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  1. #1
    Join Date
    Feb 2012
    Location
    Hampstead, MD
    Posts
    13

    Lennox iComfort Touch thermostat, AUX heat mix

    I am hoping that somebody can help me figure out the algorithm that the Lennox iComfort Touch thermostat uses to blend in AUX heat when controlling a heat pump (XP17). The system is a couple of years old now (when the system was installed the iComfort was brand new) and I'm still puzzled by some of the decisions it makes with regards to using the aux heat.

    So the aux is expensive to operate and I would expect it to make every effort possible to avoid turning it on however the iComfort seems to be more than willing to crank up those expensive heat strips. If it is very cold outside (20ish degrees) the system runs cycles lasting about 25 minutes, about 15 of which it will run the HP alone and then it'll turn on the heat strips until the cycle is finished. That's fine; at 20 degrees outside I don't expect the heat pump to keep up by itself. However I've seen it turn on those aux strips even when it is 40+ degrees outside, the HP is putting out plenty of warm air by itself, and it is only a few minutes into the cycle! At all instances of the heat strips turning on the thermostat is still holding steady at its set point of 68 degrees so it isn't like it is falling behind or has caught a cold draft.

    Does anybody familiar with the original iComfort Touch know the logic behind the aux blending? Are there any settings changes I could make to mine to make it more efficient? Do the newer iComfort thermostats handle the aux in a more efficient manner? I like how the iComfort thermostat exposes all of the system settings/error codes and don't really want to replace it but are there any others that would heat the house with greater efficiency?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,317
    Does it have an outdoor sensor.
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  3. #3
    Join Date
    Feb 2012
    Location
    Hampstead, MD
    Posts
    13
    Yes. The thermostat can display the correct outdoor temperature so I would assume there is a sensor somewhere on the outdoor unit.

  4. #4
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Three things that will help. 1- turn the stage delay timer to off. 2- set the high balance point to 30. 3-turn low balance point to 10 below zero or off.

  5. #5
    Join Date
    Feb 2012
    Location
    Hampstead, MD
    Posts
    13
    Thank you for your suggestions.

    The XP17 is a single-stage heat pump, what effect does the staged delay timers have on a single-stage system?
    The balance point control was disabled. I've set turned it on and set the values as you suggested. I'll see how it acts with those settings tomorrow. From what I could find about balance point controls these are usually for a dual-fuel setup. I only have the heat pump and electric strips. Is it going to switch over to pure electric strips when it goes below 30?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,317
    If you set the low to -10. that is when the heat pump will stop running.

    Balance point is so it knows when the aux heat is needed.
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  7. #7
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Stage delay timers set the amount of time the heat pump runs before the electric elements come on.With it turned off the thermostat will use temp instead of time activate the heat strips . That's also adjustable with that thermostat so if you want a 2 or3 degree drop instead of 1 degree between first and second stage heating it can be set that way.
    Low balance point locks the heat pump out below the set point.
    High balance point locks the electric elements out above the set point.

  8. #8
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,554
    Quote Originally Posted by stephen2002 View Post
    Thank you for your suggestions.

    The XP17 is a single-stage heat pump, what effect does the staged delay timers have on a single-stage system?
    The balance point control was disabled. I've set turned it on and set the values as you suggested. I'll see how it acts with those settings tomorrow. From what I could find about balance point controls these are usually for a dual-fuel setup. I only have the heat pump and electric strips. Is it going to switch over to pure electric strips when it goes below 30?
    The XP17 is a single stage heat pump, but the SYSTEM consists of the heat pump and an air handler with electric heat strips. The aux heat strips are considered 2nd stage.

  9. #9
    Join Date
    Feb 2012
    Location
    Hampstead, MD
    Posts
    13
    Thank you all very much for the information! The balance points make sense and for the heating cycle this morning with 40 degree weather it hasn't turned on the aux strips once. Before it was using them quite liberally in the morning.

    That is interesting about the staged delay timer then, since it was ON before and set to 20 minutes, yet I've never seen it wait that long to turn on the aux strips. I had also previously experimented with the 2nd stage activation temperature, setting it to a large differential, and it had no effect on when the aux strips turned on.

    With this balance point setting will the system still be able to turn on the aux when it goes into a defrost cycle when it is above 30 degrees?

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,317
    Yes, it will still be able to use aux during defrost at temps above 30.
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