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DHW Mixing Valve on Steam Boiler Incorrect?

Kafox15Kafox15 Posts: 8Member
Hi All,

Our Peerless steam boiler also provides hot water using a tankless coil. The mixing valve on the hot side of the coil (Watts LF70A) had a slight leak which I corrected by tightening the packing nut.

But while I was doing some research in case I needed to buy replacement parts, I found the installation guide for this mixing valve and the setup looks NOTHING like how mine is configured. I am curious if its worth the effort to reconfigure my mixing valve per the instructions or if it doesn't make much of a difference.

Here are the instructions:
https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/11899-source/1910210.pdf

My setup:

Comments

  • Intplm.Intplm. Posts: 1,034Member
    @Kafox15 I didn't need to read your directions attachment to know what's wrong with your installation. It's not trapped/installed below the domestic hot water coil, and it will surely leak again.

    But before you go to the trouble of reinstalling it, please do this instead..........get rid of it.
    What you have is a incorrectly installed "tempering valve" These things are notorious for failure and incorrect installation. This type of valve needs to be installed below the coil to have it last.
    But even when you do install them below the coil they fail (old technology). So, get rid of the thing and install in its place a "thermostatic mixing valve."
    This type of mixing valve can be replaced in -almost- the same way as your current defective valve and will last much longer with little to no trouble while providing a more comfortable temperature.
    They often look like this one from the honeywell company. There are other brands that I have found that work comparatively from Caleffi, Watts, Webstone, Symmons.
    So before you go to the trouble of reinstalling the one that you have, change it too. You will be happier in the long run.
  • Kafox15Kafox15 Posts: 8Member
    Intplm. said:

    @Kafox15 I didn't need to read your directions attachment to know what's wrong with your installation. It's not trapped/installed below the domestic hot water coil, and it will surely leak again.

    But before you go to the trouble of reinstalling it, please do this instead..........get rid of it.
    What you have is a incorrectly installed "tempering valve" These things are notorious for failure and incorrect installation. This type of valve needs to be installed below the coil to have it last.
    But even when you do install them below the coil they fail (old technology). So, get rid of the thing and install in its place a "thermostatic mixing valve."
    This type of mixing valve can be replaced in -almost- the same way as your current defective valve and will last much longer with little to no trouble while providing a more comfortable temperature.
    They often look like this one from the honeywell company. There are other brands that I have found that work comparatively from Caleffi, Watts, Webstone, Symmons.
    So before you go to the trouble of reinstalling the one that you have, change it too. You will be happier in the long run.

    Thanks for the advice and sorry for the late reply! Looking at supplyhouse, there are over 100 different options of thermostatic mixing valves just from Honeywell-Sparco. How should I go about determining which one I need?

  • GrallertGrallert Posts: 358Member
    If I recall the temperature range will be listed and marked on the sticker on the valve. I forget the ranges put you'll want one that goes no higher than 120 I think. Though that's very hot. Looks like that piping is 3/4"? You will also have to do some pipe rearranging.
  • hot_rodhot_rod Posts: 12,350Member
    edited January 21
    You want a valve with a ASSE 1017 listing, that is considered a point of distribution valve.

    An ASSE 1070 is a point of use valve, lower Cv, limited to 120F maximum.

    Look at the max, inlet temperature also, some are 180, some 200°

    Install it with a heat trap as Intplm mentioned, the directions should detail how to do that.

    The Caleffi 2521 is a solar rated valve, 210°F inlet rated for high temperature systems.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • hot_rodhot_rod Posts: 12,350Member
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Intplm.Intplm. Posts: 1,034Member
    Kafox15 said:
    Yes that is a very common one. It may also be offered in different connections other then "sweat ends", if you want.
  • Kafox15Kafox15 Posts: 8Member
    Intplm. said:

    Kafox15 said:
    Yes that is a very common one. It may also be offered in different connections other then "sweat ends", if you want.
    Yea, my only experience with plumbing so far has been Sharkbite, so I would need to practice soldering before I took this on.

    I see that sharkbite does make a version of this, but looks like the max temp is 200 and I know steam gets to 212.

    Any other options that wouldn't require soldering?
  • ethicalpaulethicalpaul Posts: 1,336Member
    Watch a couple youtube videos and practice on some pipe and fittings from HD and you'll have it in no time.
    1 pipe Utica 112 in Cedar Grove, NJ, 1913 coal > oil > NG
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