Preparing a Furnace or Heat Pump for Winter Cold Snaps

Why mild winters still catch homes off guard

In the Birmingham, AL area, a heating system may sit mostly idle through a run of mild weeks and then face a sharp cold snap overnight. Ice or light snow is possible some years. A furnace or heat pump that has not run in months may start slowly, make unfamiliar noises or fail just when the temperature drops.

Testing the heat before the first freeze turns a possible emergency into a routine task. If something is wrong, the household learns about it on a comfortable day instead of a frigid night, and there is time to arrange a visit without pressure.

First checks for any heating system

Whether a home uses a gas furnace or a heat pump, the same simple starting points apply. None of them require tools or opening equipment.

• Replace the air filter if it looks dusty or gray. A clogged filter restricts airflow and can make a furnace shut itself off.
• Switch the thermostat from cool to heat and raise the setpoint above room temperature.
• Put fresh batteries in the thermostat if it uses them.
• Open supply registers in every room and move furniture or rugs that block them.
• Confirm the breaker and the service switch near the equipment are on. A tripped breaker can be reset once; if it trips again, leave it off.

A faint dusty smell during the first few minutes of heating is common, since dust settles on parts during the off months. It should fade quickly. A smell that lingers, or anything that resembles burning plastic, is a reason to turn the system off and call.

Gas furnace safety

Gas furnaces are common in homes across the region, often paired with central air. They are reliable when maintained, but they deserve respect. A homeowner should never open the burner area, adjust the gas valve or try to relight anything inside the cabinet.

If you smell gas, do not flip switches, use the thermostat or try to find the source. Leave the home with everyone inside, and once outside, call the gas utility or 911. Wait for help at a safe distance before going back in.

• Make sure carbon monoxide alarms are installed near sleeping areas and test them with their own button.
• Keep boxes, paint cans and cleaning supplies away from the furnace.
• Do not block the area around the furnace or any vent pipes.
• Call for help if the furnace starts and stops repeatedly or blows only cool air.

A provider can inspect the burners, heat exchanger, venting and safety controls during a furnace repair or tune-up visit. Those parts are not for homeowners to handle.

Heat pumps in a cold snap

Heat pumps pull warmth from outdoor air, and they work well through most of a winter here. During a hard freeze they run longer and may lean on backup heat. That is normal behavior, not necessarily a sign of trouble.

A light coat of frost on the outdoor coil is expected in cold, damp weather, and the unit will periodically switch into a defrost cycle that can send up a little steam. A unit encased in thick ice that does not clear, or one that sits silent while the house cools, needs attention. Do not chip at ice or pour water on the unit.

• Keep leaves, snow and fallen branches cleared away from the sides of the outdoor unit.
• Never wrap or cover a heat pump during winter, since it needs to move air to work.
• Use the emergency or auxiliary heat setting on the thermostat only if the outdoor unit has stopped, and then call.

The page on a heat pump that won't heat explains common causes in more detail.

Storms, outages and freezes

Winter storms in this region can bring power interruptions and debris. After the power returns, check that the thermostat still shows the right mode and setpoint, since some models reset. If the system does not restart on its own after a reasonable wait, the breaker is the next place to look.

Homes on slopes or with crawlspaces may have ductwork running through unheated spaces. Rooms that feel much colder than the rest of the house during a freeze can point to leaking or poorly insulated ducts, which a provider can evaluate.

When to call for heating help

Some problems clearly belong with a professional. A call to the number on this page can put the household in touch with an independent local HVAC provider for residential heating work.

• The furnace or heat pump runs but the house will not warm up.
• The system blows cold air when set to heat.
• A carbon monoxide alarm sounds. Leave the house and call 911 from outside.
• The outdoor heat pump stays frozen solid.
• There are loud bangs, grinding or a burning smell.