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What's a word for the opposite of Primary-Secondary piping?

JohnNY Member Posts: 3,226
Is there a word for sending the whole system through the boiler or should I invent my own term? Direct Flow Piping? Mono-Loop Piping? I've been saying "standard" but it always requires explanation.
Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
Consulting & Troubleshooting
Heating in NYC or NJ.


  • Canucker
    Canucker Member Posts: 722
    That's what I've always called it. If the system is hydraulically separated from the boiler loop, it's primary secondary. If the system pump generates flow to the emitters and the boiler, it's piped "directly". If you said you set it up with direct flow piping, I'd know exactly what you were referring to
    You can have it good, fast or cheap. Pick two
    IronmanAlan (California Radiant) ForbesJohnNY
  • hot_rod
    hot_rod Member Posts: 21,853
    Direct or direct to boiler piping, maybe
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • AMservices
    AMservices Member Posts: 610
    Looped system 
  • psb75
    psb75 Member Posts: 807
    Its a good question. Language is important. Common terminology would help folks on this forum convey clear information, if there WAS a proper, common term for what you are asking about.
    Say, wasn't this forum founded by a well known writer with a thorough knowledge of hydronics? Maybe he has the term you're looking for!
  • mattmia2
    mattmia2 Member Posts: 9,413
    Anyone look at what modern hydronic heating and idronics call it?
    EBEBRATT-Ed Member Posts: 15,317
    Take your pick.
    From Modern Hydronic Heating

    Series loop is called 'Single Series Circuit"
    One pipe is called "single circuit multizone"
    Then there is "Multi zone with zone valves
    Then there is "Multizone with circulators"
    "Parallel with direct return"
    "Parallel with reverse return"
  • For what it's worth, "direct connection" used as a verb, not a noun:

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    I would say primary. That’s a naturally linguistic introduction to primary-secondary. One proceeds the other. 
    Retired and loving it.
  • jumper
    jumper Member Posts: 2,208
    I think chilled water systems are called direct (pumping) if they don't have a shunt (bypass) pipe to allow different flow rate through chiller than through system. Primary-secondary for CW are no longer in favor.
  • JohnNY
    JohnNY Member Posts: 3,226
    Thanks, guys. Good answers here. It's best to standardize the terms and it comes up quite a bit in our industry.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.