Illinois Recommended thermostat differential for Geo

Discussion in 'Maintenance and Troubleshooting' started by Chris Moody, Apr 20, 2022.

  1. Chris Moody

    Chris Moody New Member

    I have a series 5 waterfurnace 6 ton, 2800 sqft house with aurora controls 2 zone intellizone 2 controlled. The installer wants to set the differential at .5 degrees but this causes the system to kick on about every 30 mins for about 10 mins. This seems like it would be hard on the compressor and shorten its life, maybe they just want to sell me a compressor at 10 years and 1 day. What is a good differential setting. Ive had it set at 1 degree which causes the system to run longer ( which he also said is bad and will burn up compressor) contradictory to everything Ive read about geo which says longer run times are better.

  2. SShaw

    SShaw Active Member Forum Leader

    The default differential is 0.5, so I would leave it at that and not worry about it.
  3. bpsmicro

    bpsmicro New Member

    Assuming you're talking Celsius, I'd leave it at the default 0.5C. A 1-degree swing may be noticeable if you're a bit sensitive. And depending on house layout & insulation & sun exposure, the actual swing may be higher.
    What I did was left the Stage 1 at 0.5C but set Stage 2 to 1C and Aux to 2C. The default on mine was 0.5 for all three, which seemed a bit dopey.
  4. SShaw

    SShaw Active Member Forum Leader

    The default is 0.5F/0.5F/0.5F, which is where I leave mine.

    The differentials are cumulative, so with your settings, Stage 2 won't come on until the temp is 1.5C (2.7F) off the set point. To each his own, but I wouldn't find that comfortable, and one of my reasons for going geo was improved comfort and consistent temps inside.

    Leaving the AUX at 2C would be OK with me, since AUX would rarely (or never) come on with a properly sized system.

    However, the OP has Intellizone2, and the AUX differential does not apply in the same manner it would without zoning. With Intellizone2 the AUX is triggered not by the differential, but by the total heating demand, which is based on the total of H1/H2/H3 demand calls calls from all the thermostats. By default the load needs to be 90% for AUX to come on.
    Last edited: Apr 22, 2022

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