Why is My Mini-Split Freezing Up in Heat Mode?

Mini-splits work hard throughout the year. They work even harder when the outdoor temperature drops below freezing. If the increase in wear and tear isn’t enough, mini-split units are prone to freezing in winter and being damaged by ice. The occasional icicle on the outdoor unit isn’t a concern. But you may wonder why your mini-split is freezing up in heat mode.

To explain why this happens, let's look at how a heat pump works. It does not generate heat of its own. Instead, it moves heat, transferring it from the outside air to your home. As the refrigerant moves through a closed-loop system, heat is pulled from the air, and the temperature around the heat pump drops, sometimes low enough for condensation to form on the coil. In extreme cold, this condensation will freeze.

Your Ductless Mini-Split Has Built-In Protection Against Ice

Colder temperatures are bound to affect your mini-split system, but a defrost mode protects it. It is controlled by an internal thermostat that triggers a defrost cycle when the unit’s temperature drops below a certain threshold. The unit then automatically switches to cooling mode to increase the temperature of the outdoor coil. Once the ice melts and the internal thermostat senses the coil is warmer, the system will automatically switch back to a heating cycle.

But if the unit keeps freezing up or doesn’t defrost properly, the following issues may be the cause:

• Faulty wiring
• Poorly installed fan
• Malfunctioning thermostat
• Refrigerant leak
• Stuck reversing valve
• Outdoor coil damage

An issue with air circulation can make your mini-split more prone to freezing. Unless air moves constantly over the evaporator coil, cold air will remain above it and freeze any condensation that forms. A dirty filter can also restrict airflow enough to cause freezing. Dirt on the coil can lead to frost and ice too. So, anything that blocks air movement is a potential contributor to a mini-split freezing up in heat mode.

Can I Unfreeze a Mini-Split Myself?

If the unit isn’t defrosting effectively, turn it off and disconnect it from its power source. The ice may then melt on its own. Or, if necessary, you can gently remove the ice and wipe the coils with a dry cloth. Completely dry the system before powering and restarting it. Even though it may start working, it’s important to address the cause of the problem, whether by changing the filter, having the coils cleaned, or having the refrigerant level filled.

How Do I Stop My Mini-Split From Freezing Up?

Regular maintenance and calling a technician when you suspect a problem can prevent ice from forming. Routine inspections let contractors find small issues that can lead to freezing, so your ductless mini-split will operate normally. However, there are steps you should take to avoid a frozen unit. You don’t need a professional to:

• Turn on the defrost setting at the condenser controls.
• Check the unit daily for ice and take the appropriate actions.
• Cover the mini-split to prevent contact with the snow.
• Elevate the unit (about two feet) so it doesn’t suck in snow and ice.
• Brush off any snow that falls on the outdoor condenser. 

Contact NEXGEN If Your Mini-Split Freezes Up in Heat Mode

If your mini-split keeps freezing up while providing heat, it may need to be repaired. NEXGEN provides reliable ductless heating and cooling system repair no matter what the issue is. We specialize in servicing high-efficiency equipment so it works more effectively and lasts longer. When your mini-split is freezing up in heat mode, it’s susceptible to damage, so contact NEXGEN today to schedule immediate repairs.