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Heating & Air Conditioning

AC over cooling. Thermostat?

16 years ago

I have the opposite problem of many people here. Lately, my central AC system has been over cooling the house...

Stats: New Lennox G61MPV, New Lennox Coil, New Lennox CO (13 seer, new refrigerant). The thermostat was installed by the company and was new (but seems be a pretty basic digital thermo). The house didn't have AC before so they added new wires too.

Problem: A few days ago the thermostat was set at 76, the AC was on and I started to feel pretty darn cool. In passing, I looked at the thermo and the temp was down to 70! The thermo was still set at 76... I turned the AC off at the thermo and then turned it back on, problem solved... Until it happened again yesterday. After work, Thermo was set to 76, thermo temp was down to 72!

So, I'm assuming it is this cheap thermostat they installed. Any thoughts? Thanks!!

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Comments (3)

garyg
16 years ago
Could be the contactors on the outside unit sticking closed.
davidandkasie
16 years ago
or if your tstat has a dehumidify setting it coul dbe set too low making it try to get humidity down to 0% or something dumb like that. i saw one programmed like tha tat the local Sherrif's office once, they thought it was SUPPOSED to keep the room at 58 since it always had!
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WOW... Why and how would your HVAC guy configure a new system like this??? And why would you LET HIM?? The 315 is a wonderful furnace... had you gotten an Evolution A/C, then the Evolution Controller t-stat would have been perfect. It will tell you exactly what your equipment is doing and allow you more flexibility than you would ever need to run things however you want. Unfortunately, the 127 is not Evolution compatible. But since you already have your A/C, what's done is done. Your HVAC guy is right in that when multi-stage A/Cs don't get hooked up to intelligent t-stats, they take it upon themselves to determine what stage to run. The circuit board in the unit does this by taking into account what variables it can read by itself... like how long it's been running, how often the t-stat is requesting it to run, possibly outside temp, etc. From that, it determines what mode to best run in. It's not anything even close to having an intelligent communicating T-Stat like the Evolution Controller, but it's better than nothing. I think the simple answer here is to go spend some money and buy a multi-stage aware thermostat. That is a no-brainer to me. Bryant model T6-PRH is one option... and you can find it yourself on E-bay for $200 or so. Or I'm sure there are a bunch of other options out there.
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udarrell_2007
16 years ago
If it should happen to have a Dehumidifier TH combo, you would have to set the Dehumid stat to a higher setting.

If the AC is oversized for the temperatures where high humidity is a problem, then you would need to look at ways to reduce the infiltration of humidity, or reduce (Vent,etc.) the interior sources.

I am thinking that when you slide the button to cool or AC the controls are miswired, & the AC will run until you slide the botton to off.

Do NOT short cycle the AC, leave it off for 5 minutes before restarting it!

Some have a differential Stat, where it cycles on at say a setting of 77-F & off at your setting of say 74-F. It would not have a differential as wide as yours is performing.

A two or three degree Temp diferential will save energy.
When the unit is off during the three degree differential, use other fans to move air over the occupant areas.

This can be a real money saver especially with oversized AC & Heat Pump equipment systems. udarrell _ 2007

Here is a link that might be useful: udarrell.com

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