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buying a domestic hot water heat exchanger for my OWB

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by 2rod, Jan 8, 2014.

  1. 2rod

    2rod New Member

    Joined:
    Jan 8, 2014
    Messages:
    1
    Loc:
    north carolina
    hello all new to this site and looking for some educated advise.

    I am currently heating my home with an Earth outdoor water furnace. After heating with it for a few years my wife and I are wanting to also start heating our domestic hot water with the furnace as well.

    I will have to install a heat exchanger at the electric water heater to accomplish this as the OWB does not have a coil in it for domestic water. There seems to be two options a brazed plate in series with the current water heater's supply or a sidearm exchanger that mounts to the drain and relief valve of water heater.

    It seems like the sidearm would keep the water heater from needing to run while we were at work and not using water, whereas the flat plate would only heat the water when the hot water was being used and the tank was refilling.

    Could the brazed plate heat exchanger be used in an "on demand" fashion, where I could plumb it so that I could bypass my water heater when I am heating the house with the OWB? Or would a sidearm heater work better to eliminate the need for an electric hot water heater all together?

    Also, will either of these heat exchangers work efficiently if I plumb them in series and downstream of the water to air exchanger for the furnace? Will heating my domestic water in any of these fashions drastically increase my wood consumption?

    Sorry for being so wordy and thanks for any help.

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  2. phantomblack

    phantomblack New Member

    Joined:
    Jan 3, 2014
    Messages:
    27
    Loc:
    wisconsin
    I am using the sidearm with my OWB. We have a 60 gallon gas fired hot water heater and when the OWB is running I unplug the water heater and turn off the gas supply. The hot water that the system will supply is almost limitless.

    Only time that I ran out of hot water was when I was using the super hot water that the sidearm provides in my pressure washer to pressure wash an old john deere tractor project I had. It was a pretty nice hot water pressure washer! I washed for about 1.5 hours before the hot water supply ran out.
  3. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    4,925
    Loc:
    Nova Scotia
    How big is your existing hot water heater?

    Generally, a sidearm works by convection on the domestic side while a plate HX is pumped. But those aren't fast rules, some do the opposite. I have a sidearm installed heating by convection, and later bought a plate HX & pump - but haven't put those in yet. I did that (got the plate) mainly because when heating from storage in the non-burning season, the sidearm doesn't transfer heat as good. I wouldn't aim for replacing or bypassing the existing tank, but rather for heating it with wood - it's nice to have a backup in place for when the fire goes out. Sidearm is simple and will likely do the job with hot enough water going to it. I've found that if the water going to mine is below 140 or so, it isn't very effective. Make sure you temper the hot water leaving the tank, it can get pretty hot.

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