Often, homeowners think the best course of action is to replace an old air conditioner with a new one with the same tonnage rating. It makes sense because the old air conditioner worked just fine for several years, and the tonnage rating is directly correlated with that. Comfort issues can still arise even after installation, because the tonnage rating provides no information about how the system will operate in a particular house. The house itself could have changed, with new windows, insulation, a remodel, or even changes in daily habits that increase heat and moisture. The ductwork could also be restricting airflow, and a new air conditioner may respond differently to this restriction than the old one.
Same size, different outcome
- Old Tonnage Does Not Equal Current Load
The amount of cooling a home needs doesn’t stay the same, even if the square footage is the same. Adding insulation, sealing air leaks, changing the roof, and planting new trees to block the sun can all lower the load. Adding more space, an open floor plan, and more west-facing windows can all raise the load. People also change how they use the house. More people living there, working from home, cooking more often, and electronics running all day can all make the room hotter and raise the humidity. If the old system was too large, it might have cooled quickly and shut off, resulting in uneven temperatures and higher humidity. The household might have thought this was normal. However, if you swap the unit for one of the same tonnage, oversizing may still occur, and the new unit may cycle faster under normal conditions. If the old unit was undersized, it might have been running for a long time, and duct leaks might have been hidden. A new unit of the same tonnage might indicate airflow issues, since it must be properly delivered to function as expected. If you size the unit by tonnage without recalculating the load, you could end up with outdated assumptions that no longer apply to the house.
- Airflow and Duct Losses Can Turn Matching Tonnage Into Trouble
Problems with comfort after replacing the same tonnage often relate to airflow. The previous system may have operated at a low airflow rate for many years due to restrictive returns, small ducts, dirty coils, or high static pressure, and the home may simply have tolerated it. A new air conditioner with the same tonnage rating could have a different indoor coil, blower shape, or required airflow range, which could cause other problems in the same ducts. At low airflow rates, the coil may be colder, leading to noisy operation, reduced capacity, and humidity issues that can make the home feel unstable. At high airflow rates, the dehumidification rate could decrease, and the air could be cool but feel sticky. Duct leakage is also important because the new equipment may produce higher pressures that can force more air out of leaks or more hot attic air into returns. In many changeout projects, a contractor overseeing Air Conditioning Installation in Tarzana will see that return size corrections, duct connections, or blower changes can resolve comfort problems that would have occurred even though tonnage capacity remained the same. A tonnage-matching system requires an air-delivery system that matches to feel right.
What Same Tonnage Replacement Misses
However, even if the replacement AC has the same tonnage, there can still be a difference in comfort because the conditions are never the same as before. The loads change due to insulation, windows, air leakage, and shading, so the old size may no longer be appropriate for current conditions. Duct restrictions and air leakage can reduce airflow, and a new coil and fan may perform differently under the same static pressure. Cooling may be quicker, but removing humidity and reducing air mixing could result in warm spaces, cold air, or constant cycling.
Fleetwell Air Conditioning, Heating, and Plumbing
Address: 18356 Oxnard St #3, Tarzana, CA 91356, US
Phone: 747-349-3377
Eli Moshehai