🏠 Introduction: The Most Overlooked Part of System Design
Most homeowners think a thermostat is just a fancy temperature dial.
Most installers think it can go “anywhere convenient.”
Tony thinks both are wrong.
In his words:
“Your thermostat is the brain of the whole system.
If you put the brain in a dumb place, you get dumb comfort.”
Thermostat placement affects:
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What temperature the system thinks the home is
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How long the system runs
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How often it cycles
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How much humidity it removes
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Whether it overheats or overcools
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Whether it short-cycles (which kills efficiency and comfort)
This article is Tony’s complete field guide — 35+ years of trial and error — for thermostat and sensor placement that actually delivers real-world comfort and efficiency.
3 Ton 15.2 SEER2 80,000 BTU 96% AFUE Goodman Upflow Air Conditioner System
🎯 1. Why Thermostat Location Matters More Than the Thermostat Brand
Homeowners obsess over smart thermostats:
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Nest
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Ecobee
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Honeywell T9/T10
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Emerson Sensi
Tony says:
“You can buy the smartest stat in the world.
Put it in the wrong place and it becomes the stupidest.”
That’s because thermostats measure air temperature, not:
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Wall temperature
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Floor temperature
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Human comfort
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Humidity distribution
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Duct imbalance
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Solar gain
If the thermostat sits in a location that doesn’t represent the home’s average conditions, your system will ALWAYS run wrong.
✔️ Verified thermostat fundamentals: https://www.energy.gov/energysaver/thermostats
🚫 2. The 10 Worst Thermostat Locations (Tony Sees These Every Week)
❌ 1. Near Supply Registers
This is the #1 error Tony sees.
Cold air blasting on the stat:
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Makes AC short-cycle
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Prevents humidity removal
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Causes high humidity (60–70% RH)
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Leaves the rest of the home hot
❌ 2. Above Return Air Grilles
The thermostat reads the temperature of the air being sucked into the system — not the room.
This causes:
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Extremely inaccurate readings
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Constant temperature swings
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Hot–cold complaints
❌ 3. In a Hallway With No Supply Air
Hallways often have no airflow because they’re not “occupied spaces.”
Stat reads 74°F
Bedrooms are 78–80°F
System shuts off early
Comfort suffers
Tony calls this:
“The hallway lie.”
❌ 4. Near Exterior Doors
Drafts ruin readings, especially in winter.
❌ 5. In Direct Sunlight
Sun elevates thermostat reading by 3–10 degrees, depending on wall insulation.
❌ 6. On Exterior Walls
Exterior walls pick up:
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Solar gain
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Wind chill
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Temperature conduction
The stat reads the WALL temperature, not the ROOM temperature.
❌ 7. Behind TVs or Electronics
Electronics generate heat.
Stat thinks the house is warmer than it is.
❌ 8. Near Lamps or Accent Lighting
Heat rises directly onto the sensor.
❌ 9. In Kitchens
Ovens, stoves, dishwashers, and even refrigerator compressors skew temps dramatically.
❌ 10. Above Heat Sources
Fireplaces, space heaters, radiant floors … all ruin temperature accuracy.
✔️ Thermostat placement guidelines: https://www.energystar.gov
📍 3. The Best Places to Put a Thermostat (Tony’s Rules)
✔️ 1. On an Interior Wall
Interior walls stay closer to the true average house temperature.
✔️ 2. In a Central Living Area
Tony prefers:
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Living room
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Family room
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Main hallway IF it has a supply register
✔️ 3. Away From Windows & Exterior Doors
No drafts = stable readings.
✔️ 4. Eye Level (57–62 inches from floor)
This height aligns with standard human comfort readings.
✔️ 5. At Least 4–6 Feet From Supply and Return Air
This prevents supply blast or return suction from skewing readings.
✔️ 6. Near the Center of the Home’s Airflow Pattern
This is the “average zone” where temperature matches general occupant experience.
Tony says:
“The best thermostat location is where YOU spend most of your time — not where the installer feels like putting it.”
🔍 4. How Poor Thermostat Placement Wrecks SEER2 Efficiency
SEER2 (the new efficiency standard) requires more precise airflow and pressure management.
Thermostat misplacement causes:
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Short cycling
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Long cycling
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Overcooling
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Overheating
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Bad humidity control
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Increased runtime hours
Which directly drops real-world efficiency by 10–25%.
Tony explains:
“SEER2 is based on lab testing. Your house ain’t a lab. One bad thermostat placement and you lose half your efficiency gains.”
✔️ SEER2 efficiency documentation
🌬️ 5. Thermostat Placement & Airflow — The Hidden Connection
Most installers treat airflow and thermostat location as separate topics.
Tony doesn’t.
Thermostat placement impacts:
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How sensors read airflow temperatures
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Coil temperature split
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Heating heat rise
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Party loads (big crowds = heat)
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Kitchen loads
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Sun exposure to thermostat wall
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Pressure zones created by closing doors
If the thermostat sits in a location that receives wrong airflow, the blower speed, staging, or cooling demand will always be incorrect.
This is why Tony says:
“Airflow and thermostat placement are married. You can’t separate them.”
✔️ Airflow and pressure reference: https://www.acca.org
🌡️ 6. Thermostat Placement vs. Humidity: Why You Can Have Perfect Cooling but Miserable Air
Humidity is the silent destroyer of comfort.
Many thermostats have:
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No humidity sensor
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A humidity sensor far from the main thermostat
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A sensor influenced by drafts or supply blasts
The worst-case scenario?
AC short-cycles → humidity stays high → coil warms up → home feels sticky
Tony solves this by placing the thermostat where humidity stays most stable, NOT where temperature is easiest to read.
He prefers:
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Open living rooms
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Central stair landings in two-story homes
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Areas that have consistent airflow
Humidity readings here match the house “average,” which is essential for variable-speed systems.
✔️ Indoor humidity reference: https://www.epa.gov/indoor-air-quality-iaq
🧠 7. Tony’s Real-World Examples: Bad vs. Good Thermostat Locations
🟥 Bad Example #1 — Thermostat in a Hallway With No Supply
AC shuts off early.
Bedrooms stay hot.
Homeowner thinks the AC is undersized.
Tony moves thermostat 12 feet → instantly solved.
🟥 Bad Example #2 — Thermostat on an Exterior Wall
In winter, wall is 4°F colder than room.
Stat thinks house is cold → furnace runs too long → 5–12% energy loss.
Tony moves thermostat to interior wall → furnace runtime normalizes.
🟥 Bad Example #3 — Thermostat Behind a Curtain
Curtain traps heat from supply vent.
Thermostat reads 79°F → AC runs nonstop.
Tony removes curtain → problem vanishes.
🟩 Good Example #1 — Main Living Area Interior Wall
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Normal airflow
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No drafts
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No sunlight
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No electronics nearby
System cycles perfectly.
🟩 Good Example #2 — Multi-Sensor Smart Thermostats
Tony often uses:
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Ecobee remote sensors
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Honeywell T10/T9 sensors
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Smart room-balancing features
He places remote sensors in:
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Hot bedrooms
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Frequently used rooms
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Second floors
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Rooms with high solar gain
The thermostat uses the AVERAGE — not one room’s extremes.
Tony says:
“Multiple sensors are the only way a smart stat becomes smart.”
✔️ Multi-sensor thermostat info: https://www.ecobee.com
🧭 8. Thermostat Placement Rules for Different Home Types
🏠 1. Small Single-Story Homes (1,000–1,500 sq ft)
Ideal location:
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Interior living room wall
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Away from kitchen
Avoid:
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Long hallways
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Bedroom wings
🏢 2. Two-Story Homes
Tony’s rule:
“Thermostat ALWAYS goes on the first floor, sensors go upstairs.”
Upstairs naturally runs warmer.
Putting the stat upstairs overheats the downstairs.
🧱 3. Homes With High Ceilings
Don’t place thermostat near:
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Air stratification zones
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Tall staircases
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Great rooms with 18–20 foot walls
Warm air rises → stat reads too hot → AC runs endlessly.
🌞 4. Homes With Large South-Facing Windows
Tony avoids interior walls that face the sun side of the house.
Why?
The wall itself heats up and tricks the stat.
🚪 5. Homes Where People Close Bedroom Doors
Closing doors creates pressure zones.
Tony uses remote sensors in these bedrooms to “average out” the closed-door problem.
🛠️ 9. Tony’s Installation Checklist: The Perfect Thermostat Location
Here’s the checklist he teaches all new techs:
✔️ Interior wall
✔️ 57–62 inches from floor
✔️ Center of main living space
✔️ Away from direct airflow
✔️ Away from sunlight
✔️ Not near appliances
✔️ Not near return or supply
✔️ Near consistent airflow
✔️ Representing home’s average temperature
✔️ Compatible with remote sensors if needed
If a home violates these rules, Tony relocates the thermostat — period.
⚙️ 10. The Hidden Cost of Bad Thermostat Placement
Bad placement leads to:
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10–25% higher energy bills
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5–10 extra years of equipment wear
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Short cycling
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Furnace limit trips
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Poor humidity removal
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Longer summer runtime
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Hot/cold complaints
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False equipment diagnosis
Tony sums it up:
“If your thermostat is dumb, your whole system acts dumb — even if the equipment is high-end.”
🏁 Conclusion: Your Thermostat Is the Brain — Put It in the Right Place
Thermostat placement isn’t optional.
It dictates:
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Efficiency
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Comfort
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Runtime
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Humidity control
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Staging
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Blower performance
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System lifespan
Tony never installs equipment without verifying the thermostat location first.
His final rule:
“If the thermostat isn’t in the right place, the system can NEVER operate right — no matter what brand you install.”
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In the next topic we will know more about: Don’t Kill the Coil — How Tony Sizes Filters and Returns So the CAPTA3626C3 Doesn’t Become a Block of Ice
