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Help with Hi/Lo Aquastat

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Hello,
I have a gas fired, hot water boiler with a Hi/lo Aquastat. The system has 3 pumps. 2 for basement area, 1 for 1st floor area. It is a old system.

I set the hi to 180 and the boiler hits 180 and stops firing. I set the Lo to 160. Now the 2 pumps for the basement, keep running and running, unless I raise the Lo to about 200..then they shut off. if I lower the Lo to even below 160 those 2 pumps keep running. The 1 pumps for the 1st floor, it is not coming on. I changed the relay but still no luck.

So is my stat not wired right..or is my setting wrong. I also do not see a differencal to adjust on the stat. I could just be missing it. I attached a pic. Any info anyone can provide me would be great. any more info someone might need, let me know and I can provide.

Thanks.

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    It's working as expected. Why are you messing with it?
    Hi is the high limit
    Lo is low limit, assuming you have a boiler that makes domestic hot water.

    On a call for heat, the burner fires any time the temperature is below the high limit and stops when the temperature reaches the high limit. It will stay off during a call for heat until the temperature drops 10° below the high limit. During this call for heat, the circulators will continue to run.
    Also during a call for heat, the circulators will run anytime the temperature is above the Lo limit setting.

    For domestic hot water, the burner fires anytime the boiler temperature drops below the low limit, and runs until the temperature reaches the low limit, plus the differential.

    That's the basic operation. Important also is the difference between the Lo and Hi limit should be at least 20°, assuming they are sensing the temperature noted on the dials, which they usually are not.

    There was an error rendering this rich post.

    MikeAmann
  • Boobie69
    Boobie69 Member Posts: 13
    edited March 2023
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    No domestic water. Reason I am messing with it. Radiators not getting heat on 1st floor. Basement floor over heating. sorry.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    edited March 2023
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    you have the wrong control.  Is that control connected to a L8124 with lots of additional stuff in it?  Or. Is that off white control the only thing in the control box?

    how many thermostats are there?  Just one for the whole house, or do you have 3, one thermostat for each circulator?

    Edward Young Retired

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

  • Boobie69
    Boobie69 Member Posts: 13
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    Only thing on boiler for operation aquastat and pump controls....like I said..very old system.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    edited March 2023
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    It appears that you have the L4081B aquastat. one switch is used as a high limit and the other is used as a low limit in order to operate a circulator pump without the use of a circulator relay. That model does not have a differential dial for the low limit. Some of the reason for the confusion is that most of those controls are used for boilers with tankless DHW coils


    You said you have 3 circulator pumps. I still want to know how many thermostats you have in your home?
    I believe I can help you if I know a little more about your situation... How long has the basement been Too Warm? Just this season? For the last 10 years?

    Can you post pictures of the boiler and the pumps from far enough back so we can see all the pipes from the floor to the ceiling?

    Edward Young Retired

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

  • HVACNUT
    HVACNUT Member Posts: 5,887
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    Have you checked voltage at the first floor circulator?

    The basement zones are overheating because the Lo side was at 160°, or its overheating even when set to 200°?