ACR Journal

June | July 2023 Fresh air has always been crucial in occupied buildings both for health and wellbeing and to maximise productivity, but the recent COVID19 pandemic highlighted its need in the most powerful way possible. As the UK government has pointed out: “The amount of respiratory virus in the air can build up in poorly ventilated areas. This increases the risk of spreading COVID19 and other respiratory infections… Bringing fresh air into a room… helps remove older stale air that could contain virus particles and reduces the chance of spreading infections.” So, there is the need for some sort of air handling system to ensure the right fresh air ratio in commercial properties. Normally, fresh air is supplied using a heat recovery system or an air handling unit (AHU) system carefully designed in terms of filtration, humidity, and recovery for the building requirements. A heat recovery system – also sometimes called mechanical ventilation with heat HEAT PUMP AHUS 16 Combining temperature control with improved air quality, heat pump air handling units boast high efficiencies and year-round comfort and are particularly well-suited to high-demand applications such as healthcare establishments or data centres. Tim Mitchell, Sales Director of Klima-Therm, explains. Creating the right atmosphere recovery (MVHR) – employs a heat recovery ventilation unit usually located in the roof space or plant room of a building. Rather than simply extracting air from an internal space and replacing it with outside air, a heat recovery system is designed to draw the heat from the extracted air and passes it to the air filtered in from outside. Increased flexibility Extract and supply air flow within separate pipes so there is no cross contamination of the di erent air flows. The heat recovery unit will generally be linked to room air valves through a network of ducting that runs throughout the building. A typical standard AHU has two coils, one for cooling and the other for heating. Water is provided to the coils through inline pumps from the chiller for cooling and from the boiler for heating. This traditional system is generally very stable but has a high installation cost compared to a fully packaged solution. The AHU is generally installed in the basement, roof, or plantroom, from where the processed fresh air is fed to the building interior. However, along with fresh air, a source of cooling and heating will be required, often via a variable refrigerant flow (VRF) or heat pump system – thus, the heat pump AHU. As chiller technology has improved over the past few years – in particular, the development of variable speed fans on the air handing units together with variable speed compressors (inverter driven) on the chiller side – air volumes can be varied, which gives the client a lot more flexibility, energy savings and, therefore, better overall system e ciency. Heat pump technology is, however, far more cost e ective in terms of initial capital cost and installation cost, often using reversible VRF condensers for Volume 9 No.4 The 3DxHP Series fully packaged heat pump AHU range is ideal for displacement ventilation and other air conditioning applications