Tempering tank before electric water heater?

Discussion in 'Water Heater Forum, Tanks' started by Scuba_Dave, Feb 6, 2009.

  1. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    So after measuring the water temp (about freezing) I'm thinking that a "tempering" tank before the electric hot water heater might be a good idea.
    Its a 50g water heater, no problems with getting enough hot water
    Its set to 120 degrees

    If I wanted to install a "pre-heat" tank of sorts what would be a good tank to use? My basement in single digit weather is around 55. Most of the time its 60-63

    Heating that water from 32-55/63 must take a bit of energy

    Thoughts?
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,485
    Location:
    Cave Creek, Arizona
    tank

    Unless you connect power to it, which would then not save you any energy, just distribute it differently, a plain, unjacketed storage tank would eventually make the water temperature equal to whatever the ambient temperature is.
  3. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Thanks, that's what I'm thinking of doing
    Unjacketed would allow it to reach room temp, which is my aim
    Since the majority of hot water is used in the morning I think this would help
  4. jch

    jch New Member

    Yes, but your room temperature would drop (the law of conservation of energy). So, in the summer when you're not heating your house, it might help.

    But in the winter it would not save you any energy usage--any energy saved for heating water would be exactly offset by increased energy usage in bringing your room back up to temperature.

    You're better off installing a GFX (Gravity-Fed heat eXchanger) on your DWV piping to recover heat from the warm water leaving your house. Typically you can save about 40% on your water heating bill.

    .../j
  5. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    The same amount of water would be coming into the house
    So I don't see the room temp dropping any more then it does now

    Electric HW, no vent pipe
    But a good idea fore the main boiler exhaust
    My only concern is that if the boiler exhaust is cooled too much, it will not rise properly (2 floors up to chimney)
  6. it works great

    as long as youhave the room,
    a water heater with a naked back up tank
    will literally last forever due to less shock on
    the hot water tank...

    I havent got a clue as to how much money you will save,
    and just for fun you ought to put a blanket on the
    main tank to hold that heat in.....

    thats like squeezeing the very last drop of energy you
    can out of it....very close to overkill.....


    now if you really want to go nuts,
    go buy a 300 foot
    roll of wirsbo pex and lay that out in your attic,,,and run the cold
    water through that before going into the back up tank.....
    Last edited: Feb 26, 2009
  7. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    I don't have an attic :(

    I picked up a water heater for free
    Now I have to see if it holds water, they said it did
    If not they may find it back on their front lawn :p

    I will need to build a cradle to hold it
    Unless I can strip the insulation/sheathing off the outside & leave the bottom intact

    I want to collect a few more tanks & build a solar hot water heater outside. The back of the house faces due South. I have a solar water heater for the pool & initial water coming out is 130+
    After continuous running it is between 95-105 depending upon how sunny/hot it is outside
  8. chris8796

    chris8796 New Member

    Messages:
    100
    Location:
    Illinois
    The overall heat transfer coefficient for an air-steel tank-water system is about 2 btu/ft^2 hr F. You'll need (50g x 8.8 lb/g x 25 F) 11000 btus of heat to bring your tank up to room temp. I don't think you'll get much usefull heat this way. link

    I would use it as a pre-heat/storage tank and combine it with your solar system.
  9. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Actually there have already been several systems built using tanks
    One system has 3 tanks totaling over 120g of water
    Tubing is also used in the system to heat the water
    Temps over 160 are quite common & in fact a way of cooling the system was needed as the person had the glass glazing shatter

    I will use a secondary loop to my pool as an over temp limit
  10. I wish I had the time

    I wish I had the time to putz around with

    solar systems in my back yard....
    too busy to mess with them...

    If I did have the time I would put a flat air solar panel
    up on my flat roof and put a fan on it and heat one half of the house with it...


    but that is for retired people to dream of...
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