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Old 12-11-2010, 10:11 AM   #1
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Pro IAQ and CPH setting


My new two stage Trane XV95 gas furnace is doing a fine job of keeping the house warm but it runs often. I'm using the Honeywell VisionPro IAQ thermostat. I checked the thermostat settings #240 and 250 ( stage one and two CPH ) and they are set to "auto discover" and that equates to a CPH of 5 on each stage. If I change those settings to CPH of 3 will the furnace run three times in the first half hour and not run again until the next hour or will it run every 20 minutes throughout the hour? What effect will changing it have on the temperature swing in the house? Would it be best to just leave it where it is? Thanks for any comments.

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Old 12-11-2010, 10:20 AM   #2
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Pro IAQ and CPH setting


cph of a 90% gas furnace PER YOUR INSTALLATION INSTRUCTIONS IS 3. follow the install manual

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Old 12-11-2010, 10:33 AM   #3
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Pro IAQ and CPH setting


3 cph = 3 cycles of 20 minutes. Not quite as simple as it sounds though. With a 2 stage furnace you have an extra stage/cycle and that will even out the temp swing in the house. Try it both ways and see which one you like better. I would go with 3. Less starting and stopping is more efficient and saves wear and tear. Running the fan continuos on low (costs VERY little, uses 80watts) will be more comfortable in some homes and not in others. Try it, evens out the cycles more.
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Old 12-11-2010, 10:36 AM   #4
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Pro IAQ and CPH setting


There's nothing in the Owners manual, Installation Manual, or thermostat manual that says it should be CPH of 3 for the furnace. Any other suggestions?
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Old 12-11-2010, 10:38 AM   #5
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Pro IAQ and CPH setting


Thanks Yuri, I'll give that a try. Should I put it to 3 CPH in both stages?
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Old 12-11-2010, 10:43 AM   #6
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Pro IAQ and CPH setting


I would. Depending on where you live it may heat up your house mostly on first stage and only go to high fire in really cold weather. GOOD quality tstat. I am not a great believer in huge temp setbacks at night. 4 degF is all I would use. Drives the heck out of the furnace to recover and sometimes cycles on the limit control if the ducts are undersized.
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Old 12-11-2010, 10:58 AM   #7
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Pro IAQ and CPH setting


Great! I'll try that. I have the stat programmed to drop back only one degree at night because this is a dual fuel system with air-to-air heat pump but I'm running the gas exclusively now because it's so cold out.
Thanks for your input.

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