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Air Source FAQs

Some questions we are frequently asked about our services in air source heat pumps. If you can't find your answer please contact us.
  • Do heat pumps make a lot of noise?

    No, the 9kW produces 50dB and the 16kW makes 53dB. These sound pressure figures lie between the noise level of a domestic 'fridge and normal human conversation. Visitors to the Harvest Cornwall's stand at the 2014 Royal Cornwall Show were pleasantly surprised at how quiet the heat pump on demonstration was having heard criticism that they were noisy. Also, the quoted figures are for maximum output which is not the usual running level of the heat pump. Apart from the intrinsic quietness of the compressor and the fan in the heat pump, it is installed on two large sound-absorbing rubber feet that minimise any vibration. Usual installation positions produce no sound that can be heard within the property as the pumps are not sited under bedroom windows.

  • Can I have hot water and central heating from an air source heat pump?

    Absolutely! Most installations use the primary circuit of the heated water from the heat pump to circulate round the house through radiators or underfloor heating as well as through a coil in a specially designed cylinder. This coil transfers heat into the insulated cylinder into which cold water is fed at the bottom, heated to 50ºC and pushed to the secondary circuit from the top of the cylinder to the taps and showers on demand. At this temperature less mixing with cold water is required at the taps compared to the traditional hot water temperature of 70ºC.

  • What is the difference between an air source heat pump (ASHP) and a ground source heat pump (GSHP)?

    All air which is warmer than absolute zero (-273ºC) contains energy. The ASHP uses compression and evaporation cycles, like a fridge, to extract this energy and put it into water to heat the home and the domestic hot water. They look like air-conditioning units and sit unobtrusively in your garden, requiring only some electrical and plumbing connections.
    The GSHP takes its energy from the ground at a depth of up to 2m where the temperature is always between 10ºC and 16ºC. This however does require trenching and pipe work in the order of 50/80m of pipe per kW of heat pump rating. Very suitable for larger properties with considerable grounds, an approximation is: Area of property x 2 = area of ground for pipework. Both systems will produce domestic water and heating at 40-50ºC, but GSHP will do this slightly more efficiently. Both require a weekly boost of temperature by electricity to 60ºC for a short period to reduce eliminate Legionella which could be present in stored water at lower temperatures.

  • Can I run my heat pump run from my solar panels? 

    Yes. This is a very effective conversion as the 4kW solar PV system will supply the electricity required for the compressor and the fan in the heat pump unit  thereby minimising your reliance on mains electricity.

  • If heat pumps run off electricity, how can they be cheaper to run than electric heating?

    This apparent conundrum is explained as follows: Electric heating is done by resistance to current through a wire generating heat. A heat pump only moves already existing heat from one place to another using 25-30% less electricity to run a pump and fan. So it easier and therefore more efficient to move existing heat from air to water than it is to create heat in a cold coil of wire in an electric element. The heat energy in the air and ground is already there from the nuclear fusion in our nearest star, the type-G, yellow dwarf we call the Sun.

  • How far away does the heat pump need to be from my neighbours house?  

    At 1m away from a neighbour's door or window of a habitable room, the sound level must not be higher than 42dB. The heat pump must be 1m inside the boundary of the installed property.

  • I have radiators in my house, can I use an air source heat pump or do I need underfloor heating?

    You can use the radiators in the house with an ASHP, but the water temperature in the central heating will not be as high as the originally designed sizing required so the radiators will need upsizing accordingly. This is by a factor of about 30% and can be achieved by moving the larger existing radiators into the smaller rooms and fitting new bigger radiators into the larger rooms.

  • Do I need planning permission for a heat pump?

    No, they are considered permitted development although a listed building/conservation area setting may need local council confirmation.

  • How hot will my domestic hot water be?

    Hot enough for showers, baths, washing dishes and clothes at between 40ºC and 50ºC (body temperature is 37ºC)

  • How much electricity do they use?

    Depending on your usage, but if you need 15,000kWh (units of electricity) of energy every year and your heat pump has an efficiency (COP) of 3 then you will use 3 time less energy in the form of electricity to run the pump. i.e 5,000kWh or 5,000 units of electricity at eg.14p per unit. In this case, £700.

  • Who installs the heat pump?

    Only qualified, trained and experienced plumbing engineers and electricians install heat pumps. Each install is different, drawing on expertise and know-how gained over time to produce a tailored product solution to each customer's particular circumstance.