BT exchange for Edenaire & Colman
Mast climbers have helped Eaton-Williams tackle a difficult installation at one of BT’s key telephone exchanges in the Midlands.
The project involved Edenaire and Colman, both members of Eaton-Williams, supplying and installing several NBTX air handling units and louvres as part of a major refurbishment and upgrade at the BT exchange.
BT had recently installed a new switch, which was generating 200kW of heat. “Modern telephony produces a lot of heat,” says David Tibbles, BT’s Power Planner and Contracts Supervisor. “The key objective was to match the heat load and overcome the obstacles of limited space and having to work around existing cabling.”
The installation was also representative of a major change in BT’s cooling strategy. Previously the building relied on a centralised chilled water plant. Now a policy of localised cooling is being implemented with the aim of making maintenance easier and having each floor operating independently in case of cooling failure.
The exchange houses a mix of old and new equipment with the old cable runs held on wire mesh above the racking systems. ‘Live’ buzz bars carrying the power run overhead. Heat build-up is continuous. The bulkiness of the existing cabling combined with the limited space above each racking system prevented heat from escaping and room temperatures were often hitting 30°C. Edenaire’s task was to provide a solution that tackled the heat and addressed the space constraints. In addition the installation of Colman louvres also had to be installed externally on a high-rise tower block typical of the 1960s.
As one of BT’s specified suppliers, Edenaire has extensive experience of working in exchanges and their associated problems. As a result seven NBTX 30kW upflow units were installed. The units were linked together with a duct header, which were decreased to in height and increased in width so as not to come into contact with the buzz bars overhead. Colman drum jet diffusers were installed into the duct header, positioned just below the wire mesh between each.
With the units constantly running, chilled or fresh air from the NBTX units pressurises the duct header and is discharged through the drum jet diffusers, forcibly blowing the conditioned air down the aisles between the racks. This pressurises the room, forcing the hot air to be drawn back to the NBTX units through the return air grilles sited on the front of the unit or out through the PRV (pressure relief vanes) mounted within the discharge section of the unit, when running in fresh air mode.
A number of Colman louvres had to be installed externally. BT contractors were using mast climbers to re-clad the building, so Edenaire took advantage of the opportunity to use them and assist with the installation of further vent louvres, a forward planning cost saving exercise.
“The project presented a number of hurdles to overcome” comments David Tibbles “Edenaire offered the best solution and the NBTX range has proven to be reliable and was ideal for this particular site.”
The NBTX range of vertical packaged air handlers were designed specifically to function in demanding environments such as switching centres and Internet hubs and to provide reliable cooling. There are six models in the range with cooling duties from 6.0kW to 45.0kW. All models in the range provide DX and fresh air free cooling wherever possible.