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Sizing a central AC system for a Franklin County home starts with what the compressor is actually asked to do. Homes in Franklin County, MO run cooling about three months a year, from June through August. The contactor, the condenser fan, and the compressor itself cycle hard through those weeks, then sit dormant the rest of the year. Long idle periods let small faults develop quietly, and a refrigerant leak or a failing contactor shows itself only when the homeowner flips the system on during the first heat of June. A contractor quoting a new installation here factors that stop-start pattern into equipment selection and commissioning checks, because a system that does not start cleanly on day one of the season has already failed its only real test window.
Ductwork laid out for an older system often cannot move the volume a modern central AC unit needs without modification, and the electrical service in the same house may not carry the load the new unit draws. Half the homes in Franklin County, Missouri were built in 1984 or earlier (2020-2024 ACS 5-year). That is the physical reality a contractor is working inside when a homeowner here schedules an installation: not just swapping equipment, but finding out whether what is already in the walls and ceiling can do the job the new system asks of it. Where the ductwork falls short, the contractor sizes new runs or seals leaking ones before the unit ever goes in.
What a Central AC System Includes
The outdoor condenser unit sits outside the house, usually on a concrete pad beside the foundation, and it holds the compressor and condenser coil. Inside, the air handler or furnace-mounted evaporator coil sits in a utility space, basement, or closet and works with the outdoor unit to move conditioned air through the home.
The refrigerant line set runs between the two units, carrying refrigerant through insulated copper tubing that a contractor routes along the exterior or through wall cavities. A thermostat mounts on an interior wall and serves as the control point for the whole system.
The drawing shows the general layout of a central AC system, and a licensed contractor determines what that looks like in your specific house.
Get matched in Franklin CountyFranklin County, by the numbers
129 severe weather events were recorded in Franklin 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 Franklin County, Missouri were built in 1984 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesFranklin County, Missouri holds 46,312 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 76.5% of the occupied homes in Franklin 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 Franklin County, Missouri8 sourced rules and standards
What HVAC Installation Looks Like in Franklin 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 Franklin County
The workload a central AC system carries is shaped by local conditions, and Franklin County's weather history is part of what determines how hard that equipment has to work. Sizing and installing a system here is a local decision, and local climate data belongs in that picture.
129 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.