FAN COILS AND CHILLED BEAMS
Are multi service chilled beams the future?
Michael Ainley, managing director of Frenger Systems explains how multi service chilled beams (MSCB) solutions not only provide the optimum in energy efficiency, but also long life expectancy and low maintenance, and provide virtually all the different building services in a single pre- fabricated architecturally inspired unit that only requires ‘plug and play’ installation.
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SCB solutions are pre-fabricated off site in a controlled environment to ensure not only high build quality, but also that projects are easier to manage and deliver on time. MSCB solutions are usually pre-designed in 3D to ensure all incorporated services are co-ordinated correctly and specification compliant.
The MSCB solutions are assembled within a controlled factory environment which helps negate the difficult task of trying to coordinate the interface of many different building services on site and this can also create a shorter build programme, as nowadays everyone wants things straight away; ‘time is money’. For example installations are commonly extended to allow for different trades to install their element of works and/ or other trades cannot proceed with their scope of works until another interfacing trade has completed their works. This approach can also help to reduce risk of health and safety incidents on-site, and likewise nowadays health and safety at work is a key driver for building site works.
It is customary for all services to be factory tested and many are then factory set prior to dispatch to ease any on-site commissioning. MSCB units are simple ‘plug and play’ solutions
26 June 2019
and as such this greatly reduces the length of the site installation programme.
At the heart of an MSCB unit is the chilled beam technology itself. These can be ‘active’, with forced ventilation through the chilled beams, or ‘passive’ – cooling by convection and/or radiant absorption), both of which have water as the medium for the transportation of heat to and from the building via the chilled beam heat exchanger concealed within the unit. This adds other plus points for MSCB solutions, given that the specific heat capacity of water is nearly four times greater than that of air, and as such the distribution duct sizes associated with chilled beam solutions is considerably smaller than that of all air systems.
This equates to much shallower construction depths for the HVAC system which can either give the larger room volumetric space, or in new multi-storey buildings could squeeze extra floor levels within the same total building height for multi-story applications. Having lower air volumes also enables the AHU to be significantly reduced in size as the overall system will not need approximately three times as much fresh air as needed for respiratory requirements to achieve the cooling loads. Mr Ainley says: “Let the water from the chiller
do the cooling, and leave the fresh air for respiratory purposes” as this leads to improved energy efficiencies.
Chilled beam technology utilises water temperatures above dew point (the coil operates dry) which significantly increases the COP (coefficient of performance) of the chiller. With the coil operation above dew point, it also negates the need for any condensation drainage on the chilled beams (terminal units), which further removes the need to clean and maintain any condensate facilities as opposed to other HVAC systems, which helps with whole life cycle cost savings.
Having the forced ventilation (fresh air) at the correct amount for respiratory requirements (10 to 12 L/S/ person) and the use of elevated water to provide the cooling (and heating if required) is one of – if not the most – energy efficient methods of providing air conditioning. Elevated flow temperatures also work well in conjunction with geothermal and heat pump technologies (instead of a chiller unit) to provide sustainable solutions and greatly reduce carbon emissions for green credentials.
Many high profile buildings that achieve BREEAM Excellent/Outstanding in the UK have achieved this by use of chilled beams as part of
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