HVAC Questions, Straight Answers

This is the most common complaint we hear in Florida, and it almost always comes down to one of four root causes. The AC is running — it's just not dehumidifying.

Use our interactive dehumidification calculator to see your actual latent load by season, and whether a standalone dehumidifier makes sense for your home.

No — sweating vents are a warning sign, not normal. It means the surface temperature of the vent cover has dropped below the dew point of the room air, so moisture is condensing on it. The same way a cold glass sweats in summer.

Left unaddressed, sweating vents cause water damage to ceilings, drywall, and can grow mold on and around the vent cover. If you're seeing this, it's worth a service call — it's usually diagnostic of a larger issue. See our full explainer: Why Are My Vents Sweating?

Uneven temperatures are almost always a duct design or airflow problem, not an equipment problem. Common causes:

• Undersized supply duct to that room — not enough CFM reaching the space. Rule of thumb: 1 CFM per square foot of room area, more for rooms with large windows or west-facing walls.
• No return air in the room — supply air goes in but can't get back to the air handler. The room pressurizes and the supply register effectively shuts itself off. Fix: a dedicated return grille or a transfer grille above the door.
• Duct leak between the air handler and that room — conditioned air is dumping into the attic before it gets there. Check duct connections at the air handler and at the register boot.
• Sun load / envelope issue — a west-facing bedroom with a large unshaded window can add 2–3 tons of heat in the afternoon that the duct system wasn't designed for.
• Closed doors isolating the room — if you keep the door closed, there's no return path and no airflow. Add a gap under the door or a transfer grille.

A system that runs constantly without reaching setpoint is trying to tell you something. Here are the most likely causes in order of frequency:

A frozen coil means the evaporator is getting too cold — below 32°F — and moisture in the air is freezing on the coil surface instead of draining away as liquid. Two main causes:

• Airflow restriction — a dirty air filter is the #1 cause. With restricted airflow, the coil gets too cold because there isn't enough warm air passing over it. Check and replace your filter first. Also check for blocked return grilles or closed supply registers.
• Low refrigerant charge — with too little refrigerant, the pressure in the coil drops and the temperature drops below freezing. The ice you see is the symptom; the leak is the problem.

It depends on where it's dripping. Some water management from the AC is normal — the coil removes gallons of moisture from the air every day, and that condensate needs to drain somewhere.

• Water dripping from the condensate drain pan — normal if draining properly. The primary drain line should route to the outside. If it's flowing outside, everything's working.
• Water overflowing the drain pan — clogged drain line. Florida's humidity means algae and mold love growing in condensate lines. If the primary drain line is clogged, water backs up and overflows the pan. This is the most common cause of ceiling water damage from AC systems. Fix: flush the drain line with diluted bleach (a cup of 50/50 bleach/water poured into the drain pan access port every 3–6 months prevents this).
• Water on the ceiling below the air handler — secondary pan is overflowing. This means the primary drain has been clogged long enough to overflow into the secondary pan, and now the secondary is overflowing too. Turn the system off and call immediately — ceiling damage is likely.
• Water around the indoor unit on the floor — frozen coil thawing. Shut off the AC, run fan only, replace the filter, and call if it repeats.

HVAC noises are diagnostic. Here's the translation:

• Banging or clanking — something loose or broken inside the air handler or outdoor unit. Blower wheel, fan blade, or loose component. Turn off the system and call. Running it risks more damage.
• Squealing or screeching — blower motor bearings failing, or the belt on an older belt-drive blower is worn. This is a warning — a bearing failure will follow if not addressed.
• Clicking at startup or shutdown — normal. The contactor in the outdoor unit clicking on and off is normal. Rapid clicking that keeps repeating without the unit starting is a contactor or capacitor failure.
• Humming from the outdoor unit without the fan spinning — capacitor failure. The capacitor starts the compressor and fan motor. It's a cheap and common repair. Don't ignore it — a failed capacitor that keeps cycling can damage the compressor.
• Hissing or bubbling — refrigerant leak. Hissing is refrigerant gas escaping under pressure. Bubbling at the refrigerant lines or coil is refrigerant and oil mixing at a leak point. Call a tech — this is an EPA-regulated repair.
• Rattling from supply registers — loose duct connection or loose register. Usually harmless but annoying. Check if the register screws are tight.

A sudden jump in your electric bill almost always has a diagnosable cause. Work through these in order:

• Low refrigerant charge — a system running low on refrigerant works much harder to move the same amount of heat. It runs longer, draws more amps, and your bill climbs. If your bill went up gradually over a year, this is a common culprit — slow leak.
• Dirty air filter or coil — restricted airflow makes the blower motor work harder and reduces heat transfer efficiency at the coil. A clogged filter can increase electricity use by 5–15%.
• Duct leakage — studies show the average Florida home loses 20–30% of conditioned air to duct leaks into the attic. That's money you're paying to cool your attic. A duct blaster test measures exactly how much you're losing.
• Failing capacitor or contactor — a weak capacitor makes the compressor work harder to start, drawing more power per cycle. A failing contactor causes the system to cycle on and off more frequently.
• Equipment aging past its efficiency curve — a 15-year-old system may be rated SEER 10 and running at SEER 7 due to wear. A new SEER2 16+ system can cut cooling costs by 30–40% in Florida's long cooling season.

The industry rule of thumb is the 5,000 rule: multiply the system age (years) by the repair cost (dollars). If the result exceeds $5,000, replacement is usually the smarter financial decision.

But in Florida, we'd modify that rule with a few additional factors:

• Coil material — if the system has copper evaporator coils and you're in a coastal or high-humidity area, ask whether formicary corrosion has already started. A repaired coil that fails again in 2 years makes the math worse.
• Refrigerant type — R-22 systems are being phased out. R-22 refrigerant now costs $100–$200/lb. If you have an R-22 system that needs a refrigerant charge, that repair cost alone can tip the scale.
• System age over 12–15 years — Florida systems run harder than average due to year-round runtime. Expected service life here is 12–16 years vs. the national 15–20 average. An older system in Florida is at increasing risk for compressor failure, which is usually not worth repairing.
• Efficiency delta — a new SEER2 16+ system vs. a 10-year-old SEER 13 system can save $400–$700/year on cooling costs in Florida. That savings pays toward the replacement cost.

Florida is in DOE Climate Zone 2 (hot-humid), which has the highest minimum SEER2 requirement in the country — currently 15.2 SEER2 (roughly equivalent to SEER 17–18 by the old standard) for new residential central AC systems.

In Florida's long cooling season (9–10 months), the return on a higher-efficiency system is real. A rough breakdown:

• SEER2 15–16 — meets minimum code, fine for budget installs. Good choice if you're not planning to stay in the home long-term.
• SEER2 18–20 (variable speed) — the sweet spot for most Florida homeowners. Variable-speed compressors also dramatically improve humidity control — worth more than the efficiency rating suggests in this climate.
• SEER2 22+ — premium tier. The payback period is longer (8–12 years for the efficiency premium alone), but if humidity control, comfort, and noise matter — these systems run near-silent at low speed most of the time.

The honest answer: it depends on your filter type, return configuration, and what's happening in your home. Manufacturer recommendations of "every 90 days" are based on average conditions — Florida is not average.

• 1-inch standard filter (MERV 7–8) — check monthly, change every 30–45 days in Florida. The high humidity, year-round runtime, and airborne pollen/dust load it faster than manufacturers assume.
• 4–5 inch media filter (MERV 11–13) — change every 6–12 months, but check quarterly. These last longer but can restrict airflow severely if ignored.
• During construction, renovation, or high dust events — check every 2 weeks. Construction dust will clog a filter in days.
• Pets — add one month to your normal interval as a check frequency.

Annual maintenance is real. The upsell is real too — they're not mutually exclusive. Here's what a legitimate tune-up should actually do:

• Refrigerant charge check — a technician measures superheat and subcooling to verify the charge is correct. A system running 5% undercharged loses meaningful efficiency. This requires gauges and training.
• Electrical check — capacitor and contactor testing. Capacitors fail on a wear curve and are cheapest to replace on a maintenance visit rather than an emergency weekend call.
• Coil cleaning — both evaporator and condenser coils should be inspected and cleaned. A dirty condenser coil can increase energy use by 30%.
• Condensate drain flush — prevents the clogged-drain ceiling damage scenario described above.
• Filter check — yes, they check your filter, but you should already know the answer to this one.
• Temperature differential check — supply vs. return air temp tells you at a glance whether the system is moving the right amount of heat.

What a legitimate tune-up should not do: tell you the system needs refrigerant without measuring it, recommend a part replacement without showing you the test result, or quote a $3,000 add-on on a system that's running fine.

For most Florida homes, a heat pump is the better choice — and not primarily for efficiency reasons.

Florida winters are mild (40–65°F), which is exactly the range where heat pumps are most efficient. A heat pump in Florida's climate will use 40–60% less electricity for heating than electric resistance heat strips.

But here's the Florida-specific consideration most contractors skip: heat pumps have a reversing valve that changes refrigerant flow direction for heating mode. In heating mode, the outdoor coil becomes the evaporator — it gets cold and pulls moisture out of outdoor air. This means in Florida's humid winters, your indoor coil runs dry during heating cycles, which actually reduces indoor humidity. Straight cool systems with electric strip heat do the opposite — they add heat without touching the humidity, so your house gets warm but damp.

• Heat pump — better for efficiency, better for humidity management in transitional seasons, better total comfort in Florida's mild winters. Standard choice.
• Straight cool + gas heat — only makes sense if you have natural gas and want the fastest heat output. Not worth it for most Pinellas County homes.
• Straight cool + electric strips — the least efficient option. We don't recommend it for Florida new installs unless there's a specific reason.

Your AC was designed to dehumidify as a byproduct of cooling — not as its primary function. In Florida, that distinction matters for about 6 months of the year.

Your AC can handle it if: the system is properly sized (not oversized), has a variable-speed compressor, and you're running it enough to process air volume. During high summer with the system running most of the day, a correctly installed system will keep humidity in range.

You likely need a standalone dehumidifier if:

• Your indoor RH stays above 55–60% when the AC is running
• You have a vacation home or run the AC on a setback schedule
• You notice condensation on windows or cold surfaces in fall/winter/spring
• Your system is correctly sized but it's a single-stage compressor
• You're seeing mold recurrence on walls, in closets, or in the air handler

Use our Dehumidification + Sizing Calculator to calculate your actual latent load, see the season-by-season picture, and size a dehumidifier correctly using AHAM derate factors.

Yes, with one important caveat specific to Florida.

Smart thermostats save energy through scheduling and learning — the typical claim is 10–15% savings. In Florida's long cooling season, that's real money. They also give you remote access, runtime data, and filter reminders, which are all practical benefits.

The Florida caveat: setback schedules and humidity. In most climates, letting the house get warm while you're away and then cooling it down when you return saves energy. In Florida, that logic can backfire. If you let the house sit at 82°F while vacant, the humidity rises — especially in a house that isn't particularly tight. When the AC kicks back in, it has to remove all that accumulated moisture in addition to cooling the air. That moisture spike can feed mold growth in the ductwork and walls over time.

For vacant or seasonal homes, pair a smart thermostat with a smart humidity sensor or a whole-home dehumidifier on its own humidity controller. The dehumidifier can run independently of the AC to maintain RH below 55% even when the AC is on a setback.