ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 37 AIR CONDITIONING When energy is rejected to ambient, for example in cooling with a heat pump, that energy is lost from the system, meaning e ciency is calculated at that point and cannot be changed. But if the energy can be reused, system e ciency can be improved. A heat pump system has two main refrigerant pipes, a gas line and a liquid line, running from the outdoor unit to each indoor unit. A heat recovery system has three main pipes; a suction line, hot gas line and a liquid line. This allows both cooling and heating to operate simultaneously and reuse the energy recovered elsewhere. Operating half of the illustrated system in cooling would generate 50 kW capacity from 12.5 kW of electricity, meaning 50 kW of energy is rejected to ambient and an EER of 4. By reusing that energy and rejecting it into rooms requiring heating, another 50 kW capacity would be generated in the form of heat energy, taking the total to 100 kW, but still only needing the system to power half of that. No energy is lost from the system and so e ciency, in e ect, doubles. The amount of energy recovery taking place is fluid depending on the ratio of cooling to heating operation. The best e ciency ratings are usually when the system is operating in a 60/40 split and it is possible to achieve ratings of 9.0 with KXZ. Go with the flow Flow Selectors are required on a 3-pipe heat recovery system to divert the refrigerant flow if the associated indoor unit is in cooling or heating. They are available in single and 4 port versions, and are selected by the capacity and number of indoor units. Both the low and high pressure gas lines connect to the box from the main run with the liquid line connecting straight to the indoor unit. On the 4 branch model, the liquid line is a small header which splits four directions. Because the liquid line bypasses the PFD box, it means that there are less joints and so less chance of refrigerant leaks, as well as less time spent on installation. The flow selector determines what mode the indoor unit is operating in. In cooling it opens up the low pressure gas line to the unit and in heating it opens up the high pressure gas. This determines if the flow is suction from the indoor unit or hot gas into the unit. Normally, a single unit would be connected to one branch of the flow control box. However, connecting more than one unit to a branch creates a small 2-pipe system, ideal for common areas and awkward shapes where airflow needs to be split and optimised. www.mhispec.co.uk How the ratio of energy consumed to energy produced can reduce operating costs for VRF systems KXZ VRF Beijer Ref offers MHI’s KXZ range of VRF, including both heat pump and heat recovery models , mini and maxi chassis and a capacity range covering 12 to 168 kw from a single system. Micro KXZ covers mini VRF, with single fan models of 12, 14 and 15.5 kW, which are available in single and 3 phase, as well as the 3 phase twin fan which covers 22, 28, and 33.5 kW. This range also includes R32 options. Maxi VRF covers both heat pump and heat recovery options. The modular heat pump KXZE2 option is available from 28 to 56 kW from a single module, with up to 168 kW achievable from 3 unit system. High coefficient of performance (COP) variations are available from the KXZ- XE20 range, covers 22.4 to 100 kW and sees COP increased from 3.6 to 4.5. Heat recovery systems complete the line-up, again with high COP variations, capable of meeting loads from 22.4 to 168 kW. All products are approved by Eurovent, the independent testing body which supports operating and sound level data. “Careful selection can maximise efficiency”