System Replacement in Houston
Nobody wants to replace a system that one more repair could save. But there comes a point where each repair only buys a few months. A new system makes sense when a repair no longer does, and the way to find that point is to look at the whole system, not just the part that failed.
Signs It May Be Time to Replace
- Repeated breakdowns, with a new repair every season or two
- An older system, with parts that are getting hard to find
- Rooms that never even out: one too warm, another too cold
- Energy bills that keep rising while your habits stay the same
- A system that runs all afternoon and still can’t keep up
What Replacing a System Means
Most homes heat and cool with a split system. The outdoor unit, an AC condenser or a heat pump, sits on a pad beside the house. The indoor unit lives in the attic, a closet or the garage: either a gas furnace with an evaporator coil on top, or an air handler with a coil and electric heat strips. Copper refrigerant lines and a thermostat wire tie the two halves together, and the ducts carry the air.
Replacing a system usually means replacing both halves at once. The outdoor unit and the indoor coil are built and rated as a matched pair. A new outdoor unit on an old coil may fall short of its rating, and it may not even use the same refrigerant. The refrigerant lines get checked and reused or replaced, and the thermostat is matched to the new equipment. The ducts usually stay, as long as they’re sized right and sound.
Rooms Without Ducts
For a garage conversion, an addition or a room the ducts never reached, a ductless mini-split is another way to go: a slim head mounted high on the wall, joined to a small outdoor unit by a refrigerant line through the wall.
Sizing a New System
Two numbers describe any new system, its tonnage and its SEER2 rating: how much cooling it delivers and how efficiently it does it. One ton of cooling moves 12,000 BTUs of heat an hour, and most houses land somewhere between 1.5 and 5 tons. A higher SEER2 means less electricity for the same cooling.
Bigger isn’t better. An oversized system cools the air fast and shuts off before it pulls the moisture out, so the house feels cold and clammy, and that matters in a humid climate. The short on-and-off cycles wear parts faster too. An undersized system runs nonstop on the hottest afternoons and still falls behind.
How is the right size for a new system worked out?
With a load calculation rather than a rule of thumb. The trade’s standard method, Manual J, adds up how much heat each room gains on a hot day and loses on a cold one, using the square footage, insulation, windows and the way they face, air leaks and ducts in a hot attic. The old unit’s size is only a starting point. It may have been wrong from day one, and a house with new windows or more attic insulation often needs less.
Can a new system use the old ductwork?
Often, yes, if the ducts are sized for the new system’s airflow, sealed and in good shape. Ducts that are too small push the static pressure up, so the blower strains and the system moves less air than it’s rated for. Crushed flex duct, loose joints and bare ducts in the attic are worth a ductwork repair at the same time.
When Repair Wins, and When Replacement Does
No single rule decides it. The system’s age, its overall condition and the part that failed all count, and the same failure can point either way.
| Situation | Repair Usually Makes Sense | Replacement Usually Makes Sense |
|---|---|---|
| One part fails: a capacitor, a motor or a drain line | The rest of the system is sound and runs well | The same part keeps failing, or others are close behind |
| The compressor fails | The system is fairly young and the coil is healthy | The system is older, or it runs on R-22, which is no longer made |
| A refrigerant leak | A single leak at a fitting or valve, found and sealed | Leaks keep turning up on an older system, or the coil is corroded through |
| Rooms heat and cool unevenly | Leaky or crushed ducts are starving some rooms of air | The system was never sized for the house, or an addition changed the load |
| Energy bills keep climbing | Dirty coils, a low charge or a clogged filter are stretching run times | A clean, tuned older system still runs long and can’t keep up |
| A furnace heat exchanger cracks | A newer furnace can sometimes take a replacement heat exchanger | On an older furnace, a new furnace is the usual answer |
Age is a guide, not a rule. Many systems last somewhere around 12 to 15 years in Houston’s long cooling season, while a furnace, which works far fewer hours here, often outlasts the air conditioner it’s paired with.
A Typical Install Day
Installers generally start by disconnecting and removing the old equipment. The new outdoor unit goes on a level pad, and the new furnace or air handler and coil go in where the old ones sat. The refrigerant lines are brazed, pressure-tested with nitrogen and pulled into a deep vacuum to clear out air and moisture before the refrigerant is released into the system.
Then come the electrical connections, the condensate drain with its float switch, and the thermostat. Startup checks finish the job: the refrigerant charge, the airflow across the coil, the temperature drop at the vents and the safety controls, so the new system runs the way it was designed to.
How long does an install day take?
A straight swap of the indoor and outdoor units, on ducts in good shape, generally fits in one full day. Moving equipment to a new spot, running new refrigerant lines, changing the ductwork or adding a mini-split can stretch the job to two or three days. Expect the heating and cooling to be off for most of the work.
What happens to the refrigerant in the old system?
It gets recovered into a tank before the old equipment is disconnected. Venting refrigerant into the air is against federal law, so recovery comes first on any replacement.