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Honeywell 8124 Aquastat

Rob_31
Rob_31 Member Posts: 17
in THE MAIN WALL
I'm wondering if the Honeywell 8124 Aquastat relay on my Crown TWZ-125 oil fired boiler with tankless water heater is working like it should. High limit is set at 180*, low limit is at 160*, and differential is set at 15*.

When there is no call for heat, the burner will turn on at 170*, and off at 180* to maintain water temperature. On a call for heat, (with boiler at 180*), the circulator will run until the gauge is at 170*, then circulator will stop, and burner will come on. Burner will run, and when temp reaches 175*, circulator will start up, temp will reach 180*, burner will shut off, and circulator will run until temp hits 170* again, then circulator off, burner on.

This process will repeat itself, until the heating demand is satisfied. My concern is the constant starting, stopping of the burner - 3 minutes on, 3 minutes off - is that normal, or can one of the settings be tweaked to try and get the burner to run longer during a heat cycle?

Thanks

Comments

  • Rob_31
    Rob_31 Member Posts: 17


    I'm wondering if the Honeywell 8124 Aquastat relay on my Crown TWZ-125 oil fired boiler with tankless water heater is working like it should. High limit is set at 180*, low limit is at 160*, and differential is set at 15*.

    When there is no call for heat, the burner will turn on at 170*, and off at 180* to maintain water temperature. On a call for heat, (with boiler at 180*), the circulator will run until the gauge is at 170*, then circulator will stop, and burner will come on. Burner will run, and when temp reaches 175*, circulator will start up, temp will reach 180*, burner will shut off.

    This process will repeat itself, until the heating demand is satisfied. My concern is the constant starting, stopping of the burner - 3 minutes on, 3 minutes off - is that normal, or can one of the settings be tweaked to try and get the burner to run longer during a heat cycle?

    Thanks
  • Rob_31
    Rob_31 Member Posts: 17


    I'm wondering if the Honeywell 8124 Aquastat relay on my Crown TWZ-125 oil fired boiler with tankless water heater is working like it should. High limit is set at 180*, low limit is at 160*, and differential is set at 15*.

    When there is no call for heat, the burner will turn on at 170*, and off at 180* to maintain water temperature. On a call for heat, (with boiler at 180*), the circulator will run until the gauge is at 170*, then circulator will stop, and burner will come on. Burner will run, and when temp reaches 175*, circulator will start up, temp will reach 180*, burner will shut off, and circulator will run until temp hits 170* again.

    This process will repeat itself, until the heating demand is satisfied. My concern is the constant starting, stopping of the burner - 3 minutes on, 3 minutes off - is that normal, or can one of the settings be tweaked to try and get the burner to run longer during a heat cycle?

    Thanks
  • mark schofield
    mark schofield Member Posts: 154


    http://customer.honeywell.com/techlit/PDF/95-0000s/95-6571.pdf#search='honeywell L8124 c'

    a link to the instructions for the aquastat. I thought that when maintaining the low limit temperature with NO call for heat, the boiler would fire when the temp reaches 10 degrees below low limit and then fire until the temp rises to the diffrerntial set point. In your case, with no call for heat, low limit at 160, differential at 15, boiler on at 150 and off at 165.
  • Alan R. Mercurio_3
    Alan R. Mercurio_3 Member Posts: 1,624


    Usually a 20 degree difference between the high and low limit is where they would be set. In your case I’d have the low set at 160.

    Your friend in the industry,
    Alan R. Mercurio

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

    There was an error rendering this rich post.

  • realolman
    realolman Member Posts: 513


    when it is calling for heat the burner should go off at the "hi" temp setting and come on at 10° below that.

    For DHW the burner should go off at the "lo" set point and come on at whatever you have the differential set at lower then "lo"... Boy that's a lousy explanation!



    Yours should light at 170 and off at 180 when calling for heat... and light at 150 and off at 165 for DHW.
  • J.C.A._3
    J.C.A._3 Member Posts: 2,980
    Are you....

    Trying to run "microzones"? If your zones are real small, you'll get the problems you're seeing. Maybe it's time to think about some sort of buffer tank, or dumping the coil and installing an indirect. JMHO. Chris
  • realolman
    realolman Member Posts: 513


    This does not seem sensible to me. I see no reason for the circulator to stop at 170°. The only time it would make sense to me for the circulator to stop ws if the room temperature was satisfied or if the domestic hot water got too cold. It seems like you have some sort of overlap between the DHW and the heat hi limit.

    Why don't you try setting your lo limit to 140 and the hi to 180.
  • realolman
    realolman Member Posts: 513


    Are you sure you don't have the low and the high mixed up?
    With the circulator action you describe and the high temperature it maintains without a call for heat it kinda sounds like it's backwards.
    There is no reason for it to be 170-180 when the thermostat is not calling for heat... and there is no reason for the circulator to quit until the thermostat is satisfied or your boiler temp drops below 150 until it reaches 165 ( at your settings )




    I gotta say it's kinda confusing...I've edited this thing a couple of times.
    Why don't you make sure you got the right knobs, and try setting the lo at 140 and the hi at 180 and the differential at 10? .... see attached. It should come on at 130° and off at 140 for DHW and on below 170 and off at 180 when calling for heat.... I think.
  • Rob_31
    Rob_31 Member Posts: 17


    Thanks for the replies.

    I'm sure I don't have the highs and lows mixed up. However, after reading how this thing is supposed to work, I turned the low limit to 140 as suggested, and the differential to 10. I turned on the heat and kept my voltmeter on the circ. terminals to see when it would go on/off. Boiler was at about 170, burner off, when I called for heat. Now, the circulator came on, and the burner stayed off until the temp reached 150, then circ. stopped, and burner came on. Burner ran until temp reached 160, then burner off, circulator back on. It seemslike it's workiing how it should with the low limit setting at 160, not 140 where I have it. Is it possible the knob got put on wrong? I then ended the call for heat, and the burner shut off immediately with temp at 150. I then ran the domestic hot water (with no calls for heat), and the burner came on at 150, and shut off at 160.

    What do you guys think?
  • Rob_31
    Rob_31 Member Posts: 17


    Thanks for the replies.

    I'm sure I don't have the highs and lows mixed up. However, after reading how this thing is supposed to work, I turned the low limit to 140 as suggested, and the differential to 10. I turned on the heat and kept my voltmeter on the circ. terminals to see when it would go on/off. Boiler was at about 170, burner off, when I called for heat. Now, the circulator came on, and the burner stayed off until the temp reached 150, then circ. stopped, and burner came on. Burner ran until temp reached 160, then burner off, circulator back on. Does it seem like it's working how it should with the low limit setting at 160, not 140 where I have it? Is it possible the knob got put on wrong? I then ended the call for heat, and the burner shut off immediately with temp at 155. I then ran the domestic hot water (with no calls for heat), and the burner came on at 150, and shut off at 160.

    What do you folks think?
  • realolman
    realolman Member Posts: 513


    I don't see any reason why the burner and the circulator should not run at the same time. Something gotta be wrong.

    Your thermometer may not read perfectly... you'll have to keep that in mind... there may be a lag or something, but your circulator should not shut off unless the room thermostat is satisfied or the boiler water temp. falls below the domestic hot water low limit.

    If you have the hi limit set at 180° and the lo limit set at 140, and a differential of 10°, your circulator should run as long as the room thermostat calls for heat until the boiler temp. falls below 130°. The circulator will not run again until the boiler temp is above 140°. The burner should be running the entire time the thermostat calls for heat unless the boiler temp is above 180°. Once it shuts off at 180° it will not come on again until the boiler temp drops to 170°.

    On the diagram the R,B,W. designations are wire colors... and B1 and B2 are burner terminals and C1 and C2 are circulator pump terminals...is that how yours is wired?

  • Rob_31
    Rob_31 Member Posts: 17


    Realolman,

    Yes, mine is wired like the diagram.

    I called for heat again, and watched it. It worked exactly like you said - with thermostat calling, burner running, the circulator ran until temp hit 150, then shut down (burner running). When temp hit 160 circulator came back on, burner still running until it shut off at 180, circulator still running. Temp falls back to 170, burner back on.

    So everything appears to be working as it should, exept that my low limit knob is on 140, and acting like it is on 160. That could explain the erratic behavior I described in my original post. If I had the low limit set at 160, and it was really at 180...
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