13 Nov 2014
A new Turbomiser chiller installation at Swansea Civic Centre is believed to have the longest pipe work run ever used on a Turbocor-based air conditioning project.
Designed and project-managed by the council’s in-house mechanical and electrical design and maintenance section, the project uses two 420kW “split” Turbomisers, installed by Cool-Therm’s Wales branch in the building’s plant room.
They are connected to two air-cooled condensers some 70m away on the rooftop. The Turbomisers replaced a pair of conventional, aging Carrier chillers based on R22. To avoid disruption, it was essential to use some of the existing refrigeration pipe work.
Dave Blackmore, Cool-Therm director, explains: “The internal building pipe work runs through library archives, risers and ceilings, and into office spaces. Replacing it would have been complex and expensive, and would have caused considerable upheaval for the building.
“The project manager was understandably keen to retain it and replace the outdoor condensers and chillers in the plant room, resulting in minimal disturbance to the operation of the building.”
This posed a number of design and installation challenges. The original chillers were based on different pipe sizes to those on the Turbomisers. Integrating the two required careful design and installation onsite.
In addition, the original dual-circuit Carrier system had four pipes running through the building per chiller, two liquid and two discharge pipes, compared with Turbomiser’s single circuit. To overcome this, Cool-Therm designed and manufactured its own bespoke Refnet Y-joint pipe connecting system.
The design for the new chiller system itself posed a particular challenge due to the complex configuration. It required intensive planning as well as detailed flow calculations to ensure it would perform efficiently and as intended.
Dave Blackmore says: “We needed to make sure there was no excessive pressure drop across any specific component or pipe length, in order to deliver the correct cooling capacity at the flooded evaporator - rather than in the pipework.
“This entailed a forensic focus on pipe sizing, vertical and horizontal pipe lengths. The evaluation had to be right first time, there was no margin for error. Calculations had to take account of all system pressure drops, factoring in bends and 45 degree angles, all components and the properties and behaviour of refrigerant via psychrometric charts.”
A further issue arose due to the oil-free nature of the Turbomiser chillers, which run on magnetic bearings. The previous chillers, based on reciprocating compressors, used conventional lubricant and therefore pipe work incorporated oil traps. This meant that all oil residues in existing pipe work had to be flushed out and thoroughly cleaned prior to installation.
“We couldn’t allow any oil to remain in the system. This required removing all the oil traps and blowing the pipes out with oxygen-free nitrogen (OFN). As a back-up, we also ran a separate recovery rig with an oil accumulator in series with the chiller to catch any residual oil that remained after treatment with OFN.”
The existing chillers were disconnected and dismantled in situ, and taken out in manageable sections through public access areas in the civic centre. The Turbomisers were transported to the plant room in the same way.
Dave says: “Fortunately, Turbomiser chillers are fully modular so we were able to break them down, bring them in into the building in ‘kit form’ and rebuild them in situ in the plant room, reducing disruption to the customer as well as saving a great deal of time and effort on-site.”
Cool-Therm fitted new refrigerant leak detection and emergency extract ventilation in the plant room to comply with current F-Gas regulations. The plant room also features a fully integrated compressor input/output board with an RS232 connection to a laptop or building management system. All the controls can be integrated with the Turbocor compressors.
Given the coastal location, the specification of the aluminium condensers required special attention in order to safeguard them against maritime conditions and potential corrosion.
The micro-channel condensers are designed to reduce refrigerant charge while, at the same time, increasing the effectiveness heat exchange. However, Swansea Civic Centre is located just 20m from the seafront and is constantly exposed to salt and sand and corrosive sea breezes. To protect against this, the micro-channel condensers were treated with an anti-corrosion coating to protect them from the elements.
“The client wanted an extended warranty on the system. To achieve this given the location, we ensured that condensers were galvanised and then epoxy coated and that copper pipe work was PIB (pipe insulation billet), covered with galvanised wrapping on top of that. This ultra-corrosion resistant treatment enables the equipment to withstand the effect of the sea air and coastal weather conditions.”
Turbomiser chillers are based on the Turbocor oil-free compressor, which uses virtually frictionless magnetic bearings to produce the most energy efficient product of its type on the market. Turbomiser chillers reduce energy costs by up to 50 per cent compared with traditional chillers based on screw or reciprocating compressors.
Apart from offering dramatically lower energy consumption, the main benefits of Turbomiser chillers are reduced refrigerant leakage; less maintenance due to the oil-free design and limited number of moving parts; light weight (the unit’s compressor weighs just 125kg compared with 600kg for traditional compressors); excellent part load efficiency; quiet operation, and an exceptionally low start-up current (5 Amps compared with up to 600 Amps for conventional chillers).