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Thermostat not controlling heat - l7224u

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Hmmmm3
Hmmmm3 Member Posts: 1
in Oil Heating
We have a oil heater.  A few months ago we replaced the controller unit after the electric pole saw was hit by a car.   The surge fried the control unit.We replaced the fried l7224u with a new unit.   A picture of the new controller is the included.  It is a resideo boiler control l7224u.  Since we have replaced it, the thermostat is no longer controlling the temperature of the unit.  Ie, if we turn on the boiler unit and set a desired temp at the thermostat of 69Deg, it just keeps heating past the desired temp.  The only way to stop it is to turn off the boiler unit.  

Was there a step that was skipped when the control unit was replaced that is needed to correctly configure the wall thermostat.  We tried a new thermostat but still no success.

Thanks in advance.

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,861
    edited February 2022
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    Hmmmm3 said:

    Was there a step that was skipped when the control unit was replaced that is needed to correctly configure the wall thermostat



    Yes there is a program that needs to be turned to OFF

    Hold the three white buttons to get to the programing menu

    then tap the up arrow until you get to LL on the display

    Lower the temperature with the down arrow until it says OFF

    From to look of your boiler, that is not a boiler with a domestic hot water coil. the L7224U comes from the factory with a setting to make hot water by maintaining a boiler temperature of 150° or 160° Since you did not turn that feature off, the boiler will maintain a minimum temperature. That hot boiler will allow a gravity flow of heated water rom the boiler to rise into the radiators. The heavier cooler water will migrate back to the boiler and be heated to the minimum Low Limit temperature. By changing the LL from a temperature number, to OFF the burner will only be able to fire when the thermostat calls for heat.

    I loved that control, because it took the place of 3 different oil boiler controls, so there was less truck stock needed to be able to repair many different oil heaters.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Hmmmm3
  • HVACNUT
    HVACNUT Member Posts: 5,841
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    So basically it's a constant call for heat.
    Try removing one wire from TT on the aquastat. If the circulator stops, then there's a short in the thermostat wiring. 
    Is it set up as cold start?
    Is it just one zone?
    Hmmmm3

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