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  1. #1
    Join Date
    May 2008
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    Thermostat Control for Dual Zone

    I have a new house with a dual zone system. Both floors of the house have a Honeywell TH5110D thermostat and the zone system is controlled by a Honeywell HZ322. Overall, I have been happy with the cooling of the house (it is warm here in Arizona). However, it seems like the system doesn't work as efficiently as it could.

    I have read that the Honeywell thermostats have a small deadband of approx. .5 degrees F. What happens is that one thermostat will call for cooling and after a few minutes it is satisfied. I can hear it click off which turns the compressor off. Then within a minute or two the other thermostat will call for cooling, the system waits the 5 minute compressor protection period and the cycle repeats. I can achieve better results if I set the upstairs thermostat 1-2 degrees higher than the downstairs. To a new home owner it just seems like there would be a better way for the system to work.

    I am thinking about replacing each thermostat with a Totaline brand that has an adjustable deadband. My thoughts are that this would allow the A/C to run a little longer for one thermostat which should allow the other thermostat to call while the A/C is still running. Do you think this would help make the system more efficient?

    Also, as a side question for a dual zone system. If the CPH is set to 3 for each thermostat does this mean that it really could cycle 6 times? 3 from each thermostat?

    Thanks in advance for helping a first time homeowner out!

  2. #2
    Join Date
    Aug 2006
    Dallas (Plano), TX
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    I have 3 zones on a single compressor and observe the same phenomena. It's almost like you wish the thermostats could somehow synchronize amongst themselves in some fashion to reduce the amount of compressor cycling.

    I look forward to learning from the pros here if this is a situation that can be improved! I would think compressor lengevity would be lengthened if so.

    Best regards,


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