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Sizing a central AC unit for a Union County home is not a generic calculation. The compressor starts and stops through a long run of months, and a system that is undersized for the house strains those cycling parts every single day it runs. Homes in Union County, SC run cooling about five months a year, from May through September. A contractor has to establish the actual load the house puts on the equipment before settling on a unit, because an undersized system in a county with this kind of cooling demand shows wear in the contactor and condenser fan well before it would in a place that barely taxes the equipment. The install quality carries the same weight: ductwork that leaks or a refrigerant charge that is off by even a small amount forces the compressor to work harder through every one of those months.
Ductwork laid in for one generation of equipment does not automatically carry the next. Half the homes in Union County, South Carolina were built in 1972 or earlier (2020-2024 ACS 5-year). That depth of housing stock means a contractor sizing a new central AC system here has to assess the existing duct layout before the equipment conversation goes anywhere, because ducts built for a smaller load may restrict airflow enough to undercut whatever unit gets chosen. The electrical service in houses of this vintage is the same question: a panel sized for an older draw may need an upgrade before a modern system can run on it at all.
What Gets Installed With a New Central AC
The outdoor condenser unit sits on a pad beside the house and holds the compressor and condenser coil, the two components that do the heaviest work in the refrigeration cycle. Inside, the air handler or furnace-based evaporator coil assembly mounts in a utility closet, attic, or basement and is where cooled air enters the duct system.
A refrigerant line set runs between the outdoor and indoor units, carrying refrigerant back and forth through insulated copper tubing. The thermostat mounts on an interior wall and gives the homeowner control over when the system runs and at what temperature.
The drawing shows a typical central AC layout, and a licensed contractor determines exactly what applies to your house and how each piece fits into it.
Get matched in Union CountyUnion County by the Numbers
73 severe weather events were recorded in Union County, South Carolina 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 Union County, South Carolina were built in 1972 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesUnion County, South Carolina holds 13,527 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 71.3% of the occupied homes in Union County, South Carolina (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesRules & Standards Behind Central AC Installation in Union County, South Carolina9 sourced rules and standards
What happens when the contractor arrives
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.
Licensing and Legal Requirements in Union County, South Carolina
South Carolina requires a mechanical contractor license for contracting work whose total cost of construction is greater than ten thousand dollars.
Severe Weather Events in Union County
Weather puts a load on cooling equipment that no generic spec accounts for. How hard a system has to work, and how long it holds up, depends on what the local climate actually does.
73 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.