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  1. #1
    Join Date
    Dec 2010
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    Question programmable thermostat for boiler system

    We have a 1927 house that has boiler heating with radiators in all rooms. My question is what type of programmable thermostat do we use for this type of heating system? We have inquired at Home Depot and Lowe's about this and the ones they carry are not suitable for our heating system. Any suggestions?

  2. #2
    Join Date
    Feb 2008
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    554

    Default Re: programmable thermostat for boiler system

    Do you have a steam boiler, or a forced hot water boiler??

    Best bet is to take down the info as to the make and model of the boiler (and any installation manual you may have) along with the make & model of the aquastat on the boiler (usually a little square box attached to the middle of the boiler), or the primary control, if the t-stat wires attach to the primary control; & how many wires the present t-stat has (carefully remove the t-stat cover & see if it has more than 2 wires); also see if there are thin wires (24v system) or thick wires (120V system).

    Consult the Yellow Pages under "Heating Supplies" for the local heating parts houses in your area; the counterman should be able to match you up with the right t-stat---caution; try to find a parts house that's "diy friendly" & ask them what their return policy is--some places may not allow returns.

    Also Google "how to install a programmable thermostat"
    Last edited by NashuaTech; 12-08-2010 at 11:29 AM.

  3. #3
    Join Date
    Dec 2010
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    2

    Default Re: programmable thermostat for boiler system

    Thank you for the reply. The boiler is forced heated water; it's not steam. So, my thought is your suggestions remain the same, right? Also, the boiler is the original one from when the house was built.

  4. #4
    Join Date
    Feb 2008
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    554

    Default Re: programmable thermostat for boiler system

    My thoughts remain the same----if it's a very old boiler with no name on it, you still should be able to trace the wires from the t-stat in the living room down to the "control module" on the boiler to which the two t-stat wires are attached (the color of the wires at the t-stat will be the same as at the "control module" (aquastat)).

    Your present t-stat is no more than a low-voltage 24v on/off switch; usually a drop of liquid mercury inside the t-stat closes the switch in the living room & 2 thin wires (usually red & white) go down to the "aquastat" (usually to two terminals labeled "TT" terminal) on the boiler (a mechanical relay box) that transmits the closing of the two t-stat wires into an 120v closed switch that activates the 120v boiler burner motor (or gas burner) & the 120v boiler water circulator pump to produce flame & heat from the boiler.

    When the room fills with heat, the mercury switch inside the t-stat "opens", breaking the 2-wire contact & shutting down the boiler until the next time the t-stat "calls for heat".

    If you can trace the wires to the boiler aquastat (usually made by Honeywell) & it has a little metal cover, see if you can loosen the cover screw & get the model number of the aquastat & bring this info with you to the parts dealer.

    Try to verify that you indeed have a 24v t-stat---by the wire size, & if you have a voltmeter (multimeter) measure voltage at t-stat when the system is running.

    Multimeters are low-cost tools available at Wal-Mart. Harbor Freight, etc., for $6 to $9.

    Post back if you have trouble locating the components mentioned.
    Last edited by NashuaTech; 12-08-2010 at 12:05 PM.

  5. #5
    Join Date
    Feb 2010
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    1,210

    Default Re: programmable thermostat for boiler system

    one word of caution. If the boiler and thermostat are original from 1927 then it will be a high voltage thermostat that in connected to the stack switch. The stack switch is on the flue pipe.

    John

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