CHILLERS & REFRIGERANT Space – the final frontier
Refurbishing or replacing HVAC plant on restricted metropolitan streets can pose significant logistical challenges. Anthony O’Connor of LH-plc offers examples of solutions
A
ccess for the repair or replacement of bulky and awkwardly shaped HVAC equipment can be a real problem in confined urban spaces. Not only can it be
challenging to get at the plant but, even if this is possible, it can also cause severe disruption as the contractor struggles to keep the service going. It can be particularly difficult to overcome the
problems associated with access but there are several options when it comes to alleviating potential interruption to a building’s operation. One way to help mitigate interference to a building’s smooth operation is to carry out retrofit or replacement operations at times when the area is not so busy, and the work will result in less disturbance. This was precisely the option chosen when LH-plc was employed by facilitates management giant Bouygues E&S to deliver a major turnkey chiller replacement project for North Middlesex University Hospital in Edmonton, London.
All the crane lifts, changeover operations and equipment commissioning were carried out at night to avoid any disturbance to the hospital theatres. A key requirement on the project was to maintain continuity of cooling to the building throughout the entire installation. To this end, a pair of hire chillers – one 500kW and one 750kW – were installed on the runway immediately outside the chiller compound. Chilled water is provided by two dual circuit packaged air-cooled water chillers, with remotely located associated pumps and strainers. The project included removal of the old chillers and installation of a pair of Daikin screw compressor chillers.
My own company, together with sister business Klima-Therm, worked on another big healthcare contract – this time Queen Elizabeth Hospital located in Woolwich, southeast London – to deliver a chiller replacement and upgrade project. The chilled water services which provided chilled water to various air handling units throughout the hospital were located in plantrooms which distributed conditioned air via ductwork systems throughout the building.
The system was served by two dual circuit packaged air-cooled water chillers with remotely located associated pumps and strainers.
Replacement or repair – which is the best option?
Although access and the need for operational continuity are critical factors in any HVAC contract, they are not the only considerations. Before they are decided upon, a decision must be made about whether to replace or repair the equipment. When it comes to the repair versus replacement dilemma, the age of the HVAC unit is the number one consideration. If, by repairing the system, you will only extend its lifetime by a year or two, replacement is probably going to be the most appropriate choice. The return is typically greater when you invest in an energy efficient HVAC unit, and replacement will almost certainly save you more money further down the line. However, complete replacement of a HVAC system is not always the best option. There are many compelling reasons to choose refurbishment and/or repair. For example, it is less expensive than replacing a HVAC system and offers the opportunity to upgrade the existing equipment by exploiting the latest energy efficient components. It also minimises disruption by boosting flexibility during installation, cuts downtime, prevents the transport and access difficulties associated with replacing a unit, and is more environmentally friendly because it re-uses pre-existing equipment. Repair or refurbishment can also dramatically reduce energy consumption, it extends the service life of the system, and it leaves existing services such as ductwork, pipework, and wiring intact.
Installation work (which was completed on
a turnkey basis) included removing existing equipment and ancillaries from the roof plantroom, installing scaffolding, temporary chillers, new steelwork support, and new equipment (a pair of 531kW screw compressor chillers with remote condensers and separate pumps). A key requirement for this project was that the operation of the building had to be maintained throughout the entire installation. To this end, a temporary chiller set up was hired – two 530kW chillers and two pump sets were installed opposite to the hospital entrance while pipework from these chillers were run on scaffolding up to the chiller compound area. To ease access to the work area, three-floor tall scaffolding was erected and made as a walkway access to the working area and also to support the temporary chillers’ services.
As in the North Middlesex University Hospital contract, continuity of cooling was maintained by commissioning the equipment at night. The project required exacting attention to detail
in order to ensure plant fitted in a particularly tight space, with sufficient room needed for service and maintenance operations. This was achieved thanks to LH-plc’s many years of experience operating in cramped inner-city projects of this kind, coupled with the space-saving design of the replacement equipment. Meanwhile, another big chiller replacement and upgrade project in confined conditions took
place for one of the City of London’s most iconic buildings – the Lloyd’s building (also known as ‘the Inside-Out Building’), the home of the insurance institution Lloyd’s of London in Lime Street. It required disassembly and removal of two existing chillers from the building’s sub-basement plant room, and replacement with two high performance Turbomiser chillers. Replacement was necessary as the existing chillers were nearing the end of their working life, and the refrigerant they employed was subject to phase-out. On top of this, the plant was proving expensive to operate and maintain. A key requirement was that continuity of cooling for the building had to be maintained throughout the project. An additional challenge was that chilled and condenser water pipework also had to be replaced along with the chillers. LH-plc and Klima-Therm worked closely with building services specialist MEIT Consultants on the equipment specification and on-site logistics. The new chillers chosen were two water-cooled units, each with a cooling capacity of 1.7MW. This time, a third existing chiller on site, a centrifugal unit, was not part of the replacement project, and therefore available to assist in the change-over process. It was a project requirement that, at any one time, one chiller must be operating with another chiller on standby.
18 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JANUARY 2023 Read the latest at:
www.bsee.co.uk
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