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  1. #1
    Join Date
    Nov 2019
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    Thermostats with/without a Separate Em Heat Provision

    I've been looking at Honeywell thermostats and noticed that some, like the round Lyric, have no E (Em Heat) provision where others, like the T6, do. For a single-stage heat pump with electric heat where the heating stages are connected together (W/Bk and W/Bl are connected together for 13kW or higher system), wouldn't a thermostat sending a signal to E or to W2 (Aux) initiate the same heating action? Because the wires are connected, both W1 and W2 would be energized, correct? So is the electric heat energizing every time the heat is on? Does that mean that if W1 and W2 were not connected together, the thermostat could independently initiate W2 without energizing E?

    Or am I confused about heating, aux heating, and emergency heating?

    Would a thermostat not using a separate Em Heat wire (like the Lyric) be unsuitable for this setup or would the E wire just not be used because W2 is already receiving that signal?

  2. #2
    Join Date
    Nov 2006
    Athens, Ohio
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    If the thermostat does not have an emergency heat position then the thermostat is a heat/cool thermostat, not for heat pumps.
    As site rules do not allow giving advice for DIY you may be better off calling Honeywell customer support.
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  3. #3
    Join Date
    Dec 2007
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    Read the instruction.

    If you can't answer your own question then you are in over your head.

    As suggested call Honeywell for an explanation or a professional to properly install and set up a thermostat for your system.
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  4. #4
    Join Date
    Nov 2019
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    Thread Starter
    I have a house with two round Lyric thermostats and a house with a T6. I don’t need one installed and was merely curious why they had such different connections. I found an HVAC-101 article that answered my questions. Thanks.

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