Why Your Heat Pump Hisses and How a Simple Upgrade Can Help

Heating and Air Conditioning | Knoxville | Heating and Air Conditioning in Knoxville

When a homeowner in Knoxville heard a persistent hissing sound and even saw a hint of smoke from their outdoor heat pump, they called in HEP for help. With temperatures dipping below freezing, the unit had iced over overnight, raising concerns about a serious malfunction. After advising the homeowner to switch to emergency heat to protect the system, an HEP technician returned the next morning for a closer look.

In this article, we’ll walk through how this common scenario was quickly diagnosed and resolved—and share practical tips every homeowner can use to keep heat pumps running smoothly all winter long.

Understanding the Defrost Cycle

Heat pumps automatically enter a defrost mode when frost builds up on the outdoor coils. During defrost, it’s normal to hear a soft hiss or see wisps of steam (which can look like smoke) as ice melts away.

Tip: If your outdoor unit is frozen, switch to emergency heat and let it thaw for a few hours. Running a frozen unit can overwork the compressor and lead to larger repairs.

The HEP technician verified the homeowner’s observations by manually putting the unit into defrost mode. The system was operating exactly as intended—no leaks or electrical faults were found.

A Simple Upgrade: Hard Start Kit Installation

While everything checked out in terms of normal operation, the technician noted that the compressor sometimes struggled during cold starts. To give the system a hand, they recommended—and then installed—a hard start kit. This add-on helps the compressor start more easily, reducing strain and improving reliability.

After the upgrade, the heat pump started smoothly even on chilly mornings, and the homeowner enjoyed quieter, more efficient operation.

Keeping Your Coils Clean

Efficient heating also depends on clean indoor components. A dirty or clogged evaporator coil can lead to frost build-up, reduced airflow, and higher energy bills.

Regular maintenance by a HEP technician ensures that coils stay free of dust and debris, so warm air can flow unobstructed through your home.

Enhancing Indoor Air Quality

Beyond heating and cooling, many homeowners in Knoxville add air-cleaning accessories to their systems. Devices like the REME HALO™ by RGF® reduce airborne particles, allergens, and odors for healthier indoor air.

If you’re interested in breathing cleaner air, HEP technicians can help you select and install the right air purification solution for your home.

Proactive Tips for Homeowners

• Listen for unusual sounds – Hissing during defrost is normal, but loud bangs or grinding noises deserve a call to your HEP technician.
• Use emergency heat when needed – Protect your heat pump from damage by switching modes if it becomes iced over.
• Schedule annual tune-ups – A yearly inspection catches minor issues before they turn into costly repairs.
• Consider targeted upgrades – Hard start kits and air purifiers are small investments that offer big gains in reliability and comfort.

By understanding how your heat pump works and teaming up with experienced HEP technicians in Knoxville, you’ll keep your home cozy, efficient, and trouble-free all winter long.