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Injection loops vs three way valves

I have a design build job with 22 hot water coils in air handlers with 2 peerles boilers that are 1.3 millpn btu's total. I have desgined a boiler loop in the boiler room then three injection loops sized off of that. With in the three loops are the 22 coils with seperate circs and check valves. all pumps and circs are sized for their prosective loads and head. the goverment engineer says he has never seen a job done like this and doesn't think it will work. He wants three way valves installed instead. I need to find information on injection loops to satisfy this engineer and prove that it will work and be more cost effective and efficent in this setting. Thanks


  • Brad White
    Brad White Member Posts: 2,398
    Where is Dale Carnegie when I need him?

    Hi George-

    I need more information, if you do not mind.

    1) Does each coil have it's own circulator or each loop? Meaning 22 circulators off of each secondary loop?

    2) Of the three loops, does each require the same temperature? I sort of assume they do as coils tend to be the same material composition even if loads are different.

    3) Is there a need for circulators at each coil beyond normal control operation? In other words, is coil freeze protection a requirement?

    4) Does each coil also have a control valve to further meter heat to each? Or if a 1:1 coil-circulator ratio, do the coils just run on-off to deliver capacity?

    5) Is it really a matter of using 3-way valves as the loop-setting means versus injection? Maybe that is all you mean.

    Where I am going is, I am going to ask you to assess the number of circulators and their wattages. Make a tally of the total Watts and the number of BTU's per Watt.

    If you have as many circulators as I think you do, your transport costs compared to fewer larger circulators serving more coils could be quite high. This is a reasonable thing for an owner to ask.

    Again, not criticizing, but I want to get my head around what the actual system architecture is, while telegraphing my concerns (which may be mis-placed for all I know).
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Gene_3
    Gene_3 Member Posts: 289
    I think it would work

    but that is not good enough

    I would suggest that you contact the manufacturers you mentioned Peerless, and the coil or air handler manuf's

    they should have engineers that will help you if you are buying their product at no cost
  • Weezbo
    Weezbo Member Posts: 6,232
    This is quite fortunate indeed :)

    Take a quick internet sojourn to TACO. check out the design programs that they have to offer. you can even get a free copy to bash in a quick design of your choosing...it will fill in the blanks .

    There is a study guide that allows you to click along with Hamburger man:)

    basically the solutions have even more solutions this year in 4.1
  • Jay_14
    Jay_14 Member Posts: 39
    injection piping

    I would recommend having the engineer read the tekmar essay on injection piping. See attached.

This discussion has been closed.