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Aquastat accuracy

Steve Garson_2
Steve Garson_2 Member Posts: 648
I just installed a new L4006A aquastat because my boiler temp never exceeded 180, which on cold 0* days, means my house peaks at 68*. So I figured the 30-year old aquastat needed replacement. Wrong!

Tonight I got the new aquastat, filled the well with conductive grease and installed the new one. Setting it at 240* with 10* differential, the boiler maxes at 190*.

How accurate are the aquastat temp settings? The thermometer/pressure gauge is also new. The boiler is a WM GV-5. It just feels wrong setting the temp so high. Can the acquastat be recalibrated to allow hotter water?
Steve from Newton, MA


  • hot_rod
    hot_rod Member Posts: 15,392
    sounds like the sensor or well is not in the fluid for some reason
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    HVACNUT Member Posts: 4,336
    Where is the aquastat bulb in relation to the tridicator gauge?
    And why 240°?
    Is there an economy setting on the control module?
  • BDR529
    BDR529 Member Posts: 205
    180 is the magic number. 240 any air in the system will allow the water to flash to steam and another set of problems.

    Everything is +/- 5% Numbers on a dial are not something to hang yor hat on.
    EBEBRATT-Ed Member Posts: 11,126
    Not enough flow through the boiler? The water temp in the boiler will stratify if not moving
  • Steve Garson_2
    Steve Garson_2 Member Posts: 648
    edited January 14
    240* on the Aquastat results in 190* hydronic water flow. I guess there is simply a 50* variance from from the Aquastat dial setting. The aquastat bulb is ten inches downstream of the tridicator gauge?
    Steve from Newton, MA
  • clammy
    clammy Member Posts: 2,678
    I have completely stop using bulb style aquastats there accuracy stinks . Most of the time I ll update w a hydrolevel digital aquastat ,circ controll and for indirects I’m basically using a ranco etd there dead accurate about zero failure and costs I believe is about 1/2 a no brainer and have a set-able differential and keypad lock out . I only use the 110 v model easier and more reliable , I ve used them for many many years and have yet to replace a single one . They have a lot of application for temp control in the hvac business from walk in boxes to anything that requires repeatable accuracy ,I know a lot of guys don’t look outside From the same old same old there always given at the supply houses . What basically got me to change is Honeywell terrible accuracy in recent years and a few complete failures right out of the box which when your in business is a complete failure ,waste of time and lose of money and no good ,so I stay away and use etc when needed
    Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating