HVAC questions, answered plainly

Start with the air filter and the thermostat. A clogged filter chokes airflow, and a thermostat set to 'on' instead of 'auto' can make it feel like the system never catches up. If the filter is clean and the outdoor unit isn't running, or the air from the vents isn't cool, the usual causes are a failed capacitor, a dirty outdoor coil, or low refrigerant from a leak. Those need a technician.

A healthy system usually holds about 20 degrees below the outdoor temperature. On a 95-degree afternoon, 75 to 78 inside is normal. Asking it for 68 in the peak of the day will keep it running nonstop without getting there. The better test is the air at the vents: it should be roughly 15 to 20 degrees cooler than the air going into the return.

Ice almost always means too little airflow or too little refrigerant. Turn cooling off and set the fan to 'on' so it thaws, change the filter, and open any closed vents. If it freezes again after a full thaw, there's likely a refrigerant leak or a blower problem, and running it frozen can damage the compressor.

Use 'auto' in the summer here. With the fan on 'auto,' water that condenses on the indoor coil drips into the drain pan and leaves the house. With the fan on 'on,' the blower keeps pushing air across a wet coil between cycles and puts some of that moisture back in the air, which makes the house feel clammy even when the thermostat says it's cool.

Yes. The condensate line carries water pulled out of your indoor air, and on a humid day it can be a steady drip. What isn't normal is water inside: a full drain pan, a wet ceiling under an attic unit, or water around the indoor unit in a closet or crawlspace. That usually means a clogged drain line, and it should be cleared before it causes damage.

SEER2 measures cooling efficiency under test conditions updated in 2023 to better match real ductwork. Higher is more efficient. In the Southeast, new central air conditioners must meet at least 14.3 SEER2 (smaller systems) or 13.8 SEER2 (larger ones). Going higher saves on summer bills, but the savings depend on how much you run the system and how well it's installed.

R-22 hasn't been produced since 2020, so the only supply is recycled and expensive. R-410A is still available for servicing existing systems, but new equipment has moved to lower-impact refrigerants like R-454B and R-32. If an older system has a major leak, that refrigerant cost is one of the things that tips the repair-or-replace math.

That's often normal. A heat pump heats with air around 90 to 100 degrees, which feels cool on your hand compared with a gas furnace's 120-plus. What matters is whether the house holds temperature. If it can't keep up, if the air is truly cold, or if the outdoor unit is caked in ice that never clears, have it checked.

Probably not. In cold, damp weather frost builds up on the outdoor coil, and the heat pump runs a defrost cycle to melt it. During defrost the fan stops, you may hear a whoosh as the valve switches, and steam rises off the unit. A defrost normally lasts a few minutes. A unit that stays encased in ice is a different story.

Aux heat is the backup electric heat strip in your air handler. It kicks in automatically when the heat pump needs help, during defrost or on the coldest mornings. Emergency heat turns the heat pump off and runs on the strips alone, which works but costs a lot more to run. If 'aux' shows up constantly on mild days, something is wrong with the heat pump.

Both work well in York County's mild winters. A heat pump heats and cools with one outdoor unit and is very efficient above freezing, which is most of our winter. A gas furnace gives hotter air and doesn't slow down on the coldest nights. Many homes with gas pair a heat pump with a furnace (a dual-fuel system) and let the thermostat use whichever is cheaper at the outdoor temperature.

Check the easy things first: the thermostat is set to 'heat' and above room temperature, its batteries aren't dead, the furnace switch (it looks like a light switch) is on, the breaker isn't tripped, and the filter isn't clogged. Many furnaces also shut down if the front panel isn't seated. If it still won't fire, count the blinks on the control board's light; that code helps a technician diagnose it.

Any gas appliance should have a working carbon monoxide alarm nearby and on each sleeping floor. A cracked heat exchanger or a blocked flue can leak CO into the house. If a CO alarm sounds, or everyone feels headachy and nauseous at home and better away from it, get outside and call 911 or your gas utility. Yearly furnace inspections exist largely to catch this.

For the common 1-inch filter, check it monthly and change it every one to three months. Change it more often with pets, construction dust, or anyone in the house with allergies. Thicker 4- or 5-inch media filters usually last six months to a year. When you can't see light through it, it's past due.

Twice a year is the standard: the cooling side in spring before the heat arrives, and the heating side in fall. A heat pump runs all year, so it benefits most from two visits. At minimum, a yearly check keeps coils clean, drains clear, and electrical parts tested, and it's often a condition of the manufacturer's warranty.

A real tune-up is more than a quick look. It typically includes checking refrigerant pressures and temperatures, testing capacitors and contactors, measuring the blower and compressor amp draw, cleaning or rinsing the outdoor coil, flushing the condensate drain, checking the thermostat, and changing the filter. You should get a written note of what was found.

Yes, and it helps. Turn the power off at the outdoor disconnect or breaker first, then spray the coil gently from the inside out if you can, or from the outside with low pressure. Never use a pressure washer, which flattens the fins. Keep shrubs and grass at least two feet away so the unit can breathe.

No, and with a heat pump you shouldn't, since it runs all winter. Covers trap moisture and invite rodents. If you have a straight AC with a gas furnace, a piece of plywood on top to keep leaves out is fine, but leave the sides open.

Here, a central air conditioner or heat pump typically lasts about 10 to 15 years, since it cools hard for much of the year. A heat pump works in both seasons, so it tends to sit on the shorter end. A gas furnace often lasts 15 to 20 years or more because it only works a few months a year. Maintenance and installation quality change those numbers more than the brand does.

A common rule of thumb: multiply the system's age by the repair cost. If that's more than about $5,000, replacement deserves a serious look. Also weigh whether it uses R-22, whether it has had repeated repairs, how high the bills are, and whether rooms are uncomfortable. A good contractor will tell you when a repair is the smarter money.

It depends on the house, not just the square footage. The right way is a load calculation (ACCA Manual J) that accounts for insulation, windows, direction, ductwork and air leakage. An oversized system cools fast but shuts off before it pulls out humidity, which is a real problem in our summers. An undersized one runs nonstop on the hottest days.

A straight replacement of an existing split system usually takes one day. Adding ductwork, changing where equipment sits, switching fuel types, or converting to a heat pump can add a day or two. Permits and inspections are part of the job in York, Lancaster and Chester Counties.

In almost every case, yes. The outdoor unit and the indoor coil are designed and rated as a matched pair. Mixing a new outdoor unit with an old coil can lower efficiency, shorten the compressor's life, and void the manufacturer's warranty. With the refrigerant change, older coils often aren't compatible with new equipment at all.

The federal energy-efficiency tax credit (section 25C) that covered heat pumps and high-efficiency equipment ended for equipment installed after December 31, 2025. Rebates from your electric utility may still apply, so check with Duke Energy, Rock Hill Utilities, or your electric co-op before you buy, and ask your tax preparer about anything installed in 2025.

Aim for 40 to 50 percent, and keep it under 60 percent. Above that, the house feels muggy at any temperature and mold and dust mites thrive. An air conditioner removes moisture as it cools, but only if it runs long enough cycles. A cheap hygrometer from a hardware store will tell you where you stand.

It's usually the ductwork or the room, not the equipment. Common causes are a long or crushed duct run, a room with no return air path when the door is closed, leaky ducts in the attic, or a bonus room over the garage with poor insulation. Fixes range from sealing and balancing ducts to adding a return or a ductless mini-split for that room.

The Department of Energy suggests about 78 degrees when you're home in summer and 68 in winter, and turning it back when you're away or asleep. With a heat pump, keep setbacks small (2 to 4 degrees) in winter, because a big morning recovery can trigger the expensive backup heat strips.

For the right space, yes. Mini-splits are efficient, quiet, and don't need ductwork, so they're a strong fit for additions, garages, sunrooms, bonus rooms, older homes without ducts, and rooms the main system never reaches. For a whole house, a ducted system is often simpler, but multi-zone mini-splits can work well there too.

Some do. A good media filter (MERV 11 to 13, if your system can handle the airflow) does most of the work for dust and allergens. UV lights help keep the indoor coil free of mold and biological growth. Be skeptical of any device that promises to kill everything in the air; ask for independent test data.

Weather is the first suspect: a hot July or a cold January can double usage. Past that, look at a heat pump running on aux heat, a system that runs without shutting off, a dirty filter or coil, leaky ductwork in the attic, or a failing component drawing extra power. Compare the same month last year before assuming the worst.

Usually not. Central systems are designed for a certain amount of airflow, and closing vents raises pressure in the ducts, increases leakage, and can freeze the coil or strain the blower. Closing one or two is fine. Closing a lot of them costs more than it saves. Zoning or a mini-split is the right way to condition only part of a house.

It can, mostly by making setbacks automatic so you don't forget. The savings are real but modest, often in the range of 8 to 10 percent on heating and cooling. With a heat pump, choose one set up correctly for heat pumps, with aux-heat lockout and gradual recovery, or it can raise your winter bill instead of lowering it.