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Buffer tank with one return connection

bluehils Member Posts: 1
Hi. I am after a little help.
I am have installed a wood pellet boiler and a 500litre buffer tank. The tank will feed 3 underfloor heating manifolds. The tank has only one connection port at the bottom which I have connected to the boiler return i.e water will be flowing out of the tank back to the boiler.
I now need to connect the return from the underfloor heating manifolds - do I tee off the boiler return which would mean the cool heating water would return directly to the boiler if the boiler was running . It couldnt return to the tank as the boiler pump is pulling water out of the bottom of the tank. Or the other alternative is to connect the heating return to a port half way up the tank - if I do this will the full capacity of the tank be used or only the top half??
- Hoping someone out there can point me in the right direction!!


  • hot_rod
    hot_rod Member Posts: 22,143
    What size ports in the tank? I've made up these curved dip tubes to "place" the flow where you want it.

    Use a double tapped bushing from OEM, now owned by Beckett I believe. It is threaded inside from both directions, an oil tank fitting, i guess.

    Screw a curved or ell piece on the inside, connect your piping to the outer part. They have a variety of sizes, this is a 2X1 that fits the ThermoCon tanks.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    You should still have some type of return protection. What is the min return temp spec from boiler manufacturer?

    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • VelvetFoot
    VelvetFoot Member Posts: 48
    edited October 2015
    Hi. I'm no expert, but I have a pellet and oil boiler both connected to the same headers and both go into my 120 gallon buffer tank. Boiler protection is on those headers so it is shared and the pellet boiler also has its circ pump shut down if boiler temp is below a certain temp.

    There are only two connections to my buffer: at the top and at the bottom. The piping for the zones are connected on the headers between the tank and the boilers.

    When the zone circs pumps (I have baseboards, not radiant) are running, and a boiler with circ pump is also running, water is drawn direct from the boiler and sent through the zones, bypassing the tank. If a zone pump is running and the boiler pump is not, it draws from the top of the tank.

    The headers are bi-directional, depending on whether heated water is coming from the tank or the boiler. It seems to work.

    Geez... I just looked at the date. 10 months too late.