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New Lochinvar Knight with Cross manifolds

Pechan Member Posts: 4
edited November 2019 in Radiant Heating
I am planning on a new boiler install for a home I am building. Based on the home size and construction I will be using the Knight 110 Firetube boiler. I have the system layed out but I would like to run it by youguys to see what I am missing. Here is what I currently have. Boilers are not very common in my area of Wyoming so local support is sketchy.
All my loops are embedded in concrete slab, I have 7 zones, each with multiple ~250 foot circuits with 1/2" pex.


  • GroundUp
    GroundUp Member Posts: 1,549
    Your piping is a bit cobbled, the boiler loop needs to be on one side of the hydrosep and the load piping on the other- the way you have it drawn with the indirect WH kinda teed into the boiler loop will not work properly. Also I would not recommend the bullhead on the supply piping before the circs to the manifolds, use one regular tee and one 90* to create two independent loops. A bullheaded tee will create unnecessary turbulence in the tee while the water decides which way it wants to go
  • Pechan
    Pechan Member Posts: 4
    Thanks for the reply!
    I believe I have corrected the problems you mentioned.
    Here is the updated layout:
  • Pechan
    Pechan Member Posts: 4
    Here is a third layout that eliminates some piping.
  • hot_rod
    hot_rod Member Posts: 18,918
    There are some installers that prefer the indirect taken off before the separator. This assures the hottest SWT from the boiler to the indirect. When you flow thru a sep, there is generally some temperature blending unless you balance so both flows are identical.

    With a Caleffi zone control powering the circulators you can configure which circulators run on indirect call.

    Not a huge deal breaker either way.

    If you use a quality hydrosep, no need for the additional air purger at the tank.

    I'd prefer to see the expansion tank on either of the blue "return" pipes at the sep, that way all circulators are pumping away from the PONPC. The way you have it drawn the boiler circulator inside the boiler is pumping at the PONPC.

    Ignore the multiple boilers in this schematic, the piping is correct and recommended.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream