What if you could combine the zoning flexibility of VRF with the safety and simplicity of water-based systems — all in one design? That’s exactly what the new generation of Hybrid VRF systems promises. It looks familiar from the outside, but what’s happening inside is completely different. In this article, we’ll break down how this technology works, why it’s changing the way we think about HVAC design, and where it makes the most sense to use it. Let’s get started.
The Outdoor Unit
The outdoor unit in a Hybrid VRF system works just like a traditional VRF heat pump. It’s the heart of the system — where heating or cooling is generated. The unit uses refrigerant to absorb or release heat to the outside air, depending on the season.
Hybrid Branch Controller
The Hybrid Branch Controller is the key component that makes a Hybrid VRF system different. It acts as the bridge between the refrigerant and the water loops. Inside the controller, the refrigerant transfers its heating or cooling energy into water, which is then circulated to the indoor units. This setup keeps refrigerant contained to the mechanical area and uses only water inside the occupied spaces — making the system safer, easier to install, and more flexible for zoning. The Hybrid controller contains two small pumps to serve the hot and cold-water loops.
Refrigerant Piping
Refrigerant piping connects the Outdoor unit with the Hybrid branch controller using only two pipes, such as in a typical split system heat pump. This is the only refrigerant piping required for this system, so the amount of refrigerant is limited to the distance between the outdoor unit and the indoor Hybrid branch controller. There are various rules for the allowable distances but should be find for most applications as we’re talking hundreds of feet.
Indoor Fan Coil Units
There are several options for indoor units, such as the ceiling cassettes, wall mounted fan coils and concealed ducted fan coil units.
Water Piping
In each zone, water (hot or chilled) is delivered, enabling heating or cooling in each indoor unit without refrigerant piping in that zone. Water piping is run between the Hybrid branch controller and the indoor fan coil units. The piping can be run in copper or polyethylene as indicated by the manufacturer.
This effectively replaces the refrigerant piping portion to indoor units with water piping, thus making indoor spaces “refrigerant-free.” Many of the safety, regulatory, and leak detection challenges associated with refrigerants in occupied areas are reduced. Another advantage is that only two pipes need to be run between the branch controller and the fan coil instead of the four pipes run in a chilled water and heating hot water 4-pipe system.
Because the HBC supports simultaneous heating and cooling, heat recovered from cooling zones can offset heating in other zones, just as in advanced VRF systems. In effect, hybrid VRF combines the zoned flexibility of VRF with the safety, piping ease, and hydronic advantages of conventional chiller boiler systems.
Next, you’ll need the main water supply to the branch controller with a strainer, shutoff valve and PRV. Since this is a hybrid system where water is heated, an expansion tank will be required to be attached to a port on the controller. The size of the expansion tank will need to match the amount of water contained in the system. The expansion tank needs to be at the same height or above the Hybrid branch controller.
Electrical
The hybrid branch controller will need 208 230 voltage for power. Of course, power is also required at the outdoor unit and each of the fan coils.
Multiple Zones
The hybrid branch controller allows you to connect to three fan coils on a single port with some exceptions. This would require that all the zones have a similar thermal profile as only one mode of operation is allowed for the connected group. All connected zones must either be in heating or cooling mode together as there is only one set of pipes that can carry either hot or cold water.
Condensate Drain lines
The Hybrid branch controller requires a drain as do all of the fan coils. Often wall mounted fan coils require an internal condensate pump to lift the condensate into the attic space where it can pitch by gravity to the main drain line.
Controls
The control wiring is like the standard VRF system. Each remote controller or thermostat is connected to their respective fan coil, and then each fan coil is daisy chained together all the way back to the hybrid branch controller.
The branch controller is than wired to the outdoor unit. This allows the outdoor unit to discover all the connected components. If the occupant wants a remote controller that oversees the system from a convenient location, then a main controller can be mounted in the building facilities office and wired back to the outdoor unit.
Key Benefits
1. Reduced Refrigerant Charge & Lower Risk
By localizing refrigerant to only the outdoor-to-HBC loop, the total refrigerant required is substantially lower compared to fully refrigerant-based configurations. This can simplify compliance with refrigerant concentration limits (ASHRAE 15 and 34) in tight or low-volume spaces. The occupied zones are free of refrigerant piping, reducing the risk of leaks in critical areas.
2. Simplified Interior Piping & Installation
Water piping (especially modern composite or multilayer pipes) is often less expensive, easier to route, and easier to join (no brazing, welding) compared to complex refrigerant piping. The system typically does not require external pumps, valves, sensors, or actuators (beyond what’s built into the HBC), reducing installation complexity. Furthermore, the hybrid system uses only two refrigerant pipes (not four or three), saving piping runs relative to more complex systems.
3. Simultaneous Heating & Cooling with Heat Recovery
Like advanced VRF systems, hybrid VRF supports simultaneous heating and cooling by shifting heat from zones requiring cooling to those requiring heating (via the water loop). This internal heat reuse improves overall efficiency and avoids wasting excess heat. In many cases, hybrid VRF can reduce total energy consumption and maximize seasonal efficiency.
4. Regulatory & Safety Advantages
Because occupied zones are refrigerant-free, many regulatory burdens (such as leak detection, ventilation requirements, refrigerant containment) are alleviated. This is especially significant in small rooms, multi-family units, medical or educational facilities, or spaces with occupancy constraints. Designers are not limited by refrigerant concentration regulations in each zone.
Additionally, the use of water as a distribution medium is benign and safe from toxicity or flammability issues associated with refrigerants.
5. Scalability and Flexibility
The hybrid VRF architecture is modular and scalable. Sub-HBC modules can be added to expand the number of zones or increase capacity. Because the indoor units are water-fed, there is more flexibility in routing piping and integrating with other hydronic systems (e.g. integration with radiant panels, floor heating/cooling, or domestic hot water systems). Additionally, hybrid VRF can intermix with conventional VRF systems in projects where some zones are better served by direct refrigerant, and others benefit from hydronic delivery.
Because the outdoor condenser loops and control systems are similar or identical to conventional VRF outdoor systems, many design and control elements can carry over.
Challenges & Considerations
No technology is without trade-offs. Below are key challenges for hybrid VRF systems.
1. Higher First Cost / Complexity
Because hybrid VRF is relatively new and specialized, component costs (especially the HBC) may be higher, and supply chain or market familiarity may be limited. The integration between HVAC, controls, and hydronic design requires careful coordination.
2. Hydronic Balancing & Pumping Losses
While water piping is simpler, hydronic systems require careful balancing, pump sizing, and flow control. Pressure drop, head loss, and delta-T control must be well managed to avoid losses that offset the efficiency gains. Systems operating with low ΔT (temperature differential) require more flow and thus higher pump energy. Also, the design of water piping (routing, insulation, pipe sizing) becomes important.
3. Control Complexity
Because hybrid VRF bridges two domains (refrigerant and water), the control logic must handle coordination, zone water temperature resets, valve control, fault handling between the HBC and indoor units, and integration with building automation systems (BAS). Mistuning or poor control design can degrade comfort or efficiency.
4. Thermal Buffering & Thermal Storage
In systems with rapidly changing loads, the hydronic loop may require buffering (e.g., small buffer tanks) to smooth flow transients and avoid frequent cycling. Designers must consider thermal inertia, water temperature reset schedules, and response times.
5. Limited Product Competition (for now)
As of now, one of the most widely cited hybrid VRF systems is this specific two-pipe hybrid VRF implementation as being the first of its kind. It is sometimes claimed that this is the only commercially available two-pipe hybrid VRF solution with simultaneous heating/cooling. That said, other manufacturers are exploring or offering hybrid or hydronic-VRF variants (for example, VRF systems with hydronic heat recovery, or VRF systems connected to chilled water loops), though not necessarily with the same architecture.
Because competition is limited, specification, maintenance know-how, parts availability, and installer training are critical considerations.
6. Efficiency Trade-offs at Extreme Conditions
In extreme ambient conditions, the efficiency of the hydronic heat exchange or temperature lift in the HBC may degrade performance compared to conventional VRF. The HBC becomes a central device whose thermal performance is crucial; losses there can erode gains from reduced refrigerant usage.
Future Trends & Outlook
Given rising focus on refrigerant regulation, electrification, and energy efficiency, hybrid VRF is likely to gain more attention. Industry commentary already positions hybrid VRF as one of the key trends in HVAC for 2025. As more manufacturers enter the market and product maturity improves, the first-cost barrier may come down. Hybrid VRF may evolve to support lower-GWP refrigerants, modular HBC designs, and tighter integration with other hydronic systems (e.g. radiant heating, domestic heating).
Additionally, some VRF manufacturers are already exploring or offering variants of hydronic integration, such as VRF systems that can drive or recover heat to/cold from chilled water loops or “hydro kits” that convert refrigerant energy to water heating.
However, wide adoption will depend on educating designers, expanding service networks, and proving lifecycle cost advantages.
