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Radiant 3 zone help

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Gta
Gta Member Posts: 138
Hi

I have radiant floor heat throughout my house main living 2000 ft 1500 ft garage, 900 ft bonus room.

The system has 3 zones
1/2 inch pex 11 runs main area
5 runs garage and 3 runs bonus room.

How do I calculate head loss? I’m running bell and gosset Nrf-25 3 speed pumps.

Thanks Sean

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  • Gta
    Gta Member Posts: 138
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    Oops all runs are aprox 300 ft each
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
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    Longest loop length of each zone.
    steve
  • Gta
    Gta Member Posts: 138
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    300
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
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    As @STEVEusaPA said. It’s the head loss of the longest loop. Plus the head losses of the piping to the supply and return manifolds from the pump, and back

    Then you need to know the “design flow rate” for the longest loop.

    Is this a one pump system with zone valves I assume.?

    Flow meters on the manifolds?
  • Gordy
    Gordy Member Posts: 9,546
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    Example: 1/2” pex at 300’ has a head loss of 11.73’ @1gpm.

    We don’t know what flow rate the design is so your head loss is different depending on flow rates required.
  • Gta
    Gta Member Posts: 138
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    Oh I see ok.... it has 3 separate pumps
    11 runs main floor .... longest run is 300
    5 runs garage longest run is 300
    3 runs bonus room longest run 300

    Rehau manifolds on all with flow meters

    Main set to .5 gpm
    Garage set to .6 gpm
    Bonus room set to .75 gpm

    All 3 separate circ pumps are bell and gossett nrf-25 set in speed 1

    Thx s
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
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    So if you have flow meters are they reading the correct designed gpm per zone? Or is what you posted what they are reading?

    Is this per loop, or per zone?
  • Gta
    Gta Member Posts: 138
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    It’s what they t reading per loop ..... I’ve been having little luck getting proper info .... lol they sold it to me but even the installer I don’t fully think knows all the stuff.

    I was told use what works ...🙄🙄🙄...
  • hot_rod
    hot_rod Member Posts: 22,122
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    1/2 pex loops typically run .5- .6 gpm. In theory a load calc and system design would indicate what each zone or loop would require.

    Certainly you can adjust them to fine tune loop to your comfort.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gordy
    Gordy Member Posts: 9,546
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    Next question is how is everything heating?

    Those are not ridiculous gpm numbers per loop.
  • Gta
    Gta Member Posts: 138
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    The boiler runs a lot .... the rooms are ok the farthest ones are notable as they are a bit cooler ..... are the delta t pumps worth the price? I see taco makes a really cool one .
  • Gordy
    Gordy Member Posts: 9,546
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    In correlation to flow rates above which zones are cooler?
  • Gordy
    Gordy Member Posts: 9,546
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    What is your boiler type?
  • hot_rod
    hot_rod Member Posts: 22,122
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    Gta said:

    The boiler runs a lot .... the rooms are ok the farthest ones are notable as they are a bit cooler ..... are the delta t pumps worth the price? I see taco makes a really cool one .

    Not in my opinion :) I think you would be happier with a ∆P circulator with a zoned system like that.

    Really no value to a constrained ∆ operation IMO.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gta
    Gta Member Posts: 138
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    I have s 23 kw “ lion” boiler

    The rooms that are a bit cooler are the opposite side of the house farthest away from the boiler. I’ve tried several times to change the speed of the pumps ... I note the faster circ speeds seem to keep the room more evenly warm.
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2018
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    You're more evenly heating at higher flow rates because you are narrowing the delta of the panel. Especially if the zone is farther away.

    Usually shoot for a delta of 10 for floor panels, to keep the panel more evenly heated as you noticed.

    You can confirm this by checking supply, and return temps at different circulator speeds.

    You could ditch the three circulator zoning set up for one delta p circulator with three zone valves. Saving you money on electricity.


    But then you already have the three circs.