Heat Pump Repair in Unionville, PA
A heat pump that steams on a frosty morning is usually doing its job.
Heat pumps carry many Unionville-area homes through fall and spring, and dual fuel setups hand off to oil, propane or gas when it gets truly cold. This page explains what is normal in winter, what each symptom usually means, how the backup heat should be set, and what repairs typically cost.
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How an air-source heat pump heats a house in winter
A heat pump doesn't burn anything. Refrigerant in the outdoor coil absorbs heat from the outside air, the compressor concentrates it, and the indoor coil releases it into your ducts. Because it moves heat instead of making it, Energy.gov says a well-installed unit can deliver up to three times the energy it uses in electricity.
There is still usable heat in 20-degree air. But the colder it gets, the less heat the unit can deliver, and most standard models eventually need help from electric strips or a furnace.
That matters here. Nearby West Chester averages a January low around 22°F, and the record low is minus 16°F. A heat pump around Unionville spends many winter nights near or below the point where it needs backup. Knowing how that handoff works explains most of the calls heating companies get about heat pumps.
Defrost mode: steam, silence and a whoosh
In cold, damp weather the outdoor coil frosts over. The heat pump briefly reverses itself to melt the frost, and that cycle is normal. Trane says its defrost cycles usually last three to five minutes before heating resumes.
The outdoor coil runs colder than the air around it, so frost can form even in the low 40s. Trane notes defrost is most common in the 20s and 30s, which describes a typical Unionville January.
Normal during defrost
- A cloud of steam rising from the outdoor unit
- The outdoor fan stops for a few minutes
- A whoosh as the refrigerant changes direction
- AUX or AUX HEAT shows on the thermostat
- Slightly cooler air at the vents in homes without backup heat
Not normal
- Ice keeps building until it covers the coil or the top
- Defrost cycles get longer or seem constant
- The unit sits encased in ice for hours
Those point to a failed defrost board or sensor, low refrigerant, a bad fan motor or a drainage problem.
Auxiliary heat vs emergency heat
Auxiliary heat turns on automatically when the heat pump can't keep up or is defrosting. Emergency heat is a manual setting that shuts the heat pump off and runs only the backup. Lennox describes it that way, and it's why EM heat should stay off unless the outdoor unit has failed.
| What the thermostat shows | What is running | When it's normal | Cost to run |
|---|---|---|---|
| HEAT | Heat pump only | Most of fall, spring and milder winter days | Lowest |
| HEAT plus AUX | Heat pump plus electric strips, or the furnace alone on dual fuel | Defrost, deep cold, or recovering from a big setback | Higher while it lasts |
| EM HEAT or EMERGENCY | Backup only. The heat pump is locked out. | Outdoor unit damaged, iced solid or waiting for repair | Highest with electric strips |
Electric strips are resistance heaters, like a giant toaster. They make heat one-for-one from electricity, so a house left on EM heat for a week can produce a startling PECO bill. Energy.gov also warns against setbacks deep enough to trigger backup heat every morning.
Balance point and dual fuel, explained
The balance point is the outdoor temperature where the heat pump alone can no longer hold the house at your setting. Dual fuel pairs the heat pump with an oil, propane or gas furnace, and a control switches to the furnace below a chosen outdoor temperature.
A heat pump's output drops as it gets colder outside, while the house loses heat faster. Where those two lines cross is the thermal balance point. It depends on the heat pump's size and model, plus your insulation, windows and air leaks. A drafty 1800s farmhouse hits it at a warmer temperature than a tight 2010s home.
There is also an economic balance point: the temperature below which burning fuel costs less per unit of heat than running the heat pump. It moves with electric and fuel prices.
How the switchover temperature is set
- An outdoor sensor or a thermostat with outdoor data tells the system how cold it is.
- The installer sets a lockout. Below it, the heat pump stops and the furnace runs. Lennox gives 40°F as an example aux lockout setting.
- On dual fuel, the two don't run at once. Lennox notes the furnace shuts the heat pump off rather than running alongside it, because furnace heat would overwhelm the coil.
- Some systems balance automatically, using the heat pump's own data instead of a fixed number.
- Revisit the setting when electric or fuel prices change a lot, or after insulation work.
Burning more fuel than expected can mean the lockout is set too warm. Chilly cold mornings can mean it's set too cold. Both are adjustments, not repairs. For the bigger fuel decision, see the oil vs propane vs heat pump guide.
Cold-climate heat pumps: what the label means
A cold-climate heat pump keeps more of its capacity in deep cold. To earn the ENERGY STAR cold-climate designation, a unit must reach a COP of at least 1.75 at 5°F and deliver at least 70% of its 47°F heating capacity at 5°F.
COP is coefficient of performance. A COP of 1.75 means 1.75 units of heat per unit of electricity at 5°F. Electric strips deliver exactly 1.0, which is why cold-climate models need much less backup.
The Northeast Energy Efficiency Partnerships (NEEP) also keeps a cold-climate air-source heat pump specification and a public product list. Its current version 4.0 took effect January 1, 2023, and covers ducted central systems and multi-split systems. Several utility rebate programs use the list to decide eligibility, so it's a useful cross-check when comparing quotes.
Ask for the numbers. When a company proposes a heat pump, ask for the model's heating capacity at 5°F and 17°F, not only at 47°F. A unit that looks big enough on a mild-day rating can come up short on a January night.
A standard heat pump that leans on backup in deep cold isn't broken. That's its design. If you want less AUX time, the answer may be a replacement rather than a repair.
Heat pump symptoms and what they usually mean
Note the outdoor temperature when the problem happens. A symptom at 15°F can be normal that would be a fault at 45°F.
| What you notice | Likely causes | What you can safely check | How urgent |
|---|---|---|---|
| Thick ice on the coil that never clears | Failed defrost board or sensor; low refrigerant; outdoor fan motor; water dripping from a gutter onto the unit | Look for a leaking gutter overhead. Don't chip ice off the fins. | Soon. Switch to EM heat if it's iced solid. |
| Blowing cool or lukewarm air for long periods | Low refrigerant; reversing valve stuck; compressor not running; thermostat set to COOL or fan ON | Thermostat mode and fan setting; dirty filter | Soon, especially in deep cold |
| Short cycling: on and off every few minutes | Oversized unit; clogged filter; thermostat placement; refrigerant problem | Replace the filter; open closed registers | Within days |
| Indoor blower runs, outdoor unit silent | Tripped outdoor breaker or disconnect; failed capacitor or contactor; compressor fault | The breaker and the disconnect box by the unit | Same day in cold weather |
| Outdoor fan stopped, compressor humming | Failed fan motor or capacitor | Nothing. Turn the system off to protect the compressor. | Call now |
| Electric bill much higher than last winter | Running on AUX or EM heat; lockout set wrong; low refrigerant; leaky ducts | Is EM heat on? Does AUX show in mild weather? | Soon. It costs money every day. |
| Water on the floor near the indoor unit | Clogged condensate drain; failed condensate pump | Pump plugged in; drain line not kinked | Soon, before it damages ceilings or floors |
Five heat pump checks before you call
These cover the most common no-heat and low-heat calls on heat pumps. None of them involve opening the outdoor unit's panels.
- Mode and fan. HEAT, not COOL or EM. Fan on AUTO. Fresh batteries.
- Filter. A clogged filter starves the indoor coil and the strips. Energy.gov suggests checking about every three months, more often with pets and barn dust.
- Two breakers. Heat pumps usually have one for the outdoor unit and one for the air handler or strips, plus a disconnect box outside.
- Clear the unit. Brush snow off the top and shovel around it. Keep plants trimmed back.
- Give it time. If it steamed and went quiet, wait ten minutes. It was probably defrosting.
Switch to EM heat and call if
- The outdoor unit is iced solid and has stayed that way for hours.
- The outdoor fan isn't turning while the compressor hums.
- You hear grinding or metal on metal from the outdoor unit.
- The house is losing heat with someone elderly, an infant or ill at home.
On a dual fuel system, the furnace side still needs the usual safety rules. A gas smell or CO alarm means leave the house and call 911 from outside. See carbon monoxide safety.
Mini splits for stone houses, geothermal for big lots
Ductless mini splits heat rooms that never had ducts, which fits stone farmhouses, additions and converted barns. Geothermal heat pumps trade the outdoor unit for buried loops and suit larger lots where there's room to trench or drill.
Ductless mini splits
A small outdoor unit feeds one or more wall, ceiling or floor heads through a narrow line set. No ducts need to fit through thick stone walls. Common repairs are clogged drains, dirty filters and coils, failed fan motors, sensor faults and refrigerant leaks at flare fittings. Each indoor head has a filter to clean on the maker's schedule, which NYSERDA notes could be monthly.
Heating old stone homesGeothermal (ground source)
Energy.gov says the shallow ground stays about 40°F to 70°F year round. Horizontal loops go in trenches at least four feet deep, and vertical loops in holes 100 to 400 feet deep. Energy.gov puts indoor components at up to 24 years and the loop at 50 years or more. Ask whether a company services ground-source systems before the visit.
What Unionville winters do to heat pumps
Wet cold, not dry cold
Southern Chester County winters hover around freezing with plenty of moisture. That's prime frost weather, so heat pumps here defrost often. A defrost board or sensor that's starting to fail shows up quickly.
Snow and roof runoff
West Chester averages about 28 inches of snow a year. Units set too low get buried, and units under a roof edge get soaked by dripping meltwater that refreezes on the coil. Raising the unit on a stand or adding a gutter often fixes chronic icing.
Oil and propane homes adding a heat pump
Many farmhouses and estates past the gas lines have added a heat pump on top of an existing oil or propane furnace. Those dual fuel setups work well, but the lockout setting and the control wiring between two brands are frequent trouble spots.
Historic village homes
In the Unionville Village Historic District, listed on the National Register in 1979, outdoor unit placement on a street-facing wall may need thought. Ask the township about any rules before planning a change.
Storm outages
Heat pumps need power for everything. A generator big enough for a heat pump is a different size than one for a furnace. See power outages and heat.
Refrigerants and what to ask a heat pump company
New heat pumps now use R-454B or R-32 instead of R-410A. Existing R-410A systems can still be repaired and recharged, but that refrigerant is getting more expensive, and the new ones can't be poured into an old system.
Under federal rules summarized by New York's Clean Heat program, heat pumps using refrigerants like R-410A could not be made or imported after January 1, 2025, or installed after January 1, 2026. R-454B and R-32 are rated A2L, meaning mildly flammable, and need specific tools and training. R-410A production is capped, so recharges cost more over time.
So a failed R-410A outdoor unit usually can't be paired with a new R-454B indoor coil. A good company explains whether to repair or replace both halves.
- What's your HICPA registration number, and are you insured?
- Are your technicians EPA Section 608 certified for refrigerant?
- Do you service my brand and type: ducted, mini split, geothermal, dual fuel?
- If refrigerant is low, will you find and fix the leak?
- Which refrigerant does my system use, and what does a pound cost?
- Can you check my dual fuel lockout and aux settings?
- What warranty comes with the part and the labor?
Pennsylvania has no statewide HVAC license. Look up any registration at hic.attorneygeneral.gov, and see Pennsylvania contractor rules. These questions apply to any company, including any you're connected with here.
Heat pump questions from Unionville homeowners
Why is steam coming out of my heat pump?
It's almost always defrost. The unit reverses for a few minutes to melt frost off the outdoor coil, and the melting ice gives off steam. If it then goes back to heating, it's working as designed.
Is it normal for my heat pump to ice up?
A light coat of frost that clears every so often is normal in damp cold weather. Thick ice that keeps building, or a unit encased in ice for hours, is not. That usually means a defrost control, sensor, fan or refrigerant problem.
Should I switch to emergency heat when it gets very cold?
Usually no. Auxiliary heat already turns on automatically when the heat pump needs help. Use EM heat only when the outdoor unit is damaged, iced solid or waiting for repair, because it shuts the heat pump off and runs only the backup.
What temperature should my dual fuel system switch to the furnace?
There's no single number. It depends on your heat pump's cold-weather capacity, how tight the house is, and the price of electricity versus your oil, propane or gas. Ask the technician to set it based on your house and current prices, and to revisit it when prices change.
Why does my heat pump blow air that feels cool?
Heat pump air is usually not as hot as furnace air, so it can feel cool on your hand even when it's heating. If rooms aren't warming, check the mode and filter. Long stretches of truly cold air can mean low refrigerant, a stuck reversing valve or a compressor issue.
Can I still get my R-410A heat pump repaired?
Yes. Existing R-410A systems can still be serviced and recharged. Supply is capped, so the refrigerant costs more than it used to. A big leak or a failed compressor on an older unit is a good time to compare repair with replacement.
Is there a tax credit for a heat pump in 2026?
No federal one. The 25C credit ended for equipment placed in service after December 31, 2025. PECO electric customers may qualify for a heat pump or mini split rebate, so confirm current amounts on peco.com before you buy.
How often should a heat pump be serviced?
Energy.gov recommends professional service at least once a year, with filters changed or cleaned between visits. See the tune-up checklist.
Is this site a heat pump company?
No. UnionvillePAFurnaceRepair is a free referral service that connects you with independent local HVAC companies. Those companies set their own prices and terms. This site doesn't perform or guarantee any work and may be paid for referrals.
Sources
- Energy.gov: Air-source heat pumps.
- Energy.gov: Operating and maintaining your heat pump.
- Trane: What is a heat pump defrost cycle?
- Lennox: Emergency heat vs auxiliary heat.
- ENERGY STAR cold-climate heat pump criteria, as summarized by NY Engineers.
- NEEP: Cold climate air source heat pump specification and product list.
- NYSERDA: Heat pump maintenance fact sheet.
- Energy.gov: Geothermal heat pumps.
- NYS Clean Heat: Refrigerant changes fact sheet.
- PECO heat pump, mini split and maintenance rebate amounts as listed on the Unionville furnace guide; confirm at peco.com.
- West Chester climate figures as summarized on the Unionville furnace guide.
- Pennsylvania Attorney General: Home Improvement Contractor registration.
Written by Lawrence. Updated October 25, 2026. Facts on this page were checked against the public sources listed above.
This is general information from a free referral service, not a heating contractor. For gas smells or carbon monoxide alarms, leave the house and call 911.
Related furnace help
Heat pump struggling in the cold? Get connected with local help.
Tell the company whether you have backup strips or a furnace, what the thermostat shows, and whether the outdoor unit is icing. It saves a second trip.
One call to (724) 241-4851 connects you with independent local HVAC companies that serve Unionville and nearby Chester County communities. It's free, with no obligation.
Have this ready when you call
- Your town or road
- Your fuel: oil, propane, gas or electric
- What the system is doing, and any blinking light code
- Whether you smell gas or oil (if so, leave and call 911 first)
Free referral service. Not a heating contractor. Companies are independent and set their own prices.