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  1. #1
    Join Date
    Aug 2009
    Posts
    154

    What size portable generator for my Lennox G71V Furnace?

    I am going to purchase a portable generator for a few items in my home in the event of power failure. How much power will it take to run my Lennox G71V 110,000 Btu Gas Furance with ECM motor. I utilize this furance in 2 stage mode and not in modulating mode. Stage 2 for heat puts out about 1550-1600 cfms, however it very rarely gets out of stage 1. I will not be using the generator for my AC.

    Thanks.

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,272
    Quote Originally Posted by tomwk View Post
    I am going to purchase a portable generator for a few items in my home in the event of power failure. How much power will it take to run my Lennox G71V 110,000 Btu Gas Furance with ECM motor. I utilize this furance in 2 stage mode and not in modulating mode. Stage 2 for heat puts out about 1550-1600 cfms, however it very rarely gets out of stage 1. I will not be using the generator for my AC.

    Thanks.
    I did not discover the exact G71V spec required, but G61MP requires up to 1400 watts.

    See page 50
    http://www.lennox.com/pdfs/installat..._G61MP_IOM.pdf

    See page 51
    http://www.lennox.com/pdfs/installat...G71MPP_IOM.pdf
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,077
    You need a good generator with clean juice to run today's electronic furnaces. There's another board with many northeast members and there's been a lot of dicussion about this. Some were not able to get their modern products to work on their generators due to the quality of the AC current.

  4. #4
    Join Date
    Aug 2009
    Posts
    154
    I was looking into buying a Winco tri fuel 5000 continuous watt portable generator run on natural gas. My other option us a 20kw Kohler whole house generator, but the cost is very high. Was hoping to find a quality option for a reasonable cist.

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by tomwk View Post
    I was looking into buying a Winco tri fuel 5000 continuous watt portable generator run on natural gas. My other option us a 20kw Kohler whole house generator, but the cost is very high. Was hoping to find a quality option for a reasonable cist.

    There are options in between. Standby generators come in smaller sizes. You could get a 8KW genrators and run just the furnace and critical appliances like fridge and maybe 1 wall outlet for a toaster oven or microwave and a couple ligting circuits. They also have smart switches which can cycle various circuits based on demand. If I understand them correctly, it might allow for example allow you run the AC, but not the refrigerator at the same time, or run 1 AC at a time if you have 2. Even in this very hot July, in my larger home with 2 AC's, I still only averaged around 2.2kw-hrs. Take the oven and an electric clothes dryer out of the equation, and you peak requirments drop quit a bit.

    Carrier Infinity for example allows a remote input to disable 2nd stage as well. That would limit the running load to I think around 1500W or less on a 2 ton unit. IT definitely pays NOT ot have an oversized AC when your tryign to pair it with a standby generator.

  6. #6
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    3,113
    as long as it's a quality standby generator, not a portable cheapo, it will handle the load of any basic furnace under 3 tons of blower capacity. above that, the 115V blower motor will pull too high a load on the generator unless you go over 10KW.
    forget trying to start an air conditioning system with less than 15KW there are just not enough surge amps available to start the compressor.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  7. #7
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,272
    Quote Originally Posted by tomwk View Post
    I was looking into buying a Winco tri fuel 5000 continuous watt portable generator run on natural gas. My other option us a 20kw Kohler whole house generator, but the cost is very high. Was hoping to find a quality option for a reasonable cist.
    As soon as one buys generator, one has insurance that they won't need it 'for a decade'.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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