Ground and Air Source Heat Pumps

Ground Source and Air Heat Pumps are covered under the Green Deal as a measure under Microgeneration. Ground Source and Air Heat Pumps are certified under the Microgeneration Certification Scheme. This means as an MCS Certified installer with the additional standard MCS 023, you are able to install MCS Certified Ground Source and Air Heat Pumps under the Green Deal and offer consumers The Renewable Heat Incentive.

Ground and Air source heat pumps use pipes buried in the garden to extract heat from the ground. This is usually used to heat radiators or underfloor heating systems and hot water.

Although we may not know it heat pumps as a technology are very familiar to us - domestic fridges and air conditioners are two examples. Ground source heat pumps (GSHP) transfer heat from the ground into a building to provide space heating and domestic hot water.

For every unit of electricity used to pump the heat, 3-4 units of heat are produced. As well as ground source heat pumps, air source and water source heat pumps are also available.

How much will you save?

How does it work?

There are three important elements to a GSHP:

• The ground loop. This is comprised of lengths of pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is usually a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground.
• A heat pump. This has three main parts:
• the evaporator - (e.g. the squiggly thing in the cold part of your fridge) takes the heat from the water in the ground loop;
• the compressor - (this is what makes the noise in a fridge) moves the refrigerant round the heat pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit;
• the condenser - (the hot part at the back of your fridge) gives up heat to a hot water tank which feeds the distribution system.
• Heat distribution system. Consisting of under floor heating or radiators for space heating and in some cases water storage for hot water supply.

What options are available?

The ground loop can be:

• borehole;
• straight horizontal - trench costs less than a borehole, but needs more land area;
• spiral horizontal (or 'slinky coil') - needs a trench of about 10m length to provide about 1kW of heating load.

How much does it cost?

Installation

A typical 8-12kW system costs £6,000-£12,000 plus the price of connection to the distribution system. This can vary with property and location.

Running costs

The efficiency of a GSHP system is measured by the coefficient of performance (CoP). This is the ratio of units of heat output for each unit of electricity used to drive the compressor and pump for the ground loop. Typical CoPs range from 3 to 4 although some systems may produce a greater rate of e. The higher end of this range is for under-floor heating, because it works at a lower temperature (30-35ºC) than radiators. If grid electricity is used for the compressor and pump, then you should consult a range of energy suppliers to benefit from the lowest running costs, for example by choosing an economy 7 or economy 10 tariff.

Ground source heat pumps and your home

What to keep in mind when considering a ground source heat pump.

• The type of heat distribution system. GSHPs can be combined with radiators but under-floor heating is better as it works at a lower temperature.
• Is there space available for a trench or borehole to accommodate a ground loop?
• Is the ground suitable for digging a trench or borehole?
• What fuel is being replaced? If it's electricity, oil, LPG or any other conventional fossil fuel the payback will be more favourable. Heat pumps are a good option where gas is unavailable.
• Want to be 100% renewable? Buy green electricity, or install solar PV or some other form of renewable electricity generating system to power the compressor and pump.
• Need a back-up heating system?
• Is there also a cooling requirement?
• Is the system for a new building development? Combining the installation with other building works can reduce costs.
• Can you incorporate insulation measures? Wall, floor and loft insulation will lower your heat demand.

The estimated costs can often be quickly covered by the Renewable Heat Incentive due to be introduce in 2011 which can be offered by Microgeneration Certification Scheme (MCS Certified) Installers who offer MCS Certified Ground Source Heat Pumps.

Air Source Heat Pumps are covered under the Microgeneration Certification Scheme as an MCS approved technology. This means as an MCS Certified installer you are able to install MCS Certified Air Source Heat Pumps and offer consumers The Renewable Heat Incentive.

Air source heat pumps absorb heat from the outside air This is usually used to heat radiators, underfloor heating systems, or warm air convectors and hot water in your home.

Air source heat pumps (ASHP) absorb heat from the outside to heat buildings. It is even possible for air source heat pumps to extract useful heat from air at temperatures as low as minus 20°C.

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.

How much will you save?

How does it work?

In the same way that a fridge uses refrigerant 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 and hot water. 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.

In an air-to-water system the heat produced is used to heat water, which can be used to pre-heat water in a storage tank or circulate through underfloor heating or radiators. Heat pumps produce hot water that is a lower temperature (typically 35-45°C) than standard boiler systems, which makes 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.

What options are available?

There are two types of air-source heating systems. Air-to-air systems provide warm air, which is circulated to heat the building. Air-to-water systems heat water to provide heating to a building through radiators or an underfloor system.

How much does it cost?

A typical 5kW domestic system, suitable for a well insulated detached property, costs in the range of £6,000 to £8,000 installed (ex VAT).

Is it suitable for my home?

What to keep in mind when considering an air source heat pump.

• You will need space on an external wall outside your house to fit the evaporator coil.
• An air source heat pump should cover the heating requirements of a well insulated property. Due to the lower temperature compared with traditional boilers, it is essential that your home is insulated and draught proofed. These measures will lower your heat demand 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 gas. Heat pumps are a good 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. Air-to-air systems require a ventilation system with fans to circulate the warm air.
• Is the system for a new building development? Combining the installation with other building works can reduce costs.
• If you want to further reduce your home's CO2 emissions you can purchase a green electricity tariff or install solar PV or some other form of renewable electricity generating system to power the compressor and pump.

The estimated costs can often be quickly covered by the Renewable Heat Incentive which can be offered by Microgeneration Certification Scheme (MCS Certified) Installers who offer MCS Certified Air Source Heat Pump Equipment.

For further information on Green Deal Certification for Heat Pumps, please contact our team on 0161 768 5807. Alternatively please email us at [email protected].