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Piping Caleffi 280 as bypass for boiler protection

super_snop Member Posts: 48
Hello everyone. Thanks to all your help I have pretty much narrowed down how I will install my new Buderus G115. After kicking around the idea of P/S, I started looking into a more simple boiler bypass. I have 2 zones consisting of fintube baseboard with one kickspace heater that is diverted from the series loop with a monoflo tee placed on the return. Would piping the system this way with a Caleffi 280 thermo mic valve with 140 degree thermostat help to protect the boiler? I would like to utilize outdoor reset and I figured if this works it would be a simple solution using one delta P pump on a constant pressure setting. Forgive my amateur sketch. I know I didn't include all the necessary valving and auto feeder. Just looking to see if anyone has input on this type of setup. Thanks!


  • Brent H.
    Brent H. Member Posts: 161
    I run that exact Buderus with fin tube baseboard in my house. My understanding is that boiler protection is generally used for converted gravity systems. Also, not sure you want a bypass if you are running outdoor reset or you’ll be bypassing when your curve sets the temp below 140…. You’ll be chasing your tail. My system uses the Logamatic with a pile of zones and no bypass.

    The pros will have more thoughts. I think @hot_rod provided you a nice simple piping diagram in your other post that meets the Buderus requirements.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Your mixing valve may like it better if you were pumping away from it. On the return going into the boiler, I'd put the circulator pumping into boiler, behind that the expansion tank, and behind that the mixing valve. Leave the spirovent where it is.
    Buderus can take a little lower return water temperature over other cast iron boilers, but I would do it anyway.

    There was an error rendering this rich post.

  • super_snop
    super_snop Member Posts: 48
    Thank you guys. This is a learning process for me. Just trying to figure out every option possible to figure the best way to do this from an efficiency and longevity point of view. 
  • hot_rod
    hot_rod Member Posts: 22,491
    I’m not convinced that with that low mass distribution and Buderus ability to take cool return that a return valve is needed?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream