Honeywell Thermostat Heat Pump Settings Guide

Honeywell Thermostat Heat Pump Settings help homeowners optimize comfort, efficiency, and equipment protection. This guide explains key settings, wiring, and troubleshooting for Honeywell thermostats paired with heat pumps, including reversing valve configuration, auxiliary/emergency heat, compressor protection, and programming tips.

Topic	Quick Take
Reversing Valve (O/B)	Set O or B based on outdoor unit manufacturer; wrong setting reverses heat/cool.
Aux/Emergency Heat	Configure for backup electric or gas. Emergency disables heat pump.
Compressor Lockout/Minimum On	Enable to protect the compressor and reduce short cycling.
Staging/Heat Pump Balance	Use balance/lockout settings to favor efficiency or backup heat based on outdoor temp.
Thermostat Models	Settings available on T Series (T5/T6), RTH, and Lyric; screens differ but functions similar.

How Heat Pumps Differ From Standard HVAC And Why Settings Matter

Heat pumps move heat rather than generate it, so thermostat settings must account for reversing valves, auxiliary heat, and protection for the compressor. Incorrect settings can cause inefficient operation, unnecessary use of backup heat, or system damage.

Key differences include: the need for a reversing valve (O/B), staging logic that may call for electric or fossil-fuel backup (AUX vs Emergency), and compressor short-cycle protection options built into many Honeywell thermostats.

Identifying Thermostat-Wire Terminals For Heat Pump Controls

Most Honeywell thermostats use standard terminals for heat pumps: Y (compressor), O/B (reversing valve), AUX/E (auxiliary or emergency heat), G (fan), C (common), R and Rc/Rh (power). Identify each wire before changing settings.

• Y: Calls the outdoor compressor.
• O/B: Reversing valve; set for O (energize in cooling) or B (energize in heating) depending on equipment.
• AUX/E: Activates backup heat for low-temperature conditions or emergency heat mode.
• G: Fan control.
• R/Rc/Rh: 24V power supply.

Setting The Reversing Valve (O/B) On Honeywell Thermostats

The reversing valve setting is critical. If the reversing valve is set incorrectly, the system will attempt to cool when in heat mode or heat when in cool mode.

On Honeywell thermostats the setting is found under Installer or Equipment Setup. Typical steps are: access Installer Setup, navigate to Equipment Type, choose Heat Pump, then set O or B for the reversing valve.

Rule Of Thumb: If the outdoor unit energizes in heating, choose B; if it energizes in cooling, choose O. Consult the outdoor unit manual if uncertain.

Auxiliary vs Emergency Heat Configuration

Honeywell thermostats let users configure AUX (automatic backup) and E (emergency) modes. AUX heat supplements the heat pump below a set balance point; Emergency Heat disables the compressor and forces only backup heat.

When To Use Emergency Heat: Use Emergency Heat when the heat pump fails or outdoor temperatures make the heat pump ineffective. Do not use Emergency Heat for regular operation since it is usually less efficient and more expensive.

Setting Heat Pump Balance And Lockout Temperatures

Many Honeywell models provide balance or heat pump lockout settings to control when backup heat stages on.

Setting	Effect
Heat Pump Balance	Determines whether system favors efficiency (heat pump) or comfort (backup heat).
Backup Heat Lockout	Prevents AUX/backup heat until a specified outdoor temperature or indoor temperature differential is reached.
Outdoor Sensor (if available)	Allows thermostats to use outdoor temp to trigger balance or lockout.

Practical Tip: Set a conservative balance point to minimize electric backup activation. For cold climates, lockout may be set lower to allow heat pump operation at colder temps if the system supports it.

Compressor Protection: Minimum On/Off and Time Delay

Short-cycling harms compressors. Honeywell thermostats offer settings such as minimum run time, minimum off time, and compressor lockout. These settings reduce wear and improve efficiency.

• Minimum On Time: Ensures the compressor runs long enough to satisfy a call and prevent short cycles.
• Minimum Off Time: Prevents the compressor from restarting immediately after shutdown.
• Compressor Lockout: Temporarily prevents the compressor from restarting after a power interruption to allow pressures to equalize.

These settings are typically found in Installer or Advanced settings and are often recommended to be enabled for heat pump systems.

Programming Temperature Setbacks And Schedules For Heat Pumps

Honeywell thermostats support programmable schedules that can save energy while maintaining comfort with a heat pump. Use modest setbacks to avoid triggering emergency or AUX heat unnecessarily.

Best Practices: Set small setbacks (2–4°F) for occupied/unoccupied transitions and allow the thermostat’s adaptive recovery to bring the home to setpoint before occupancy to avoid prolonged backup heat use.

Fan And Stage Control With Heat Pump Systems

Configure fan control (Auto vs On) and staging carefully. Heat pumps often use staged heating with electric or fossil-fuel backup. Honeywell thermostats let users set the number of stages for heat and cool.

• Fan Auto: Recommended for most operations to reduce energy use.
• Staging: Configure 1-stage heat pump plus 1-stage backup, or multiple stages depending on equipment.
• Smart Response/Adaptive Recovery: Use to improve comfort and efficiency by learning system run times.

Thermostat Model Differences: T5, T6, RTH, Lyric

Different Honeywell models expose settings using different menus, but the core options for heat pumps remain similar. T5 and T6 offer intuitive installer menus; RTH series are basic but include heat pump functions; Lyric offers advanced scheduling and geo-fencing features.

Accessing Installer Setup: Commonly press and hold menu or settings buttons for several seconds. Consult the model-specific manual for the exact sequence to reach equipment configuration and set O/B, AUX/E, stages, and compressor protection.

Wiring Considerations And Common Wiring Mistakes

Incorrect wiring is a frequent cause of heat pump issues. Verify each wire is properly connected to the correct terminal and that the thermostat is configured for a heat pump system rather than conventional heat/cool.

Common Mistake	Symptom
O/B Misconfigured	Heat mode cools or cool mode heats
AUX/E Not Connected Or Wrong	Backup heat not available or emergency heat not working
Y And O/B Confused	Compressor doesn’t run, or reversing valve behavior is incorrect

Safety Note: Turn off 24V power at the breaker before changing wiring and consult a licensed HVAC technician for complex wiring or if the thermostat shows errors.

Troubleshooting Common Heat Pump Problems With Honeywell Thermostats

If the thermostat commands are sent but the system behaves unexpectedly, check wiring, reversing valve setting, and AUX/E configuration. For short cycling, enable minimum run/off times. If backup heat runs excessively, adjust balance or lockout settings.

1. Verify thermostat is set to Heat Pump equipment type.
2. Check O/B setting and test heat and cool to confirm reversing valve operation.
3. Inspect AUX/E wiring and mode; test Emergency Heat to confirm it disables the compressor.
4. Enable compressor minimum off time to prevent short cycling.

Error Codes on some Honeywell units may indicate wiring faults or sensor failures; refer to the manual for model-specific troubleshooting steps.

Energy Efficiency Tips For Heat Pump Thermostat Settings

Optimize the thermostat to maximize heat pump efficiency: use modest setbacks, enable adaptive recovery, avoid prolonged Emergency Heat, and keep the system maintained with regular outdoor unit and filter cleaning.

• Use Programmable Schedules to reduce runtime when the home is unoccupied.
• Limit Emergency Heat Use to actual heat pump failure situations.
• Maintain Equipment to ensure efficient operation and accurate thermostat response.

When To Call A Professional HVAC Technician

Contact a licensed technician if the reversing valve behavior is unknown, the heat pump won’t switch modes correctly after changing O/B, or if there are persistent short cycles despite settings changes. Wiring ambiguity and control board faults also require professional diagnosis.

Signs That Warrant Professional Help: Continuous backup heat operation, strange noises from the outdoor unit after thermostat changes, or repeated compressor lockouts are all reasons to call a technician.

Useful Honeywell Menu Paths And Default Settings

Menu paths vary by model. Typical installer menu sequence: Settings > Advanced > Equipment Setup > Heat Pump > Select O or B, set stages, configure AUX/E, and enable compressor protection. Default settings often assume conventional HVAC; always change equipment type to Heat Pump.

Setting	Typical Default	Recommended For Heat Pump
Equipment Type	Conventional	Heat Pump
Reversing Valve	O (may vary)	Set per outdoor unit: O or B
AUX/E	Off/Not Configured	Enable and wire as needed
Compressor Min Off	0–2 minutes	Enable 3–5 minutes

Final Practical Checklist For Honeywell Thermostat Heat Pump Setup

• Confirm Wiring matches heat pump terminals (Y, O/B, AUX/E, G, R).
• Set Equipment Type to Heat Pump in Installer Settings.
• Configure Reversing Valve to O or B according to the outdoor unit manual.
• Enable Compressor Protection (minimum off/on times and lockout).
• Set Balance/Lockout to control backup heat usage.
• Program Schedules with modest setbacks to avoid AUX/E activation.
• Test Emergency Heat and normal heating/cooling to confirm correct operation.

Note: This guide provides general recommendations. Model-specific menus and options vary. Always consult the Honeywell thermostat manual and the heat pump manufacturer documentation, and consider professional assistance for complex installations or persistent issues.