What a Cheap Install
Actually Looks Like

A Manual J calculation is a room-by-room analysis of your home's heat gain — windows, insulation, ceiling height, orientation, occupancy, local climate data. It takes 1–2 hours and tells you exactly what size system your home needs. Most low-bid contractors don't do it. They use square footage ÷ 500 = tons, or they just match whatever you had before.

The result is almost always an oversized system. Oversized in Florida means short-cycling — the system cools the air quickly, hits setpoint, and shuts off before it can remove meaningful moisture. Your house is cool but clammy. You set the thermostat lower trying to fix it. The electric bill goes up. The humidity stays. The system runs in short bursts, which is the hardest operating condition for a compressor.

A system oversized by one ton in a Florida home wastes roughly $600–900/year in electricity and reduces system lifespan by 3–5 years.

The return duct is the opening through which your system pulls air from the house to condition it. It needs to be large enough for the system to breathe. Cutting return duct size saves time and sheet metal — and it's invisible once the drywall is up.

An undersized return creates high static pressure, which the blower motor fights against on every single cycle. Static pressure above 0.8 in. w.c. stresses the blower motor, reduces airflow, lowers both sensible and latent capacity, and in severe cases causes the coil to freeze. The homeowner notices the house doesn't cool well and calls for a refrigerant charge — which isn't the problem. The return duct is the problem.

We use a duct size calculator on every install to verify return sizing before we touch anything. It takes 10 minutes. Most low-bid contractors skip it entirely.

Flexible duct is faster and cheaper to install than sheet metal. It's legitimate when installed correctly — fully extended, with gentle bends, properly supported. When it's thrown in an attic without care, the physics become brutal. A single 90-degree kink in a flex duct run reduces airflow by 50%. A duct lying on the attic floor compressed under its own weight loses 30–40%.

Rooms at the end of compromised flex duct runs are always the worst in the house. Hot in summer, doesn't cool down at night, humidity climbs. The homeowner gets told they need a bigger system. They don't — they need their flex duct hung properly.

Your air handler is under negative pressure — it's pulling air in. Without a P-trap on the condensate drain line, that negative pressure draws air backward through the drain, which either prevents the condensate from draining or allows sewer gases into the air handler cabinet. In Florida, where a 3-ton system removes 20–30 pints of water per day, a drain that doesn't drain is a water damage event waiting to happen.

A P-trap is a $4 PVC fitting that takes two minutes to install. It gets skipped because it requires a few extra inches of vertical drop below the drain pan — which sometimes means raising the air handler slightly, which takes time. So it doesn't happen.

Water damage from a backed-up condensate drain — saturated ceiling drywall, wet insulation, mold in the air handler bay — runs $2,000 on the low end and can exceed $15,000 if it reaches floor joists or gets into walls before it's found.

Verifying correct refrigerant charge requires measuring superheat or subcooling under actual operating conditions and cross-referencing against the manufacturer's charging chart for the ambient temperature. It takes 20–30 minutes of the system running. Charging by "pressure" or by feel is not commissioning — it's guessing.

A system running 10% low on refrigerant loses roughly 20% efficiency, dehumidifies less effectively, and stresses the compressor on every start. A system overcharged by 10% has the opposite problems and can cause liquid slugging in the compressor. Neither shows up immediately — they show up in your electric bill and in a compressor that fails at year 7 instead of year 15.

High-efficiency systems (16 SEER2 and above) are AHRI-rated with a TXV (thermostatic expansion valve) as the metering device. A piston orifice is cheaper and simpler. Some installers swap the TXV for a piston to save cost and time. The result: the system you paid for is not the system you got.

A piston-equipped system running at Florida's variable conditions — morning humidity vs. afternoon heat vs. evening cooldown — will charge-shift throughout the day, running slightly rich or lean depending on conditions. The AHRI efficiency rating you bought is voided. The warranty on some equipment may also be voided by installing an non-approved metering device.

Every duct connection — boot to flex, flex to trunk, trunk to air handler — needs to be sealed with mastic or foil tape. Not duct tape (which fails in attic heat within 2 years). Skipping sealing saves 30–45 minutes of labor. It costs you in conditioned air leaking directly into your attic.

A Florida attic in July runs 130–145°F. When conditioned 75°F air leaks into that environment, the system has to replace it with more conditioned air — continuously. Industry studies put duct leakage losses in unsealed systems at 20–30% of total system output. That's roughly $500–$1,200 per year in Pinellas County, depending on system size and usage.

The suction line — the larger copper refrigerant line running from the air handler to the outdoor unit — carries cold refrigerant and will sweat if not properly insulated in a Florida attic. Factory insulation on refrigerant lines is typically 3/4" wall. In a Florida attic environment, that's often not enough — and cheap installs use whatever insulation came with the line set, applied hastily.

A sweating suction line in the attic means moisture dripping onto the attic floor, potentially onto the air handler cabinet, and in some cases into the living space below. It also means the refrigerant is picking up heat before it reaches the coil, reducing efficiency. Split or missing insulation on a line set that runs through an unconditioned attic can void manufacturer efficiency ratings.

Every air conditioning system has a nameplate minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP) — the wire size and breaker size the manufacturer requires. When a larger system replaces a smaller one, the existing wiring and breaker may not be adequate. Verifying this takes 10 minutes. Upgrading it takes more time and sometimes requires an electrician — which costs money the low-bid contractor didn't allow for.

An undersized circuit causes nuisance tripping, voltage drop at the compressor on startup, and in severe cases overheating of the wiring. A missing or inadequate disconnect at the outdoor unit is a code violation that shows up during permit inspection — if there is one.

HVAC replacement in Florida requires a permit in virtually every municipality. The permit triggers an inspection — an independent check that the installation meets code. A contractor who skips the permit is telling you they don't want anyone else looking at their work.

An unpermitted HVAC system is a liability that follows the home. When you sell, it shows up in the permit history search. Your homeowner's insurance may deny a claim related to an unpermitted system. If something goes wrong — a fire, a flood from a failed drain line — the insurance company will ask whether the work was permitted. The answer will matter.

Permits cost $75–$200. They add a week to the timeline. Some contractors pass the cost to the homeowner, some absorb it. None of these are reasons to skip them.

Commissioning means verifying the system is operating correctly under actual load conditions — measuring delta-T, static pressure, refrigerant charge, airflow, and electrical draw — and documenting the results. Without a commissioning report, there is no baseline. When the system develops a problem in year 3, nobody knows whether it was there at installation or developed over time.

A complete commissioning report protects you: it proves the system was installed correctly and performing to spec on day one. It's your evidence if a warranty claim is ever disputed. It's the starting point for every future maintenance visit.