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Double set back 24volt thermostat digital

carol_3carol_3 Member Posts: 397
Why your preference for Lux, guys? Here's the problem I have with Lux--lots of product problems, including very loose temperature control. I would recommend only thermostats made by the "majors," Honeywell or W-R.

Here's where the bad temp control comes from on Lux. In order to be inexpensive and "slim," instead of a mechanical relay, they use a triac. A triac is a resistor, and resistors always create heat when there's current going through them. So whenever there's a call for heating or cooling, the thermostat is making its own heat inside itself. As a result, it doesn't know what the room temp really is.

Honeywell for sure, and maybe still W-R, uses real relays. You can hear the click-click of its action. That means there's no artificial heat being created by an electronic relay, and there's tight temperature control (plus or minus one degree from setpoint).


  • J ResnickJ Resnick Member Posts: 9

    Does anyone know of a thermostat that will replace a White Rogers double set back programable. I am looking for one that is digital It is for a hot air system 24 volts.Original White Rogers comfort set/w/ battery
  • frank_25frank_25 Member Posts: 202
    From one old man... another. I would look at the Lux 511.
  • Empire_2Empire_2 Member Posts: 2,343

    Say's it all. They have many to choose from.

    Mike T.
  • carol_3carol_3 Member Posts: 397

    Don't listen to those guys on this one. :) For programmable, go for the top of the line Honeywell TH8110 touch screen stat.
  • jp_2jp_2 Member Posts: 1,935

    a triac is NOT a resistor, its a solid state switch!
  • Ron SchroederRon Schroeder Member Posts: 998

    I believe is a resistor/diode type combination used as an electrical switch, as best as I know how to explain. So it does have smoe of the heat giving properties of the transistor.
  • jp_2jp_2 Member Posts: 1,935

    you wouldn't want a resistor in series with a switch, of course all soild state device give off heat, and you can model this as a resistor.

    but is a low power triac reallly going to heat the stat?
  • Ron SchroederRon Schroeder Member Posts: 998

    not anywhere near where a true transistor would but remember it is in a confined space. If you don't beleive resistors are used in switches think about a dimmer switch, try this site and click on "the old way" "the new way" and "triacs".
  • jp_2jp_2 Member Posts: 1,935

    don't see where a resistor is in a traic dimmer, plus we are not talkinng about 'dimming' the furnace :)

    so the above post suggests that short cycling is caused by the stat in this case?

    I'd have to see the power draw from the furnace before I agree or disagree.

    by the way, a traic is more of a bi-directional SCR. in a sense, all solid state stuff are diodes!
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