Frequently Asked Questions


FrostShield is a revolutionary new mechanical and unit control technology that not only extends the operating range of air-source heat pumps, but also removes the need for the unit to enter defrost mode during heating operation.


When the unit enters heating mode, the control begins to monitor outdoor ambient air temperature, dewpoint, and evaporator coil (heating mode) temperature. As the evaporator begins to approach the point where frost has the possibility to form, hot discharge gas begins to be injected into the header of the evaporator. The level of hot gas injection will be varied and maintained as long there is the possibility of frost forming. This allows the unit to continually operate while only utilizing up to 5% of the available hot discharge gas from the compressor for FrostShield operation.

By not having to enter defrost mode, there is no shock to system components by switching modes, thermal mass in the condenser and evaporator to overcome, wasteful auxiliary heat usage, and the disruption to occupant comfort within the space. An additional benefit is the extended operating envelope of the unit down to -20°F (-29°C) ambient.

Why Hasn’t Anyone Thought of This Before?

While hot gas bypass has long been used in the industry as a form of capacity control during cooling, it was never really thought of beyond that. Additionally, heat pumps have only recently seen a rise in popularity, and defrost has always been seen as a cost of doing business.

If You’re Using Some of the Discharge Gas, Doesn’t That Mean There’s Less Capacity?

FrostShield only utilizes a maximum of 10% of the available discharge gas to keep outdoor coils clear. While that means a slight reduction (between 2-4°F) in discharge air temperature, it can be easily made up by increased compressor capacity via VFD overclocking.

Will I Still Need a Form of Auxiliary Heat?

This will all depend on the outdoor environment, and what you’re trying to accomplish. Even today, applications may require auxiliary heat to reach the desired discharge air temperature. The amount of heat needed by a unit with FrostShield is only that small amount the unit cannot produce by itself, and not the full amount that would be required by a unit requiring defrost. Additionally, in the case of a mechanical failure, it’s always good practice to have a backup just in case.

What Does This Mean for Lower Ambient Climates?

With FrostShield, the application range is extended by keeping the outdoor coils clear and able to properly complete the refrigeration cycle. While at a certain point, under -20°F, there’s just not enough there to work with and the unit would have to revert to using an auxiliary heat source. However, for the vast majority of applications, the unit can function just fine.

Will Equipment with FrostShield Last Longer Than Other Products that Have to Defrost?

Without having to switch modes to enter defrost, all of that additional stress and shock will not be placed on system components. With proper maintenance, FrostShield equipped units last longer than standard equipment that is forced to continually defrost.

Is This Technology Patented?

Yes, FrostShield is currently patent pending with the United States Patent Office.

What Other Special Equipment Will the Unit Require to Operate?

That’s the beauty of FrostShield; there’s only two additional components (for multi-circuit units), and some additional piping. No complex hardware or costly additional components to add to the system.

When Will I Be Able to Order a Unit with FrostShield?

FrostShield is available for limited application selections now, and will be fully available for selection and order in Q2 2022.