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Mercury free honey well T stat

Norm Harvey
Norm Harvey Member Posts: 684
in THE MAIN WALL
I am probably not going to adequately put into words what is in my head,.. but the relationship between the thermistor and the dial,..

The thermistor gives a chip inside an ohm reading that relates to a temperature? What kind of action takes place on the dial end to make or break the circut based on the info that the thermistor is providing, and what the dial is set for?

Thanks for entertaining my curiosity. Im aware you probably have many more productive things you could do with your time, and I appreciate the time spent on me.

- Norm

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Comments

  • Norm Harvey
    Norm Harvey Member Posts: 684


    In curious about how these new thermostats operate.

    A norman digital thermostats use a thermistor (ohm resistance to determine temperature) But where this mercury replacement looks and operates like a T87, how does the manual know interact with the thermistor, assuming there is one? And how is the room temperature dial (the bottom number) controlled?

    The room temperature is what is most confusing to me. With no murcury how does the dial move?

    I may be way behind the times with how thermostats work now, (Where is Mr Wizard when you need him?) but the other day I just got to wondering.

    - Norm

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  • BillW@honeywell
    BillW@honeywell Member Posts: 1,099
    Not exactly Mr. Wizard, but...

    On the new T87N&K, the bottom red pointer is attatched to a coiled bi-metal(spring). It has nothing to do with the switching action of the stat; it merely indicates room temp. The upper red pointer is part of the dial, and when you turn the dial, you point it at whatever setpoint you want. An electronic sensor called a thermistor actually senses the temperature, and makes or breaks the t-stat switch to start & stop the equipment based on the setpoint you choose. Instead of the old mechanical heat anticipator, you set a pair of dip switches to match the cycle rate of the equipment you are operating.
  • Unknown
    Unknown


    I have a feeling that rotating the dial controls a variable resistance in the thermistor circuit. Then a circuit compares the thermistor resistance to the resistance setting of the dial and activates a relay or electronic switch when the dial setting is reached.
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