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Old 06-30-2014, 12:56 PM   #1
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Thermostat setback and 2 stage A/C

Just curious what people think about this......

So it has long been held that indeed it is better (from an energy savings perspective) to set your thermostat higher when you are not home (e.g. work) during the day, let the temperature rise then cool your house off before/when you get home.

I have a 2 stage A/C system now and I am wondering if this practice would apply to my new setup.

Is it better to leave the thermostat at a constant temp and let the 1st stage of the A/C run all/most of the day/afternoon to maintain it or let the temp rise and have the 2nd stage run to cool the house down when I get home?


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Old 06-30-2014, 01:03 PM   #2
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I think it is better to let it run. The point in a 2 stage is to get rid of moisture and that takes run time. Get rid of moisture and you may be able to set it 2 degF higher. It will override to 2nd stage the other way and probably never go to 1 stage except when the sun goes down or at all. If you are concerned about saving NRG then increase the insulation, fix all drafts and get better 3 pane low e-argon tinted windows and create shade with awnings or trees. A few degrees temp difference by jacking it up may not saving that much $$ as it is proportional to the big picture. Insulation is King and air sealing 2nd.


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Old 06-30-2014, 03:28 PM   #3
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I have mine set for 70 during the day, 68 at night for Summer. Winter is 68 during the day, 65 at night. Differential on my thermostat is 3.0, Swing is 1.5. As long as you can keep Solar gain out, have the house properly sealed. The humidity levels in the home should not go too high or too low.

Most a/c units are only Single Stage, even though the furnace is two staged. My setup is exactly that. My thermostat will start up in stage one, and if demand is not met within two minutes, will kick up to Stage 2. Then will ramp down to stage 1 at the end. Winter time, it will run mostly in Stage 1. Even when going from 65 to 68 in the morning.

I let the thermostat decide what the furnace is going to do. Rather then have the factory coded program on the furnace decide.

Last edited by gregzoll; 06-30-2014 at 03:31 PM.
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Old 06-30-2014, 07:48 PM   #4
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Don't set your 2 stage more then 2 degrees higher when your a way.
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