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Simple outdoor reset

Hi,  does anyone have any thoughts on what kind of control I can use to shut my system off except when it is approaching freezing?  On my new ModCon Alpine I can do this with warm weather shut down but this is for an older Slantfin Concept 21 with 3 zones in a different house.  The house is unoccupied and I am looking for a simple inexpensive way to cut back on fuel use.  I do not want to get into draining the entire plumbing system and putting antifreeze in the boiler.    I am looking to leave the thermostats set at 50 degrees and have the system only go on if the outside temperature were to go below 35 degrees or so.   Thanks.


  • zacmobile
    zacmobile Member Posts: 211
    remote sensor

    Just wire a thermostat with remote sensor capability in series with your existing thermostat & put the sensor outside. Set the stat to read the remote sensor only & turn the temperature setting down to whatever you want the warm weather shutdown point to be. A Tekmar 508 thermostat would be a good choice but i'm sure there are others.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,368
    how far can you adjust..

    your WWSD? A Tekmar will go down to 35 degrees f.
  • Tim Potter
    Tim Potter Member Posts: 273
    HD outdoor t-stat control


    I use this to control the Heat Trace cable (Ice dam prevention) on my roof. over 40* its off, under 40* its on. HD contacts.

    AMC-F5 is the model #, several people rebrand the same basic control for various uses.


    Winter Park, CO & Arvada, CO
  • Empire_2
    Empire_2 Member Posts: 2,343
    Cheap, Cheap, and Cheap....

    If you really want to go super cheap, get a snap action t-stat for about $9.00 and wire it into your burner circuit, set to aprox 40*f.  Beware of outside weather affecting the t-stat.  Also, if your existing t-stat in the conditioned space has an anticipator you will smoke it, so wire it so that it will not interfere with operation. 

    Mike T.
  • lchmb
    lchmb Member Posts: 2,997

    Keep in mind that setting thing's that close do not leave you much area for the oops factor. I woud strongly suggest a low temp alarm to call you if the house drops below 47. That way you can get there before it freezes....
  • sgall
    sgall Member Posts: 37

    everyone for some great ideas - I will give these some thought.

  • Wesman
    Wesman Member Posts: 16
    Warm weather shutdown

    Consider the Johnson Controls A419, powered 24vac or 120vac.  The included probe goes outdoors.  Put it under a fabricated shield so it stands slightly off of the house but is shielded from direct sun and bad weather.  The control goes indoors and includes a digital display.  Wire into the SPDT relay on the common and normally closed contacts,  That way it fails "safe".  The green LED would indicate the relay is active and you are "saving".  This unit would be half the cost of a T775A.  For comparison you can alternately look at an electromechanical  T6031 if you don't want to provide external power.
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