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Commercial Heat Pumps in Winter: Defrost, Backup Heat, and Performance
What Central Ohio facility managers should know about cold-weather operation, heating costs, and when to request service.
Your heat pump is running, but employees say the building feels cold. Someone notices frost on the outdoor unit. Then the building automation system shows auxiliary heat operating.
Is the equipment struggling—or doing exactly what it was designed to do?
Commercial heat pumps in winter can behave differently from gas furnaces and boilers.
Understanding those differences helps building owners and facility managers respond to comfort complaints, evaluate energy use, and prepare for cold weather.
This guide focuses on air-source heat pumps, including rooftop, split, and air-to-water equipment. Water-source and ground-source systems have different winter considerations.
In This Guide
Can commercial heat pumps handle Central Ohio winters?
Understanding defrost
Why backup heat runs
What Does COP Mean for Your Heating Bill?
The operating data to record
Winter preparation and FAQs
Can Commercial Heat Pumps Handle Central Ohio Winters?
Yes—when the equipment, heating capacity, backup strategy, and controls are selected for the building and local conditions.
The useful question is whether the installed system can deliver enough heat at the temperatures your facility experiences.
Trane’s commercial design guidance calls for comparing building heating loads with available equipment capacity and determining whether auxiliary heat is needed.
Its rooftop examples also distinguish electric supplemental heat from dual-fuel arrangements that switch between heat-pump and gas heating. [1]
For an existing building, ask your contractor for three things:
The installed model’s heating-performance tables at relevant outdoor temperatures.
A current heating-load assessment, including ventilation and changes in building use.
The documented backup-heat sequence and operating limits.
A cooling-tonnage label does not answer those questions.
For air-to-water systems, required water temperature matters too. Available capacity and operating limits depend on both outdoor conditions and supply-water requirements.
Equipment selection should reflect those conditions rather than relying only on standard rating points. [2]
Understanding Heat Pump Defrost
Why Frost Can Be Normal
An air-source heat pump extracts heat from outdoor air.
During heating, its outdoor coil can be colder than the surrounding air, allowing moisture to freeze on the coil—even when outdoor air is above freezing.
Defrost temporarily changes the refrigeration cycle to warm that coil and remove frost.
Depending on the equipment, observers may notice a vapor cloud, changing sound, or a temporary outdoor-fan pause. [3]
Look at whether frost clears and heating recovers before drawing a conclusion.
When to Request a Review
Record repeated defrost events that seem different from the unit’s established behavior, especially when ice remains or room temperatures fall.
Persistent icing and increasingly prolonged or frequent defrost behavior are reasons to seek service. [3]
Do not use one generic cycle duration as a pass/fail rule for every commercial system. Your technician should compare operation with the model’s control sequence and current conditions.
Avoid chipping ice from coils or bypassing defrost controls. Use normal operator displays and safe observation points to document the issue.
Why Is Backup Heat Running?
Backup or auxiliary heat can be part of normal winter operation. Depending on the installation, it may provide additional capacity, support comfort during defrost, or take over when heat-pump operation is unavailable.
Trane’s commercial rooftop guidance describes both demand-based and time/temperature defrost strategies, along with equipment-specific auxiliary-heat and compressor-lockout controls. These settings are not interchangeable between models. [1]
The question to ask is:
What condition caused this heating stage to start?
Useful possibilities to investigate include:
Cold-weather heating demand.
Scheduled morning recovery.
A compressor lockout.
An active equipment fault.
An incorrect control signal.
A Simple Capacity Example
Suppose your building needs 120,000 Btu/h of heat at a particular outdoor condition, but the heat pump can supply 90,000 Btu/h at that condition.
That leaves 30,000 Btu/h to supply through another source if the building is to maintain temperature.
These are illustrative numbers, not a sizing recommendation. The actual comparison needs verified building loads and manufacturer performance data, including applicable defrost effects.
In air-to-water plants, thermal storage and supplemental heating can help manage the interruption associated with defrost. That requires a coordinated system design. [2]
What Does COP Mean for Your Heating Bill?
Coefficient of performance (COP) tells you how much heat a system delivers for the electricity it uses.
At a COP of 3, a heat pump delivers three units of heat for every unit of electricity consumed. It does this by moving heat from outdoors into the building.
Electric-resistance heating converts electricity directly into heat and operates at approximately COP 1. [4]
Here’s how that affects the electricity needed to deliver the same 30 kWh of heat:
Illustrative COP | Electricity Required |
1 | 30 kWh |
2 | 15 kWh |
3 | 10 kWh |
Higher COP means less electricity is needed to deliver the same amount of heat.
The calculation is straightforward:
Electricity used = heat delivered ÷ COP
These are illustrative examples, not ratings for your equipment. Actual performance changes with outdoor temperature and other operating conditions.
When comparing systems, account for electricity used by fans, pumps, defrost, and backup heat.
What Does Electric Backup Heat Cost to Run?
Electric backup heat helps maintain building temperatures when needed, but its operating hours affect electricity use.
For example, a 20 kW electric-resistance heater running at full output for three hours uses:
20 kW × 3 hours = 60 kWh
At an illustrative electricity price of $0.12 per kWh, that equals $7.20 in energy charges.
That covers only the resistance heater during those three hours. It excludes demand charges, other fees, and electricity used by the rest of the HVAC system.
Use your facility’s actual electricity rate when estimating costs.
The useful question is why backup heat is running—and whether that operation is expected.
ETS can review controls, operating schedules, and equipment performance to investigate unnecessary runtime while preserving the backup heat your building needs.
Why Morning Warm-Up Deserves Attention
A building that feels comfortable all afternoon may still be cold when employees arrive.
Review when occupied heating begins, how far temperatures fall overnight, and which heating stages operate during recovery.
A large setpoint jump may change the way the controls stage heat.
PNNL’s thermostat guidance explains how adaptive recovery can start heating earlier and reduce reliance on electric auxiliary heat during setback recovery.
Its examples are residential; a commercial building needs a sequence appropriate to its equipment, occupancy, and building automation system. [5]
For your facility, compare two observations:
Did occupied areas reach their targets on time, and what heating stages were required to get there?
Have your contractor evaluate recovery trends before applying a blanket “no setbacks” policy or changing lockout temperatures.
Six Operating Trends Worth Recording
A useful service request connects the complaint to what the equipment was doing.
Trend | What to Record |
Outdoor temperature | A reliable reading associated with the equipment |
Room temperature | Actual temperature, setpoint, affected zone, and time |
Operating mode | Heating, defrost, lockout, off, and exact status messages |
Backup heat | Active stages, runtime, and available power data |
Supply temperature | Supply air—or water temperature for hydronic systems |
Alarms and schedules | Fault codes, occupied hours, and temporary overrides |
Record conditions before, during, and after the complaint. A screenshot taken after recovery can miss the event entirely.
For a multi-unit facility, identify the specific equipment serving the affected area. One cold office does not establish that every heat pump is underperforming.
Your building automation system needs to record data often enough to capture the problem.
Hourly averages can miss brief changes in defrost, backup heat, or equipment status. ETS can help review trend settings so the information is useful when troubleshooting.
Put those observations in one place.
Download our Winter Heat Pump Observation Checklist to record equipment details, temperatures, operating modes, and what happened during the complaint.
Share the completed checklist with ETS to help guide your service visit.
Prepare Before the Next Cold Spell
Use your winter service visit to establish what normal operation looks like for each system.
Ask the service team to verify these items against manufacturer requirements:
Filter condition and airflow.
Outdoor-coil condition and drainage.
Temperature sensors and control readings.
Backup-heat operation.
Heating, defrost, and lockout sequences.
Maintain required outdoor-unit clearances and plan snow removal so equipment access and airflow remain available. Arrange safe service access; rooftop inspections should be handled by personnel trained and equipped for those conditions.
Owners should also identify spaces where lost heat has a higher operational consequence.
Document who receives alarms, who can authorize service, and what happens during an extended equipment outage.
Frequently Asked Questions
Do Heat Pumps Stop Working at 32°F?
No. Freezing is not a universal shutdown temperature.
Commercial equipment has model-specific operating limits, so check the installed unit’s operating envelope and available capacity at lower temperatures. [1][2]
Does Auxiliary Heat Mean the Heat Pump Is Broken?
No. Auxiliary heat can be part of the designed heating and defrost sequence. [1]
Unexpected operation, recurring faults, or poor comfort calls for investigation.
Should a Heat Pump Run Longer Than a Gas Furnace?
Runtime alone is not a reliable comparison between different heating systems.
Evaluate delivered comfort, operating mode, energy use, and whether the unit follows its intended sequence.
Can I Compare Winter Bills Without Adjusting for Weather?
You can identify changes, but not their cause.
Compare outdoor conditions, occupancy, schedules, production activity, and heating-stage operation before attributing the difference to equipment efficiency.
Get Your Facility Ready for Winter
Understanding defrost, backup heat, and operating data helps you make better decisions about commercial heat pumps in winter.
If your Central Ohio facility has recurring cold spots, unexplained auxiliary-heat operation, or concerns about winter performance, contact Engineered Temperature Solutions to discuss your commercial HVAC service needs.
Request heat pump service from ETS. Share the equipment model, affected areas, and available operating trends so the conversation starts with your building’s actual conditions.
Tony Guilfoy
“In the middle of the winter, Jon responded to my call in 30 minutes and had a crew out in two hours. Prompt, fair, and honest. Highly recommend.”
Rob Orlowski
“Definitely my number one call for any commercial HVAC equipment help.”
Shane Duty
“They are always available to walk me through a situation and educate me on our systems. Couldn’t ask for a better group.”
Key Takeaways
Defrost is a normal operating function; persistent ice and poor recovery warrant investigation.
Cold-weather heating capacity matters more than a unit’s nominal cooling tonnage.
Auxiliary heat can support normal operation. Unexpected use deserves a controls and performance review.
Compare energy use alongside weather, schedules, and heating output.
Record operating conditions before changing settings or approving equipment replacement.
Sources
Trane Commercial. Modern Unitary Heat Pumps. — Commercial rooftop applications, auxiliary heat, load analysis, and defrost.
Trane. Air-to-Water Heat Pump Systems Application Guide. — Hydronic performance, operating limits, and defrost integration.
Trane. What Is a Heat Pump Defrost Cycle? — General defrost explanation; residential examples are not commercial timing specifications.
Electric Power Research Institute (EPRI). Quick Insight: Cold Climate Heat Pumps. — COP and heat-transfer principles; residential findings are not used here as commercial performance predictions.
Pacific Northwest National Laboratory (PNNL), Building America Solution Center. Thermostat Controls. — Adaptive-recovery principles; commercial sequences require application-specific review.
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