One freeze night, hour by hour, as your heat pump lives it

Why this guide exists

Lake City is inland and far enough north that winter counts. Afternoons in July run hotter than the coast and nights in January run colder. Several freezes a year are normal, hard freezes into the 20s happen in many winters, and the record for the town is in single digits. Heat pumps installed here by people who think of Florida as cooling country are set up for the wrong climate, and the night this guide walks through is where that shows.

5:30 p.m., 48 degrees and falling

The sun is down behind the pines and the forecast says 24 by dawn. The thermostat is set to 68 and the house is holding it easily. The heat pump is doing what it does best: moving heat from outside air to inside air at a fraction of the cost of making heat from scratch. At 48 degrees outside, that is efficient and quiet. If the house is comfortable right now and the outdoor unit is running steadily, the system is healthy.

9:00 p.m., 38 degrees

The heat pump is running longer cycles. The outdoor coil is now colder than the outside air and has started to collect frost. Nothing else has changed inside. This is the hour to notice one thing: is the outdoor fan turning? A heat pump with a dead outdoor fan looks like it is working from indoors, right up until the bill.

11:45 p.m., 32 degrees

First defrost. The unit briefly flips into cooling mode to warm the outdoor coil, melts the frost, and steams in the porch light. Indoors, the strips come on for those few minutes so the air from the vents does not go cold. The AUX indicator may flash. This is correct behavior. Defrost cycles repeat through the night every so often, controlled by a board that checks coil temperature and run time. A failed defrost board leaves the coil to turn into a block of ice, and by morning the unit is a frozen cube that heats nothing.

3:00 a.m., 27 degrees

Below about 35 degrees the heat pump alone cannot carry the house, and the thermostat brings in the auxiliary heat: electric resistance strips in the air handler, five to fifteen kilowatts of them. The AUX light is on and staying on. The vents blow warm, the house holds 68, and the meter spins faster than it has all year. This is also normal. Strip heat on the coldest hours of a few nights a year is what the strips are for, and the cost is real but bounded.

What is not normal is the house slipping to 64 with the AUX on. That means the strips are undersized, one stage has failed, or the heat pump side quit hours ago and the strips are carrying everything alone.

Call 866-266-5709

6:30 a.m., 24 degrees, the low

Dawn. Frost on the ground, steam off the unit, and the system has run nearly all night. The question that decides whether this was a good night or an expensive one is simple: was the heat pump doing most of the work, with the strips helping at the bottom? Or were the strips doing all of it?

A healthy system on a 24-degree night costs more than a mild night, but a predictable amount. A system where the heat pump failed in October and nobody noticed costs several times that, every cold night, until someone opens the February bill.

10:00 a.m., 50 degrees

The sun is up and the heat pump is back to doing the job alone. The AUX light should be off. If it is still on at 50 degrees, that is the single clearest sign that something on the heat pump side has failed, and it is a service call, not a thermostat setting.

What the night asks of the equipment

• A working defrost cycle. Board, sensor and reversing valve all have to cooperate.
• An outdoor fan that runs. The most common silent failure in winter.
• Strips that are sized and staged correctly. Enough to carry the coldest hour, not so much that they mask a dead heat pump.
• A thermostat set up for a heat pump. Many are left in a mode that calls strips too early, which is quietly expensive on a Clay Electric or FPL bill.
• A fall maintenance visit. This is when all four get checked, before the first freeze rather than during it.

Where the bill comes from

Whose meter hangs on the wall depends on the address. Inside the city limits, and in Five Points and Watertown, it reads FPL; past those edges, on the acreage out SR 100 toward Lulu or down SR 47 at Fort White, it is nearly always Clay Electric. Both charge by the kilowatt-hour, and a bank of strips devours them. A system that spends a few hours a winter on strips is cheap; a system that spends every night on them is the reason winter bills in Columbia County sometimes beat the July bill. If your January bill arrived higher than August and the house was never especially warm, the heat pump needs a look.

A cold-climate installer in a hot state

Heat pumps across the Lake City area are installed and serviced by Cook’s out of Palm Coast, Fairmont Lane specifically, about two hours and twenty-five minutes away. The heat pumps we specify for Columbia County are sized for its summers and set up for its winters, with strips staged properly, defrost checked each fall and thermostats configured for the equipment they control. Lennox for new installations, every brand repaired, and the coldest night of the year is billed like a mild afternoon.