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Thread: Hot water heater vs. Indirect water heater

  1. #1

    Default Hot water heater vs. Indirect water heater

    Last fall I had installed a 48 gal. high recovery water heater manufactured by Bradfordwhite which provides barely enough hot water for 2 back-to-back showers using the Captain's Quarters 3 shower heads @ 2.5 gpm I purchased from this site. Now, my wife insists on removing the bathtub and installing a new shower with 4 Kohler Water Tiles @ 2.5 gpm and a 2.5 gpm handheld unit. The plumber who is going to do the installation has suggested that I consider installing a Munchkin Boiler and Super Stor Ultra Indirect Water Heater. While acknowledging that the Indirect Heater is not inexpensive, he states that I will save up to 50% on my gas costs. I have no way of determining how much I am going to actually save and how long the payback period would be. Alternatively, the plumber also suggest I see if the present setup will supply enough hot water and, if cannot, then we could always install the Indirect Water Heater later. I would like to get this project over at one time rather than doing it piecemeal, but I also don't want to make an unnecessary large expenditure. If I should bite the bullet now, then that's what I will do. Any thoughts or suggestions etc. would be greatly appreciated.

  2. #2
    In the Trades Bob NH's Avatar
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    Oct 2005
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    Your plumber sees a big payday ahead.

    Do a cost tradeoff to include consideration of putting an 80 gallon or larger tank type heater, maybe even an electric which has low temperature loss, in series with your high recovery gas heater. Operate both heaters at about 160 F and put a tempering valve after the second heater set at about 130F. In fact, for the space and cost of the indirect setup, you could put in two 80 gallon electrics.

    You will do very little heating with the electric heaters. You could even set the electric temp about 10 degrees below the gas setting and they would only use energy when after you have a very high demand. The electric heaters are largely storage tanks with temperature control.

    Variations on the theme would be to add another high recovery gas heater in series instead of the electric, or to put in a small circulator to let the gas heater add more of the total energy for recovery by circulating from the electric to the the gas heater.

    If you are in an area where you need space heating, you could get a unit that would combine water and space heating with an indirect heater.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
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    New England
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    A typical tank type heater uses maybe 30-50K BTU. An indirect is limited by the boiler size. That can be 250K BTU or more, (or less, smallest are usually around 80K). So, for the smaller area, an indirect can produce more hot water. But, do you need it, is the question, and are alternatives as good or better. Take a look over at the site for the boiler they are recommending, check out the size, look at the tank they are recommending. There will be charts of first hour delivery rate and volume.

    An indirect will be more expensive, but you may be able to do it in a fairly small area. If you have a need for hydronic heating (do you want or need to keep your sidewalks or driveway free of snow and ice), the boiler could give you those options that you would not have with plain HWH installation.

    Some boilers can be in the mid-90% efficiency, and good indirect tanks insulated so they only lose mayb 0.25 degree per hour sitting there. An electric HWH is about as close to 100% efficient, but what are your electric rates vs gas? No "normal" gas HWH gets to the same efficiency of the new boilers that I've seen.

    Take into account the space available, future options, maintenance issues, and see what works best for your situation.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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