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  1. #1
    Join Date
    Mar 2007
    Western Montana

    Default Air Source Heat Pumps - controller

    I don't see many air source heat pumps in this part of the country, though do inspect a fair number of A/C units in newer homes. Yesterday's house had a Lennox XP15 heat pump combined with a class IV Lennox propane furnace.

    Question #1: similar to prior thread, "How do you check an ac unit?"
    Should I expect to find the same temperature difference between a return vent and supply register (i.e. preferrably 10-20 degrees diff) with a heat pump as I would for a standard electric A/C? Or, are heat pumps not as dramatic, or slower to show a significant difference? I can't find the owner's manual on the Lennox web site.
    The house was already pretty cool inside, 65-70 degrees at the return vent, and I couldn't get any major difference at a supply register. I didn't really test heat mode (I forced the system into emergency heat mode in order to make the Lennox furnace fire up).

    Question #2: This system has two zones (two thermostats), running through a Lennox controller (see Pic - sorry, no model #). I have only seen one other of these Lennox controllers before. What happens if someone set one thermostat to Heat mode, and the other to Cool mode? Is the logic in the controller smart enough to not try and do both?


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  2. #2
    David Bell's Avatar
    David Bell Guest

    Default Re: Air Source Heat Pumps - controller

    As far as 1 stat in heat and another in cool, normally there is a primary stat and a sub stat, the primary dictates heat ,cool, or off position, the sub stat only operates a zone damper. There are zone controls that allow each stat to be primary, but they take readings from all zones to supposedly decide primary necessity. Much of this decision is base on an outdoor sensor. I am not a big fan of these systems as they are not user friendly and after all ,the homeowner should be able to control thier own system.

  3. #3
    David Bell's Avatar
    David Bell Guest

    Default Re: Air Source Heat Pumps - controller

    As a side note, homeowners that were taught to operate a programmable t-stat correctly saved more on electricity than people with these elaborate zoning systems. Most of the zoning systems owners ran thier systems in manual mode negating any savings that may have been had. Programmable owners were able to "time thier schedules to save money"


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