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Electric Water Heater In A Power Outage

Post in 'DIY and General non-hearth advice' started by velvetfoot, Jul 31, 2013.

  1. velvetfoot

    velvetfoot Minister of Fire

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    A while ago I switched over from an oil-fired indirect tank to an electric water heater. We had a short power outage the other day, which got me thinking of how to operate the electric water heater in an outage.

    I have a 7500 w continuous gasoline generator that can run the deep well pump. I figure turn that off, and heat up the water and then turn the water heater off and then take showers, etc.

    Thinking of (precious) fuel consumption, how long does it take to heat up a tank of water?

    I could re-align valves, and place the indirect tank back in service, but that'd take some time and thought and then I'd have to drain the tank, etc, ie, laziness factor.

    Thanks.

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  2. vinny11950

    vinny11950 Minister of Fire

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    don't know the type of generator you have, but your water heater might need clean inverter electricity.
  3. maple1

    maple1 Minister of Fire

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    A newer electric hot water heater will stay hot for quite a while in a power outage - how long are your outages usually?

    I wouldn't think it would need 'clean' electricity - it should just be a couple of resistance elements. It should work, but the elements might not heat at full capacity - but should still not take that long to heat, electric heaters have pretty quick recovery as is.
  4. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    The elements are 4,500 watts and just fire one at a time. Should warm it right up with that genny. I have never timed mine but it doesn't take long.

    You could get a guess using the BTU info for 4,500 watts.
  5. ewdudley

    ewdudley Minister of Fire

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    50 gallon times 8.33333 lb per gallon times 1 btu per degF lb times 80 degF = 33,333 btu to heat 50 gallons from 60 degF to 140 degF.

    4500 watts times 2 hours = 30,709.275 btu.

    Power outage plus hot showers from gasoline generator equals expensive luxury.
  6. Highbeam

    Highbeam Minister of Fire

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    No clean energy required. Super simple resistance heat. The balanced 240 resistance load will be easy for the genny to handle. No surge or anything at the startup.

    Though the tank will hold hot water for a long time, taking showers will drain it and fill the tank with cold water as you consume the hot.

    Do you have enough expansion tank capacity on your well to allow a full shower before you lose pressure? Either the water pressure or water temperature will be your weak link. One will fail you first and that is the one that I'd leave on genny power while you're showering.
  7. velvetfoot

    velvetfoot Minister of Fire

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    BB, so it doesn't take too long. Thanks.
  8. velvetfoot

    velvetfoot Minister of Fire

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    I know the well and water heater would have to be phased.
    Two hours seems like a long time when trying to conserve gasoline.
    The scenario would be multiday outages. Maybe I'll rethink the oil-fired indirect. The boiler needs next to nothing in the way of electricity.
  9. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Highbeam is correct. My pressure tank will crap out long before I run out of hot water. Shower takes about ten gallons.
  10. Highbeam

    Highbeam Minister of Fire

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    This assumes some things that aren't true. First, you don't need 50 gallons for a shower so you don't have to reheat 50 gallons. Second, you don't need 140 degree water for a shower so of the 50 gallons, you are mixing it 50/50(?) with cold water.

    Then, two hours on a genny at one gallon of gas per hour plus whatever fuel it takes to pump the water is less than 10 bucks. When the power has been out for a few days, that 10 bucks is well spent on a hot shower.
  11. velvetfoot

    velvetfoot Minister of Fire

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    My concern isn't expense but availability of gasoline.
  12. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Another thing to keep in mind is that if that electric water heater level gets below either element, when that element fires it fries. Killed both elements in mine once after I had drained the house for a long trip in winter. Rushed back in the house, started the stove and flipped the water heater breaker before the one for the well pump. Whoops. Killed both elements instantly.

    The water heater we have now is protected against that happening. The trade-off being that it sometimes loses it's electronic mind after a power failure and doesn't restart without manual reset.
    fbelec likes this.
  13. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Our emergency cabinet contains two cases of baby wipes. $11 bucks a case. Not good for hair washing though. >>
  14. Highbeam

    Highbeam Minister of Fire

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    We have an RV in the shop with a shower and 60 gallon tank full of water all winter. Two 7 gallon tanks of propane provide lots of hot water, the pump is 12 volts and powered by two big deep cycle batteries that are also full, furnace, television, lights. It's not just for camping, it is a self contained safety cabin.

    On the element issue... you only fry elements if you run them dry so you not only must lose water pressure but you must somehow let air into the water heater. This is pretty hard to do accidentally. You would have to leave a hot water faucet open upstairs while also leaving a hot water faucet open in the basement to siphon the tank dry.

    Simply losing pressure to the water heater won't create a dry element issue.
  15. Jack Straw

    Jack Straw Minister of Fire

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    Heat water on wood stove and take a bath:cool:
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  16. fbelec

    fbelec Minister of Fire

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    if your boiler has a hot water coil in it pipe the coil with shut off's to the hot water coil with a pump and a strap on aquastat set at 140 degrees or what ever you like and a flow check and your allset for your water to come off your boiler that your generator runs
  17. fbelec

    fbelec Minister of Fire

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    every hot water tank that i've wired from dead cold to 125 degrees with 4500 watt elements takes 45 to 50 minutes to come up to temp. one shower would be around 20 mins depends on if you have alot of hair or bald like me:)
  18. velvetfoot

    velvetfoot Minister of Fire

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    I guess I could turn off the valves to the electric heater, turn on the valve to the Amtrol and fill it, opening the blow off valve to let the air escape, then start the boiler (if it wasn't already working as backup in winter). Then, I'd have to drain the thing later.

    Is opening the blow off valve a good way to do this? Last time I think I used a fixture upstairs.

    [​IMG]
  19. ironpony

    ironpony Minister of Fire

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    my high efficiency/ energy saver WH has a circuit board on it so it probably would like to see "clean" power. might want to check yours. also have 80 gallon tank and when used wisely had hot water for 7 days
  20. woodgeek

    woodgeek Minister of Fire

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    A well insulated tank will stay hot for days. I had (brief) hot showers through a 5 day Sandy outage.
  21. Jags

    Jags Moderate Moderator Staff Member

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    5 gallon stainless pot on the wood stove - bring it to 200F. Pour into bathtub and add equal amounts of cold water. Easy peasy.

    If it is summer time - replace the stove with the turkey burner.
  22. basod

    basod Minister of Fire

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    The thing with running showers is you're having to fill the entire length of pipe from the heater to the bathroom.
    You can plumb in a double valve(preferably locking if kids are around) at the hot water heater or use the drain with a hose and fill buckets for hot water - then mix with cold at the tub 1/wash 1/rinse.
    I keep two clean 5gal buckets with lids for outages, my master bath is on opposite wall of the heater so I catch water from the faucet in a bucket and then turn on the shower head to rinse.
    I've found running the hot water heater ~20mins prior to bathing is sufficient for two people. If more you may have to take shifts.
  23. btuser

    btuser Minister of Fire

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    I could figure out the proper solution for you but so far no one has mentioned the most important variable.

    How many women do you have in your house?
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  24. fbelec

    fbelec Minister of Fire

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    i had a friend the used a cheap electric heater with piping thru the inlet and outlet of heater with pump of the domestic hot water coil on the boiler it worked great.
  25. btuser

    btuser Minister of Fire

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    Figure out what your tank inlet temp is, then use that to figure out the rise (raw btu) needed for a "comfortable" shower.

    You may not have to heat the tank to 120-140F. There's a big difference between 40F and 90F.

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