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Honeywell aquastat setpoint temperature shift?

LarryC Member Posts: 331

My hot water boiler uses a Honeywell triple aquastat L8124L.  I was observing its operation last night and noticed that the setpoints idicated don't seem to agree with the existing temperature / pressure gauge.


I heard the safety valve vent.  I had previously added some water so I wasn't too concerned about the valve lifting.  When I went down to investigate, the temp / press gauge was reading about 210 F and about 10 psi.  I noticed one air vent was making noise like it was releasing air.  The high limit was set to 180 F, differential to 20 F and the tankless limit was set to 140 F.  I turned off power to the burner and let the thermostat call for heat cool down the boiler to about 180 F.


Because the pressure / temp gauge was reading around 210 F and the air vent was releasing gas, I believe the gauge is accurate.  <strong>VALID ASSUMPTION ???</strong>


Assuming the gauge is correct, I set the high limit to 170 F. and turned the burner back on.  Watching the boiler thru a couple of cycles and the burner turn off point is about 185 F and the turn on point is 170 F.  As I understand the operation of the L8124L, the burner should turn off at 170 F and turn on at 170 -20 = 150 F during a call for heat.  <strong>IS THIS STATEMENT CORRECT ??</strong>


What could cause this behavior?


Thanks for your help.


  • billtwocase
    billtwocase Member Posts: 2,385
    I would

    Check the control sensing bulb to make sure it is bottoming out in control well. The more they are out of the well, the less accurate they are
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