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Piping question

Finnman Member Posts: 12
edited January 18 in THE MAIN WALL
Picture shows my slab radiant piping. I am questioning if the piping is correct. Have two radiant panels zones plus the basement slab, TT PS110 boiler with Smart 40 DWH, with OD sensor.
This is the issue I have, when only the panel zones are operating, water temps are where they should be as OD requires. When only slab operating, supply water temps are low, I assume because of low return temps and slowly ramp up to 100+as return water increases.
When both zones operating at same time, water supply water temps stay low, assuming the low temp return from the slab is reason.
Do I need a piping loop around the radiant mixing valve? Any suggestions?


  • Intplm.
    Intplm. Member Posts: 1,786
    What temp is the mixing valve set for? Can you get a accurate temperature reading proving the mixing valve is doing what it is designed to do?
  • Finnman
    Finnman Member Posts: 12
    Set at 110 and was replaced, the original mixing valve had failed, no replacement internals available, reason I replaced.
    Thought that was the reason for the issue. But still the same.
  • Intplm.
    Intplm. Member Posts: 1,786
    I would think you have low temps simply because the temperature out doors is very cold?
    (A guess from here :) .)
    Some zones are shut off.
    The area you are heating is absorbing the heat at a higher rate than in the past?
    From the picture, I don't see anything piped incorrectly at first look.
    Has this ever happened before?
    Are you heating under higher then normal demand?
  • Finnman
    Finnman Member Posts: 12
    Was working on a radiator at the time, reason pic shows valves off.
    This may have been going on for sometime, not sure. Using the basement more since retirement so I became aware of it. Radiant now operates more..
  • Finnman
    Finnman Member Posts: 12
    edited January 18
    Reading up on P/S piping, I assumed the primary piping was a loop from the boiler and the secondary pulled and retuned to the loop. Now I think my radiant is part of the primary loop not a secondary, four 300 ft loops in the slab. Returning cool water to the boiler, thus resulting in cooler supply water. When radiant is off the primary piping become shorter.
    This is what happens when you have time in retirement, you start over thinking.