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  1. #1
    Join Date
    Mar 2007
    Location
    Western Montana
    Posts
    261

    Default Loop tween WH and Floor radiant heat

    Are you allowed to mix domestic (potable) water from conventional water heater, with a radiant floor heat system?
    If so, is a anti-backflow valve required?
    Any common brand names for backflow valves?

    House has a standard electric water heater. Looks like someone recently added an electric on-demand water heater, that has primary mission to heat floor radiant tubing in a new addition to house.

    The cold water supply comes into the DWH (for pre-heating?), then over to the electric tankless heater. After more heating, it then splits off to domestic water fixtures, and also to a small radiant floor loop. Cooled water from floor radiant heat system then loops back to mix with the incoming cold water supply, and starts all over again.

    Manufacturer is no help in install manual. I also see no expansion tank.

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  2. #2
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
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    26,252

    Default Re: Loop tween WH and Floor radiant heat

    From the 2006 IRC.
    - SECTION P2802
    - - WATER HEATERS USED FOR SPACE HEATING
    - - - P2802.1 Protection of potable water.
    Piping and components connected to a water heater for space heating applications shall be suitable for use with potable water in accordance with Chapter 29. Water heaters that will be used to supply potable water shall not be connected to a heating system or components previously used with nonpotable-water heating appliances. Chemicals for boiler treatment shall not be introduced into the water heater.

    - - - P2802.2 Temperature control.
    Where a combination water heater-space heating system requires water for space heating at temperatures exceeding 140F (60C), a master thermostatic mixing valve complying with ASSE 1017 shall be installed to temper the water to a temperature of 140F (60C) or less for domestic uses.



    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  3. #3
    Join Date
    Mar 2007
    Location
    Western Montana
    Posts
    261

    Default Re: Loop tween WH and Floor radiant heat

    Yeah, I read both of those IRC codes before I posted my question. If I read them correctly, those codes do not prohibit what I showed in the picture.

    The statement,
    Water heaters that will be used to supply potable water shall not be connected to a heating system or components previously used with nonpotable-water heating appliances. Chemicals for boiler treatment shall not be introduced into the water heater.
    do not seem to apply here because there is no chemical treatment of the water supply.

    The other statement,
    for space heating at temperatures exceeding 140F
    also does not seem to apply because the water temperatures are below 140 degrees.

    So what I see in the picture is OK then? No need for any sort of backflow valve?


  4. #4
    Join Date
    Mar 2007
    Location
    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: Loop tween WH and Floor radiant heat

    Looking at the picture, it looks like it would work fine. I agree that it is not addressed in the code cite. If it started as a potable water system, then it should be OK.

    As for backflow valves, it looks like two PRV's are installed. If this is the case then they will act like a check valve. I do not see an expansion tank or valve on the system. You need one or the other because the PRV's make it a closed system.

    Also I do not see a TPR line for the tankless water heater.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  5. #5
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,252

    Default Re: Loop tween WH and Floor radiant heat

    I should have been more specific, but I had to leave and meet our daughter at her new apartment to sign the lease and do her walk through with her.

    I was basically pointing out some questions which needed to be answered.

    (new highlighting with bold and underlining are mine)
    Quote Originally Posted by Jerry Peck View Post
    From the 2006 IRC.
    - SECTION P2802
    - - WATER HEATERS USED FOR SPACE HEATING

    - - - P2802.1 Protection of potable water. Piping and components connected to a water heater for space heating applications shall be suitable for use with potable water in accordance with Chapter 29. Water heaters that will be used to supply potable water shall not be connected to a heating system or components previously used with nonpotable-water heating appliances. Chemicals for boiler treatment shall not be introduced into the water heater.

    - - - P2802.2 Temperature control.Where a combination water heater-space heating system requires water for space heating at temperatures exceeding 140F (60C), a master thermostatic mixing valve complying with ASSE 1017 shall be installed to temper the water to a temperature of 140F (60C) or less for domestic uses.




    *IF* ...

    The piping and components of the space heating system are rated for potable water, and ...

    The nothing has previously been used for non-potable water ...

    Then it should be okay.

    What material was used for the potable water radiant heating system (I stated it that way because the two systems are interconnected with potable domestic water being run through the radiant heating loop per your description) - is all the piping rated for potable water use?

    Also, on the electrical front, you got the box with exposed wires (no cover) with the exposed NM cable running to the water, needing a cover for the box and something to protect the NM cable to the water heater (such as flexible conduit).

    Then there is that cold water supply pipe to the left of the Sq D safety switch which is in front of, and blocking the opening of, something (I cannot tell what it is in the photo)

    Then there are the two cords which look like they should be either NM cable or cord-and-plug sets plugged into receptacles, that flexible cord is not made for that use.

    Then you also got the exposed paper facing on the insulation, I presume.



    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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