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  1. #1

    Wattage of gas furnace and gas water heater for generator

    Hello Pros,

    After Superstorm Sandy many are thinking of getting a generator. No power for several days was not fun. I need to understand my power needs.

    How many watts of electricity does my gas furnace consume (normal and peak)? Here are the specs: Carrier Infiniti 96 Furnace, Model 58MVB080-1-14. I have two of those and could probably run just the 2nd floor for sleeping comfort.

    How many watts of electricity does my water heater consume (normal and peak)? The specs: Bradford White, Model MITW50L6EN12 (48 gal). It's gas, but has an electric fan on top to vent to the outside. Not sure if electricity is used in any other way there.

    Many thanks!

  2. #2
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,140
    Your furnace Is very complex unit with lots of electronics. The first time you are running a gasoline generator and a high load appliance such as a freezer or sump pump comes on, you could fry your electronics. You will also need to pound an 8' grounding rod in the ground if you want any chance of saving your electronics. My opinion,,, install a natural gas home standby generator. They are way way more forgiving. The answer to your question,,, I would assume 1500watts to be safe. That is a very overkill number though.
    ...

  3. #3
    Yes, I know that some cheap gasoline generators can produce low quality electricity. But what about the higher end gasoline models? Stationary standby generators are very expensive. $7K-10K is an average price with installation. I am hoping that a gasoline model with inverter, connected through the inlet installed by an electrician could be solution that won't fry my furnace's electronics. However, I would like to hear more opinions.

    Also, 1500W for a gas furnace blower seems like a lot. I was under the impression that the blowers are not energy hogs, but I wasn't sure. When we run A/C (heat pump), I was told to keep blower running all the time in low mode and it only consumes as much as a lightbulb.

    In any case, if anyone knows the wattage for those appliances, please let me know. Your opinion on the generator is also welcome.

  4. #4
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,557
    I would say you definitely need to talk to a local electrician who understands the local code requirements for standby generators, and can advise you on how many appliances you can run on a reasonably priced generator. A good gen with a sinuousoidal output and load regulation can be had for much less that the permanently installed variety which are powered by natural or LP gas. It is no longer common practice to go driving extra ground rods all over the place. That's the way electricity was done 10 years ago. The electrition can advise you on placement of an equipment grounding conductor that will do the job just fine.

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I bought a basic Generac 2000Watt Inverter generator so I could run my furnace & tankless water heater, or Microwave, or Toaster oven, or refrigerator, or coffee maker along with dragging out seom LED christmas lights and stringing them for temp lighting.

    Antoher option is to buy a power inverter and use one of your vehciles to run thet furnace. You could probably run it for 15 minutes every 3 hours and keep the house at 60F. A 1000Watt inverter should be plenty for the furnace.

    One catch, you may need to run an independant ground so that the flame sensor will work correctly. My builder grade Carrier furnace throws a code for incorrect polarity, but still runs. I haven't tried it with a dedicated ground, but I bought a large cable ot groudn hte genrator. A good ground for a portable generator is a good idea for safety. Metal plumbing tied to hte houses ground is OK, but a dedicated grounding rod is better.

    A transfer switch is best, but as an alternate I wired in a plug, so I can unplug the furnace then plug it into an extension cord. However, this may not meet most local codes or manufacturers installation requirements, so I can't recommend doing that.

    How clean is the power on standby generators? Good question. I suspect it's better than smaller portable units, mostly because it won't have as much of a voltage droop when a large load comes on. However, it's still not a clean sine wave. We have quite a few commercial standby generators at my work and one hte one that has rooftop package gas heat, doesn't have any issues. All of our computer systems and instrumentation however that runs off back-up standby generators usually have a UPS. THe best system is to have a UPS, but it adds a lot of cost and maintenance. On the upside, you could combined a UPS with a solar charging system and get some tax credits and generate power year round.


    For hte cost of a standby generator, I'd almost rather install a direct vent fireplace, then get a small inverter generator just for computer, lights TV and maybe the furnace on a small dedicated transfer switch.

  6. #6
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,557
    Sorry, a grounding rod is not okay in place of an equipment grounding conductor. A good generator will have a nice sinusoidal output you can run just about anything on.

    On the other hand, many inverters used in vehicles are most certainly not able to produce a sine wave and instead they produce a modified square wave that will play havoc with most electronics.

  7. #7
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 11-06-2012 at 05:36 AM. Reason: Non Pro * Member

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,082
    [Bcindyandwade][/B], this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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