Everything you need to know about heat pumps

In an environment that is fast running out of non-renewable resources, and with Eskom’s load shedding threats hovering over our households, saving energy should be a key consideration in eco building and sustainable home building. Furthermore, with the National Building Regulation now stating that all new homes must meet the maximum energy demands as set out in the regulations, homes will be forced to start using alternative methods to heat their water. In line with these factors, Home Inspirations explains the in and outs of heat pumps, allowing home owners to make informed decisions when it comes to their water heating needs.

Solar energy from the sun radiates onto every portion of the earth’s surface. While 46% of this solar energy permeates the surface, 23% is absorbed into the atmosphere. This means that just less than 70% of the solar energy radiating onto the earth is sucked up by the earth, resulting in an environment filled with heat energy. Heat pumps can tap into this energy and convert it into heat that can be used in our homes.

Put simply, a heat pump is just an air conditioner functioning in reverse. While an air conditioner takes heat from inside a room and transfers it outside in order to cool the room, a heat pump does the opposite. Instead of eliminating heat energy, the heat pump stores it in a body of water, commonly the water contained in a geyser, for domestic use in our homes.

Heat pumps function by means of a process known as a ‘refrigerant cycle’: a heat pump gathers the heat energy stored in the surrounding environment, and increases this energy’s temperature to a temperature suitable for household heating purposes. In this way, heat pumps are efficient as well as eco-friendly building materials used for generating heat, as they make use of already-available heat stored in the environment.

Conventional electrical geysers use an element, powered by electricity, to create heat energy which heats the water they contain. However, instead of creating energy, heat pumps move already existing heat energy from the ground, water or the air, and make it available to heat household water. Therefore, they use far less electricity. Electricity saved as a result of the performance of the heat pump is measured by the value of the Coefficient of Performance (COP), the ratio between the electrical energy used and the heat transferred to the water. In simpler terms, the COP measures the amount of heat moved by the heat pump in comparison to what you pay for the electricity needed to move this heat.

integrated heat pumpThere are currently two types of heat pumps available for home building: the retrofitted heat pump unit and the integrated heat pump unit. Both function by heating water, and both, installed on the exterior of the house, endure all weather conditions. However, while the retrofitted heat pump unit makes use of an existing geyser to store the water it heats, the integrated heat pump unit combines the retrofitted heat pump and a geyser storage cylinder into one complete unit.

When choosing a heat pump, take note of these specifications:
• Choose a heat pump with the correct size. Retrofitted heat pumps are available in different sizes, depending on how much hot water is needed. Geyser’s of 100 litres or 150 litres require a heat pump that has a heating capacity of 2-3KW. Geyser’s of 200 litres or 250 litres require a heat pump with a heating capacity of 3.5-5KW.
existing geyserEskom offers a heat pump rebate programme for individual home owners, game lodges, bed and breakfast operators, metros, people buying in bulk and corporate organisations. However, these rebates only apply when consumers are retrofitting or replacing existing electrical element geysers. In order to claim a rebate, the heat pump installed must be Eskom accredited and registered. The contractor installing the heat pump must also be accredited by the manufacturer or supplier. Only the manufacturer or supplier is entitled to claim the rebate. Rebate monetary values depend on the amount of water heated by the installed heat pump. The current monetary value of the rebate for a geyser of up to 300 litres is R4 181.00, and for geysers over 300 litres, the rebate is R4 944.00.
• Heat pump contractors must be qualified, registered with the Plumbing Industry Registration Board, and they must be specifically trained to work with heat pumps. Heat pump plumbers must issue a Certificate of Compliance (COC) on completion of the installation. This is an assurance that the plumber has worked according to the national standards, and it also holds the plumber accountable for work done incorrectly.
• Only products that have been tested and approved by the South African Bureau of Standards may be installed in your home. A guarantee or warranty should also be offered with the product.

lifestyle considerations• In order for a heat pump to function most efficiently, it should be placed on the warmest side of the house. However, when positioning the heat pump, the most important consideration should be given to the length of pipes needed. Shorter pipe work results in less heat loss in comparison to the heat loss accumulated from the placement of the geyser on the cooler side of the house.
• Heat pumps, most commonly split type heat pumps, can be retrofitted to existing geysers. In this case, the age of the existing geyser should be considered. The older the geyser, the more likely the retrofitting will result in complications. Also, the integrated system may result in a compromised guarantee or warranty.
• Heat pumps should be installed in a well-ventilated area with minimal noise transmission. Anti-vibration pads can be used to further reduce noise levels.
• Heat pumps should be installed with a minimum clearance of 300m between the unit and the wall. All obstructions should also be at least 250mm away from either side of the unit. There should be no obstruction within 1000mm from the front of the unit.

Heat pumps, when installed correctly, save up to 60% of their users’ hot water heating bill, which generally accounts for 30-40% of users’ total electricity bill. However, one of the most important factors often overlooked when calculating a heat pump’s efficiency is the human factor. The optimum efficiency of the heat pump is also dependent on its users’ lifestyle changes.

For more information, see Green Plumbing Advisory Centre's page on Heat Pumps.

Written by Daniella Favis for Home Inspirations Source: Green Plumbing Advisory Centre.