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Properly plumbed primary/secondary loop?

wkotelko
wkotelko Member Posts: 7
edited April 2020 in Gas Heating
Hey Guys,
I've attached a plumbing diagram that I sketched up of my current system. The property is new to me and I recently installed a new boiler. I am looking to do some improvements to make the system more efficient. Would this system work better with all the secondary zones piped with closely spaced Tees off an actual primary loop? My system layout doesn't actually look like a proper P/S.




Comments

  • kcopp
    kcopp Member Posts: 4,392
    Yes it would work much better. Each loop to the radiant and Air handler should be off the primary/ boiler loop. It is not done that way at all. Hottest water should come off the main 1st and then in descending order the coolest last.
  • hot_rod
    hot_rod Member Posts: 21,853
    Are you looking to repipe this? If so a hydro sep would clean up the piping and give you 4 critical functions. air, dirt, magnetic and hydraulic separation
    Loads would be taken off as parallel and receive the same SWT
    As for efficiency, returning the lowest possible temperature to the boiler drives efficiency. Use the ODR function to modulate the boiler. The fan coil will dictate the highest required SWT. If it has a large coil that would help it operate at lowest SWT
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Shane_2
    Shane_2 Member Posts: 191
    If your drawing is correct, you are piped primary/secondary.
    The pump marked primary DHW is DHW only not primary. The pump marked secondary is your boiler pump. The other six pumps are your system pumps

    If I was piping new I might use a hydraulic separator instead of the closely spaced tees off the primary loop, but I think your system will work fine as it is. I don’t know what could be gained by changing anything. The only high temp load comes of the secondary loop first. The piping doesn’t match the manual’s version, but what you have will work fine.



    Rich_49
  • wkotelko
    wkotelko Member Posts: 7
    Thanks for the info .
    I have been reading through the Caleffi books and the Hydraulic separator definitely has me intrigued. The only reason I would tackle a re-pipe is to clean up the piping and make it nice to look at but would improve it if I can. I will be adding a hydraulic separator if I go ahead with it since it does add the filtering properties and extra air separation.
    One question I have is on the diagram all the zones that come off of the secondary loop piping gradually reduce from 1" to 1/2" at the last zone (I mislabeled on the drawing, the system zones are all 1/2".). Would it make sense to keep that whole secondary loop 1" and then tee all the zones in 1/2" off of that to keep the pressure more stable?
    Also, should the zone circulators be pushing from the supply side of the piping and not pulling from the return? After all the fun reading I have been doing looks like this could cause cavitation issues.
    I have become sort of obsessed with these hydronics and have been self isolating in my boiler room haha
  • hot_rod
    hot_rod Member Posts: 21,853
    Your drawing is fine, if you were to leave it, I would move the expansion tank connection, leave the air purger where it is. The zone circulators should be on the supply of the secondary pumping away from a relocated PONPC.

    Keep those secondary branches generously sized as it is the path to the PONPC for those zone circulators. Total the gpm requirement of all the zones size to that or upsize one diameter if it is on the line.

    1-1/4 copper for example could handle 15 gpm comfortably.

    Bold lines in out drawings indicate large pipe size :)
    From Idronics 15
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 7,542
    The circs should all be "pumping away" from the expansion tank. I would move them to the other side of their loops. The header between the loops appears to be undersized. How is the underfloor pex installed?
    What temp is the fan coil designed for?
    The biggest issue I see is that the water to the floors is likely way too hot. This wastes energy and causes overshooting of room temps.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • wkotelko
    wkotelko Member Posts: 7
    edited April 2020
    The loop header coming off the right of the closely spaced tees is 1" then goes to 3/4 in the middle then to 1/2 at the last two zones. I would think that should be 1" throughout, maybe 1 1/4". The 5 circulators are Taco 006-ZB4-6 with max flow rating of 10GPM. The primary and DHW circulators are Grundfos 3 speed UPS26-99FC with a max of 33GPM. Although the zones rarely run all at the same time, it would be definitely undersized if they did.
    The basement and garage zones are pex in slab and the upper zones are under floor tile.

    Yes, trying to lower the temps greatly affects the fan coil output.
    Looks like the they spec the fan coil temp at 140F. I will need to check the exact model when I get home to verify the Btuh.


  • hot_rod
    hot_rod Member Posts: 21,853
    Ideally you want to know the BTU requirement of each zone, convert that into gpm requirement, then size circulator, valves, piping its to that number.

    This all starts back at the room by room heat load calculation to determine the correct numbers.

    After the load clc come the design phase selecting the heat emitters and the SWT they require to match the load.

    The boiler specs will indicate a circulator selection for that loop. with a high pressure drop boiler you may need a high head circuit like those 26-99.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • wkotelko said:

    Yes, trying to lower the temps greatly affects the fan coil output. Looks like the they spec the fan coil temp at 140F. I will need to check the exact model when I get home to verify the Btuh.

    I think what Zman was hinting at is to keep the water temperature at the fancoil the same, but install mixing valve(s) to the radiant loops. That can be done a few different ways.

    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
  • hot_rod
    hot_rod Member Posts: 21,853
    Idronics 25 give you some ideas on lowering or matching SWT with different emitters. Your below floor or air coil may need the highest SWT. Possibly you could get away with a two temperature system. With air coils, adding more rows allows lower SWT, the product spec will show outputs at

    https://www.caleffi.com/usa/en-us/technical-magazine
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • wkotelko
    wkotelko Member Posts: 7
    Thanks Ill do some more reading tonight.
    Boiler manual recommends a taco 0011 circ pump with 1" pipe . The specs are similar to my current pump so I should be good there