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Is a bypass needed?

Is a bypass circuit needed if you are using a storage/buffer tank to feed to remote mounted distribution manifolds? I'm confused by some of this terminology. My understanding is that the buffer tank acts as hydraulic separation. If each manifold, ie Caleffi or Uponor has a ECM pump feeding it, does it matter what type of emitter is on that manifold? Like in slab, underfloor, Panel radiator with TRV, etc.

For example the Caleffi site states this under the heading fixed point manifold station:

"The manifold mixing station incorporates a thermostatic actuator with built-in sensor which keeps the flow temperature at a constant set value for use in low temperature systems such as floor radiant panels.

A removable primary circuit hydraulic separator with check valve is also supplied. The hydraulic separator is essential when there is a primary circuit circulation pump and when radiator circuits or fan coils are controlled by thermostatic or thermo-electric valves. When connecting to a Caleffi HYDROLINKTM or hydraulic separator without a primary pump, the hydraulic separator can be removed and the manifold mixing station can be connected directly."

I was looking at these units to decide if this approach had any advantages over using a separate Grundfos Alpha, and a Caleffi TwisFlow manifold. I was surprised to see that they only use a 3/4" valves for supply. The Caleffi TwisFLow manifolds are 1, or 1 1/4".


  • hot_rod
    hot_rod Member Posts: 22,157
    correct, the manifold pump station could connect to the buffer without using the built in separator.

    3/4 on those mix stations as they are usually connected to a high temperature loop, say 180F and mixing down. Think of a mini tube distribution system.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • RetrosPex
    RetrosPex Member Posts: 56
    Thank you yet again, Hot Rod.