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Radiant Heat Circulator Distance from Boiler?

jcherold Member Posts: 1
edited September 2022 in Radiant Heating
Hi everybody, looking for a little help with a garage heating project Im currently planning.

A little background... building a 1000 sq ft attached garage in NJ. Boiler is a Weil Mclain Aqua Balance 155H with the standard Primary/Secondary loop. 2 heat zones currently for hot water baseboard on the 1st and 2nd floor.

Garage will be getting 3x300' 1/2 loops. I was looking at using the Caleffi 172 Mixing Station for the simplicity.

My question is...

A. Can/should I use the Caleffi 172...any reviews or feedback?

B. I was planning on installing the 172 in the garage or in a closet on the other side of the wall from the garage which is roughly 30-40' away from the boiler...Is it a problem having the circulator that far from the boiler/primary loop?

Im obviously a homeowner so I apologize if any of the verbiage is wrong. Thanks for any and all help!

Picture of the boiler right after switchover...everything is cleaned up now...dont mind the flue and condensate line.


  • hot_rod
    hot_rod Member Posts: 22,105
    No problem with the distance, make sure you have at least 5 psi at the 172 if you are mounting above the boiler level.

    Remove that H fitting and move the iso valves up

    The H is a small P/S device, not needed since you have primary secondary piping in the boiler room
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,818
    Think of it this way. The circulator pumps worked for over a century on the return of the boiler. Now common wisdom says to install it on the supply side. So why won't it work somewhere in the middle? It will! Just make sure there is sufficient pressure to keep the circulator in a pressure situation always.

    If the pump is installed in the attic and the water pressure that high is only 4 or 5 PSI and the pump head has a 6PSI difference between inlet and outlet. There is a chance that water pressure could drop below atmospheric pressure. If and when that happens, the 190°F water at the inlet of the pump could flash into steam vapor. And no centrifugal pump can pump any vapor.

    Extreme example, I know, but it can happen in your garage if your PONPC (expansion tank) is located in the wrong place in reference to the pump.

    You will need to look up Gil Carlson to find out what PONPC stands for. You don't think I was going to be easy, Did You? When you work for the information, it sticks with you better.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics