Heat pumps are everywhere these days — but did you know there’s a type of chiller that works as both a chiller and a boiler? Today, we’re breaking down modular air-to-water heat pump chillers — the future of all-electric heating and cooling. You have probably seen modular chillers which provide cooling only, but there are modular chillers that can do both cooling and heating. Here are the top 4 or 5 features:
# 1 Modular & Scalable Design
One of the standout features of these heat pump chillers is their modular design, allowing multiple units to be combined to meet varying building loads. Multiple units can easily fit on a flatbed truck and be off loaded using just a forklift. They also fit through the standard size doorway and into freight elevators for ease of rigging. Their compact design fits rooftops or urban sites.
Modules come in various sizes and are easily assembled to create larger tonnage systems. For instance, Trane’s Thermafit air-cooled model starts at 30 tons and can expand to 360 tons with up to 12 modules. Other manufacturers like YORK scale up to 4,480 tons with 32 modules, and LG’s reaches 300 tons with 5 modules. This scalability enables phased installation and easy expansion, making them ideal for new construction or retrofit projects where future growth is anticipated.
# 2 Redundancy
Redundancy in modular air-to-water heat pump chillers is a vital feature that ensures uninterrupted comfort and operational reliability, particularly in environments where HVAC failure is not an option. By requiring a minimum of two modules—such as the Trane AXM’s baseline configuration—these systems inherently provide a backup, allowing one unit to compensate if another malfunctions or requires maintenance.
Independent controls on each module further enhance this redundancy, enabling selective operation or isolation without shutting down the entire system, as noted in Trane’s literature with features like independent defrost cycles and easy-change filters. This is especially important in critical settings like healthcare facilities, educational institutions, or commercial buildings with high occupancy, where maintaining a stable indoor climate is essential for safety, productivity, and compliance with stringent regulations. Additionally, the ability to expand up to 12 or more modules (e.g., Trane’s 360-ton capacity or YORK’s 4,480-ton potential) ensures that redundancy scales with capacity, offering peace of mind and resilience against equipment failures or load fluctuations.
# 3 Dual Function: Heating and Cooling
These units don’t just cool like a normal chiller. With a reversing valve, they can switch modes and produce either chilled water for cooling in summer, or hot water for heating in winter. That means one machine can do the job of both a chiller and a boiler — and all-electric, no gas required. Look for the multi-pipe version for a full four-pipe system that can do cooling and heating simultaneously.
# 4 Sustainability & Low-GWP Refrigerants
Because they’re all-electric, modular heat pump chillers help buildings meet decarbonization goals and comply with new energy codes. Many models use next-generation refrigerants like R-454B, which cuts global warming potential by about 75% compared to R-410A. This makes them a powerful step toward net-zero building design.”
# 5 Efficiency and Part-Load Operation
Efficiency is a cornerstone of these modular air-to-water heat pump chillers, particularly when multiple units operate at part load. Inverter-driven compressors and variable-speed fans allow each module to adjust its output (e.g., 15 to 100% capacity) based on real-time demand, optimizing energy use during off-peak conditions.
For instance, a system with several modules can stage operation—running fewer units at higher efficiency or distributing load across multiple units at lower capacities—reducing overall energy consumption compared to a single, oversized chiller running at partial load. This part-load efficiency is especially beneficial in buildings with fluctuating occupancy or seasonal variations, where maintaining comfort without waste is key.
Two-Pipe vs. Four-Pipe Systems
Some systems are two-pipe, which means they can provide heating or cooling, but not at the same time. Others are four-pipe, allowing simultaneous heating and cooling. That’s a game-changer for buildings like hospitals, hotels, and labs where you might need cooling inside while heating the perimeter at the same time.
Modular air-to-water heat pump chillers combine flexibility, efficiency, and sustainability in one package. They’re modular, scalable, all-electric, and cold-climate ready — making them a smart choice for the future of HVAC.
