Air source heat pumps in France: Aerothermie - Pompe a chaleur
Air source heat pumps absorb heat from the outside air to heat the air inside your home in France. There are two types of air-source heat pump systems:
- Air-to-air systems provide warm air, which is circulated to heat the building.
- The other type, air-to-water, heat water to provide heating to a building through radiators or an underfloor system.
Benefits of Air Source Heat Pumps (Aerothermie - Pompe a chaleur)
The benefits of air source heat pumps (aerothermie - pomps a chaleur) are similar to ground-source heat systems (geothermie - pomps a chaleur). Firstly, neither type of system requires the use or storage of external fuel. The systems instead run on electricity, which eliminates the need for a gas connection or storage of oil/solid fuel. Air source heat pumps present an advantage over ground source heat pumps because they require less space to install. Instead of requiring the installation of buried underground coils of pipes, air source systems can be fitted using much less space, typically around half a square meter on the ground or externally wall mounted.
How it works - what makes an Air Source Heat Pump Tick?
In the same way that a fridge uses a refrigerant gass to extract heat from the inside, keeping your food cool, an air source heat pump extracts heat from the outside air, and uses it to heat your home in France and sometimes your hot water too. An air-source heat pump has three main parts:
- The evaporator coil absorbs heat from the outside air,
- The compressor pumps the refrigerant through the heat pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit,
- The heat exchanger transfers the heat from the refrigerant to air or water.
Typically the first two parts of the heat pump system are situated outside of your house, and the final part, the heat exchanger is fitted inside your home.
In an air-to-water heat pump system, the heat produced is used to heat water, which can be used to preheat water in a storage tank or circulate through underfloor heating or radiators. Heat pumps produce hot water that is a lower temperature (typically 35-45C) than standard boiler systems, which makes the choice of underfloor heating the most effective option. In an air-to-air system, this heat is used to produce warm air, which is circulated by fans to heat a building directly.
The efficiency of air source systems is measured by a coefficient of performance (CoP). CoPs for air source systems are comparable with ground-source heat pumps, and generally range between 3 and 4. This means that for every unit of electricity used to power the pump, 3-4 units of heat are produced, making it an efficient way of heating a building. For example I've just bought two Airton pompes a chaleur from Bricodepot France with a COP of 3.61 giving them an energy rating of A for heating. If the unit consumes 1KW of electricity I will actually gain 3.61KW of heat from the unit. The unit is one of the latest technology DC inverter systems and was on promotion.... I think there were two left of part number 820260. If I had bought their unit which is rated C for energy efficiency I would get 3.41KW per 1KW of electricity used. Not a massive difference but over the years it will add up.
It is even possible for air source heat pumps to extract useful heat from air at temperatures as low as minus 15oC.
Is an Air Source Heat Pump suitable to heat my house in France?
You should consider the following issues if you're thinking about installing an air source heat pump in your house in France.
You will need space on an external wall outside your house to fit the evaporator coil, or mount in on a concrete pad.
- An air source heat pump should cover the heating requirements of a well insulated home. Due to the lower temperatures generated compared with traditional boilers, it is essential that your home is insulated and draught proofed. These measures will lower your heat requirement and make the system more effective.
- Consider what fuel is being replaced: if it's electricity, oil, Liquid Petroleum Gas (LPG) or coal, the payback will be more favourable than mains gas. Heat pumps are a great option where gas is unavailable.
- The type of heat distribution system. Air source heat pumps can be used to heat water that is circulated through radiators but under floor heating is more effective due to the lower temperature of the air/water produced.
- Is the system for a new building development? combining the installation with other building works can reduce costs.
- Using an air to air system like I'm installing you'll have the added benefits of being able to quickly heat or cool a room, dust and bacteria will be filtered from the air, you can also ionise the air and dehumidify the air.
Costs and savings of using an Air Source Heat Pump in France
A typical 6kW domestic heat pump system, suitable for a well insulated detached property, costs in the range of 8,000€ to 12,000€ installed. Though if you do it yourself you can pickup units capable of heating a house from as little as 400€. The effectiveness will also depend on the layout of your house. I received a quote from a French company called ThermoSeme to install a heating system, they quoted 27,000 euros - I told them where to go and have bought two units costing well under 1000€ - in fact it was a 50% promo and the two units came in at under 600€.....
When installed in an electrically heated home in France, an air source heat pump (aerothermie - pomps a chaleur) could save around 800€ a year on heating bills and almost 6 tonnes of carbon dioxide a year. Savings will vary depending on the fuel replaced.
||Saving per year
All savings are approximate and are based on an air source heat pump (aerothermie - pomps a chaleur) providing 100% of space heating in a detached property in France.
Quick Buying Guide for Air Source Heat Pumps in France Aerothermie pomp a chaleaur
Key things to ensure your heat pump in france has:
- R410A gas allows the unit to work down to -15C lesser types of gass only work down to -5C
- DC Inverter - Much more effiecient than an AC inverter. The DC Inverters vary their speed to suite the energy demand. AC inverters just switch on and off, wasting energy.
- COP 3.5 or higher - try and get a cop value of 3.5 or higher, try and get an A class energy efficient unit for heating.
Bricodepot prices for a monoblock (single head) heat pump in France are around 600 euros for an A class Heat and Cooling unit or 300 euros for a unit which is class C for heating and A class for cooling.
Installing Air Source Heat Pumps in France Aerothermie pomp a chaleaur
We've been running air source heat pumps for a few months and have just discovered that with the constant cold weather there is an important tip that will help ensure the efficiency of your air source heat pump installation.
As the units transfer heat energy (even though it's below freezing outside) to the inside of your house. The external unit will be very cold indeed and will ice up, much like the inside of a freezer. The external compressor heat exchanger can ice up in an hour or so. This however is not a problem because it's normal and the heat pump will automatically go into a defrost cycle where it defrosts the external heat exchanger.
The problem is that if your heat pump is too close to the ground, the melt water will freeze as it touches the ground and over time this accumulation will rise up and engulf the bottom of your air source heat pump.
When the amount of ice forms a large enough contact area, the 'Thermal Bridge' can be enough to drastically reduce the efficiency of your heat pump. Basically the ice sucks the heat energy out of your external heat exchanger into the ground.
Sitting your heat pump directly onto a concrete slab will give you problems, ensure it's installed on blocks a good few inches above the ground, allowing the melt water to run off. The units as standard only have about an inch of ground clearance, which is not enough when the air/ground temperature stays below freezing during the day.
I figured this out the hard way :o and had to defrost the air source heat pump from a frozen sheet of ice in order to raise it up!
Other than that the air source heat pumps have been providing a great source of heating for our house in France, even when we've had very cold nights as low as minus 5C, the benefit of the R410A gas giving us operation down as low as -15C.