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Sizing central AC for a house in Clark County means planning around a compressor that runs hard for a concentrated stretch and then stops. Homes in Clark County, MO run cooling about three months a year, from June through August. That idle period works against the equipment in its own way: seals dry, contactors corrode, and a system that was undersized or poorly charged at installation has nowhere to hide its faults until the first call for cooling. A contractor quoting the job has to run a proper load calculation against the actual house, because a unit that cannot keep up on the first genuinely hot day will not recover once the season is running.
Ductwork laid in for an earlier generation of equipment is the first thing a contractor has to evaluate in Clark County before anything else in the job can be priced. Half the homes in Clark County, Missouri were built in 1970 or earlier (2020-2024 ACS 5-year). That gap between what the house was built around and what a new unit requires is where the installation work actually lives. Ducts sized for an older system may not carry the airflow a modern central AC unit pushes through them, and the electrical service in a house of that vintage was sized for a smaller load than today's equipment draws. Both get looked at before the unit itself is selected.
What a Central AC System Includes
The outdoor condenser unit sits on a pad outside the house and holds the compressor and condenser coil, the two components that do the heaviest work in the system. Inside, the air handler or furnace cabinet stands in a utility space, basement, or closet and moves air across the evaporator coil, which is mounted directly on or above it.
The thermostat goes on an interior wall where it reads the air temperature and signals the system to run. A refrigerant line set, two copper lines wrapped in insulation, runs between the outdoor unit and the indoor coil and is the physical link that ties the whole system together.
The drawing shows a typical layout, and a licensed contractor determines exactly what applies to this house.
Get matched in Clark CountyClark County, Missouri, by the numbers
89 severe weather events were recorded in Clark 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 Clark County, Missouri were built in 1970 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesClark County, Missouri holds 3,233 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 78.3% of the occupied homes in Clark 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 Clark County, Missouri8 sourced rules and standards
What the installation looks like in Clark 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 Clark County
Extreme weather puts real strain on cooling equipment, and the load a system carries depends on what the local climate actually delivers. That makes the weather record for Clark County a practical input when sizing and installing central AC here.
89 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.