Electric Heat Pumps


Air to Water Heat Pumps – Low Cost Heating Technology


Heat Pumps – What are they, and what are they used for?

Air Source Heat Pump technology has become very popular. Energy is used to draw the heat from the surrounding air, and use it to generate a much greater amount of heat. Even when temperatures are considerably below zero, the cold air contains energy which can be used for efficient heating. Air source heat pumps are efficient even at minus temperatures. In the U.K. we have relatively mild temperatures meaning that the heat pump will run with excellent efficiency all the year round.

What are they used for and can I use one?

If you have a typical wet radiator system, or underfloor heating system then this Heat Pump technology could be ideal for you. The Heat Pump technology and method of working is not new – indeed they were invented more than 50 years ago.

So if you are building or refurbishing a property and want long term low running costs without loss of comfort, and at the same time you save energy and CO2 emissions then a Heat Pump is a must.

CO2 emissions are considerably reduced as 75% of your energy usage is now coming from the outside air. An air source heat pump only produces around 40% of the emissions of a typical gas condensing boiler.

Our air source heat pumps can be used for a wide range of applications including heating, cooling, domestic hot water and swimming pools.

What type of heat pump do I need and what’s involved with the installation?

Put simply in a domestic application then one of two types.

An Air to Water Heat Pump – Which takes heat from the air and converts it for heat into water, and you will need a box outside similar to this.

A Ground Source Heat Pump – Which takes heat from the ground as the temperature is a regular 12 C all year round. However there will be considerable ground works required to install the heat exchanger coil.

For normal wet central heating with modern high efficiency radiators, underfloor heating or skirting radiators, then we recommend either an Air to Water Heat Pump, which is ideal for virtually any property, or a ground souce heat pump if you have the space to put large coil into the ground.

There are several makes around – how do I know whats best for me?

The COP of an air source heat pump is the Coefficient Of Performance. A COP of 4 means that for every kilowatt of electricity put in, you get 4 kilowatts of energy in the form of warm water. The COP rating we use for our calculations is based on a yearly average, which we have found to be 3.8. Many other manufacturers us a COP reading based on 20 F. However as we rarely reach these temperatures in the U.K. we have provided a full range of COP readings with the corresponding temperatures.

Our Air source heat pumps consist of one simple compact unit. The smaller models such as the 3 kW and the 5 kW are generally used for quick and easy installation to provide cost effective domestic hot water. These units have the added advantage that they can be located internally (generally in roof spaces) as well as externally, and they can easily be plumbed into an indirect cylinder. For those wanting hot water & heating, larger models are available which are suitable for underfloor and radiator heating but will need to be sited externally, as per the image above. In addition the larger units have a hot water tank which ascts as a buffer when used for central heating water.

The co-efficient of performance or COP of a heat pump is the ratio of the output heat to the electricity input supplied, i.e, one kilowatt of energy used produces 4 kilowatts of heat. The Therma air pump unit works out at a COP rating of between 3.6 to 4.8 depending on the air temperature . Below is an average cost per kWh for the main fuels, when calculating the heat pump one needs to divide the kWh by the COP. I.E. 10p per kWh peak divided by a COP off 4 equals 2.5p per kWh; off peak is 1.4p per kWh.

Natural Gas 3.4p per kWh Electric off peak 5.6p per kWh
Coal 13.p per kWh Oil 6.9p per kWh
LPG bulk 8.8p per kWh Wood logs 1.0p per kWh
LPG cylinder 9.2p per kWh Wood chippings 1.5p per kWh
Electric 10.p per kWh Wood pellet 3.0p per kWh

These units are becoming more and more popular, more so on oil and LPG boiler replacements as they are four times cheaper to run than oil and LPG, working in conjunction with solar photovoltaic panels you could have a situation where you are heating and lighting you r house free of charge

Therma Airpump System
This is a split system i.e., it has both inside and outside units. The outdoor unit extracts low temperature energy from the environment; it upgrades the temperature then via a refrigerant circuit transfers it to the indoor unit, giving a typical COP range from 3 to 5, which means extracting heat from renewable sources requires only 1 kW of electric input to produce 3 to 5kW of heating, making this unit more than capable of warming a house completely even during our coldest winter days.

The indoor unit is known as a “aqua box”, which can be connected to existing radiators, under floor heating, skirting radiators or convector heaters. There are two options of this box; one that does heating only and the other does heating and cooling. Inbuilt to this unit is a standby electrical booster heater so that heat can be maintained should the pump malfunction. A domestic hot water tank is required which is constructed of stainless steel to maintain the highest standard of energy efficiency. With the combination of electric booster heaters and heat pump exchanger ensures rapid water heating with the lowest possible energy consumption.

The system controls are user friendly and gives you flexibility throughout the year for your heating and cooling functions.

This unit is very flexible as far as positioning is concerned, the outside unit having the ability to be up to 70 meters from the aqua box, it can also be installed on walls. The noise level is comparable to the exhaust of a modern condensing boiler whilst working. The aqua box is wall mounted and can be positioned anywhere within the property. The hot water cylinder has the option of mains pressure or vented versions and again can be positioned anywhere within the property, including the loft area, solar thermal can also be added on installation or at a later date, and comes with a 3 year parts and labour warranty.


Leave a Reply