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About Heat Pump Technology: Heat Pumps are widely used all over the world to heat water. Energy savings come about because it is more efficient to separate hot molecules from cold in a fluid medium (such as air) than it is to make the medium hotter by using direct heating, such as an electric heating element.
What is a Water Heat Pump? A heat pump is a device that uses a compression vapour cycle, similar to that used in fridges and air conditioners to heat up some sort of fluid such as water. There are two main types of Heat Pumps – air to water and water to water. We will focus on air to water Heat Pumps. Simply put, the heat found in the air is transferred to the water through three key components – an evaporator, a condenser and a pump. The Heat Pump is therefore mounted in a well ventilated area where the heat exchange process can take place. Heat pumps are used in domestic, commercial and industrial applications and are accepted worldwide as the number one water heating technology (According to the French conference on energy efficiency). Heat Pumps are common in Europe, Asia and the Americas as energy efficient water heating devices. Due to their higher initial installation cost, they have not been as widely used on the African continent. The following pictures show what a Heat Pump looks like in various sizes:  |  | Commercial Heat Pump | Industrial Heat Pump |  |  | Domestic Heat Pump | Domestic System |
How does a Water Heat Pump Work? A refrigerant fluid is pumped around in a circuit where it evaporates on one side of the circuit and condenses at the other. Evaporation absorbs heat whilst condensation releases heat. In a heat pump, heat is absorbed into the refrigerant fluid by the evaporator at one side of the circuit, the fluid is pumped around to the other side of the circuit where the absorbed heat is released in the condenser. To most people heat pumps will look very similar to an air-conditioning or refrigeration units because they are very nearly identical, with the only difference being the roles of the condenser and evaporator are used for different functions. What are the Benefits of using Water Heat Pumps? While the product does have some draw-backs which are listed below, the fantastic advantage they do have is their ability to produce heating power at a fraction of the cost of other technologies. Many studies and comparisons have been done to show the energy saving capability of the product. In most of these studies the savings average at between 60 and 70%. A recent study commissioned by Eskom was carried out by the University of the North West which found the same overall result. Water Heat Pumps although not a new technology have been identified as one of the foremost products needed worldwide for energy saving. The following table shows the Pro's and Con's of Heat Pumps: Pro's
75% Energy Savings Achievable Well established technology Simple installation in either a new application or retro-fit Low maintenance required Not dependant on the weather for operation Good return on investment Cold air as a bi-product Small installation foot print
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Operational noise level Higher initial capital outlay compared to other water heating systems Needs well ventilated area Operation in extremely cold environments (<-10°C) problematic Calcium build-up in water can lead to extra maintenance Not well known in South Africa
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Maintenance on Heat Pumps A maintenance table below describes the measures that need to be taken to ensure long life and maximum efficiency. The table should be used as the basis for any maintenance schedules that need to be compiled and given to the maintenance staff. The typical lifespan of a Heat Pump should be in excess of ten years and although very little maintenance is required, regular checks should prevent possible damage to the unit and prolong the life of the Heat Pump. Typical maintenance staff might comprise of plumbers, electricians and air conditioning professionals. The only addition to the list of maintenance staff when compared with electric boilers (geysers) is that of an air-con technician. Heat Pump Gas Specifications Heat Pumps require a refrigerant to complete the vapour compression cycle. The Deron Heat Pumps that are installed by Light and Sensor use R417A which is a blended gas. It is directly interchangeable with R22 as it is considered the replacement gas for R22. In South Africa, R417A is less commonly used and more expensive than R22 or R134a. Although it is the choice of most manufacturers, Heat Pumps can be run on either of these gasses. R417A can be interchanged with R22 if not available, however under normal conditions, the need to re-gas or change gas is not necessary. The gas should not need replacing during the lifespan of the unit in most instances and if the need arises to do this, we recommend R417A be used. Although R134a can also be used with some initial modification to the Heat Pump, it will change the specifications of the Heat Pump unlike R22! Typically, R134a is only used when higher than normal tank temperatures are required. We do not recommend this as it is not common and not necessary. Comparison with Other Existing Technologies There are six main technologies used worldwide for water heating; Electric Boilers (Geysers), Coal Boilers, Oil Boilers, Liquefied Gas, Solar Electric and Heat Pumps. The table below shows the six types of technology compared. This information in the table has been extracted from one particular report compiled in China. There are numerous reports that compare water heating technologies, most of which come to the conclusion that Solar Water Heaters and Heat Pumps are by far the most energy efficient. Unfortunately Solar Water Heaters do not have a good commercial application as they require a large amount of space at a high cost. The following two simulated graphs are an extract from the Eskom report compiled by the university of the Northwest. The simulation shows that Solar Electric systems slightly out-perform Heat Pumps in a residential environment. They also show that the payback period for Heat Pumps is better than that of Solar – again in a residential environment. Typically, most Solar Electric installations are residential because of the amount of space needed to produce adequate heat. In a commercial application, Solar Electric systems can become very expensive and cumbersome to install. For this reason, Heat Pumps have found majority of their market in commercial and industrial environments. These types of installations include, hospitals, mines, apartment blocks, hotels, offices and similar. Heating Type | Calorie/ kWh | Energy / Perf. Ratio | Unit Price | Requ'd Energy/ ton of Water | Requ'd Cost / ton of water | Lab Cost | Cov- erage | Ann- ual Oper- ational Cost | Coal Boiler | 4000 kcal/kg | 40% | $0.08/kg | 25.10/kg | $2.32 | $5 128 | 20m3 | $12 641 | | Oil Boiler | 8429 kcal/kg | 80% | $0.61/kg | 6.401 | $3.84 | $5 128 | 20m3 | $19 141 | Liquefied Gas | 10800 kcal/kg | 73% | $0.85/kg | 5.30/kg | $4.48 | $2 564 | 10m3 | $18 936 | Solar Electric | 860 kcal/kg | 85% | $0.09/ kWh | 51.6kWh | $1.92 | NO | 150m3 | $7 028 | Electric Boiler | 860 kcal/kg | 90% | $0.09/ kWh | 51.6kWh | $4.63 | NO | 10-15m3 | $13 487 | Heat Pump | 860 kcal/kg | 400% | $0.09/ kWh | 13kWh | $1.17 | NO | 3-10m3 | $4 256 |
. The graph depicted below was compiled by the Plumbing Industry Association of South Australia. The results of their report show that the Heat Pump out-performs the Solar Electric system – again in the residential sector. Why the variance in results from report to report? Firstly, Heat Pumps are fairly consistent and are not normally affected by weather. Cloudy and rainy conditions produce less efficient results for Solar Electric systems whereas these factors do not reduce the efficiency of Heat Pumps as drastically. The reason for this is that the Heat Pumps COP (Co-efficient Of Performance) is directly related to the ambient air temperature. Most Heat Pumps operate comfortably in temperatures between -5°C and 40°C, which means their COP values in general fluctuate between 2 and 6. In some instances where the ambient air temperature does not permit the use of an air-to-water Heat Pump, water-to-water systems can still be used. South African conditions are perfect for Heat Pump installations because our ambient air temperatures are generally high throughout the country and throughout the year. 
Installation of Heat Pumps Heat Pump installation, while simple at a glance – are engineered solutions. Many factors are taken into account before an adequate Heat Pump can be recommended. Since a Heat Pump comprises of a compressor, evaporator, fan, piping and valves, each component must be matched to the required solution. In addition to the internal components of the Heat Pump, other external factors are calculated. Water Storage Tank size, number of tanks, water flow rate, external pump specification, volume of water used, water temperature required, unit mounting and location are but a few of the elements used in the calculation of the specification. Although there are many ways that a Heat Pump installation can be engineered, the most common installations fit into two main categories as follows: New Installations A new installation usually occurs in the design phase of a building project. The Heat Pump engineers will work closely with the architects and designers to provide the perfect solution matched to the application. Water usage, ventilation, pipe length, water tank size, location and insulation are just a few of the variables considered when designing the correct solution. The Heat Pump specification once complete will be included in the final design for production. The following diagram shows a simplistic simulation of a typical installation. A Heat Pump is not always installed in this manner and it should by no means be seen as a blueprint for installation. In most industrial and commercial applications, more than one water storage tank is used and they could be connected in series or parallel, in addition, multiple Heat Pumps may be installed to produce the required result. 
Retro-fit Installations Retro-fitting of Heat Pumps to existing installations is very common since both corporates and end-users are either required by law to look at energy efficient (or environmentally friendly) technologies or there is a requirement to save on running costs. The term retro-fit implies that the Heat Pump (in this case) is installed to an existing solution for water heating. The most common retro-fit occurs where clients have an electric boiler (geyser) which needs to be retro-fitted with a Heat Pump to replace electric element heating. As is common with the new type installation, design and engineering is critical to the success of the installation. In most cases, retro-fitting designs are more complex since buildings may not be designed with adequate ventilation, insulation and so on… What is also common practice as part of a retro-fit is the continued use of the existing electrical elements as a back-up means of heating the water. The following diagram shows one possible simplistic retro-fit solution. Again, it is not a blueprint and rather a visual representation. 
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