What Defrost Actually Does

A heat pump moves heat from outside air into the house. In cool, wet weather the outdoor coil gets colder than the air around it. Moisture freezes on the fins. Left alone, that ice would choke airflow and the unit would stop heating.

Defrost is the system’s answer. The reversing valve flips, the outdoor coil becomes the warm coil for a few minutes, and the ice melts. You often see steam. The outdoor fan may stop. Inside, many systems kick on auxiliary or emergency heat so you do not feel cold air from the vents during those minutes.

In a dry climate this happens less. In Longview, Kelso, Castle Rock, and the rest of Cowlitz County it happens a lot from November through February. That is normal.

Normal Defrost vs. a Problem

Use this as a field check before you pick up the phone.

Usually normal

• A light coat of frost on a cool, damp morning.
• The unit steams for a few minutes, then the ice clears.
• The outdoor fan pauses during defrost and restarts.
• Supply air feels milder for a short stretch, then warms again.
• The cycle happens a few times on a cold, wet morning and then the unit settles.

Call for service

• Ice builds into a solid shell that does not melt after a defrost.
• The unit stays in defrost for long stretches or defrosts every few minutes all day.
• Water pools under the unit and refreezes into a block around the base.
• The house never catches the setpoint, or auxiliary heat runs constantly.
• You hear grinding, screeching, or a hard bang that was not there last week.
• The outdoor coil is packed with leaves, moss, or fir needles and the unit cannot breathe.

Those symptoms usually point to a dirty coil, weak airflow, a failed defrost sensor or control board, low refrigerant, or a reversing valve that is not shifting fully. Guessing which one it is from the living room wastes a cold evening.

What You Can Safely Do Right Now

None of these replace a technician visit. They do keep a normal defrost from turning into a frozen cabinet.

• Give the unit space. Pull leaves, grass, and anything leaning against the cabinet. Two feet of clearance on every side is the goal.
• Do not chip ice or pour hot water on the coil. You can crack fins or damage the fan. Let defrost do the melting.
• Check the filter. A dirty indoor filter is one of the most common reasons a heat pump ices over in November. Replace it if you cannot see light through it.
• Open the returns. Rugs, sofas, and storage bins blocking return grilles starve the system of air and make icing worse.
• Note what you see. How long the ice stays, whether the fan stops, and whether the house is still warming. That detail helps the technician on the first visit.

Why November Is Harder on Heat Pumps Here

Southwest Washington adds two things most heat pump manuals treat as footnotes: long stretches of cool, wet air, and debris. Outdoor coils collect leaves and fir needles. Condensate from defrost has to drain, and a blocked base pan turns that water into a sheet of ice. Defrost boards and sensors work harder than they do in a dry climate.

Homes on both sides of the Columbia see the same pattern. If the unit cooled fine in August, that does not mean the reversing valve, defrost control, and auxiliary heat were tested. Those parts get their real workout starting now.

What a Service Call Covers

A Feltons’ visit for a defrost complaint is a working inspection, not a filter swap. Depending on the equipment, technicians typically:

• Confirm the unit is actually entering and exiting defrost.
• Check coil cleanliness and outdoor airflow.
• Test the defrost sensor, control board, and reversing valve.
• Check refrigerant pressures and electrical draws.
• Inspect the indoor filter, blower, and obvious duct restrictions.
• Verify auxiliary or dual-fuel heat is available if the system has it.

We service all major brands and are a Ruud-authorized dealer. Manufacturer warranties on many systems require documented annual maintenance. A November tune-up also keeps you ahead of the first hard cold snap, when every no-heat call in the county lands at once.

FAQ

Is it normal for a heat pump to ice up in November?

Light frost on the outdoor coil is normal in cool, damp Pacific Northwest weather. The unit should enter defrost, steam for a few minutes, and clear the ice.

Why does my heat pump blow cool air during defrost?

During defrost the outdoor unit briefly reverses to melt ice. Many systems turn on auxiliary heat indoors so you do not feel a cold draft. A short cool burst can be normal. A long one, or air that stays cold, is not.

How long should a defrost cycle last?

A typical defrost lasts a few minutes. If the unit stays in defrost for long stretches, ices into a solid shell, or never clears, it needs service.

Can I pour hot water on a frozen heat pump?

No. Hot water can crack the coil or damage the fan. Clear debris around the unit and call if the ice does not clear after a normal defrost.

Will this hurt my electric bill?

A clean, correctly charged heat pump uses auxiliary heat only for short stretches. A unit that is iced over, low on refrigerant, or stuck in backup heat runs the expensive heat strips for hours. That is usually when the bill jumps.

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