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New Thermostat - Circulator Issue

RDKing_66
RDKing_66 Member Posts: 2
in Thermostats and Controls
I just replaced the thermostat (line voltage) for a gas fired, hot water baseboard, zone in my house. The zone is operating at the correct temp, but the circulatator pump for that zone keeps cycling on and off every 10secs for a 5 sec run. This is 2 wire connection. Any ideas why pump keeps cycling? 

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 24,852
    edited February 2022
    The thermostat directly controls the circulator pump? Direct connection, no relays, no boards, no... ? If that's true, then there's something amiss with the thermostat. Could be the wrong thermostat for the application, or could have some setting wrong if it's a fancy one with settings, or... ?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Zman
    Zman Member Posts: 7,611
    Line voltage t-stats are a bit unusual in a baseboard system. Can you provide more details or pictures of the controls?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RDKing_66
    RDKing_66 Member Posts: 2
    Thanks Jamie. There are no relay boards or connections that I know of. I believe it is direct. I metered the connection at the box and it was 120v so I purchased a line voltage thermostat. It is a fairly basic unit. Digital read out, temp up/down, but not programmable. 
  • HVACNUT
    HVACNUT Member Posts: 6,331
    A lot of old gas and oil systems used line voltage thermostats, but they were usually wired through the low side of a dual aquastat, or a B control. 
    The cheapo builders special was to run a 14/3 romex to the first floor thermostat, and a 14/2 to the second floor from the first floor gem box. White was Common, Red first floor, Black second floor. 
    The bimetal Honeywell T451 thermostat only had about a 4 degree swing.

    What are the operating controls on the boiler? 
    What type of circulator, Older 3 piece, motor cutting out on thermal overload?


  • mattmia2
    mattmia2 Member Posts: 10,930
    Maybe the thermostat is designed for a resistive electric heat load only and is unhappy about the starting current of the circulator motor.
  • pecmsg
    pecmsg Member Posts: 5,291
    We need pics of the t-stat wires and boiler.
    mattmia2
  • wmgeorge
    wmgeorge Member Posts: 222
    RDKing_66 said:

    I just replaced the thermostat (line voltage) for a gas fired, hot water baseboard, zone in my house. The zone is operating at the correct temp, but the circulatator pump for that zone keeps cycling on and off every 10secs for a 5 sec run. This is 2 wire connection. Any ideas why pump keeps cycling? 

    Wrong Tstat or its set up wrong.
    Old retired Commercial HVAC/R guy in Iowa. Master electrician.

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