Cottage Supplemental System

Discussion in 'Tankless Water Heater Forum' started by Jshape, Nov 9, 2009.

  1. Jshape

    Jshape New Member

    Nov 9, 2009
    We have a 5 bedroom cottage in Northern Michigan that we do not heat in winter. We drain out the cottage in fall and open it in spring. We do not have natural gas or propane – all of the heat is either oil or electric.

    The biggest problem we have for winter use is with hot water. We have a very good 50 gallon workhorse electric water heater that is plenty for our needs in summer. However, if my wife and I were to decide to go north for the weekend in the winter, we must fill the existing water heater, take a couple of showers, wash some dishes, and then drain it out when we leave. It’s not only time-consuming it is energy inefficient.

    I was thinking of adding an auxiliary system that would be used only in the winter and would allow me to bypass the rest of the cottage and only have hot water in one bath and the kitchen. Would an electric tankless heater work for this or am I better off to install a smaller (say 30 gallon) capacity tank-type heater for this limited use? My guess is that it would be used maybe two to four weekends per year. Energy costs are not an issue here because of the limited use.

    Any thoughts would be appreciated, including advice on tankless models that might work.

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Your incoming cold water there is likely to be near freezing. So the heater must raise the water temperature something in excess of 70-degrees. Since the water is only in contact with the heat exchanger for barely a second or so, it much transfer a LOT of energy in a short time. As a result, you'd need a really significant power input. It is likely that you would need to update your electrical service, but it could will be expensive because of the power upgrades you'll likely need (and this may change your monthly base cost since you'd have a bigger possible use...depends on how your utility bills things). You'd need to have some some special valves installed so you could blow the heater dry, as it would likely be damaged by even a small amount left in the heater.

    It would be far cheaper to dump the existing tank when you want to leave. Energy-wise, you aren't really thowing much away to do it a few times a season.
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  4. Thatguy

    Thatguy Homeowner

    Aug 27, 2008
    A bounty hunter like in "Raising Arizona"
    30 gals of 120F water mixed with 10 gals of 40F water gives you 40 gals. worth of 100F showers.
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