Getting your heat pump ready for a mountain winter

Why elevation changes the math

A heat pump does not make heat. It moves heat from outside air into your house, and the colder that outside air gets, the less heat there is to move. Every heat pump has a balance point — the outdoor temperature below which it can no longer keep up on its own and has to call for backup heat.

In Western North Carolina that balance point matters more than it does almost anywhere else in the state. A house in Asheville at 2,200 feet sees a very different January than one in Burnsville or Banner Elk sitting above 3,000. Cold air also drains downhill overnight and pools in the coves, which is why a house in a hollow can read ten degrees colder at 6 a.m. than a house on the ridge a mile away.

None of that means a heat pump is the wrong choice up here. Modern variable-speed and cold-climate units hold usable capacity well down into the teens. It does mean the equipment has to be sized and set up for where your house actually sits, and that the annual once-over is not optional.

The five-minute walk-around

Do this on a mild afternoon in October or early November, before you need the system.

• Clear 18 inches on all sides of the outdoor unit. Leaves, mulch, a stack of firewood, an ornamental grass that grew all summer — all of it chokes airflow. The unit has to breathe.
• Look straight up. A gutter that overflows or a roof valley that drips onto the top of the unit will build an ice cap over the winter. That one is worth fixing permanently with a diverter.
• Check that the unit sits level and clear of the ground. Heat pumps shed a surprising amount of water during defrost. If it sits flat on dirt, that water has nowhere to go and freezes into a block under the coil. Units up here belong on a stand or riser, not a slab in the mud.
• Think about snow and drift. If you are on the north side of a slope, or the unit sits where the plow throws snow, plan for it now.
• Put in a fresh filter and write the size on the inside of the return grille so you stop guessing.
• Walk the house and unblock vents. A sofa moved for the holidays covers more supply registers than anything else we see.
• Run the heat for fifteen minutes on a day you do not need it, and listen. Grinding, squealing, rattling and a burning-dust smell that does not clear after a few minutes are all worth a call now rather than on the first 18-degree night.

What a defrost cycle should look like

This is the single most common reason we get a panicked call in December, and nine times out of ten nothing is wrong.

When it is cold and damp, frost forms on the outdoor coil. To clear it, the heat pump briefly reverses itself — it runs in cooling mode outdoors while your indoor backup heat covers the house. For anywhere from thirty seconds to about fifteen minutes you will see:

• The outdoor fan stops while the compressor keeps running.
• A cloud of steam rolling off the top of the unit. It looks like smoke. It is water vapor.
• A whoosh or clunk as the reversing valve shifts.
• Water running off the unit and onto the ground.

Then it shifts back and goes on heating. On a wet, near-freezing night that cycle might repeat every 30 to 90 minutes. That is the system doing its job.

And never chip ice off a coil with anything metal. The fins and the tubing behind them are thin aluminum and copper, and a screwdriver through a refrigerant line turns a service call into a much larger repair.

Auxiliary heat, emergency heat, and the light on your thermostat

These two get used interchangeably and they are not the same thing.

Auxiliary heat is the backup — usually electric resistance strips in the air handler — coming on alongside the heat pump because it is very cold or because you asked for a big temperature jump. That is normal, occasional, and expected on the coldest nights.

Emergency heat is you telling the thermostat to shut the heat pump off entirely and heat the house on strips alone. It exists for one situation: the outdoor unit has failed and you need heat until we get there.

The cost difference is not small. A heat pump typically delivers two to three units of heat for every unit of electricity it consumes. Resistance strips deliver exactly one. Leaving a house on emergency heat through a cold week is how people end up with a power bill that makes them think something is broken — and something is, just not what they expected.

What the annual tune-up actually covers

The walk-around above is the part you can do. Here is what needs gauges and a meter:

• Refrigerant charge verified against actual conditions — not topped off by feel. A heat pump that is even slightly low loses a large share of its cold-weather capacity.
• Defrost board and sensor tested through a full cycle.
• Reversing valve operation confirmed in both directions.
• Capacitors and contactor checked under load. A weak capacitor is a cheap part that takes out an expensive compressor.
• Strip heat amperage measured and staging confirmed, so all of them are not firing at once.
• Indoor coil and blower wheel inspected, condensate drain cleared, static pressure read.
• Electrical connections tightened — they loosen with every heat-and-cool cycle.

Two visits a year, spring and fall, is what we recommend, and it is what our maintenance plan covers.

Call us if you see any of this

• Ice on the outdoor unit that does not clear within a few hours
• The auxiliary or emergency heat indicator on for days in normal cold
• The system running continuously and still not reaching the set temperature
• A breaker that trips when the heat comes on
• A burning or electrical smell that does not clear in ten minutes
• Air from the vents that feels cool even though the system is calling for heat
• A power bill that jumped with no change in the weather

One more thing worth saying plainly: heat pump air does not feel hot on your hand the way furnace air does. It comes out around 95–105°F, which is below your body temperature, so it can feel drafty even while it heats the house perfectly well. That alone is not a fault.