Aux vs. Emergency Heat in Crossville: What Your Thermostat Buttons Really Do

When the first cold snap rolls through Crossville, many homeowners see AUX or EM HEAT on the thermostat and wonder what to do next. At Crossville Heating & Cooling, we take pride in helping local families stay comfortable all winter. Here is a simple and straightforward guide to Aux and Emergency Heat, what’s normal, and when to call us for fast, reliable heat pump repairs in Crossville, Fairfield Glade, Lake Tansi, or surrounding areas in Cumberland County.

How a heat pump works

A heat pump moves heat from the outdoor air into your home. In cold, humid weather it runs short defrost cycles to melt frost off the outdoor coil. You may notice a brief whoosh, some steam outside, or slightly cooler air at the vents for a few minutes. That can be normal.

If you have any questions about your heat pump, we’d be happy to help. Contact Crossville Heating & Cooling today.

What is Auxiliary Heat (AUX)?

AUX is automatic backup heat. When it is very cold, you raise the thermostat several degrees at once, or the system is in defrost, the thermostat can call for supplemental heat to help the heat pump keep up. You do not manually turn this heat pump setting on; your system handles that on its own.

AUX commonly turns on when:

• Outdoor temperatures dip and recovery takes longer
• You bump the setpoint up several degrees at once
• The unit is in a defrost cycle and needs a brief boost

Seeing AUX a lot or for long periods of time? That can drive up bills. Book a system check with Crossville Heating & Cooling and we will make sure the heat pump and controls are dialed in.

What is Emergency Heat (EM HEAT)?

EM HEAT is a manual mode for emergencies. Switching to EM HEAT tells the thermostat to shut the outdoor unit off and run only the backup heat until a technician repairs the heat pump.

Use EM HEAT and call us if you notice:

• The outdoor unit is frozen solid or will not run
• Breakers trip when the heat pump starts
• Grinding, squealing, or other alarming noises
• No heat after basic checks

“My heat pump is blowing cool air sometimes. Is that normal?”

During defrost, yes, cool air is normal for a few minutes. If it never warms up, runs long, or repeats constantly, something is likely off with your system.

If your heat pump continues to blow cool air, schedule a diagnosis with Crossville Heating & Cooling.

Thermostat tips that can lower your bill

• Set the thermostat around 68°F when you are home and awake.
• Avoid big temperature jumps that can trigger AUX.
• Consider a smart thermostat with adaptive recovery and outdoor-temperature logic.

Quick checks before you call

1. Make sure the thermostat is in HEAT (not EM HEAT).
2. Replace or clean the air filter.
3. Open and clear supply and return vents.
4. Gently clear leaves and debris around the outdoor unit.
5. If the outdoor unit is encased in ice or will not start, switch to EM HEAT and contact our team for assistance.

When to contact Crossville Heating & Cooling

If you’re facing no heat or repeated breaker trips, notice persistent burning or electrical odors, see the outdoor unit frozen solid or refusing to run, or your system simply can’t maintain temperature even in mild cold, it’s time to reach out. We’ll diagnose the issue and provide immediate repairs.

Get warm fast. Request Service with Crossville Heating & Cooling now. We offer 24/7 emergency heat pump repairs in Crossville, TN and surrounding areas.

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FAQ

Is AUX the same as EM HEAT?

They often use the same backup heat source, but AUX is automatic and assists the heat pump. EM HEAT is manual and turns the heat pump off while the backup runs alone.

Should I switch to EM HEAT when it is really cold?

No. EM HEAT is for when the heat pump is not working or is iced over. Otherwise leave it in HEAT and let AUX engage automatically if needed.

Why do I see steam coming from the outdoor unit?

That is usually the defrost cycle thawing frost off the coil. Short bursts are normal. If it runs long or repeats constantly, schedule a checkup.