How Doed Heat Pump Thermostat Work? 9 Facts You Should Know!

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By Debarghya Roy

What Are Heat Pump Thermostats?

How Does Heat Pump Thermostat Work

Heat pump thermostats are the bosses of the home temperature, also helping to control energy bills. They make sure the heat pump system is on when the home needs more heating or cooling.

The thermostat has three modes: 

  • Heat.
  • Cool.
  • Emergency heat.

 It uses a reversing valve solenoid to switch between heating and cooling. If the outdoor air is too cold, electric heat strips come on as secondary heat.

During defrost, the valve reverses refrigeration flow to stop frost from forming. Programmable thermostats let people set schedules and save energy when away. For max efficiency, keep the thermostat at 68 degrees or lower in winter and 78 degrees or higher in summer.

 Don’t keep changing the settings; it’s a waste of electricity and can mess with the HVAC system’s control board. If outdoor temps stay below freezing for a while, consider a backup heating system like electric strip heaters.

Components Of A Heat Pump System.


How Does Heat Pump Thermostat Work

When it comes to a Heat Pump System, various components work together to ensure efficient heating or cooling. 

Here are the essential parts of this system:

ComponentDescription
Heat PumpExchanges hot air with cool air to regulate temperature.
Reversing ValveChanges the direction of the refrigerant flow for heating or cooling mode.
Electric HeatProvides supplemental heat when necessary.
Air HandlerResponsible for moving air through the system and distributing it throughout the home.
ThermostatControls the temperature by sending signals to the Heat Pump System.
Defrost Cycle BoardPrevents ice buildup on the outdoor coil during cold weather.

In addition, the Heat Pump System may have a backup heating system, such as heat strips or a furnace, which will come on when the temperature drops too low for the Heat Pump to work efficiently on its own

Pro Tip: Regular maintenance is key to ensuring your Heat Pump System runs smoothly. Have a professional HVAC technician check your system annually and change air filters monthly to improve efficiency and lower energy bills.

 Why choose between heating and cooling when your heat pump can do both? Thanks, for reversing the valve and valve solenoid!

  • Reversing Valve and Valve Solenoid.

The valve solenoid and reversing valve are both integral to the heat pump system. The first one regulates the refrigerant flow, while the latter reverses it, allowing both heating and cooling.

A table can illustrate details about each component, such as its location, purpose, and features. 

The following table shows the details of the components:

ComponentLocationFunctionKey Features
Valve SolenoidIntegral to Heat Pump System.Regulates refrigerant flow.Controls compressor speed and pressure.Powered by a magnetic coil and switches between cooling and heating modes.
Reversing ValveIntegral to Heat Pump System.Reverses refrigerant flow, allowing both heating and cooling.Essential for optimal performance.

The valve solenoid also controls compressor speed and pressure. It’s powered by a magnetic coil that switches it between cooling and heating modes. These components are essential for optimal performance.

Regular maintenance is essential. Check wiring connections, power supplies, coils for dust and debris, and refrigerant levels for leaks. This ensures long-lasting performance from these components. Lastly, the defrost cycle gives the heat pump a break before initiating secondary heat.

  • Defrost Cycle and Secondary Heat.

Defrosting the Pump and Heating with Secondary Sources.

A vital part of a heat pump system is managing ice accumulation on the outdoor unit in cold weather. This cycle of defrosting is called the ‘heat-pump defrost cycle.’ It helps with optimal airflow and energy efficiency. Also, extra heating is available on cold days from auxiliary or secondary sources.

Below is a table of related components:

ComponentDescription
Defrost ThermostatDetects outdoor unit temperature below a certain threshold.
Defrost Control BoardActivates the defrost cycle when triggered.
Defrost RelaySends power to the defrost control board.
Reversing ValveSwitches refrigerant flow.
Auxiliary Heat OptionsDifferent ways to supplement heat when needed.

Excessive ice buildup affects system efficiency, leading to wasteful energy consumption and a shorter lifespan. Maintenance checks can help prevent this.

To keep up-to-date with heat pump capabilities, monitor these components and know what backup offers you have in place.

No need for a knight in shining armor when you have an air handler and emergency heat!

  • Air Handler and Emergency Heat.

Air circulation and emergency heat are essential for a heat pump system. The air handler distributes the conditioned air, while the emergency heat provides warmth if the other sources fail.

A table outlines the details of the air handler and emergency heat:

ComponentDetails
Air HandlerDistributes air throughout the building.
FiltersRemoves contaminants from the air.
ThermostatControls temperature.
Emergency HeatAn alternative heating source.
Backup Heat StripsElectrically heated strips if needed.

A faulty air handler can cause heating or cooling issues. Emergency heat is energy-intensive, so only use it if necessary.

Tip: Regular maintenance checks are recommended to ensure the heat pump system is working correctly, especially in peak seasons. Even a broken thermostat can’t deny winter is coming.

How A Heat Pump Thermostat Works.


Heat pump thermostats regulate the temperature in a home by controlling the operation of the heat pump system.

  •  The thermostat switches the heat pump between heating and cooling modes as needed, and can also activate emergency heat (heat strips or a backup heating system) when temperatures fall too low. 
  • A key component is the reversing valve solenoid which controls the flow of refrigerant. In heating mode, the valve reverses the flow of refrigerant, allowing the outdoor unit to act as the source of heat for the indoor air handler.
  •  During a defrost cycle, the valve switches to cooling mode to melt any frost on the outdoor unit.
  • Programmable thermostats can help homeowners save energy and money by allowing the temperature to automatically adjust depending on the time of day.
  • It is important to note that issues with the thermostat or heat pump system can cause problems with temperature regulation and high electricity bills.

 In one instance, a homeowner had a malfunctioning thermostat that caused the backup heating system (a furnace) to run constantly, leading to a spike in their energy bills. The problem was traced back to a faulty control board in the thermostat, and once replaced, the heating system ran efficiently once again.

Keeping up with regular maintenance and checks on the thermostat and heat pump system can prevent these types of issues and ensure a comfortable temperature in the home. 

By understanding how a heat pump thermostat works and its role in heating and cooling a home, homeowners can better manage their energy use and save money on utilities.

I’m not saying my heat pump thermostat is smarter than me, but it knows how to switch between electric heat mode and cooling mode with ease.

  1. Electric Heat Mode and Cooling Mode:

The Heat Pump thermostat is great for adapting to temperature changes. 

It has two main modes: 

  • ‘Electric Heat Mode’
  • ‘Cooling Mode’

When the temperature drops below the set threshold, the system shifts into Heating Mode. On the other hand, when there’s an increase in room temperature above the set threshold, Cooling Mode is activated.

It also has additional modes like ‘Fan Only’ or ‘Emergency Heat’. These give users more control over their home climate.

Interesting fact: Early thermostats had only a mercury switch for motion detection, but modern digital thermostats have more advanced sensors and algorithms for accurate data gathering and energy management.

Heat Pump mode and Auxiliary Heat mode are like having a backup plan for your backup plan. Enjoy!

  1. Heat Pump Mode and Auxiliary Heat Mode:

Switching between Heat Pump and Auxiliary Heat Modes is key to understanding a thermostat. 

Heat Pump Mode uses the ambient air around it to keep the house warm, whilst Auxiliary Heat Mode kicks in when the outside temperatures drop too low for the heat pump to keep up. 

Here’s a table to differentiate the two:

Parameters Heat Pump ModeAuxiliary Heat Mode
ActionUses heat from ambient air.Electric Resistance Heating
Functioning Temperature Range32°F – 40°F<32°F
Energy efficiencyHighLow

Be aware that there might be a slight delay when switching from Heat Pump to Auxiliary Mode before you feel a temperature change.

 Also, prolonged use of Auxiliary heat leads to higher electricity bills. So, don’t forget to program your thermostat with no heat in an empty house!

  1. Programming a Thermostat for Optimal Energy Use:

Maximizing energy efficiency with your heat pump thermostat can save you money. To do this, you must program it properly. 

Here’s how:

  1. Set the temperature about 7-10 degrees lower when you’re not home.
  2. Make sure the thermostat doesn’t turn on during the day when you’re away.
  3. Use a programmable thermostat to customize settings based on your schedule.

Read the manufacturer’s manual for instructions. To save even more, get newer models or upgrade to smart thermostats. You can also install a zoning system so only certain parts of your house are heated.

Program and optimize your heat pump thermostat to reduce costs while still staying comfortable. Now, you can simply sit back and enjoy the warmth!

Common Issues With Heat Pump Thermostats.


As someone who works in HVAC, I’ve come across various issues with heat pump thermostats that homeowners face.

 Below are three common issues that may arise:

  • Wrong wiring of the thermostat

This is a common issue and can lead to incorrect communication between the thermostat and the heat pump system. If the wiring is not done correctly, the thermostat will not be able to control the HVAC system, leading to issues.

  • Faulty thermostat settings:

 Incorrect programming of the thermostat can also lead to issues. If the homeowner sets the thermostat to a temperature that is too high or too low, the heat pump system may not function properly, leading to discomfort and increased energy bills.

  • Emergency heat mode not working:

 If the emergency heat mode is not functioning correctly, the system will not work during extremely cold temperatures. This can leave the homeowner with no heating system backup.

Homeowners must avoid these common errors to keep their homes heated comfortably and avoid inflated energy bills.

Another issue that homeowners may encounter is the thermostat’s failure to activate the backup heating system when the heat pump fails. It is essential to ensure that the thermostat is correctly wired to activate the secondary heat or heat strips when necessary.

As a professional in this industry, I recall facing an issue where a homeowner’s heat pump thermostat was not communicating correctly with the HVAC system, leading to incorrect temperature readings. It resulted from a faulty connecting wire between the thermostat and the control board. This issue was resolved by running new connecting wires, and the homeowner had no further issues.

My backup heating system failed, leaving me colder than a polar bear’s toenails – but thankfully, my heat pump thermostat came to the rescue.

  1. Backup Heating System Failures:

Heat pumps need a backup heating system, in case of extreme cold. But if it fails, it can cause problems. Reasons for this failure can be incorrect wiring, thermostat defects, power supply issues, and fan/compressor malfunctions.

To avoid such a breakdown, call in a professional technician for regular inspections. Also, check thermostats and air filters. Doing this will help prevent the backup heating system from failing.

Backup Heating System Failures can lead to money loss and health hazards. Diagnosing the problem with the naked eye is difficult. So, get an expert HVAC technician to inspect it.

A customer once faced an issue when the heat pump wouldn’t give out any warm air. Turns out, lack of maintenance and repair work had caused the backup heating system to fail. The customer had to endure a cold night before calling an HVAC technician for repairs. 

The control board and wiring had vanished like in the Bermuda Triangle!

  1. Thermostat Control Board and Wiring Issues:

Control boards and wiring can cause a lot of heat pump issues. They run the HVAC system and can fail for many reasons, like power surges or pest damage.

Consequences range from minor, like incorrect temps, to serious malfunctions, like short circuits or tripped circuit breakers. Homeowners can often spot simple wiring problems, but some need a professional.

It’s important to address these problems ASAP, as they can cause not only inconvenience but also safety hazards. Maintenance can help prevent these failures.

Airxpertsnj.com says that control board failure accounts for up to 80% of electric furnace failures.

Looks like your heat pump thermostat is having trouble; between hot flashes and cold sweats!

  1. Temperature and Time Setting Malfunctions:

Issues with temperature and time settings on heat pump thermostats can cause a variety of malfunctions. This can lead to the system being less efficient or even not working at all.

Common issues include inaccurate temperature readings, due to incorrect calibration or an issue with the sensing device. 

Sometimes the thermostat won’t turn on; this could be caused by dead batteries or an electrical problem. Programming errors can also cause the thermostat to run at the wrong times or temperatures. See the table below for causes and solutions.

IssueCauseSolution
Inaccurate temperature readings.Incorrect calibration or issue with sensing device.Calibrate the thermostat or replace the sensing device.
Thermostat won’t turn on.Dead batteries or electrical issues in the system.Replace batteries or call a technician for repair.
Programming errors.User error or software malfunction.Double-check program settings or update software if necessary.

Remember, every HVAC system may have unique reasons for malfunctions. Always follow manufacturer guidelines when trying repairs. Improper repairs may cause more severe issues.

Tip: For best results, take care of your thermostat. Regular maintenance can prevent most malfunctions. Navigating the world of thermostats is like a maze, but the prize at the end is perfect temperatures!

Manufacturers And Models Of Heat Pump Thermostats.


As homeowners, choosing the right thermostat for your heat pump system can be a daunting task. There are numerous manufacturers and models of heat pump thermostats available in the market. 

Here’s a list of some of the most common manufacturers and their models:

ManufacturerModels
HoneywellTH8320R1003, RTH7600D, TH6320R1004, RTH9580WF.
NestLearning Thermostat, Nest Thermostat E.
ecobeeSmartThermostat with voice control, ecobee3 lite, ecobee4, Smart Si.
EmersonUP500W, ST55, P210, Sensi Smart Thermostat

In addition to these, there are many other manufacturers and models of heat pump thermostats available in the market. It is important to check the compatibility of the thermostat with your heat pump system before making your purchase.

When choosing a heat pump thermostat, it is important to consider some unique details such as the location of the thermostat, the type of auxiliary heating system, and the use of a programmable thermostat. These details can affect the performance and energy efficiency of the heat pump system.

To ensure optimal performance and energy efficiency, homeowners can follow these suggestions:

  • Use a programmable thermostat to set temperature schedules based on occupancy patterns. This can help to reduce energy bills.
  • Use the auxiliary backup heating system only when necessary. It can be expensive to run and can increase your electricity bills.
  • Check the thermostat settings regularly to ensure that the heat pump system is operating in the correct mode.
  • Schedule regular maintenance of the HVAC system by professionals like Deziel Heating to ensure proper operation and reduce the frequency of issues.

By following these suggestions, homeowners can ensure optimal performance and energy efficiency of their heat pump system, minimize their electricity bills, and reduce the frequency of issues related to the HVAC system.

I’m not saying my heat pump thermostat is smarter than me, but it knows how to keep me warm.

  • Popular Brands and Features.

Discovering the top heat pump thermostat picks? Look no further! We’ve got renowned brands and their features listed right here.

  • Ecobee offers energy-saving models with Wi-Fi and Alexa compatibility.
  • Nest Learning Thermostat has a unique feature of learning user settings and providing smartphone connectivity.
  • Honeywell Home’s T9 and T10 Pro models have wireless remote sensors, humidity control, geofencing, customizable displays, and secure options.
  • Emerson Sensi Touch is perfect for easy installation and has a user-friendly touchscreen interface.
  • Lux Products provide budget-friendly thermostats to match any style.
  • Bosch Thermotechnology has programmable thermostats for multiple zones and voice assistant compatibility.
  • Johnson Controls is the go-to for custom manufacturing solutions.
  • Consider Lux Products for cost-effective models. 

The ideal heat pump thermostat depends on your daily patterns and budget. I hope these heat pump thermostats are more compatible than my last relationship!

  • Compatibility with Different Heat Pump Systems.

Heat pump thermostats come in different models and are only compatible with certain heat pump systems. Let’s take a look!

Here’s a table showing the compatibility of certain thermostats:

ManufacturerModelCompatibility
HoneywellTH9320WF5003 Wi-Fi 9000 Color Touchscreen Thermostat.Compatible with most heat pump systems.
NestLearning Thermostat (3rd Gen).Compatible with most heat pump systems.
ecobeeSmartThermostat with Voice Control (5th Gen).Compatible with most heat pump systems.

Before making any changes, it’s important to check if additional wiring or equipment is needed. Consulting a professional technician is recommended.

When choosing a thermostat, consider the system type and age, desired features, and budget. Programmable thermostats help save energy. Wi-Fi-enabled models let you control your heating system remotely.

Selecting an appropriate heat pump thermostat can improve system performance and comfort levels. Plus, no more heating an empty house for hours!

Frequently Asked Questions.


Q: What is a heat pump?

A: A heat pump is a type of heating system that moves heat from the outdoors into your home during the winter months and moves heat from your home to the outdoors during the summer months for cooling.

Q: What is emergency heat?

A: Emergency heat is a setting on your heat pump thermostat that bypasses the heat pump system, and instead uses an electric heating element or a furnace to provide heat. This setting is used when the heat pump system fails or can’t keep up with the outdoor temperatures.

Q: How does a heat pump thermostat work with a reversing valve?

A: The reversing valve is controlled by a valve solenoid in the heat pump system. When the thermostat calls for heat, the valve solenoid sends a signal to the reversing valve to switch the flow of refrigerant in the heat pump, allowing it to provide heating or cooling.

Q: What is a defrost cycle?

A: A defrost cycle is a process in the heat pump system where the outdoor unit defrosts itself when ice or frost builds up on the condenser. During the defrost cycle, the system switches to cooling mode to melt the ice and then switches back to heating mode once it’s done.

Q: What is the difference between auxiliary and secondary heat?

A: Auxiliary heat is electric heating that is used in conjunction with the heat pump system, while secondary heat is a backup heating system that is used when the heat pump system fails or can’t keep up with the outdoor temperatures.

Q: How can a programmable thermostat save me money on energy bills?

A: A programmable thermostat can be set to automatically adjust the temperature according to your schedule, such as lower when you’re not home or asleep. This can reduce the amount of energy the system uses, thereby lowering your energy bills.

Conclusion: 


For efficient heating and cooling, proper thermostat operation is key. To control a Heat Pump (HP) thermostat accurately, homeowners need to know how it works. It has a reversing valve solenoid that switches between heating and cooling modes. An electric strip serves as a backup when temperatures drop. And, its defrost cycle protects outdoor coils from ice buildup. To keep the system efficient, homeowners should set the temperature right. Setting it too high could damage the condenser and consume more electricity. Programmable thermostats can help regulate temperatures better; users can set different temperatures at specific times. Back-up heat strips are necessary in an emergency. Understanding each terminal on the thermostat board can help with any HVAC issues. Consulting with professionals like Deziel Heating & Plumbing’s trusted contractors may help to optimize home efficiency and keep costs low.

Heat Pump