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cold rooms w/radiant floor heat

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TFramer
TFramer Member Posts: 1
in Radiant Heating
I am looking for advice on a radiant heating system installed in my home. During cold days (outside temp 32 or below), the rooms never reach setpoint of 65 degrees.  Here is the basic setup- Each room is individually zoned and has a thermostat.The furance is a Peerless Purefire modulting gas furnace. There are (2) 6-port SS manifolds with zone control valves controlled by (2) Taco zone control boxes.There is (1) general circulator for the gas furnace and (1) master circulator (Taco 0011-F4) for all zone circulation. There is a total of (8) active zones. Each zone uses 1/2" radiant PEX and every zone is under 300 ft. in length. Each zone was originally setup for 1 GPM flow rate but I notice when about 5 or more zones are calling for heat at the same time, the flow rate on all zones drops from 1GPM to 0.6 GPM. I am trying to determine if the problem is due to an undersized main circulator pump or something other?  Many Thanks for your input

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  • SWEI
    SWEI Member Posts: 7,356
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    Loop lengths and more

    300' at 1 GPM, would present roughly 10' of head loss.  The 0011 has a steep curve.  A flat curve (or better yet an ECM circ) works better with that type of zoning.



    How do you know you need 1 GPM per loop?  Was there a heat loss calculation done?  What size is the boiler?  Is the outdoor temperature sensor installed?

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