How an air source heat pump works

An air source heat pump extracts heat from air by drawing air in and compressing it, to make a simple analogy you may notice that when you pump a bicycle tyre up the body of the pump gets hot. You can use them to heat
air that then directly heats your property or you can use a different type of air source heat pump that will use a heat exchanger to heat water for radiators much like a traditional central heating system.

Advantages

These systems are particularly useful in areas that may not be connected to the gas mains where expensive diesel boilers are being used. An air source heat pump uses electricity and are simpler and cheaper to fit than gas or diesel boilers and require far less ground than a ground source heat pump (hundreds of metres of tube need to be installed for a ground source heat pump) and so can be used in built up areas.

Ground source and air source heat pumps are similar in efficiency and provide three to four units of heat for every unit of electricity supplied and will operate down to minus fifteen degrees celcius

Running on economy seven

Although air source heat pumps produce three to four units of heat for every unit electricity gas is approximately a third of the price so the cost saving for gas mains supply is not much But if you can mount it outside or in a place that is well insulated for noise you could run it at night for a few hours on Economy 7 which will greatly improve the cost
advantage even over gas let alone heating oil standard emersion heaters or coal.

Disadvantages

The units can be noisy and have sound levels similar to an air conditioning unit and therefore are best mounted somewhere with good noise insulation (the loft) or outside.

And they will take approximately three to four times longer than a normal boiler to heat up a hot water cylinder.

It is perceived that ground source heat pumps perform better than air source heat pumps because air temperatures are normally lower than the ground temperatures in winter. Although the modern air source heat pumps are far cheaper to install and some of the air source heat pumps operate down to temperatures of minus fifteen degrees celsius but you will need one of the larger air source heat pumps, eleven or thirteen kilowatts to make it large enough to replace a ground source heat pump

There are three main processes to the pump. You can think of it as a refrigerator in reverse. The first process is the evaporator that will extract warmth from the surrounding air. Next the gases will be compressed via the heat pump making them hotter and finally an exchanger will convert the warmth to water/air.

Much like a traditional central heating system the heated water from an air source heat pump is then pumped through a coil in a hot water cylinder to provide hot water for the house and or to provide central heating via radiators or under floor heating. Alternatively hot air maybe produced via the heat pump and driven through your property using fans.

Should I fit an air source heat pump to my home?

They are compact so space is generally not an issue. The pumps operate at around thirty five to forty Celsius which is lower than a traditional boiler so they should be used in conjunction with good insulation. So ensure that your property already retains all of its existing heat efficiently via cavity wall insulation, draught excluders etc. It will prove cheaper to install if you are not adding to an existing central heating system, therefore a new property is always the best =
solution.

You can combine the install with a solar water heating panel that will heat your water in your hot water cylinder via its own dedicated coil. The greatest savings are in area that are not connected to the gas mains and therefore if you are using heating oil electricity or LPG you will get the best savings.

How much will an install cost?

Well some installers are quoting figures of seven to ten thousand pounds but you should really only be paying two and half to three thousand pounds for an install or five thousand to six thousand pounds for a combined solar water heating install and air source heat pump install.

What should I save in costs?

Approximate savings for air source heat pumps providing your central heating are between three hundred and nine hundred pounds a year. Gas and coal are estimated at three hundred pounds and oil at around six hundred pounds and electricity at around eight hundred and fifty pounds. These figures can be further improved by adding a solar water heating panel that will provide all of your hot water for around six to seven months of the year and part of your hot water for another two to three months. But remember these are all approximations and will fluctuate depending upon
your own personal demands for your hot water and central heating supplies.

Installing in a smaller property with limited space

You can mount the smaller units (three kilowatts) in the loft to replace the immersion heater and it will operate at approximately a third to a quarter of the cost this type of unit is typically good for supplying enough water for a couple and the air in the loft should be slightly warmer and therefore improve its efficiency.

For more information about air source heat pumps contact the Heat Pump Association’s website and or post your questions here.

This entry was posted on Tuesday, December 16th, 2008 at 11:25 am and is filed under Green Energy. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.