Air Source Heat Pumps - How do they work?

Heat pumps are effectively boilers which sit in the garden (in the case of air source heat pumps). They take around a quarter of the energy they require to operate from the electricity grid and the remaining 3 quarters of the energy that is then pumped into the property is provided by the air.

Heat pumps are installed everywhere, from churches to houseboats, from new build properties to 1600 thatched roof cottages. There are practical limits sometimes, but if a boiler can be installed, chances are that there is a heat pump solution to suit. Heat pumps are traditionally installed by plumbing and heating engineers.

They certainly can. For only the most difficult properties the only limits are budget or disruption. Considerations may have to be taken into account however depending on the property.

As the compressor, fan, circulation pump etc are all electrically powered, electricity is required. An off-grid solution may be possible, but it would require a sizeable solar PV array with significant battery storage.

The European heat pump association state that since the publication of the Directive on the promotion of the use of energy from renewable sources (2009/28/EC | RES Directive, § 2) heat pumps are officially part of this development. The Directive recognizes the technology as using renewable energy sources from air, water and ground.

Quite the opposite. Massive improvements have been made in the past 5 years to reduce the perceived noise level of heat pumps. Many heat pumps at 3m distance are no noisier than about 35dbA, which is just above a whisper.

They can indirectly be connected to solar PV panels to provide some aspect of their electricity. They can also be used in conjunction with solar thermal to provide domestic hot water.

Yes, if fan coils are used for the cooling aspect. Please note that this requires much more consideration than just central heating and hot water, so specialist advice is heavily recommended.

Many heat pumps can heat water up to 65°C with some capable of raising the water temperature to 80°C! 

They are perfect for heating correctly sized radiators.

When we think of cold, we think of below approx. 15°C outside temperature as that is when we traditionally look to switch the heating on. For heat pumps, there is a huge amount of energy available to “pump” all the way down to -273.15°C, which is extremely cold (pretty much the temperature of space) .

Correctly designed systems with correctly installed heat pump equipment will require a defrost cycle in winter, but this shouldn’t be for prolonged periods or detrimental to the comfort of the occupier.

Heat pumps remove energy from the air which passes through it, which reduces its temperature. At anything below around 4°C when frost begins to appear outside, then a heat pump may need to defrost.

Just like any mechanical device, if it isn’t maintained periodically, or correctly installed in the first place, it’s lifespan may be reduced. 

As the temperature drops outside, the heat pump must work harder to gather energy from the ambient around it. Also, as the temperature outside decreases, you may require a warmer water temperature through the central heating system, which will also cause the heat pump to work harder. In essence, the further apart the outside (source) temperature and the temperature around your radiators / underfloor heating (sink) is, the harder the heat pump works, and the lower its efficiency.

Heat pumps are expected to last anything between 10 and 20 years. Correctly installed and maintained should see 20 years.

Once a week a heat pump will raise the domestic hot water tank temperature in line with regulations to pasteurise the cylinder, to kill any legionella bacteria.

Installed around £9,000 to £15,000 dependent on works involved and run costs are very much dependent on the property but should not be more than an equivalent gas boiler.

We don’t believe heat pumps are expensive compared to the environmental and in many cases financial benefits you receive (especially when displacing oil or LPG), but with increased volume, we do believe that heat pump prices will decrease.

Depending on the fossil fuel it’s replacing, cost savings can be significant. Versus direct electric, you may find cost savings of 75% whereas closer to 40-50% for LPG or Oil. 

In new build properties that is the government’s plan as part of the future home’s standard. We hope to see something similar in retrofit properties as we get closer to the Net Zero carbon target of 2050.

Even poorly installed heat pumps are much more efficient than gas boilers. A very well installed gas boiler may be around 95% efficient. Even a poor heat pump will average no less than about 200% efficient. Very well-designed heat pump systems can see efficiencies of over 500%.

Typically, the most efficient operating or flow temperature setting is 35°C.

Any thermostats will work with a heat pump. More complex or sophisticated thermostats may require a separate relay, but it’s entirely possible.

Seek specialist advice to ensure compatibility.

We don’t believe that hydrogen as a fuel source will reach economic viability until the mid 2030’s which is too far along the carbon timeline, when heat pumps can provide a solution now.

Heat pumps work brilliantly in retrofit properties. There are 1000’s of examples of them working when the unit was fitted long after the house was built.

Heat pumps are regularly used in flats, but may require a specific engineered heat pump solution, so seek specialist advice.

Ground source heat pumps are installed indoors. Air source heat pumps need to sit outside.

Some specialist heat pumps are compatible with air conditioning. See specialist advice to ensure compatibility.

They are perfect for pools, especially outdoor swimming pools used during the summer season .

Predominantly air conditioning and refrigeration equipment manufacturers as they have the expertise and manufacturing capability which is required for a heat pump. At Huws Gray we partner with Freedom Heat Pumps who work with Midea, Samsumg, Hitachi, Clausius, RED and Mitsubishi so that you can specify exactly the right system for your job.

The best brand is subjective, but an MCS accredited unit is a good starting point, as is a long warranty. Some heat pumps now offer 10-year warranties. 

The larger the heat pump “box” outside the property, and the lesser the number of fans, generally the lower the noise level will be, as the larger amount of the “noise” produced is from the fan or fans depending on which heat pump you are looking at.

Many brands have manufacturing bases in Asia, Europe and America. The important part is not where a heat pump is made, but how it’s made.