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How Does a Hydronic Air-to-Water Heat Pump Work?

Are you looking for a cost-effective way to provide warmth to your home or office space without wasting your budget? Consider a ground source heat pump, also known as an air-to-water heat pump. This innovative technology is gaining popularity in various parts of the world and offers numerous advantages, including excellent temperature control, lower operating costs, and reduced greenhouse gas emissions.


It can be easily installed in both modern and older homes, without causing unbearable disruptions, and produces less noise compared to standard air conditioning. In fact, it is a more cost-effective and environmentally friendly way to reduce energy costs for residential or commercial buildings.


What is a liquid loop (air-to-water) heat pump?

A ground source heat pump is an air-source heat pump that extracts heat from the outside air and distributes it indoors through a circulating heating system. It is called a liquid loop system because it uses water to distribute the heat.


The heat extracted from the outside is used to heat water, which is then circulated through baseboard or underfloor piping to release heat into the underfloor heating system. These can be radiators, trench convectors, heated towel racks, or panel radiators.


Conversely, when the temperature inside the building is too high, the heat pump extracts excess heat and sends it outdoors through the same system. Therefore, ground source heat pumps can both heat and cool buildings, including residential and commercial structures, while also providing hot water for domestic use.


What are the components of an air-source heat pump?

Air-source heat pumps typically consist of an indoor unit and an outdoor unit. These include a compressor, condenser, expansion valve, evaporator, and refrigerant. In winter, the outdoor unit extracts heat from the outside air for indoor use.


The design of this technology is aimed at absorbing heat even at temperatures as low as -15 degrees Celsius. On the other hand, the indoor unit absorbs excess heat from the house during warm seasons to keep the interior comfortable.


How does an air-to-water heat pump work?

The operation of an air-to-water heat pump is based on the refrigeration cycle, typically starting with compression, condensation, and expansion, followed by evaporation.


When the interior of the building requires heating, the refrigerant absorbs heat from the outside air, converting it into gas or vapor. The gas or vapor then passes through a compressor, where its pressure and temperature increase rapidly. The compressed refrigerant then transfers the heat to the water in the circulating heating system through a heat exchanger.


After distributing the heat to the liquid loop system, the gas or vapor passes through a condenser, where it returns to a liquid state again.


When the interior of the building requires cooling, the condensed refrigerant passes through an expansion valve, designed to rapidly decrease the pressure, causing it to evaporate and absorb heat from the indoor air.


Finally, the refrigerant returns to the outdoor unit, and the cycle begins again. This continuous process of absorbing and releasing heat ensures that the interior of the house remains comfortable regardless of the weather. It also provides hot water for domestic use.


How efficient is a ground source heat pump?

Certainly, when considering using a heat pump, you would want to know if it helps reduce your energy costs. For heat pumps, this involves checking the efficiency, known as the coefficient of performance (COP).


It measures the relationship between the heat output of the system and the energy input. The higher the COP, the more efficient the ground source heat pump unit. The COP for most air-to-water heat pumps ranges from 3 to 4.


This means that for 1 kilowatt of electricity, there is a heat load of 3-4 kilowatts. This is much more powerful than wood-burning stoves, gas boilers, and electric boilers, which typically have COP ratings below 1. In fact, this is where the advantages of ground source heat pumps lie.


Highly Efficient and Energy Saving:

As mentioned earlier, ground source heat pumps use less energy to deliver the same heat load as electric, gas, or wood heating systems. Ground source heat pumps do not generate heat; they simply move it. On the other hand, traditional systems require heat generation, which increases energy costs and environmental impact.


Cost-Effective Operation:

Operating a heat pump is cheaper than running electric, gas, or wood heating systems. In fact, studies have shown that running a heat pump for 960 hours, equivalent to 120 days, with a 20-kilowatt heat load in a 200-square-meter building would cost approximately $1,500. On the other hand, using an electric boiler for the same duration in a similar house would cost you around $5,000. The relative operating costs for wood-burning and natural gas systems would be $2,200 and $1,800, respectively.


Lower Electricity Consumption:

Air-to-water heat pumps use less electricity as their power input. In fact, their electricity consumption is reduced by 60% compared to standard electric water heaters. Additionally, using a grid-connected home powered by a solar energy generation system would result in even greater savings, not to mention the environmental benefits. Running a standard-sized 300-liter ground source heat pump, you would only need about 3.5 kWh of electricity per day at home, which most solar panels can easily generate, depending on your location. Furthermore, the heat pump can extract and store heat during the hottest times of the day through programming. This simply means that the heated water is stored in a water tank located under the floor for later use.



Heat pumps make indoor spaces comfortable regardless of the climate. They have heat even when the air temperature is -15 degrees Celsius. Therefore, even in adverse external conditions, heat pumps maintain efficiency.



As mentioned earlier, air-to-water heat pumps are designed to provide heating for houses when needed and cooling when the house becomes too warm. This ensures year-round comfort without the need to purchase separate heating and cooling systems. Additionally, they can assist in meeting the hot water demand for households.


Uniform Heat Distribution:

Liquid loop heat pumps can distribute heat evenly because water is their primary medium for heat distribution. Water is an excellent heat conductor, carrying heat 4,000 times more efficiently than air. However, increasing the water temperature requires more energy, which is an advantage as it allows for easier adjustment of the rate at which the liquid loop heat pump heats or cools the house.


Furthermore, air-water heat pumps do not directly heat the air but rather heat the objects in the room through radiation. This helps ensure consistent and uniform heat distribution. Additionally, most heat pumps are equipped with thermostats that help direct heat to different areas of the house, eliminating cold spots.


Environmentally Friendly:

Air-to-water heat pumps can reduce carbon emissions and noise pollution. As mentioned earlier, heat pumps use less electricity compared to traditional heating systems. Additionally, if you enhance the electricity input with solar power, it indeed contributes to reducing your property’s carbon footprint. Furthermore, heat pumps do not disrupt your home or sleep as they are much quieter than standard heating systems.


Low Maintenance:

Another advantage of air-to-water heat pumps is their low maintenance costs. They have fewer moving parts compared to traditional heating systems. The benefit of this is that they are less prone to damage from factors such as friction.


Therefore, you don’t have to bear frequent repair costs, saving you money. Additionally, the longevity of the equipment is extended due to the absence of many moving parts. In fact, high-quality heat pumps can provide service for up to 20 years.


What Applications do ground source heat pumps have?

Air-to-water heat pumps can be used in residential, industrial, or commercial settings. Here are some specific applications:


Residential Heating and Cooling:
Ground source heat pumps can be integrated with residential radiators, trench convectors, heated towel racks, or panel radiators to provide heating or cooling for the house based on weather conditions. They can also help meet the hot water demand for households.


Pool Heating:
As mentioned earlier, liquid loop heat pumps can assist hotels in meeting their hot water needs, including the hot water demand for swimming pools. The hot water from the circulating heating system can be transferred to the swimming pool, allowing residents to enjoy a warm pool even in cold weather.


Commercial Heating and Cooling:
Air-source heat pumps are also suitable for schools, hotels, hospitals, offices, and other commercial establishments, providing efficient heating and cooling throughout the year.


Industrial Heating and Cooling:
Air-to-water heat pumps can be used in industrial environments, including workshops, warehouses, and manufacturing factories. These systems can provide heating and cooling, ensuring comfortable indoor conditions for workers.


To wrap it up:

Heating and cooling account for at least one-third of a property’s energy consumption. With rising electricity and gas prices, it’s worth exploring alternative heating and cooling systems like ground source heat pumps. Ground source heat pumps require at least 60% less electricity compared to traditional heating systems to produce the same heat load.


They are environmentally friendly, have low operating and maintenance costs, can be installed in both new and older homes, and come with fewer hassles. For high-quality heat pumps, contact Shenling. With over 25 years of experience in the global heat pump market, we provide EN14511 standard heat pumps certified with CCC, CB, CE, SAA, ROHS, ERP, TUV, and KEYMARK certifications. Let our team help you find the right air-to-water heat pump for your property.


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