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Honeywell AQ thermostats too sensitive..?

ChrisF80ChrisF80 Posts: 14Member
Hello everyone, Over the summer I replaced my Taco zone controller and Lux thermostats with the Honeywell aquatrol zone controller and AQ thermostats, specifically for the zone synchronization feature. I was tired of hearing my oil burner kicking on and off with every zone calling at separate times. Now with the cold weather finally here I am seeing how it's working for the first time. The zones all call at the same time like they are supposed to but the Honeywell thermostats react to temperature change extremely fast. I used to get between 5- 10 minute burner run times with the lux thermostats with one zone running. Now with all 4 zones calling at the same time I am getting between 3-5 minutes of burner run times because the thermostats are getting satisfied very quickly. This is the exact opposite of why I changed everything. Anyone have any suggestions?? Thanks for reading.


  • Leon82Leon82 Posts: 529Member
    I switched to the Robert Shaw 5000 because you can set the differential in .5 degree increments. My honeywell would call for heat for 30 seconds sometimes
  • Jamie HallJamie Hall Posts: 8,945Member
    Check all your possible adjustments on the thermostats. It is quite possible that the factory defaults or recommendations are unsuitable.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ChrisF80ChrisF80 Posts: 14Member
    Thanks for the replies, I can't change the thermostats, only those will work with that controller for the zone synchronization.
    I have checked all the settings, they are as they should be.
  • Leon82Leon82 Posts: 529Member
    One other thing I did was stick insulation on the top and bottom of the wall cavity just in case there was a draft coming up from the nail plate. I don't know if it actually helps but I figured it was worth a shot
  • NY_RobNY_Rob Posts: 1,221Member
    The thermistors they use on electronic t-stats is about the size of a grain of rice cut in half. They have no mass at all and are extremely sensitive to changes in temperature. I was experimenting with one last winter on an Arduino project and I saw the temperature change by just moving my hand near the thermistor.
    The t-stat software should handle quick micro changes (or have a minimum run-time and minimum cycle time options), but if it's poorly written code... you get bad results like 3-5min cycle times.

    Maybe an old school approach will work... add some mass to the thermistor on the t-sat board to temper quick thermal changes. Take a small (water drop size or smaller) dab of plumbers putty and cover the thermistor... see if that slows down reaction times.

  • GrallertGrallert Posts: 245Member
    It's been a few years but I've installed dozens of these Aquatrol controls. The room sensors are not going to give you many options as far as setting, but if you get into the installers menu on the control you should be able to bring up a number of inputs. Maybe you've already tried this. One thing you also have control over is supply water temp, this will change the cycling interval of the boiler. Again it's been a number of years.
  • NY_RobNY_Rob Posts: 1,221Member
    Leon82 said:

    I switched to the Robert Shaw 5000 because you can set the differential in .5 degree increments. My honeywell would call for heat for 30 seconds sometimes

    Thanks for the heads-up on the Robertshaw t-stats Leon.
    I just ordered a RS6110 (same as the 5110 but 7-day vs. 5+2 programming). It has up to 3deg differential adjustment too.

    My Trane Z-wave t-stat is supposed to allow you adjust the differential... and it accepts the change in the menu... but it ignores the change to differential when in use.

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