Auxiliary Heat On Constantly? Troubleshoot This Frustrating Heat Pump Problem

Is your auxiliary heat running nonstop even when temperatures are above freezing? You're not alone. Continuous auxiliary heat operation is a common headache for heat pump owners trying to control energy costs. But don't despair - with a bit of troubleshooting, you can get to the bottom of the issue and restore normal function.

What Is Auxiliary Heat and How Does It Work?

Before diving into solutions, let's review what auxiliary heat is and how it works with your heat pump. Auxiliary heat, also called emergency or supplemental heat, is a secondary heating system that kicks in when your main heat pump cannot reach the set temperature. It consists of electric heating strips that provide a boost of heat to maintain comfort on extremely cold days.

Here's how it works: On a normal day, your heat pump extracts heat from outdoor air and circulates it indoors. But as temperatures drop below 35-40degF, a heat pump struggles to extract enough heat. Its indoor coils can also freeze up below freezing. To prevent this, auxiliary strips switch on to warm the coils and supplement the main heat pump. This dual heating keeps your home cozy even in frigid weather.

When Should Your Auxiliary Heat Turn On?

Ideally, your auxiliary heat should only operate at temperatures below freezing. Some heat pumps engage it below 40degF. But it should never run constantly above 35degF unless there is an issue. Here are the main reasons auxiliary heat operates:

• Outdoor temperature drops below 35-40degF
• Heat pump cannot reach set indoor temperature alone
• Defrost cycle prevents ice buildup on coils
• Set temperature is raised significantly higher than actual indoor temp

Pay attention to the temperature differential - the gap between your set temperature and actual indoor temperature. The wider this gap, the more your auxiliary heat will operate. A differential of 2-3degF is reasonable before backup heat engages.

Why Is My Auxiliary Heat Running Constantly?

When auxiliary heating runs nonstop regardless of outdoor temperature, something is amiss. Here are the most common culprits behind constant auxiliary heat operation:

Malfunctioning Components

Issues like refrigerant leaks, sensor failures, or faulty control boards can cause the heat pump to improperly call for auxiliary heat. If your system is over 10 years old, component breakdown is a likely reason for problems.

Stuck in Emergency Heat Mode

Emergency heat mode disables the heat pump and relies solely on auxiliary heat. If accidentally left on, it will cause constant auxiliary operation. Check your thermostat settings.

Thermostat Setting Too High

A drastic difference between room temperature and thermostat setpoint can continuously trigger auxiliary heat. Lowering the setpoint or widening the differential can help.

Heat Pump Can't Handle Cold

In extremely cold climates, an undersized heat pump may struggle to extract enough heat. The auxiliary heat then runs nonstop trying to compensate. Upgrading your system may be required.

How To Diagnose The Cause of Continuous Auxiliary Heat

To pinpoint why your auxiliary heater keeps running, you'll need to do some diagnostics. Here are a few basic checks before calling in an HVAC technician:

Check Emergency Heat Switch

Ensure your thermostat emergency heat switch is set to "off." If on, it will lock out the heat pump in favor of auxiliary heat only.

Inspect Heat Pump Outdoor Unit

Examine the outdoor condenser for any obstructions, debris, or ice buildup that could impede performance. Remove any blockages.

Test Thermostat and Heat Pump Separately

Bypass the thermostat and directly power the heat pump, then call for cooling. If auxiliary heat still engages, the issue is with the heat pump. Otherwise, a faulty thermostat may be to blame.

Call An HVAC Technician

For a thorough diagnosis, contact a professional HVAC technician. They have specialized tools and expertise to evaluate all components and uncover any malfunctions.

Fixes For An Auxiliary Heater That Never Stops

Once the culprit is identified, you can move on to solutions. Here are some common remedies for runaway auxiliary heat:

Adjusting the Thermostat

An incompatible or incorrectly calibrated thermostat could be sending improper signals. Try the following:

• Lower temperature setpoint to widen differential
• Ensure thermostat is in "heat pump" not "emergency heat" mode
• Replace old thermostat with a newer, compatible model

Disabling Emergency Heat

If emergency heat is stuck on, reset it to "off":

• Locate the physical emergency heat switch on thermostat and set to off
• Access thermostat settings menu and disable emergency heat mode

Servicing the Heat Pump

For heat pump malfunctions, repairs may be needed:

• Clean coils, check refrigerant levels, fix leaks
• Replace any damaged components
• Upgrade to a higher efficiency, properly sized heat pump

Switching to a Hybrid System

In cold climates, a dual fuel system may be best:

• Add gas/propane furnace for temperatures below 35degF
• Furnace handles heavy heating, reducing auxiliary heat use
• Provides alternative heat source without solely relying on electric

Preventing Continuous Auxiliary Heat Operation

Stop runaway auxiliary heat before it starts with a bit of prevention:

• Annual maintenance and servicing of heat pump
• Proper balance point temperature setting for auxiliary heat
• Heat pump sized correctly for climate and home size
• Upgrade to hybrid dual fuel system if existing unit inadequate

Routine care will keep your system running efficiently and ensure components function properly year after year.

While some auxiliary heat problems can be DIY fixes, more complex issues require a professional:

• Advanced system failures beyond your technical skill
• Persistent auxiliary heat operation after troubleshooting
• Lack of tools, training, or ability for diagnosis/repair
• Annual maintenance and inspections for optimal performance

Don't hesitate to call in an HVAC technician for auxiliary heating difficulties. With their specialized expertise and equipment, they can accurately assess the problem and get your system back on track.

Dealing with an auxiliary heater that runs nonstop can be aggravating. But now that you know what causes it and how to fix it, you can take back control of your heat pump. With a bit of maintenance and adjustments, you can curb excessive auxiliary heating and keep comfortable all winter long without the headaches.