Published: 29 August 2025 I Updated: 8 June 2026
When it comes to modern home heating, flexibility and reliability are key. That’s where Tongyi’s air to water heat pump system takes performance to the next level with two advanced features: the cascade function and the Additional Heating System (AHS).
What Is an Air to Water Heat Pump Cascade System?
An air to water heat pump cascade system connects several heat pump units so they can operate together as one coordinated heating system. Instead of relying on a single large unit, the system uses multiple units controlled by one central logic. This allows the heating capacity to increase or decrease according to the real demand of the building.
For example, during mild weather, only one unit may be required. During colder periods or when domestic hot water demand increases, additional units can start automatically. This staged operation helps the system maintain comfort while avoiding unnecessary energy use.
In Tongyi air to water heat pump systems, the cascade function allows up to 8 units to work together under one controller. This makes the system suitable for larger homes, villas, apartment buildings, hotels, offices, and light commercial projects where heating demand can change throughout the day.
Cascade Function: Scalable Heating for Every Need
The cascade system allows up to 8 heat pump units to work together under one controller, perfectly balancing household heating and hot water needs. Whether it’s keeping your home warm or ensuring a steady supply of hot water, multiple units can operate simultaneously for different tasks—or share demand between them. This makes the air to water heat pump system ideal for larger households or commercial spaces where energy demands fluctuate.
Why Use Several Heat Pumps Instead of One Large Unit?
A cascade heat pump system offers several practical advantages compared with a single oversized unit.
First, it provides better flexibility. Heating demand is not always the same. A building may need less heating during the day, more heating in the morning, and additional capacity when domestic hot water is required. With cascade operation, the system can activate only the number of units needed at that moment.
Second, cascade systems improve reliability. If one unit requires maintenance, the remaining units may still be able to support part of the heating demand. This is especially useful in commercial buildings, small hotels, rental properties, or projects where heating continuity is important.
Third, cascade operation can support better efficiency. Instead of forcing one large unit to run at low load for long periods, several units can be staged more intelligently. The controller can distribute operation between units and avoid unnecessary starts and stops.
For installers, this also makes system design more modular. Capacity can be adapted to the project by combining multiple standard units rather than depending on one customized large-capacity solution.
Typical Applications for a Cascade Heat Pump System
A cascade heat pump system is especially useful when heating demand is higher or more variable than in a standard single-family home.
Typical applications include:
| Application | Why cascade operation helps |
|---|---|
| Large residential homes | Higher space heating and DHW demand |
| Villas | Flexible capacity for comfort and hot water |
| Apartment buildings | Shared heating demand across several units |
| Hotels and guesthouses | High domestic hot water peaks |
| Offices | Variable heating demand during working hours |
| Commercial buildings | Reliability and scalable capacity |
| Renovation projects | Modular installation with flexible capacity |
This makes cascade operation particularly valuable for distributors and installers working on projects where heating demand cannot be covered efficiently by a single standard unit.
Additional Heating System (AHS): Backup Power When You Need It
Even the most efficient systems may require a boost during peak demand or in extremely cold weather. That’s where the AHS (Additional Heating System) comes in. It integrates seamlessly with the heat pump setup and can include:
- A backup heater or gas boiler, controlled by the unit’s smart system.
- Solar and tank booster heaters (TBH) for raising domestic hot water temperature.
- A 3-way valve that automatically switches between heating mode and DHW (domestic hot water) mode.
This ensures comfort and efficiency all year round, giving homeowners peace of mind that hot water and heating will always be available, no matter the weather.
What Is AHS in a Heat Pump System?
AHS stands for Additional Heating System. It refers to an auxiliary heat source that can work together with the heat pump when extra heating support is required. This can include an electric backup heater, an existing gas boiler, or other auxiliary heating equipment depending on the system design.
The purpose of AHS is not to replace the heat pump during normal operation. Its role is to provide support during specific conditions, such as extremely cold weather, high domestic hot water demand, or temporary peak loads.
In a well-designed system, the heat pump remains the primary heating source. The AHS is activated only when needed, helping maintain comfort and system reliability.
How AHS Supports Heating and Domestic Hot Water
In real installations, heating demand and domestic hot water demand do not always happen at the same time or at the same level. A home may require space heating throughout the day, but domestic hot water demand may peak in the morning or evening. In commercial applications, such as hotels or guesthouses, DHW demand can be even more concentrated.
The Additional Heating System can support the heat pump during these peak moments. For example, a tank booster heater can help raise domestic hot water temperature when required. A backup heater or boiler can provide additional capacity during very cold weather. A 3-way valve can help the system switch between space heating and domestic hot water operation.
This gives the system more operational security. The heat pump can work efficiently as the main source, while the AHS provides extra support only when the situation requires it.
Smarter Living, Greater Savings
By combining cascade operation with the flexibility of the AHS, Tongyi’s air to water heat pump system adapts to different household sizes, weather conditions, and energy needs—delivering both efficiency and reliability.
