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  1. #1
    Join Date
    Nov 2009
    Posts
    13

    Fully Modulating Furnace, Regular or Communicating thermostat?

    The contractor quoting a Luxaire Acclimate Series 97+% says we can use any regular thermostat but I read somewhere that a communicating thermostat is required for a fully modulating furnace. I am not sure if he knows fully about these mod units but says he has installed them in the past.

    Please tell what thermostat to go with, will a regular programmable thermostat be good enough of does it need a higher end one? If it does need a higher end one, does it come with the furnace or is an additional expense. Luxaire website does not give any detais of a compatible thermostat.
    Thanks.

  2. #2
    Join Date
    Nov 2009
    Location
    South central Wisconsin
    Posts
    10
    I know Ruud mod furnace requires communicating t-stat to be fully modulating. If regular t-stat it is capable of running as a 3-stage furnace. I would imagine Luxaire unit would be similar. Also, com. t-stat is in addition to furnace

  3. #3
    Join Date
    Sep 2002
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    I don't know
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    2,903
    Luxaire uses an algorithm exclusively (no other options) to control output - no need for a specialized stat.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,712
    You can use a communicating thermostat like the Honeywell IAQ. But, it will have no more control over the furnace in heat mode. Then an old Mercury thermostat would.

    The furnaces control board will control the modulation of the furnace. It curently is not designed to take advantage of high end thermostats in teh heating mode(sometime next year, the new ones will).
    If you have A/C. then a communicating thermostat, will be able to slow the blower in cooling mode. On high humidity days.

    Furnaces don't come with thermostats. They are an optional thing.
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  5. #5
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,901
    Coleman
    No Heat No Cool You need Action Fast

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,888
    A-S/Trane's Mod requires the communicating stat to modulate properly. Nordyne's Mod as well. Rheem's requires a special stat plus they now have a really slick communicating stat. But, as the boys say, York/ Lux mods do not base their modulating on the wall stat so you don't need more than a Honeywell Round unless you want the dehumidify feature beenthere mentions or want to control a humidifier, ventilator or whatever. Then the IAQ is worth it.

  7. #7
    Join Date
    Nov 2009
    Posts
    13

    Confused

    So how do you get a fully modulating furnace MODULATE in 1% increments as it should do with a HoneyWell Round regular thermostat? I guess, at least, it has to be a 'digital' regular programmable battery powered thermostat, if not a fully communicating battery-free thermostat.

    Do those programmable thermostats clock temperature increase (though they don't show on the screen) in tenths of a degree F, so the MODULATING computer on the furnace can detect and accordingly MODULATE in 1% increments?

    Can't imagine that fine of a MODULATION with an old style Round mercury thermostat, since the furnace MOD computer might fully ramp to 100% very quickly, in which case it won't make sense to buy a MOD unit in the first place. I'd want it to be slow and steady, even if takes longer for the heat cycle. Contractors in my rural area are not that knowledgeable about this new tech stuff...please comment.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,712
    With York. It does it based on previous run times. And length of current run time.
    The thermostat has no bearing.
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  9. #9
    Join Date
    Sep 2002
    Location
    I don't know
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    If you want a t-stat controlled modulating unit, find a rheem dealer.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  10. #10
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,568
    I find Luxaire/ York modulate best with a cycle rate of 6+ CPH then they never shut down during colder weather. It takes a full 20 minutes to ramp up to 100% output then modulates down and waits for another call for heat from the stat. At that point the furnace knows about how many BTU's per hour are needed. They truely modulate, customers report constant operation during colder weather.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  11. #11
    Join Date
    Jan 2009
    Location
    Middle of the Oregon Coast
    Posts
    193
    Either the logic is conained in the furnace or in the thermostat - just think of it this way and you will be able to understand it. Rheem, Trane, A/S, and the others need the special tstat to work, but the york, coleman, and lux have "smart" boards and do not need the tstat.

    Your way of thinking on a programmable tstat is wrong - it is essentially a switch. If the temp is below the setpoint, it's on but if the temp is at or above the setpoint, it's off. The only stats that have "grey areas" are the communicating stats. Clear as mud??
    The Lord must love stupid people or he wouldn't have made so many.

    Why is it that when I am in a hurry, everyone else on the road goes 15 MPH under the speed limit?

  12. #12
    Join Date
    Nov 2009
    Posts
    13
    Freezeking2000, I take it that you mean Cycles Per Hour by CPH. Does the Luxaire have a manual setting so you can set the CPH?

    When your customers report constant operation, is it at some low setting? That is what I am looking for, a slow and steady operation, so the furnace doesn't go to 100% and runs quieter.

    amd> If you want a t-stat controlled modulating unit, find a rheem dealer

    The newer Luxaire is able to use a communicating t-stat.

  13. #13
    Join Date
    Nov 2009
    Posts
    13
    Quote Originally Posted by Au-en-boy View Post
    Either the logic is conained in the furnace or in the thermostat - just think of it this way and you will be able to understand it. Rheem, Trane, A/S, and the others need the special tstat to work, but the york, coleman, and lux have "smart" boards and do not need the tstat.

    Your way of thinking on a programmable tstat is wrong - it is essentially a switch. If the temp is below the setpoint, it's on but if the temp is at or above the setpoint, it's off. The only stats that have "grey areas" are the communicating stats. Clear as mud??
    I know that the t-stat basically gives YES/NO calls, but wanted to know if the electronic board in the programmable t-stat does something more.

    If the "smart" boards do the work, then all they know is a yes or no call from the t-stat. Then, the only way they can "modulate" is based on a set time for a set % of gas valve opening and ECM speed, eventually going to 100% after, say 20 mins, until the t-stat call is OFF. That wouldn't be true modulation. How else would they MODULATE for max efficiency unless they know that the heat they are putting out is raising the temp at some rate? Would be nice if they can sense a tenth of a degree rise in a set time, and ramp up or stay steady depending on how long it takes. I guess this is how the communicating t-stats work.

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