make them like they used to.
 

Aussietrucker

New Member
i would look at used cummins, detroit diesel or caterpillar generators.
I picked up a 125KW Cat for $8000, rebuilt it for $2K,

10 times the output and half what you will pay for a generac
You should get one of a size that it will be loaded up diesels don’t like being under loaded for long periods they will glaze up and start burning oil excessive fuel usage ect and will need pulling down and re honing
 

Diesel Pro

New Member
Echo the comments about a Secure Start for the compressor. We have a 6 ton geo and even on line voltage I could tell by the lights when it started. Now I cant tell a thing.

Kohler makes a very nice residential generator. We put in s 20kw back in 2009 when we built our new home. Would be really nice to see inverter technology work it's way into these models so they can slow (and quiet) down. Also look at configuration to determine which way the exhaust outlet faces for noise. Ours is under a corner overhang and unfortunately the outlet faces into the corner rather than away.

Last time I checked Onan had a very quiet spec.

Also one with an auto exercise feature to start and run weekly. I just run unloaded exercise on ours

For fuel I would recommend propane. Natural gas may be more convenient and less expensive, but in the event of a natural disaster having 250-500 gallons of non spoiling fuel on hand would be ideal. Gasoline or diesel fuels are not well kept for years which is often the case with backup generators.
 
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