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Mixing Valves and Pumps

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Rdriver
Rdriver Member Posts: 7
in Radiant Heating

Hello. My actuator that controls the mixing valve stopped working last year, and now my mixing valve seems to get stuck when turned all the way clockwise. Instead of replacing the valve and actuator we tried to find a point where the radiant temp was 120 and leave the valve there. I was told I needed a new pump. We had a new pump installed which is now causing noise in my other pump. My temp going to the floors is now at 170. This leads me to the following questions:

  1. In this setup, should I replace the mixing valve and actuator?
  2. If I don’t replace, what should my mixing valve be set to?
  3. If the valve is all the way clockwise, will that stop sending water to my radiant pump?
  4. If the valve is all the way counter clockwise, will that be too hot for my radiant?

Thanks all. Pics attached

IMG_7467.jpeg IMG_7468.jpeg IMG_7469.jpeg IMG_7470.jpeg

Comments

  • hot_rod
    hot_rod Member Posts: 27,329

    Yes, the valve should rotate fairly easy. If it jams, it could ruin the actuator.

    You can operate it manually, get the boiler up to temperature, run the zone pump and adjust. This is refered to as a "dumb" mixing valve. It will not respond to the control and be able to adjust the water supply temperature.

    It is a fairly simple valve under the hood, easy to disassemble. However if the rubber o-ring seal is worn or hardened, it may not last through a disassemble and reassemble. Example of a 3 port version below.

    I believe it is an ESBE valve and a repair kit, and new actuator may be available.

    Screenshot 2026-02-09 at 10.57.35 AM.png

    https://www.danfoss.com/en-us/products/dhs/valves/motorized-control-valves/rotary-valves/esbe-vrg-mixing-valves/#tab-overview

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Rdriver
  • Rdriver
    Rdriver Member Posts: 7

    @hot_rodThank you Bob. So is it the job of the actuator to adjust the mixing valve to accommodate the temperature of the water to both the floors and the domestic tank?

  • Jamie Hall
    Jamie Hall Member Posts: 27,237

    Sort of. The mixing valve is to set or adjust the temperature of the circuit following it. The way it works is you have nice hot water — hot enough for the highest temperature demand in your system. But some other part (notably your floors — 170 is much too high) — needs cooler water, so you mix some of the hot source with some of the cooler returning water to get it "just right" and then send it on its way with the pump.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 27,329

    there are 3 components to that valve. The valve, an actuator and a control. I suspect that white tekmar control was wired to the actuator?

    The valve blends down the high temperature from the boiler to a lower temperature for the radiant.

    In some cases, depending on the control it could also be protecting the boiler from too cold of return water. So it can be a dual purpose valve.

    Definitely worth getting rebuilt or replaced to get the best use of the system

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Rdriver
    Rdriver Member Posts: 7

    @Jamie Hall thank you. We ran out of hot water today so I thought I’d play with the valve manually while I look for somebody to replace it and the actual. When I turn the valve all the way clockwise, the pipe to the floors immediately cools down. Same thing when I turn all the way counter clockwise. @hot_rod yes the Tekmar control was connected to a blue actuator picture attached

    IMG_3101.jpeg

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