backup generator capacity question

Discussion in 'General Discussions' started by Guest, Oct 21, 2008.

  1. Guest

    Guest Guest

    I would like to get a diesel generator to backup a 6 ton geocomfort unit but don't know how to determine the capacity needed (even with the data on the front of the unit). Any guidance or direction pointing will be appreciated.
  2. Guest

    Guest Guest


    You'll have a hard time finding a diesel generator that small. Natural gas, gasoline (which I dont't recommend because fo flammable and fire issues) or LP gas is possible. A six ton unit consumes about 6 kw and a reasonably sized generator for that load, allowing for starting inrush would be about 12-15 kw.
  3. Guest

    Guest Guest

    Northern Tool has a 6500w Surge, 5000w running Diesel that looks reasonably priced...
  4. Guest

    Guest Guest

    Thank you! I couldn't find this information and I suspect that there are or will be some other internet searchers who will find your reply very helpful as well.
  5. I disagree that natural gas is inherantly flammable and dangerous. The only way that natural gas is dangerous is when you have serious leaks. Those leaks have to be at least at the 4% level.These systems are not installed carelessly, at least not where I live.

    I do not recommend that any of these systems be installed IN a house.

    Natural gas however, is LIGHTER than air. It dissipates naturally, which means explosions are not likely or common, because the gas goes up, and doesn't collect on the floor, etc.

    It also burns exceptionally clean which means there is virtually no wear on the engine. Oil in the generator does not have to be changed frequently!

    Now propane is slightly different. It too can work well, particularly outdoors, BUT propane is heavier than air. So when contained in an enclosed space, a leak will collect at ground level, and unless ventilated, will or can explode at 4% concentration.

    Since many, many house already have natural gas, it is very easy to install and will work when power lines go out.

  6. Designer_Mike

    Designer_Mike Member

    I agree. Get a generator that you already have the fuel for....Nat gas, propane? They are far more popular than diesel for many reasons.

    Either of which are very safe when installed properly.

    Do you want to buy another fuel tank? Have to worry about another fuel delivery?
    ...another remote possibility. At $4 a gallon, an outdoor tank might hold $1000 just waiting for someone to back up and suck it dry.

    Diesels can be noisy and stinky at start up. And it would REALLY suck when power goes out on the coldest night of the year and you learn that your fuel supplier gave you #2 fuel that just gelled up rendering your generator useless. OR just as bad, you didn't check the fuel level and the monthly exercising ran the tank empty.

  7. I am a commercial hvac tech with responsibility for about 6 commercial standby diesels in most of my buildings. They can be expensive to maintain and fix and HAVE TO BE CONSTANTLY HEATED IN WINTER MONTHS to enable them to start immediatley so you don't run the battery down at temperatures below 70 degrees. The heater alone will draw 100 - 200 watts continually, though they are not critical above 70 degrees. (With a gasoline, or natural gas or propane generator, you can fill the crankcase with the correct weight synthetic oil ((AMZOIL)) which will allow the generator to crank easily without heating (if the cranking battery is heavy duty and not El Cheapo)

    Emergency generators have to be test run every month, to prove they can start, and to keep things moving and lubricated, (just like cars) fuel filters have to be changed EVERY year, to prevent clogging.

    Even if the diesel is heated say with a cooling system tank heater, 24 / 7, remember that during a ice storm power failure at 18 degrees F, that oil in the crankcase is getter thicker and thicker and thicker quickly.

    The diesel generator has to start successfully immediately. If it does not, it becomes virtually impossible to start a completely cold diesel generator at 18 degrees ambient without two additional tractor trailor truck batteries standing by fully charged and ready to go.

    Florida or South Carolina is one thing, northern states, another.
    Last edited: Mar 3, 2011
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    We have posted the WF generator sizing chart here previously.
    You need to look at it and know whether or not you have intellistart.
  9. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    "guest"'s posts are highly suspect

    A 6 ton heat pump likely has a locked rotor amp value (startup inrush current) of 150+. Intellistart likely drops that by half or more, but I'd still want generator seller buy-in (warranted performance) for any unit less than 20 kW even with Intellistart.

    Breezily writing that 12-15 kw will start a 6 ton heat pump demands supporting documentation.

    The suggestion of a Northern Tool 6500 Watt surge / 5000 Watt Diesel generator for this application is sheer lunacy.

    Both my cars are Diesel-powered...that said NG or propane are much better suited for residential standby generators

    Exercising any standby generator for 10-15 minutes weekly is cheap insurance.
  10. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Waterfurnaces sizing chart does not require a 20K generator with intellistart.
    That said, I agree a home that requires a 6 ton unit would likely require a 20 KW back-up generator.
  11. Masoud

    Masoud New Member

    The guests have departed. They visited briefly in 2008.

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