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Dunkirk vlt

kevsul1 Member Posts: 28
I’m looking into getting a Dunkirk vlt boiler for my radiant system and to use for hot water with a storage tank the boiler has a built in primary and secondary piping I wasn’t sure though if I should put my circulator before of after the mixing valve for the radiant any input is helpful thanks


  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,950
    edited October 2018
    You shouldn't have to install a mixing valve if your only heating is radiant. Program your boiler for low temperature heating and it will be able to tell the difference between a call for heating and a call for DHW. When an end switch for heating comes through, it will heat the water for your low-temp. radiant. When a call comes for DHW, it will ramp up to 180° for efficient DHW production.

    BTW, if you ever install a mixing valve, the circulator goes afterwards, on the mixed line.

    I've never seen a boiler with on-board 1°-2° piping. I like it!
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • kevsul1
    kevsul1 Member Posts: 28
    Yea it looks slick I’m also putting in a storage tank for my hot water I talked to tech support and they said they would install a mixing valve in the case that there is a call for hot water the boiler with heat up to 180 then at the end of the call when it switches back to the radiant the water will be 180 so put the mixing valve in for this scinario
  • Ironman
    Ironman Member Posts: 7,352
    I'm pretty there's a domestic post purge feature that can be adjusted on that boiler. Regardless, what little bit of 180* water that might be introduced into the radiant would be insignificant. Add a mixing valve is adding another component that can fail and it will also add more resistance to flow (head) which MAY necessitate a larger pump.

    The tech support guys at ECR a very good, but I've gotta disagree with them on this one.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.