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When Does A Heat Pump Switch to Emergency Heat? | Phoenix HVAC

When Does A Heat Pump Switch to Emergency Heat

When it comes to the efficiency and functionality of a heat pump system, understanding the conditions under which it switches to emergency heat is crucial. A heat pump is designed to provide both heating and cooling functions, but there are instances where it may need to resort to emergency heat. In this comprehensive blog post, we will delve into the factors that influence answering the question of when does a heat pump switch to emergency heat

What is a Heat Pump?

A heat pump is a versatile and energy-efficient heating, ventilation, and air conditioning (HVAC) system designed to transfer heat between indoor and outdoor environments. Unlike traditional heating systems that generate heat through combustion, a heat pump operates by moving heat from one location to another. Here are key characteristics and components of a heat pump:

Heat Transfer Principle:

  • Heat pumps utilize the principle of thermodynamics to extract heat from the air, ground, or water sources and transfer it to the desired space for heating.
  • They can also reverse this process to provide cooling during warmer months by expelling heat from the indoor space to the external environment.


  • Evaporator Coil: Located indoors, the evaporator coil absorbs heat from the surrounding air.
  • Condenser Coil: Located outdoors, the condenser coil releases heat absorbed from indoors to the external environment.
  • Refrigerant: A special fluid circulating within the coils that alternately evaporates and condenses to facilitate heat exchange.
  • Compressor: Responsible for compressing the refrigerant, increasing its temperature and pressure for efficient heat transfer.

Types of Heat Pumps:

  • Air Source Heat Pumps: Extract heat from the outdoor air and transfer it indoors. Suitable for moderate climates.
  • Ground Source Heat Pumps (Geothermal): Utilize the stable temperature of the ground to extract or dissipate heat. More energy-efficient but involves installation of ground loops.
  • Water Source Heat Pumps: Extract or dissipate heat using water sources, such as ponds or wells.

Modes of Operation:

  • Heating Mode: Absorbs heat from the external environment and releases it inside the building.
  • Cooling Mode: Absorbs heat from indoors and releases it outside to cool the indoor space.
  • Efficiency and Energy Savings:
  • Heat pumps are known for their high efficiency, as they move existing heat rather than generating it. This can result in lower energy consumption compared to traditional heating systems.
  • They are particularly effective in moderate climates, where temperature extremes are less pronounced.

Supplementary Heating:

  • In extremely cold conditions, when the heat pump’s capacity to extract heat diminishes, supplementary or auxiliary heating elements, often electric resistance heaters, may activate to ensure consistent indoor comfort.

Environmental Impact:

  • Heat pumps are considered environmentally friendly because they use electricity to transfer heat rather than burning fossil fuels directly. The environmental impact depends on the electricity source used.

Integration with Smart Technologies:

  • Modern heat pump systems often integrate with smart thermostats and home automation systems, allowing users to control and monitor their HVAC systems remotely.
  • Smart features can optimize operation based on user preferences, weather forecasts, and energy pricing.

When Does A Heat Pump Switch To Emergency Heat?

1. Outside Temperature

Ambient Temperature

The primary factor influencing a heat pump’s transition to emergency heat is the outside temperature. Heat pumps work by extracting heat from the air outside and transferring it into the home during the heating season. However, when the outside temperature drops significantly, the efficiency of this process diminishes.

Balance Point

The balance point is the outdoor temperature at which the heat pump’s heating capacity matches the heating demand of the home. Beyond this point, the heat pump may struggle to extract sufficient heat, triggering the activation of emergency heat.

2. Heat Pump Defrost Cycle

Frost Accumulation

In cold weather, frost can accumulate on the outdoor coils of a heat pump. To maintain optimal performance, the heat pump periodically enters a defrost cycle to melt this frost. During this cycle, the heat pump temporarily switches to cooling mode, and the auxiliary heat may activate to maintain indoor comfort.

Defrost Control

Defrost controls in modern heat pump systems are designed to minimize the duration of the defrost cycle. However, in extreme weather conditions or if the defrost cycle is not functioning correctly, the heat pump may switch to emergency heat to prevent discomfort.

3. System Malfunctions

Sensor Issues

Faulty sensors in a heat pump can lead to incorrect temperature readings, causing the system to miscalculate the outdoor conditions. This can result in unnecessary activation of emergency heat. Regular maintenance and sensor checks can help prevent such malfunctions.

Thermostat Settings

Incorrect thermostat settings can also contribute to a heat pump relying on emergency heat. Ensure that your thermostat is programmed correctly, considering both indoor and outdoor conditions, to optimize the heat pump’s efficiency.

4. Refrigerant Issues

Low Refrigerant Levels

Insufficient refrigerant levels in a heat pump can hinder its ability to absorb and transfer heat effectively. This deficiency may prompt the system to switch to emergency heat to meet the heating demands. Regular maintenance and timely refrigerant checks are essential to avoid this scenario.

Refrigerant Leaks

Leaks in the refrigerant system can lead to a drop in pressure, affecting the heat pump’s overall performance. In such cases, emergency heat may be activated to compensate for the reduced heating capacity caused by the refrigerant leak.

5. Regular Maintenance

Air Filter

A clogged or dirty air filter can restrict airflow in the heat pump system, leading to decreased efficiency. Regularly changing or cleaning the air filter is a simple yet effective way to ensure optimal performance and avoid unnecessary reliance on emergency heat.

System Cleaning

Accumulation of dirt, debris, or vegetation around the outdoor unit can impede the heat exchange process. Regular cleaning and maintenance of the entire heat pump system can prevent issues that might trigger emergency heat.

6. System Size and Capacity

Undersized Systems

An undersized heat pump may struggle to meet the heating demands of a home, especially in extreme weather conditions. In such cases, emergency heat may activate to supplement the inadequate heating capacity of the undersized system. Finding the best heat pump repair in Phoenix is important when needed.

Overworked Systems

Continuous operation under extreme conditions can strain the heat pump, potentially leading to a switch to emergency heat. Sizing the system appropriately for the home’s heating needs is crucial to avoid overworking the heat pump.

7. Smart Thermostat Features

Adaptive Learning

Some smart thermostats have adaptive learning capabilities, allowing them to anticipate and adjust to the user’s heating preferences. However, if not properly configured or if user preferences change abruptly, these features may lead to unnecessary activation of emergency heat.

Remote Control

Remote control features in smart thermostats enable users to adjust settings from anywhere. While convenient, improper adjustments can trigger emergency heat unintentionally. Users should be cautious when utilizing remote control functions to avoid unnecessary energy consumption.

8. Energy Efficiency Measures


Proper insulation in a home plays a significant role in retaining heat during colder months. Inadequate insulation can result in increased heat loss, forcing the heat pump to work harder. When the heat pump struggles to meet the demand, it may resort to emergency heat. Ensuring proper insulation is in place helps maintain energy efficiency and reduces the reliance on auxiliary heating.

Windows and Doors

Drafty windows and doors contribute to heat loss, making it challenging for the heat pump to sustain a comfortable indoor temperature. Regularly checking for and sealing any gaps or leaks can improve energy efficiency. By minimizing heat loss through windows and doors, homeowners can mitigate the need for emergency heat.

9. Geographic Location

Climate Considerations

The geographical location of a residence can significantly impact the performance of a heat pump. Areas with extremely cold climates may experience more frequent transitions to emergency heat. Homeowners in colder regions should be aware of these conditions and take preventive measures, such as installing additional heating sources or using supplemental insulation.

When Does A Heat Pump Switch to Emergency Heat

Weather Patterns

Unpredictable weather patterns, including sudden temperature drops or storms, can influence a heat pump’s operation. Being aware of local weather forecasts and taking proactive steps, such as adjusting thermostat settings accordingly, can help minimize the reliance on emergency heat during adverse weather conditions.

10. User Habits

Thermostat Settings

User habits, particularly regarding thermostat settings, can impact a heat pump’s operation. Drastic changes in temperature preferences or setting the thermostat too high during cold weather can prompt the system to use emergency heat unnecessarily. Consistent and reasonable thermostat adjustments contribute to energy efficiency.

Education and Awareness

Educating homeowners about the operation of their heat pump systems and the conditions that trigger emergency heat is crucial. Increased awareness empowers users to make informed decisions, avoid unnecessary energy consumption, and contribute to the overall efficiency of their heating systems.

11. Emergency Heat Duration

System Programming

Some heat pump systems allow users to set the duration for which emergency heat remains active. Properly programming this feature ensures that emergency heat is only utilized when necessary, preventing prolonged and unnecessary use that can increase energy consumption.

12. Monitoring and Adjustments

Regularly monitoring the system’s performance and making adjustments based on the actual heating needs of the home can prevent extended use of emergency heat. Homeowners should be vigilant about system behavior and take corrective actions promptly.

Remember that emergency heat should only be used for emergency situations, hence maintaining the heat pump is the best way to keep the heat pump optimized.

How to Maintain Heat Pump In Phoenix

1. Regular Inspection and Cleaning

1.1 Outdoor Unit:

  • Phoenix’s desert climate can lead to dust and debris accumulation on the outdoor unit’s coils. Regularly inspect and clean the coils to ensure optimal heat exchange efficiency.
  • Trim vegetation around the outdoor unit to maintain proper airflow and prevent obstructions.

1.2 Indoor Components:

  • Check and replace air filters monthly. In the dusty conditions of Phoenix, clogged filters can reduce airflow and strain the system, and heat pump repair may be needed.
  • Inspect indoor components, such as the evaporator coil and blower, for dust buildup. Clean as needed to maintain efficiency.

2. Monitor Refrigerant Levels

2.1 Professional Inspection:

  • Schedule regular professional inspections to ensure proper refrigerant levels. Low refrigerant levels can impact heat pump efficiency.
  • Address any refrigerant leaks promptly to prevent further issues.

3. Thermostat Calibration

3.1 Temperature Settings:

  • Calibrate the thermostat to accurate temperature readings. Inaccurate settings can lead to unnecessary system cycling and energy waste.
  • Consider investing in a programmable thermostat to optimize temperature control and energy savings.

4. Seasonal Maintenance

4.1 Pre-Winter Check:

  • Before the winter season, inspect the heat pump for any signs you need heat pump repair. Ensure that the defrost cycle is functioning correctly.
  • Test the emergency heat function to verify its proper operation during extreme weather conditions.

4.2 Pre-Summer Preparation:

  • Prior to the summer season, clean the outdoor unit thoroughly to remove accumulated dust and debris.
  • Trim any overhanging branches or vegetation that may obstruct airflow.

5. Air Duct Inspection

5.1 Duct Sealing:

  • Inspect the air ducts for leaks, especially in attics or crawl spaces. Sealing duct leaks enhances system efficiency and prevents energy loss.

5.2 Duct Cleaning:

  • Consider professional duct cleaning to remove dust and debris, improving indoor air quality and preventing potential airflow restrictions.

6. Insulation Check

6.1 Attic and Home Insulation:

  • Ensure adequate insulation in the attic and walls to minimize heat loss during winter and heat gain during summer.
  • Proper insulation reduces the workload on the heat pump, promoting energy efficiency.

7. Professional Maintenance

7.1 Scheduled Tune-Ups:

  • Schedule annual professional maintenance to address complex issues, inspect electrical components, and ensure overall system efficiency.
  • Professional technicians can identify and address potential problems before they escalate as well as do heat pump repair in Phoenix when needed.

8. Monitor and Respond to System Changes

8.1 Unusual Noises:

  • Pay attention to any unusual noises, such as grinding or squealing. These may indicate mechanical issues that require prompt attention.

8.2 Reduced Performance:

  • If you notice a decrease in heating or cooling performance, schedule a professional inspection to identify and resolve the underlying issues.


Understanding, when a heat pump switches to emergency heat, involves a holistic consideration of various factors. Homeowners can take proactive steps, including regular maintenance, energy-efficient measures, and user education, to optimize their heat pump systems and reduce reliance on emergency heat. Einstein Pros remains your number-one HVAC professional provider in Phoenix.

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