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Thread: Hot Water

  1. #1
    DIY Junior Member essjay's Avatar
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    Default Hot Water

    Just replaced 1965 era DW supply from meter from 1/2 to 3/4 copper and added in a PRV. Now working on main HW line. Two questions I have.

    First, I am adding a 40 gal HW heater tank being fed from existing boiler HW line. Boiler has expansion tank on cold water feed already. Do I need to add another expansion tank on boiler output HW line feeding into new HW heater tank?

    Second, coming off HW heater I was thinking about using 3/4 until after 2nd floor bath feed (sort of as a 'manifold' effect) in order to minimize HW warm up time to fixtures. If both 1st and 2nd floor are using HW, the 3/4 could supply both adequately without effects of just a 1/2 HW supply throughout and potential HW 'starvation' to both.

    Thanks.

  2. #2
    In the Trades LamdaPro200's Avatar
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    If your adding an Indirect Fired Hot Water Heater it would be part of the closed hydronic heating system and the existing exp tank on the boiler takes care of that. With that said you may have to add a Thermal Expansion tank on the cold water if you added a backflow preventer on the cold water main. It should be clearly referenced in the indirect hot waters installation manual. Generally a product such as an Amtrol ST-5. http://amtrol.com/thermxtrol.html
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Code doesn't want any valves between the inlet to the WH and the expansion tank. While it could work anywhere in the cold supply after the prv, if there's a valve, it might become isolated from the WH, and then you'd have the T&P leaking since there'd be no place for the expanding water to go. Do not confuse the boiler's expansion tank on the heating circuit with one for the potable water...you need both.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    DIY Junior Member essjay's Avatar
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    The hot water tank being added is NOT an indirect (too $$$). I am going to be using a stand-alone HW heater (electric) which will be just for the cold winter months. It will be bypassed and drained for the warm summer months. It seems that the boiler, when DHW is set at 120deg (for anti-scald purposes), cannot handle the heating of 33 deg winter water to a reasonable shower temp in the cold winter months (the milder months, with 50 deg cold water are handled fine). I could crank up the boiler HW output temp, but again, anti-scald is more of a priority.

    The expansion tank will NOT be 'valved' out of the system. It will be added/supported on the stand-alone heater inlet AFTER a bypass ball valve as per code.

    Any thoughts on the 3/4 feed out of the stand-alone HW heater as described above or would there be no real benefit (ie: overkill) to doing it this way?

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    Two things: where I live, you are required to install a tempering valve on the WH; it depends on what's being fed from the lines whether it should be 1/2" or 3/4" or maybe even larger (but that wouldn't help unless the supply and WH were sized accordingly). While it isn't as efficient, if you get a well insulated WH, and use a tempering valve, you can usually run it at any temp you like and 160-degrees in the winter might be fine to keep up with your water needs with the tempering valve set to 120-degrees for safety. Larger supply lines means that after a long period of disuse, it will take longer to purge the room-temperature water from them, but ultimately, you'll be able to supply more things without noticing and loss in volume. It all comes down to how much you're asking the system to supply at any one time.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6

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    the only way you will lessen wait time for hot water at distant fixtures is to install a recirculating sytem. insulating all hot water lines is never a bad idea either - not for wait time, just generally

  7. #7
    DIY Junior Member clarissa13's Avatar
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    Sorry, i'm not sure how to ask a new question and since it's about gas lines...

    I have a small gas heater stove in my country kitchen. This week i discovered the valve has a small gas leak. I'm replacing the valve, not that big of a job. However, when I went down into the basement to shut off the gas I noticed something strange. The gas is shut off. One of the pipes coming off after the regulator - the pipe is cold then, the union is warm and the pipe is cold again. I've never experience a warm union. Does anyone know what this means or it it's okay? Thanks!
    Last edited by clarissa13; 05-11-2013 at 08:35 AM.

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