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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8678
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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We bought a new house and had a company install new AC and

Customer Question

We bought a new house and had a company install new AC and insulate the house (with some sort of government rebate). It's a split level and the thermostat is on the 2nd floor in the hallway. They also checked the house, windows etc and all seemed good.
Now the temp is set at 72, but for many hours it's 76 or 74, and will not go down after running continuously. The company claims that the thermostat is in the wrong place, the house is old etc.
1. Can we expect the temperature to be what we set it to no matter where the thermostat is located?
2. How long should it take to go from 74 to let's say 70 if it's 85 degrees outside?
3. If something is wrong, what do you think would be the problem?
Submitted: 2 years ago.
Category: HVAC
Expert:  Phil replied 2 years ago.
Hello,Tell me please what you know about the insulation, and the brand and model number of the unit that sits outside, and the local climate conditions (so that I can asses the heat and humidity levels). We can go from there.
Customer: replied 2 years ago.

Hello. Sorry it took me so long. Attic was just air sealed and 6" of insulation was installed. We are in NJ, temperatures are 70-80, don't know the humidity. The new AC unit is a Rheem 14ajm30a01

Expert:  Phil replied 2 years ago.
Hello again, No thermostat is 100% accurate, plus or minus 2 degrees F is common. Beyond that there are 'dead band' settings inside the thermostat, generally set at plus or minus one or two degrees. The way to test these is set the thermostat to extremes for instance, tomorrow, when the house gets up to 76F, set the thermostat to 68F and see if the house cools down to 72F quickly or not. That is test number one. -------------------- Test #2 requires you to buy a cheap thermometer, and then poke it into one of the cold air vents when the system is running for a while in cooling mode, and read the temperature. Next use the exact same thermometer to read the room air temperature. I am looking for the temperature difference, 15F is the least I am looking for, 20F difference is a real good number. Tell me what you discover, we can go from there tomorrow. I am off to bed tonight. .
Customer: replied 2 years ago.

thank you

Expert:  Phil replied 2 years ago.
Hello again, did you do the two tests I mentioned?

Did the house cool down quickly when you set the thermostat more than 3 degrees cooler than the room temperature?

What was the cold air temperature coming from the cold air supply registers when the system was cooling, and with the thermometer poked into the register?

We can go from there without a time limit.


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