Why Won’t My Heat Pump Reach the Set Temperature ?
You set the thermostat to 70. Six hours later it still reads 66, the system’s been running the entire time, and you’re starting to wonder what you’re paying for. That’s one of the more common calls we get in Richmond between December and February. Sometimes it’s a real failure. Often it’s something smaller or the equipment doing exactly what it was built to do on a 25-degree night.
Long Run Times in Cold Weather Are Normal
A heat pump doesn’t burn fuel. It pulls warmth out of outdoor air and moves it inside, which works beautifully at 45 degrees and gets harder the colder it gets. Richmond sits in an odd middle zone mild enough that this equipment makes sense here, cold enough that a handful of January nights drop into the teens and push it to its limit.
So when the outdoor temperature falls, cycles stretch out. That’s design, not breakdown.
What matters is whether the house is gaining ground. Set it to 70 at dinner and it reads 69 by bedtime, you’re fine. Eleven hours with no movement at all is a different conversation.
One caveat: if your backup heat strips are locked out or their breaker has tripped, you’ll see this exact symptom on the coldest nights and never at 50 degrees.
Airflow Restrictions Cause Most of These Calls
Check the filter first. A loaded filter starves the indoor coil, and starved airflow means the air leaving your vents never carries enough heat to move the set temperature where you want it.
Then go outside. Richmond’s spring oak and pine pollen leaves a yellow film on outdoor coils that nobody thinks about until heating season, and fall leaves pack in on top of it. I took a call over in Bon Air last winter where the homeowner was certain the compressor was dying. The unit was buried behind an overgrown holly a previous owner had planted about eighteen inches off the cabinet.
Give it two feet of clearance all the way around, and rinse the coil with a garden hose when it’s above freezing.
If the filter’s clean and the unit’s clear and it still won’t heat, stop there. You’ve done the part that’s safe to do.
Low Refrigerant and Defrost Cycles
Refrigerant doesn’t get used up. If it’s low, it leaked, and topping it off without finding the leak is money set on fire. Low charge looks like lukewarm air, ice building on the outdoor coil, and a system that runs forever without reaching the temperature on the display.
Defrost is a separate thing people mistake for failure. On damp Richmond mornings in the 30s, frost forms on that outdoor coil and the system briefly reverses to melt it off. You’ll feel cool air from the vents for five to twelve minutes. Normal.
Defrosting every twenty minutes, or steaming away for half an hour without clearing, points to a bad sensor, a stuck reversing valve, or a charge problem.
Refrigerant work requires EPA 608 certification. There’s no homeowner version of that repair.
When the Problem Isn’t the Equipment
A thermostat sitting in direct afternoon sun, or right above a supply register, reads a temperature that has little to do with the rest of your house. The system satisfies that sensor and shuts down while the back bedrooms sit four degrees colder.
Ducts matter more here than people expect. A lot of Richmond’s older housing the Fan and Northside especially got ducted long after it was built, and those runs live in vented crawl spaces. Leaky seams dump heated air under the floor instead of into the room.
Sizing is the last suspect and the rarest. Undersized equipment holds temperature fine in November and falls behind every cold snap. Virginia’s building code requires a mechanical permit for a replacement, and any honest contractor runs a load calculation before quoting one.
Stop Guessing Before It Costs You a Compressor
A system running nonstop for weeks isn’t just uncomfortable it’s grinding down a compressor you’ll pay four figures to replace. Our stubbornly honest AC repair techs will tell you when the fix is a $40 part and when it genuinely isn’t. Most diagnostics run 45 minutes to two hours.
Frequently Asked Questions
Why does it run all day and never hit the number I set?
Usually airflow or refrigerant charge. Start with the filter and the outdoor unit. If it’s in the teens outside and the house is holding within a degree or two of your set temperature, that’s physics the colder it gets, the less heat there is out there to move.
Is lukewarm air out of the vents normal?
Yes. A heat pump delivers air around 95 to 105 degrees, warmer than the room but cooler than your hand, so it feels disappointing. Gas furnaces run 130 and up. The house should still climb steadily toward the set temperature.
How often do I actually need to change the filter?
One-inch filters, every one to three months. Pets or a dusty house, closer to monthly. Richmond’s spring pollen is rough on filters I’d check in April even if you swapped it in March.
There’s ice on the outside unit. Do I turn it off?
Light frost that clears itself within ten minutes or so is normal. Solid ice covering the whole coil, or ice still sitting there hours later, isn’t. Shut it down at the thermostat and call before the fan blade catches it.
Repair or just replace the thing?
Depends on age and what failed. Under ten years with a repairable part, fix it. Past fifteen with a compressor issue or a major leak, replacement usually wins. If bills keep climbing while the house never holds the set temperature, the math has already answered you.
If it’s been fighting you for weeks, it won’t sort itself out before the next cold snap. Get somebody to look at it.
