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very heating system is different, from the age of the system, its volume through to the physical configuration of the pipework and


key components. Therefore, there is no one-size- fits-all solution when it comes to filters, and certain systems will require a specialised solution.


Filters for a heat pump


There are important differences between a conventional boiler and heat pump system that mean it is essential to select a filter that has been designed specifically for heat pump applications. A key difference between a heat pump and a gas or oil boiler is the flow rate. Heat pump systems typically operate at a flow rate that ranges from 6 to 40 litres per minute compared with just 12 to 15 litres per minute for a typical gas boiler system. This can be an issue if the installed filter primarily relies on magnetic filtration to remove debris. At higher flow rates it becomes more difficult for a magnet to capture debris, and wash-off is more likely to occur meaning the debris will begin circulating again, potentially causing damage and shortening the life span of system components. A filter specifically designed for heat pumps will include filtration technology engineered to capture and contain all circulating material including magnetite, haematite, scale and any installation debris, even at high flow rates. For example, the Fernox TF1 Sigma HP Filter uses a unique particle separation baffle to create an area of low flow within the filter body that causes debris particles to settle, achieving efficient debris capture.


It is also important to ensure that the filter does


not cause pressure loss in the system. While this is an issue for all heating systems, with a heat pump, a pressure drop can limit the output of the unit and reduce the Co-efficient of Performance (COP). This in turn can mean that the heating system is not able to reliably achieve target room temperatures. To prevent this, a dedicated heat pump filter with excellent flow co-efficient (Kv) values should be selected as this demonstrates that the filter will not restrict the flow of water and cause pressure losses. In addition to choosing a suitable filter for a heat pump it is also important for the system to be protected from microbiological contamination due to the lower temperature that these systems operate at. A high-quality biocide should be added to the system alongside the inhibitor to prevent microorganisms that can accelerate system degradation from growing and multiplying.


Dealing with space restrictions


For some properties, the space around the boiler may be limited, making the installation of a large filter challenging. In these situations, a specially designed compact filter should be selected. However, not all compact filters offer the same level of performance, so it is always recommended installers to look carefully at the product information. Ideally the filter should include features to capture and contain both magnetic and non-magnetic debris without restricting flow around the system.


For areas where space is very restricted or the pipework to the boiler is concealed, there are filters on the market that are designed to be installed directly under the boiler. For example, the Fernox TF1 Sigma UB Filter has a very small footprint and can be installed in place of the return valve if necessary to minimise the required space. Furthermore, there are also ultra-compact filters available for lower volume heating systems where limited space is also an issue. Some of the smallest of these filters on the market require just 105mm of pipework.


Guidance for standard systems


For a typical domestic property with no space restrictions around the boiler, there are many choices of filter. However, selecting a high-performance, high-quality option that has been engineered for reliability is of course important to ensure the system has the best possible protection. With many types of filters available on the market, it is important that installers are aware of any key design features that can help contribute towards a successful job on-site. For example, a filter with a sealed design – sometimes referred to as a lidless design, can minimise the chance for leaks as, in contrast to lidded filters, sealed units do not need to be disassembled for maintenance or chemical dosing and ‘o’ rings do not need replacing. The materials used in the construction of the filter and the level of integrity testing it has undergone


should also be considered carefully, as this will provide peace of mind about the quality.


Installation and maintenance


Regardless of the requirements of the system, it is important to choose a filter designed for simplicity of installation, such as connections to the pipework that help streamline the fitting process. It is also valuable to look for a product that can be installed on vertical or horizontal pipework to allow installation flexibility. Ease of maintenance is another factor that should


be considered. For example, selecting a filter that does not require the system to be drained down and has the drain valve or magnet positioned for ease of access will help ensure that annual servicing can be completed quickly and cleanly. It is also worth looking at how the right filter can help make dosing the system with inhibitor easier. Some market leading filters make it possible to use the drain valve as a convenient dosing point. Finally, the length of warranty is also an important element as this is an indication of quality and will provide reassurance for the customer that the filter will work as intended for years to come. System filters are an essential part of protecting a heating system but will only be effective if the correct one is chosen. With so many options on the market, it is always advisable to choose a product from an industry leading manufacturer and meets the needs of the property.


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Water treatment


Finding the right filter for the job


In line with the requirements of Part L and BS 7593:2019, heating systems should always be protected using an in-line system filter in addition to an effective inhibitor. Here, Mark Hall, head of mechanical engineering & devices at Fernox outlines how to ensure the right filter is selected for each installation


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