What is Heat Recovery?

Updated: January 2024
Mitsubishi Electric City-Multi units on commercial rooftop

Heat recovery extends the core concept of Variable Refrigerant Flow (VRF) technology to deliver higher efficiencies, utility cost savings and greater comfort control in buildings with zone diversity. METUS offered the industry’s first two-pipe VRF system with heat recovery’s most celebrated benefit: simultaneous heating and cooling.

The fundamental benefits of VRF technology stem from the ability to move heat effectively with minimal waste. Instead of burning fossil fuels like conventional systems to generate heat, a VRF system repurposes existing heat from ambient outdoor air or a nearby water source. During cooling mode, the system absorbs and extracts heat from zones and transfers the heat energy to the outdoor condensing unit. The outdoor unit’s INVERTER-driven compressor varies refrigerant flow throughout the system, so the heat-transfer capacity and energy use match the real-time conditioning needs of the zones. At every point of operation, VRF systems deliver precise comfort control, cost savings and improved sustainability by moving heat effectively.

After assessing a building’s conditioning requirements, engineers will recommend a VRF heat-pump system or a VRF heat-recovery system. VRF systems engineered for heat recovery use a special method to move heat and achieve simultaneous heating and cooling.


Zone Diversity: Challenges and Opportunities

A VRF system transfers heat by cycling refrigerant between an outdoor unit and up to 50 indoor units. Indoor units condense and liquefy refrigerant gas to release heat into zones. In cooling mode, the units vaporize liquid refrigerant to absorb heat from zones. All indoor units connected to a VRF heat-pump system operate in a single mode at a time: heating or cooling. The outdoor unit is either sending superheated gas or subcooled liquid to the indoor units.

Heat-pump systems are ideal when the building or floor(s) served by VRF technology has uniform comfort requirements across zones. But what about hotels, large offices, multifamily and multipurpose buildings where some zones can require heating while others need cooling?

Heat recovery is the solution. A VRF heat-recovery system uses a Branch Circuit (BC) controller to send refrigerant gas or liquid to zones based on the indoor unit’s mode. Simultaneous heating and cooling enhances a VRF system’s ability to customize comfort and set points for zones based on usage, occupancy and user preferences. Office spaces with large windows can be air conditioned while interior spaces far from the perimeter are heated. If the building has a server room and a gym on the same floor, no problem. A heat-recovery system keeps diverse zones comfortable with appropriate set points.


Heat Recovery Enhances Energy Efficiency

Heat recovery creates further opportunities for significant cost savings and improved efficiency with VRF technology. A VRF heat-recovery system can recover and redirect heat from zones in cooling mode to zones requiring heating. This repurposes would-be waste heat into “free” heat for the building, reducing the outdoor unit’s energy usage and delivering operational savings. By leveraging zone diversity, the system can increase total applied capacity by up to 150 percent over the outdoor unit’s rated capacity.

Need help determining whether your project requires a VRF heat-pump or heat-recovery system? Contact your Mitsubishi Electric distributor or local representative today.

VRF Systems