· Katria Melrose · HVAC Systems · 20 min read
Does Heat Pump Shut Off When Auxiliary Heat Is On

Does Your Heat Pump Shut Off When Auxiliary Heat Is On?
You might have heard a different sound from your heating system on a cold day. Perhaps you noticed your energy bill increased slightly. Many homeowners ask, “Does heat pump shut off when auxiliary heat is on?” This is a common question, and understanding the answer helps you manage your home’s heating better. Your heat pump and auxiliary heat typically work together, not as separate, exclusive systems.
This article explores how heat pumps operate, why auxiliary heat activates, and their combined function. We will look at thermostat settings and energy efficiency. You will learn to optimize your heating system for comfort and savings. Let us clear up the confusion about these essential home heating components.
Takeaway
- Heat Pump Operation: Your heat pump usually runs concurrently with auxiliary heat. It does not shut off.
- Purpose of Auxiliary Heat: Auxiliary heat assists the heat pump. It handles very cold temperatures or quick heating demands.
- System Cooperation: Both components work together. This ensures your home stays warm efficiently.
- Energy Consumption: Auxiliary heat uses more energy. Understand when and why it activates.
- Optimization: Adjust your thermostat settings. This helps manage auxiliary heat use for better efficiency.
The heat pump generally continues to run alongside auxiliary heat in most systems. It does not typically shut off. Auxiliary heat activates to assist the heat pump, especially during very cold weather or when rapid temperature increases are needed. This combined operation ensures efficient heating for your home.
Understanding Heat Pump Operation and Auxiliary Heat
Many people wonder about their heating system’s inner workings. Heat pumps offer an energy-efficient way to heat and cool your home. They move heat rather than creating it. In winter, a heat pump extracts heat from the outside air, even cold air. It then transfers this heat indoors. This process makes them very efficient in mild to moderately cold temperatures.
However, when temperatures drop significantly, extracting enough heat from the outside becomes harder. This is where auxiliary heat steps in. Auxiliary heat is a secondary heating source, usually electric resistance coils. Think of it like a backup heater. It provides additional warmth when the heat pump alone cannot meet the demand.
Your heat pump does not simply shut off when auxiliary heat is on. Instead, they work in tandem. The heat pump continues to extract what heat it can from the outside. The auxiliary heat then supplements this. This ensures your home reaches and maintains the desired temperature. Understanding this combined operation is key to smart home heating.
The Role of Supplemental Heat
Supplemental heat is another term for auxiliary heat. Its main role is to provide extra warmth. This becomes necessary under specific conditions. Imagine a very cold winter morning. Your heat pump might struggle to bring your home up to a comfortable temperature quickly. Supplemental heat helps achieve this.
It also activates if you set your thermostat significantly higher. For example, if your home is 60 degrees and you set it to 72. The system needs to raise the temperature quickly. The heat pump alone would take a long time. Supplemental heat provides a rapid boost. It prevents your heat pump from overworking.
Most modern heat pump systems are designed this way. They prioritize the heat pump for efficiency. They bring in supplemental heat only when needed. This design ensures comfort without excessive energy use, ideally. Understanding these conditions helps you predict when your system will use more power.
How Heat Pumps and Auxiliary Heat Work Together
Your home’s heating system uses a smart approach to keep you warm. The primary goal is to use the heat pump as much as possible. This is because heat pumps are incredibly efficient. They move existing heat, which requires less energy than generating new heat. However, there are limits to their efficiency, especially in extreme cold.
When outdoor temperatures fall below a certain point, usually between 30-40 degrees Fahrenheit, the heat pump’s efficiency drops. It still works, but it takes more energy to extract heat from very cold air. This is when the system calls for auxiliary heat. The thermostat senses the temperature difference and activates the backup heating source.
The heat pump continues to run during this process. It tries to contribute as much heat as it can. The auxiliary heat then adds the extra warmth needed to reach your set temperature. This combined effort is known as “dual fuel” operation in some systems, especially those with a gas furnace as auxiliary heat. Most commonly, it refers to electric resistance coils supporting the heat pump.
This combined operation ensures comfort. It also prevents the heat pump from running too long or struggling. It is a balancing act between efficiency and warmth. Your system aims to provide consistent comfort. It does this by leveraging the strengths of both heating methods.
The Thermostat’s Role in Activation
The thermostat acts as the brain of your heating system. It monitors your indoor temperature. It also senses the outdoor temperature, if it has an outdoor sensor. The thermostat decides when to engage auxiliary heat. This decision is based on a few factors.
One factor is the “balance point.” This is a specific outdoor temperature setting. Below this point, the heat pump’s capacity alone is not enough. The thermostat signals the auxiliary heat to turn on. For example, if your balance point is 35°F, auxiliary heat may start below that.
Another factor is the “temperature differential.” If you raise the thermostat setting significantly, like from 65°F to 72°F, the system needs to recover quickly. The thermostat sees a large gap between the current and desired temperature. It activates auxiliary heat for a faster warm-up. This rapid heating is called “recovery mode.” Understanding your thermostat settings can help you manage auxiliary heat use. Many smart thermostats allow you to fine-tune these settings. This gives you more control over your energy consumption. If you need to understand specific wiring or system components, knowing how to tell if heat pump use o or b wire can be helpful for troubleshooting or setup.
When Auxiliary Heat Kicks In Automatically
Your heat pump system is designed to be smart. It prioritizes energy efficiency. It also ensures your comfort. Auxiliary heat does not come on all the time. It activates automatically under specific conditions. Knowing these conditions helps you understand your system’s behavior.
One common reason is a significant drop in outdoor temperature. Heat pumps become less efficient as it gets colder. When the outside air drops below your system’s “balance point,” the auxiliary heat activates. This balance point is typically between 30°F and 40°F. Below this point, the heat pump cannot extract enough heat to warm your home alone.
Another trigger is a large temperature setback. If you lower your thermostat overnight, then raise it significantly in the morning, auxiliary heat may kick in. For example, if you set your thermostat to 60°F overnight and then jump it to 70°F, the system needs to heat up quickly. The auxiliary heat provides a rapid boost to reach the desired temperature faster. This is called “emergency heat” or “supplemental heat” depending on your system’s specific terminology.
Finally, your system may also use auxiliary heat during its defrost cycle. Heat pumps go into defrost mode to melt ice on their outdoor coils. During this short period, the system effectively reverses, blowing cooler air inside. To prevent your home from getting cold, the auxiliary heat often comes on. This provides warmth while the heat pump clears the ice. If you notice your heat pump going into defrost mode frequently, it might be worth investigating why does my heat pump keep going into defrost mode.
Why Your Heat Pump Might Seem to “Shut Off” (But Doesn’t)
It is a common misconception that your heat pump completely shuts down when auxiliary heat engages. I often hear homeowners say, “My heat pump turned off, and the emergency heat came on.” In most standard setups, this is not the case. The heat pump continues to run. It simply receives help from the auxiliary heating coils.
The main reason for this perception is the difference in airflow and temperature. When auxiliary heat activates, it is typically electric resistance coils. These coils produce very hot air quickly. This air feels much warmer coming from your vents than the air produced by the heat pump alone. Heat pump air feels warm, but not as hot as traditional furnace air.
Because the auxiliary heat produces such a noticeable warmth, it can mask the heat pump’s contribution. You might feel the intense heat from the auxiliary coils. This makes it seem like the heat pump is no longer working. However, the heat pump is still extracting what heat it can from the outside air. It continues to contribute to your home’s warmth.
Another factor could be the noise level. Some auxiliary heating systems can be louder than the heat pump’s normal operation. This increased noise might also lead you to believe the main unit has stopped. It is important to remember that these systems are designed to work together. They are not designed to alternate in a way that one completely stops when the other starts. Unless there is a specific problem, your heat pump remains active.
Understanding the “Emergency Heat” Setting
Many thermostats have an “Emergency Heat” or “Em. Heat” setting. This setting is different from automatic auxiliary heat. When you manually select “Emergency Heat,” you are telling your system to only use the auxiliary heating source. In this mode, the heat pump does shut off. This means the heat pump compressor turns off completely.
Emergency heat should be used sparingly. It is for true emergencies. For example, if your heat pump breaks down during freezing weather. Or if outdoor temperatures are extremely low, making heat pump operation inefficient or potentially damaging. Running emergency heat uses a lot more electricity. Electric resistance coils consume significantly more energy than a heat pump.
I advise my clients to use this setting only when necessary. If you constantly rely on emergency heat, your energy bills will skyrocket. It is meant for temporary use. If your system frequently struggles without it, have an HVAC professional check your heat pump. Regular maintenance, such as knowing how to clean heat pump coils, can prevent issues that lead to needing emergency heat.
Optimizing Your Thermostat for Combined Heat Pump and Auxiliary Use
Your thermostat is a powerful tool. It manages your heat pump and auxiliary heat. Proper settings can save energy. They also keep your home comfortable. Understanding these settings helps you get the most from your system.
First, avoid large temperature setbacks. If you drop your thermostat significantly overnight, say from 70°F to 60°F, your system will work hard to recover. It will likely engage auxiliary heat for a long time in the morning. This uses more energy. Instead, aim for smaller setbacks. A 3-5°F setback is usually sufficient. This allows the heat pump to recover without heavy reliance on auxiliary heat.
Second, use programmable or smart thermostats. These thermostats learn your habits. They can pre-heat your home before you wake up. This allows for a gradual temperature increase. It reduces the need for auxiliary heat to kick in aggressively. Some smart thermostats also consider outdoor temperatures. They can adjust heating cycles accordingly.
Third, understand your thermostat’s settings for auxiliary lockout. Some advanced thermostats allow you to set a “balance point.” This is the outdoor temperature below which auxiliary heat is permitted to run. You can adjust this to fine-tune when auxiliary heat activates. Consult your HVAC technician for the optimal setting for your climate. Knowing how many kwh does an air source heat pump use can help you monitor and understand your energy consumption based on these settings.
Thermostat Programming Tips
- Small Setbacks: Program your thermostat for modest temperature reductions when you are away or asleep. A 3-5 degree F drop is ideal. This minimizes the need for high-energy auxiliary heat during recovery.
- Gradual Recovery: Schedule your heating to start increasing the temperature gradually. For instance, if you wake up at 6 AM, start warming the house at 5 AM. This allows the heat pump to do most of the work.
- Avoid Manual Boosts: Resist the urge to manually increase the thermostat setting by many degrees all at once. This action almost guarantees auxiliary heat activation. Let the scheduled program manage temperature changes.
- Understand Balance Point: If your thermostat offers a “balance point” setting, learn what it means. This controls the outdoor temperature threshold for auxiliary heat engagement. Consult your HVAC technician to set this correctly for your climate and system.
- Regular Monitoring: Check your energy bills and system performance. Adjust settings as needed. A small change can lead to noticeable savings. If you feel why is my air source heat pump costing so much, your thermostat settings could be a contributing factor.
Energy Efficiency and Costs of Auxiliary Heat
Heat pumps are known for their high energy efficiency. They move heat, rather than generating it. This process uses significantly less electricity than electric resistance heating. When auxiliary heat activates, your system’s energy consumption increases. This is because electric resistance heating is much less efficient than a heat pump.
Think of it this way: a heat pump might deliver 3 units of heat for every 1 unit of electricity used. This gives it a Coefficient of Performance (COP) of around 3. Auxiliary electric resistance heat, however, delivers roughly 1 unit of heat for every 1 unit of electricity. Its COP is closer to 1. This means auxiliary heat can be three times more expensive to run than your heat pump.
Your energy bills will reflect this difference. Days with prolonged cold spells, requiring frequent auxiliary heat use, will show higher energy consumption. Similarly, if you often use large temperature setbacks, your system will rely more on auxiliary heat for recovery. This leads to higher costs.
It is crucial to balance comfort with efficiency. While auxiliary heat ensures your home stays warm in extreme conditions, minimizing its use is good for your wallet. Understanding when and why it activates empowers you to make informed decisions about your thermostat settings. This helps control your energy costs.
Managing Auxiliary Heat for Cost Savings
To manage your energy costs effectively, you need to minimize auxiliary heat activation. I always tell my clients, the less your auxiliary heat runs, the better your energy bill will look. There are practical steps you can take.
First, ensure your home is well-insulated. Proper insulation prevents heat loss. This reduces the demand on your heating system. Seal drafts around windows and doors. This keeps warm air inside. A well-sealed home requires less work from your heat pump, meaning less need for auxiliary heat.
Second, consider a professional HVAC tune-up. A well-maintained heat pump runs more efficiently. Dirty coils, low refrigerant, or other issues can reduce its performance. This forces the system to rely more on auxiliary heat. Regular maintenance keeps your heat pump at peak efficiency. This reduces the instances where auxiliary heat is necessary.
Finally, adjust your expectations for heat pump air. Heat pump air feels warm, not hot. It is a constant, gentle warmth. If you expect a blast of hot air like from a furnace, you might be tempted to crank up the thermostat. This action triggers auxiliary heat. Allow your heat pump to work at its own pace. It will warm your home efficiently over time.
Troubleshooting Common Issues with Heat Pump and Auxiliary Heat
Sometimes, your heat pump and auxiliary heat might not behave as expected. You might notice your home is not warm enough. Or your energy bills are unusually high. These are signs that something might be off. Identifying common issues helps you decide if you need professional help.
One common problem is the auxiliary heat running too often. This usually points to two main issues. Either your heat pump is struggling, or your thermostat settings are too aggressive. A struggling heat pump might have low refrigerant, dirty coils, or a faulty compressor. If your thermostat setbacks are too large, or the balance point is set too high, auxiliary heat will engage frequently.
Another issue could be the auxiliary heat not coming on when it should. If your home is cold despite low outdoor temperatures, and you notice no warm boost, the auxiliary heat might be faulty. This could be a tripped breaker, a bad heating element, or an electrical issue. In such cases, your heat pump alone might not keep your home warm enough.
Always check your thermostat first. Ensure it is set to “Heat” mode, not “Emergency Heat” unless necessary. Check the batteries if it is a wireless model. Sometimes, a simple reset of the thermostat can resolve minor glitches. If issues persist, it is time to call a qualified HVAC technician. They can diagnose the problem accurately.
When to Call an HVAC Professional
It is important to know when a problem is beyond simple troubleshooting. I recommend calling an HVAC professional in several situations. Ignoring persistent issues can lead to bigger, more expensive repairs.
- Constant Auxiliary Heat: If your auxiliary heat runs non-stop, even when it’s not extremely cold, your heat pump might be failing. This signals a need for immediate inspection.
- Insufficient Heating: If your home simply isn’t getting warm enough, and you’ve confirmed your thermostat settings, the system might have a major component failure. This could be the heat pump, auxiliary heat, or both.
- Unusual Noises: Any new or loud noises coming from your outdoor unit or indoor air handler warrant professional attention. These could indicate mechanical problems.
- Spiking Energy Bills: A sudden and sustained increase in your heating costs, without a corresponding drop in outdoor temperatures, suggests inefficiency. An HVAC technician can pinpoint the cause.
- System Freezing: If your outdoor unit frequently freezes over or stays frozen even after defrost cycles, it indicates a problem. This might be with the defrost system or refrigerant levels.
- Error Codes: Many modern HVAC systems display error codes. Look up what the code means in your manual. If it points to a serious issue, call a professional.
Timely repairs can save you money and prevent major breakdowns. For example, if you find your heat pump constantly tripping the breaker, you might need a professional to diagnose the root cause, similar to why does my pool heat pump keep tripping the breaker.
Common Misconceptions About Heat Pumps and Auxiliary Heat
Many homeowners hold outdated beliefs about heat pumps. These misconceptions can lead to inefficient system use. Let’s clarify some common ones. Understanding the facts helps you use your heating system effectively.
One common myth is that heat pumps do not work in cold climates. This is false. Modern heat pumps are designed to operate effectively in very low temperatures. They can extract heat from air that is well below freezing. While their efficiency drops, they still provide heat. Auxiliary heat steps in to supplement, not replace, their function in extreme cold.
Another misconception is that heat pumps blow cold air. This is also untrue. The air from a heat pump feels cooler than furnace air because it heats the air less intensely. A furnace produces air around 120-140°F. A heat pump produces air around 90-105°F. This is still warm enough to heat your home, but it feels different. Many people confuse this warmer, gentle flow with cold air.
Some people believe they should manually switch to “Emergency Heat” on very cold days to save energy. This is a big mistake. As discussed, emergency heat is pure electric resistance. It consumes far more energy than your heat pump. Only use it if your heat pump is truly broken. Relying on it for everyday heating will significantly increase your energy bills.
Finally, there is a belief that auxiliary heat is a sign of a failing heat pump. This is only true if it runs excessively or unnecessarily. When it activates due to very low temperatures or a large temperature differential, it is performing its intended function. It means your system is working as designed to keep you warm.
Debunking the Myths for Better Efficiency
- Myth 1: Heat Pumps Don’t Work in Cold Weather.
- Reality: Modern heat pumps work in very cold temperatures, often down to -15°F or lower. They become less efficient but continue to extract heat. Auxiliary heat supplements their operation below their balance point, not replaces it entirely.
- Myth 2: Heat Pumps Blow Cold Air.
- Reality: Heat pump air feels warm (90-105°F), but it’s not as hot as furnace air (120-140°F). It’s a subtle, consistent warmth, which some people misinterpret as cold. The system is still actively heating your home.
- Myth 3: Always Use “Emergency Heat” on Coldest Days.
- Reality: This is a costly mistake. “Emergency Heat” bypasses the efficient heat pump and uses expensive electric resistance heating. Only use it if your heat pump is broken or temperatures are truly extreme (e.g., below -10°F where heat pump is entirely ineffective).
- Myth 4: Auxiliary Heat Means Your Heat Pump is Broken.
- Reality: Auxiliary heat is a normal, intended component of a heat pump system. It activates when the heat pump needs assistance due to extreme cold or a rapid temperature demand. Frequent, unnecessary activation might signal an issue, but its mere presence is normal.
- Myth 5: Turning the Thermostat Way Up Heats Faster.
- Reality: Rapidly increasing the thermostat setting by many degrees will simply trigger auxiliary heat for longer. It might warm your home faster but at a much higher energy cost. Gradual adjustments are more energy-efficient.
Frequently Asked Questions
What temperature does heat pump auxiliary heat come on?
Auxiliary heat typically activates when outdoor temperatures drop below your system’s “balance point,” often between 30°F and 40°F. It also turns on if you set your thermostat significantly higher, demanding a rapid temperature increase. These are default settings that can sometimes be adjusted by an HVAC professional.
Is it OK for auxiliary heat to run constantly?
No, it is not okay for auxiliary heat to run constantly. If it runs non-stop, it indicates a problem. Your heat pump might be malfunctioning, unable to provide enough heat. Constant auxiliary heat use results in very high energy bills. You should contact an HVAC professional to diagnose the issue.
Can I turn off auxiliary heat on my heat pump?
Most thermostats do not allow you to completely disable auxiliary heat for safety reasons. It acts as a necessary backup. However, you can manage its use by adjusting the “balance point” setting on some advanced thermostats. This setting dictates the outdoor temperature at which auxiliary heat is allowed to engage.
Why is my heat pump running but no heat is coming out?
If your heat pump is running but not producing heat, several issues could be at play. Common culprits include low refrigerant levels, a malfunctioning compressor, or issues with the reversing valve. It might also be stuck in defrost mode. A qualified HVAC technician should diagnose and repair these problems.
How do I know if my heat pump is using auxiliary heat?
You can often tell by feeling the air from your vents; auxiliary heat produces significantly hotter air than the heat pump alone. Many thermostats also display an “Aux Heat,” “Auxiliary Heat,” or “Supplemental Heat” indicator light when it is active. Your energy bills will also show increased consumption during periods of heavy auxiliary use.
Is emergency heat the same as auxiliary heat?
Not exactly. Auxiliary heat comes on automatically to assist the heat pump during cold weather or large temperature increases. Emergency heat, however, is a manual setting that completely bypasses the heat pump, relying solely on the electric resistance coils. Emergency heat should only be used in true emergencies when the heat pump is broken.
Conclusion
Understanding how your heat pump works alongside auxiliary heat helps you manage your home’s comfort and energy costs. We have learned that your heat pump does not typically shut off when auxiliary heat is on. Instead, they work together. Auxiliary heat provides essential support during cold snaps or when you need a quick temperature boost. This integrated approach ensures your home stays warm efficiently.
You now know why auxiliary heat activates. You also understand how to optimize your thermostat settings. By making small adjustments, you can minimize your reliance on higher-cost auxiliary heating. Remember, the goal is to use your efficient heat pump as much as possible. This lowers your energy bills. Regular maintenance also plays a vital role. This keeps your system running smoothly. If you have concerns, do not hesitate to contact an HVAC professional. They can ensure your heating system operates at its best. Take control of your home’s heating today!
- heat pump operation
- auxiliary heat
- supplemental heat
- HVAC efficiency
- home heating systems
- thermostat settings
- energy saving tips