A heat pump radiator doesn't work in isolation; it's part of a larger air-to-water heat pump system that uses existing radiators to distribute heat. Here's how the system functions:
1. The Heat Pump System:
An air-to-water heat pump system, designed for use with radiators, comprises the following key components:
- Outdoor Unit: This unit absorbs heat from the outside air. Even when it's cold outside, there's still energy that can be extracted. This is similar to how a refrigerator works, but in reverse.
- Indoor Unit (or Heat Exchanger): The outdoor unit transfers the captured heat to the indoor unit. Here, a refrigerant circulates, absorbing and releasing heat as it changes state (liquid to gas and back).
- Wet Central Heating System (Radiators): The heat from the refrigerant is then used to warm water. This heated water is then circulated through your existing radiator system, similar to a traditional gas boiler setup.
2. Heat Extraction and Transfer:
- Refrigerant Cycle: The refrigerant in the heat pump is key to the heat transfer process. It evaporates at low temperatures, absorbing heat from the outside air in the outdoor unit.
- Compression: The refrigerant vapor is then compressed, raising its temperature significantly.
- Condensation: The hot, high-pressure refrigerant then flows through a heat exchanger in the indoor unit. Here, it condenses back into a liquid, releasing the heat it absorbed into the water circulating through your radiators.
- Expansion: Finally, the refrigerant passes through an expansion valve, reducing its pressure and temperature, and the cycle begins again.
3. Radiator's Role:
The radiator's function remains largely the same as with a traditional boiler:
- Heat Dissipation: Hot water from the heat pump circulates through the radiator. The radiator's design (large surface area) allows it to efficiently radiate heat into the room, warming the space.
- Cooling the Water: As the radiator dissipates heat, the water cools down and returns to the heat pump to be reheated, creating a continuous loop.
4. Key Differences from Traditional Boilers:
- Lower Water Temperature: Heat pumps typically operate at lower water temperatures than gas boilers (around 40-50°C compared to 60-80°C). This means radiators might not get as hot to the touch, and you may need larger radiators to achieve the same level of warmth.
- Efficiency: Heat pumps are far more energy-efficient than gas boilers. They can deliver more heat energy than the electrical energy they consume because they're primarily moving existing heat, not generating it.
5. Considerations for Radiator Compatibility:
- Radiator Size: Older, smaller radiators might need to be replaced with larger ones or additional radiators added to effectively heat a room at the lower water temperatures produced by a heat pump.
- Insulation: Good home insulation is crucial for a heat pump to work efficiently with radiators. Better insulation reduces heat loss, allowing the heat pump to maintain a comfortable temperature with lower water temperatures.
In short, a heat pump system uses radiators as the final stage in distributing the heat extracted from the outside air to warm your home, but it's the heat pump itself that facilitates this process by circulating refrigerant and transferring heat into your wet central heating system.
