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  • Question on Installing HAI RC-80

    I'm in the process of installing a single RC-80 thermostat to replace two individual thermostats (mercury style) which control a seperate heating and cooling system. My questions are;

    1. Both systems are powered by different 24V supplies, would it be okay to use a single 24V supply for both systems?
    2. Heating is done by baseboard while cooling is done via ducts. In heating mode, will the RC-80 also turn on the fan?

    Does anybody else have their Thermostat connected to two different HVAC units? If so, can you explain how you did it

    Thanks, Judd

  • #2
    Judd, For your HVAC system to operate as you describe;

    Make your AC system provide the power for the RC-80 T-stat.
    Install an isolation relay on your Hydronic Heating system.

    By making the the AC the primary control source, you retain control of the fan(without any extra wiring).

    Power down the systems, there will be more than 1 Service Disconnect.

    Trace the two wires(most likely, Red and White) from your Heating T-stat back to the boiler, Trim the wires at that point, install/mount a 24 volt Normally Open relay. Connect the low voltage(Red/White) wires from the boiler to the NO contacts of the relay. The relay's 24 volt coil will be powered by NEW WIRES from the AC's transformer via the RC-80B's White and Common wire. Note: There is no standard color for the COMMON wire. But we generally use Black or Brown when available.

    Now inspect the the AC's Low Voltage wiring at the T-stat. Count the wires available. You need 6, ADD wires if required.

    1- Red - Power for the T-stat
    1- Black - Common for the T-stat
    1- White - for Heat relay
    1- Brown - for Common of the Heat relay
    1- Yellow - for Cooling
    1- Green - for Fan

    Wire the T-stat as listed above. Extend the White and Common from the RC-80B to the new Heat relay. Polarity is not important for the isolation relays control coil or contacts.

    NOTE: Your existing Low Voltage wiring color scheme MAY BE DIFFERENT (numbers only no letters OR any other variation) You must follow the AC's manufactures outline.

    Note: If using the RC-80, I hope it's a RC-80B with a HAI system OR a Remote Day/Night Setback you will need additional wires.

    2 more if Dry contact OR 3 more if communicating with HAI OR HomeSeer(can be Cat5e).

    Please take your OLD T-stats to your local HVAC supply house for proper disposal of the MERCURY T-stats.

    Follow the instructions that came with your RC-80B for your individualized settings.

    Hope this helps.

    Charles


    Originally posted by jpape
    I'm in the process of installing a single RC-80 thermostat to replace two individual thermostats (mercury style) which control a seperate heating and cooling system. My questions are;

    1. Both systems are powered by different 24V supplies, would it be okay to use a single 24V supply for both systems?
    - NO

    2. Heating is done by baseboard while cooling is done via ducts. In heating mode, will the RC-80 also turn on the fan?
    - IF WIRED AS ABOVE.

    Does anybody else have their Thermostat connected to two different HVAC units? If so, can you explain how you did it
    - AS ABOVE

    Thanks, Judd

    Comment


    • #3
      Charles,

      Thanks for your reply. I'm not sure if I made it clear in my first message, but I do not want or need a fan to turn on as the heat is via baseboard and the AC is via a duct system.

      Judd

      Comment


      • #4
        Pick your pleasure

        Judd, Yes I undestood.

        That is part, of the uniqueness of the RC-80B. That option is field selectable
        Press "PROG" 3 times, "FAN" once, Puts you in programing mode.
        Press "PROG" until you reach 02 and pick your pleasure.





        02 System options








        The thermostat can be configured with the following system options:




        0 Auto changeover no fan with heat

        1 Auto changeover fan on with heat

        4 Manual changeover no fan with heat

        5 Manual changeover fan on with heat

        12 Heat only no fan with heat

        13 Heat only fan on with heat

        20 Cool only

        The default setting is 0.




        Charles















        Originally posted by jpape
        Charles,

        Thanks for your reply. I'm not sure if I made it clear in my first message, but I do not want or need a fan to turn on as the heat is via baseboard and the AC is via a duct system.

        Judd
        Last edited by Charles; April 25th, 2005, 07:52 AM.

        Comment

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