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System adjustments


Purchased a house with hydronic floor heat system and would like your input on a few things.

System specs:

4 zones of hydronic floor heat,1/2 pex, simple manifold, no zone control, no ODRest.

zone 1 : 200ft, in-between floor joists with thick ceramic tile cover

zone 2: 280 ft, in-slab

zone 3: 215 ft, in-slab

zone 4: 215 ft, in-slab

boiler: ElectroIndustries EMB-W-9 9kw mini boiler

expansion tank: Amtrol model 15

pump: Taco 009-F5

Thermostat: Luxpro, simple ambient air thermostat.

I moved tstat from corner of utility room, where above equip is located, to center of wall

as system would run for 2-3 hrs before reaching setpt of 68 degrees.

Now the system runs for about an hour and then shuts off.

Current setpt 68, boiler set at 115deg, supply is 100deg, return is 86deg after 1 hr of runtime.

Do these numbers seem OK or should adjust boiler temp up/down?

I am considering replacing tstat with an Azel D508F with sensor and use the AF mode to monitor

both air & slab temp. Would you agree?

I have not checked floor temp yet, but can borrow infrared gun to get some readings.

My concern is to get the system settings correct and not have too large of temp swings.

Currently it takes 1-2 hrs before tstat will call for heat again, does that seem normal?

Thanks for your advice.



  • SWEI
    SWEI Member Posts: 7,356
    edited November 2013
    Electric Boiler for Radiant Floors

    How is the "in-between floor joists" tubing in zone 1 installed?  Stapled?  Insulated?  Plates?  On what centers?

    That pump is seriously oversized.

    Assuming the boiler is correctly sized, they should have used an EB-MO-10 instead.  Outdoor reset control is the best way to deliver comfort in a radiant floor system.
  • Chris05
    Chris05 Member Posts: 2

    I called manuf of mini boiler today, asking if this boiler would accept ODR control.

    The tech said this unit would not work well with ODR as it does not have the ability to vary the boiler temp, except buy manual adjustment.

    I have ordered an Azel thermostat & sensor to replace the existing thermostat.

    re: the joists question.. I'll have to explore the crawl space, no basement, and see how it is installed.


  • Weezbo
    Weezbo Member Posts: 6,232
    well , thats interesting ..

    i have a tool that is as you describe for temp heat , normally we are happy just to have clean heat of any sort along this time of the construction season . i just set it and forget it and dial it down as we get a handle on the building envelope and heat loss .


    your idea projects something i never considered , a relay with outdoor reset , he he by the time anything like that would happen the painted out inside corner would exist for a boiler with more grunion .

    buh maybe for you that would be a means of dialing it in . i use constant flow on my lash up and there have been times when one room will be like 90 so i turn to the breaker panel for "Control" :)

    never even considered the relay or if i did i just considered it another "Target" on site for someone to aim at.

    Hope that helps ..

This discussion has been closed.