35 x Classair units, 1 x Tempair Heat Pump
Total air volume: Classairs 9m3/s, Tempair 2.64m3/s
Serving: Classair- Classrooms. Tempair -General areas.
Control: Tempair with supply air control. Classair with CO2 and temperature control
Rooms: The Classair units provide room temperature and fresh air control on demand. The fresh air volume is controlled by a unit mounted CO2 sensor with an override for heating and cooling.
General Areas: The Tempair supplies constant volume fresh air to the core of the building. The units have a remote summer/winter signal to change the supply air temperature set point. This allows the cooling setpoint (16°C) to be lower than the heating setpoint (19°C). This will provide more free cooling to the areas when available.
This was one of two technical colleges completed in 2013-2014.
Both colleges were cited by main roads and due to external boundary noise levels in excess of 60dbA, the building was required to be fully mechanically ventilated. Due to the layout of the building they could not be fed entirely from central plant. Each of the 32 classrooms were fitted with an individual low noise, BB93 compliant ceiling void unit. Each unit operates with power consumption of less than 200 watts at 32 occupants at full classroom ventilation rate with specific fan power of 0.70 w/l/sec. The unit was provided with the following ancillaries with pre-wired Bms controls; CO2 and temperature sensors, plant extend buttons and packaged attenuators. The units provided space heating to each of the classrooms, night time free cooling, CO 2 and room temperature monitoring to each classroom. This gives the benefit of individual classroom temperature and CO2 control allowing rooms that have high occupancy to provide free cooling and increased fresh air rate and low occupancy classrooms to be controlled on set back mode.
The central ground floor areas were fed with a Tempair packaged heat pump unit to provide fresh air to communal reception and canteen areas.
Oasis Academy MediaCity
2 x Tempair Heat
Total air volume: 16.6m3/s
Serving: General areas
Control: Supply air temp, recirculation pre-heat, VAV. The units were supplied with electric heaters for pre heat start up. When the return air reaches 18°C the electric heater switches off and the unit reverts to full fresh air and heat pump control. The temperature of the various areas and floors is controlled by VAV boxes in the supply and return. System pressure sensors were positioned in the supply and return air to control the fan speeds.
The school was a new build as part of schools for Salford and Irlam BSF building schools for the future scheme. The two Tempairs supplied were serving areas on the south facing part of building that were required to provide a degree of cooling to prevent overheating. These areas were originally designed with remote heat pumps and as units were providing full heating to space there may be issues with defrosting and loss of capacity in low ambient temperatures. The remote heat pump condensing units were omitted and the Tempair unit put forward. The Tempair uses the warm air extracted out of the building to reject the compressor heat rejection, this reduces the amount of defrosting. The units were fitted with pre-start heating in full recirculation to provide fast response to heating on start up. Another course of concern was operation, with local floor VAV variable air volume dampers and would operate at 40% air volume capacity. This was solved using the Tempair unit as each included multi circuit compressors circuits capable of turning down to 15% capacity, meaning control is not compromised at low air volumes.
Newcastle-under-Lyme College for Performing Arts.
1 x Tempair Heat Pump
Total volume: 4.2m3/s
Serving: Two performance halls
Control: Supply VAV and CAV system dampers, room temperature control. The ductwork contained a combination of supply air CAV and VAV boxes. The supply fan speed was controlled by a pressure transducer. There were no corresponding dampers in the return air. To obtain the correct return air volume, both the supply and return air fan system curves were plotted, the supply fan with increased pressure as the VAV and CAV dampers controlled and the extract fan without. This enabled an offset to be calculated for the extract fan speed from the supply pressure transducer reading to maintain equivalent volumes
The building was an extension onto an existing building. The initial designed was based upon one central air handling with constant volume boxes serving a lecture theatre and other areas of the building. The existing design had a single chiller coupled up to the air handling unit and low pressure hot water pipework fed from boiler systems. The chiller was omitted and the Tempair unit was provided. This offered cost saving by omitting the chiller and associated water vessel required to achieve capacity control. The unit was operating on pressure transducer to react in line with closing of the constant volume boxes.