Tell us about the job
Takes about a minute. No obligation.
Sizing a central AC system in Pettis County starts with what the compressor is actually being asked to carry each year. Homes in Pettis County, MO run cooling about four months a year, from June through September. The compressor, the condenser fan, and the contactor all accumulate wear with each start-stop cycle across those months, and a system that is undersized runs longer cycles to keep up, which pushes those components harder. A contractor who skips a proper load calculation and installs to a rough square-footage guess is setting the equipment up to fail at the contactor and capacitor first. Ductwork condition matters too, because leaky ducts make the compressor work against itself all season.
Existing ductwork is where most central AC installations in Pettis County either hold together or get complicated. Half the homes in Pettis County, Missouri were built in 1974 or earlier (2020-2024 ACS 5-year). Houses built by then were designed around the heating and cooling equipment of that era, and the duct layouts that made sense for that equipment often do not move air the way a modern central AC system needs. A contractor sizing new equipment has to look at the trunk lines and branch runs already in the walls before a unit gets ordered, because retrofitting to what is there is a different project than installing into ductwork that matches the load.
The Parts of a Central AC System Being Installed
The outdoor condenser unit sits outside the house, usually on a concrete pad against an exterior wall, and houses the compressor and condenser coil. Inside, the air handler or furnace-mounted evaporator coil sits in a utility room, basement, or attic and is the indoor half of the system a contractor ties into the ductwork.
The thermostat mounts on an interior wall and is the control point for the whole system. A refrigerant line set runs between the indoor and outdoor units, and a condensate drain line carries moisture away from the evaporator coil to a floor drain or outdoors.
The drawing shows a typical layout, and a licensed contractor determines exactly what applies to this house.
Get matched in Pettis CountyPettis County, by the numbers
94 severe weather events were recorded in Pettis County, Missouri between 2015 and 2024.
NOAA National Centers for Environmental Information, Storm Events Database, bulk CSV export, events 2015-01-01 through 2024-12-31.Half the homes in Pettis County, Missouri were built in 1974 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesPettis County, Missouri holds 18,673 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 69.1% of the occupied homes in Pettis County, Missouri (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesRules & Standards Governing Central AC Installation in Pettis County, Missouri8 sourced rules and standards
What happens on installation day in Pettis County
Split-system central air conditioners rated below 45,000 Btu/h manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Split-system central air conditioners rated at or above 45,000 Btu/h manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Split-system central air conditioners manufactured between January 1, 2015 and December 31, 2022 had to meet 13 SEER, the metric that preceded SEER2.
Single-package central air conditioners manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Space-constrained central air conditioners manufactured on or after January 1, 2023 must meet a federal minimum of 11.7 SEER2.
Federal efficiency standards for split-system central air conditioners and heat pumps are set on each certified combination of outdoor unit and indoor coil rather than on the outdoor unit alone.
Residential and light commercial air conditioning and heat pump systems assembled in the field, including mini-splits and unitary systems, may not be installed on or after January 1, 2025 using a refrigerant with a global warming potential above 700.
A field-assembled system whose specified components were all manufactured or imported before January 1, 2025 carries no installation compliance date under the refrigerant restrictions and may still be installed.
Severe Weather Events in Pettis County
Weather here puts real load on cooling equipment, and that load shapes what a system needs to handle over its life. Sizing and installation decisions for central AC are local decisions, and the record of what this area sees is part of that picture.
94 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.