Up until recent years learning spaces were generally not air conditioned in Australia because of our moderate climate. The seemingly ever increasing application of electronic communications equipment and a growing sophistication of standards now brings about the air conditioned learning environment. Due to the extended hours of operation of the learning centres, air conditioning designers must focus on economical plant and system selection whilst at the same time ensuring long term low cost reliability and maintainability.
Control of after hours operation, which for a learning facility, means ensuring that systems are designed to allow the closing down of air conditioning serving areas not in use, ensures minimisation of wasteful energy consumption and plant operation. Unlike commercial office buildings, the non-use (after hours) period for learning areas can occur at any time of the day or night.
These considerations impact on the types of systems selected and cause the design process to be somewhat unique when compared to other buildings with fixed periods of constant occupancy. The aim of this presentation is to provide a brief overview of the processes involved in selecting and designing an appropriate air conditioning system to meet the particular requirements of a building and its occupants. The Port Adelaide Campus is used as a specific example of the way in which an air conditioning system is selected in response to the client brief.
A well developed client brief will typically canvas the following issues:
Preliminary architectural plans indicated a two level building with significant glazing elements orientated towards north, south, east and west. Such a building envelope requires an air conditioning system which is designed to provide independent temperature control to the areas in close proximity to the glazing elements, known as perimeter zones. The temperature conditions within the areas adjacent to the glazing elements are subject to the influence of the sun which varies depending on seasonal factors and the time of day. Furthermore, the proliferation of computer based teaching potentially results in a situation where a high level of heat output from computer equipment and occupants can be concentrated in particular areas which are also subject to intermittent usage. It was therefore apparent that the air conditioning system would be required to be capable of responding to very dynamic thermal loads imposed by building fabric and the occupancy profile. Additionally, the internal partition layouts will invariably change, determining the need for the air conditioning system to be economically re-configured accordingly.
These are as follows:
Figure M1: Chilled/Heating Water Systems
Figure M2: Water source heat pump systems
|System type||Capital cost range|
|Chilled/heating water systems||$280-$350/sq metre|
|Water source heat pump systems||$220-$280/sq metre|
|Air cooled reverse cycle systems||$160-$220/sq metre|
Air conditioning systems typically account for 10% -15% of the total building cost.
Interestingly, life cycle studies recently undertaken for tertiary education facilities favour air conditioning systems with a higher initial capital cost such as chilled water/heating water systems.
Figure M3: Air cooled reverse cycle split system packaged units
Cost of energy = 15%-20% of total owning and operating costTypically these percentages translate to energy costs of the order of $10/sq metre -$14/sq metre per annum and technical maintenance costs of the order of $8/sq metre -$12/sq metre per annum, thus totalling $18/sq metre -$26/sq metre per annum.
Technical maintenance = 4%-8% of total owning and operating costs
The use of water source heat pump system offers energy savings when compared to other systems by virtue of the low condensing temperatures at which the system operates at and the ability of the plant to offset cooling and heating requirements in different parts of the building without the injection of further energy from the thermal plant. The 2 pipe condenser water reticulation system is common for both cooling and heating systems and because of the temperature at which the system operates, insulation of the pipework is not necessary thus removing a high cost and long term maintenance element from the project. As heating and cooling can take place in different units simultaneously, heat is either taken from or rejected to the condenser water system hence making the total system relatively energy efficient.
With a chilled water system' insulated pipework is reticulated to all cooling coils located in fan coil units throughout the building. Heating is achieved by a separate insulated reticulation system circulating hot water from a central boiler to heating coils in the fan coil units. This system requires 4 pipes, all of which are insulated. It also requires substantially more plant room space As previously described water source heat pump systems generally incorporate cooling towers and boilers to maintain the condenser water pipework loop within the range of temperatures over which water cooled air conditioning units can operate.
One of the disadvantages of such systems is that cooling towers require significant space, consume substantial energy to operate and require careful ongoing maintenance associated with water treatment systems to eliminate the risk of Legionella. Significant operating and maintenance costs are also attributable to the operation of heating hot water boilers associated with water source heat pump systems. However, investigation into the seasonal variations in the temperature of the Port River indicated that the river water remains within the temperature range of 8-26 degrees Celsius which satisfies the temperature requirements for a water source heat pump condenser water loop. Thus, by drawing water from the Port River to act as cooling water for the air conditioning system, the necessity to provide a cooling tower and boiler system was eliminated.
With respect to system flexibility, it was evident that any attempt to configure the air conditioning system to meet the requirements of the specific fitout immediately proposed would have the potential to restrict future flexibility. The air conditioning system was therefore designed on a block basis in which the particular thermal requirements determined by the building orientation are satisfied by providing independent perimeter zones served by separate air conditioning units and the remaining internal zones are independently served in each block.
This zoning arrangement is illustrated on the diagram - Figure M4. The air distribution systems were also designed for maximum flexibility by incorporating solid insulated sheet metal main distribution ducts and flexible insulated duct work to each ceiling mounted supply air diffuser. This configuration can accommodate minor partition changes by simply relocating the supply air diffusers to suit the space layout. More significant changes may require additional supply air diffusers to be installed, at relatively minor cost.
Figure M4: Port Adelaide Campus air conditioning zones
Changes to internal layouts may also necessitate re-balancing of the air quantities delivered to each area. However, as the building is served by a large number of relatively small capacity air conditioning units. re-balancing can be achieved in specific areas without adversely affecting the remainder of the building and at relatively minor cost. Furthermore. the return air for all areas is routed back to the plant rooms via the ceiling spaces. As the air is relieved from the occupied space via slots built into the light fittings, no modifications are required to the return air systems in the event of internal planning changes. The water source heat pump air conditioning system was installed at a cost of $228/sq metre.
In summary, we believe that by careful consideration of the client brief and close liaison with the Architect and project team a cost effective and flexible air conditioning solution has been achieved.
As a result, distribution switchboards have become more spatially demanding due to the increased requirement for power outlets. Until the advent of computer based workstations, it was common practice to provide switchboard capacities to cater for I circuit per 20sq metre of useable floor space. Currently, however, each workstation is generally provided with at least one double GPO for computer use and one for general use, leading to a doubling of previous desirable capacity. Further space is required tor lighting controllers, meters and other ancillary equipment. The above factors combine to a more appropriate design capacity of at least 1 circuit breaker space per 10sq metre of useable floor space. The spatial allocation required for switchboards has therefore increased significantly.
Similarly, due to the increased density of services, the space required tor wiring systems has become a more significant factor in building design and must be considered early in the design process.
With respect to lighting, the fluorescent tube has for many years been. and will continue to be tor the foreseeable future. the dominant lighting source in both commercial and educational office type environments.
Other sources, such as metal halide, mercury vapour, high pressure sodium, extra low voltage and compact fluorescent, have been applied but not generally been successful for a variety of reasons including glare control, capital cost, colour rendition and efficiency.
The major developments in recent years are the introduction of the triphosphor fluorescent tube, with greater efficiency and colour rendition, and the ultra low brightness (ULB) louvre. The latter consists of a grid of deep cell high purity aluminium blades which provide the excellent glare control required for extended working with computer screens whilst achieving high efficiency. However, the greater ceiling depth of 150 mm - 175 mm required for these louvres compared with conventional prismatic diffuser of 100 mm - 125 mm has placed further restraints on building design by increasing the required ceiling to slab height.
Apart from wide acceptance of ULB louvres, the major trend in interior lighting has been toward the incorporation of energy saving controls. These include:
A further rapidly developing area is that of security. As vandalism and commercial espionage becomes more prevalent, the installation of electronic access control is increasingly being included in development briefs. Consideration therefore needs to be given to the impact of traffic routes, lock types, detectors and wiring paths on the building fabric.
Obviously, then, the requirements of Electrical Services equipment and wiring systems play a significant part in the development of building design and require early consideration to ensure adequate provision is made.
Also, as the Electrical Services installation is a significant capital investment, commonly 8 -10% of the overall cost of a facility, it is imperative that functional requirements are addressed at an early stage to ensure that adequate capacities are provided tor expansion into the future.
Submains cables to the various load centres are run on well defined routes on cable tray in the accessible ceiling space of the ground floor to serve both floors of the two storey building. All submains incorporate at least 25% spare capacity above known requirements and utilise less than 50% of the installed cable tray space.
The submain cables feed miniature circuit breaker distribution switchboards strategically located, as far as possible, at load centres. The use of circuit breaker protection at these switchboards was adopted to enable rapid restoration of power by non technical personnel in the event of overloading and tripping of a circuit. The initial design of the switchboards incorporated between 25-30% spare space above initial requirements. This allowance proved adequate in most cases as fit-out needs became known. However, in a number of instances, where switchboard capacity was exceeded during fit-out, the incorporation of spare space within the switchboard cupboards proved invaluable, enabling the installation of supplementary switchboards. However, the shortfall in a few isolated instances suggests that 50% spare switchboard space should be strongly considered. In addition, switchboards should be located, as far as possible, in accessible corridor spaces for ease of maintenance and to minimise disruption in teaching spaces.
A further aspect incorporated into the switchboards, to address the safety requirements of the brief, was residual current device, or earth leakage, protection to all general purpose power circuits. This form of protection will interrupt power in the event that persons contact live conductors, causing currents through the body sufficient to kill or seriously injure, but not necessarily operate a conventional circuit breaker.
By way of illustration, figure E-1 demonstrates in simplified form, the principle of the design utilised at Port Adelaide. As can be seen, the system is simple in concept. The result, however, is great reliability and flexibility due, in no small part to the spare capacity and accessible installation methods used.
To assist in reliability in the information technology environment, all computer workstations and peripherals are provided with power on dedicated cables which supply no other type of equipment.
Thus, the electrical disturbances caused by the operation of equipment such as photocopiers and microwaves are isolated, as far as possible, from effecting computing devices. All power outlets intended for computer only use are distinctly identified to reduce the risk of connection of inappropriate equipment to these circuits.
Figure E-1: Power reticulation infrastructure block diagram
Being connected by hard wired copper conductor cable and installed by fixing to hard surfaces, only limited flexibility is attainable in consideration of potential power outlet relocation. Accordingly, there will always be some disruption and fabric damage to be repaired when a power installation is altered. However, at Port Adelaide, a conscious decision was taken to install cabling in a manner which would minimise such damage by making relocations as simple as possible.
Many methods have been attempted over the years to solve difficulties in wiring to workstation power and communications outlets. False floors have fallen into disfavour in all but heavily serviced central computing facilities due to high capital costs, increased floor to floor heights, cable management failure, tile damage and limitations in workstation location to avoid supports. The use of ceiling spaces on the floor below and penetrating slabs to workstations is restrictive, disruptive to users, inflexible and. potentially, structurally unsound. In floor ducting, popular in the early 1980s, suffers from cable de-rating due to bunching, restricted access, inflexibility and capital costs.
Accordingly, the approach adopted at Port Adelaide maximises the use of ceiling spaces for wiring, reticulating to workstations via demountable partitions, column conduit access, multiple compartment skirting ducts and integral workstation ducting. Where necessary, service columns are used to drop to workstations located remote from other wiring paths.
As a result, it is relatively simple to access and reposition wiring without major damage.
This aspect was shown to be effective during the fit-out at Port Adelaide, particularly within Block A, where the total function and Electrical requirements changed dramatically. The design solution adopted, although the rework was substantial, enabled rearrangement within a tight time frame and without excessive drama.
To maximise flexibility, all recessed fluorescent luminaires are connected by flexible cord and plug to facilitate relocation in the event of refurbishment. As compared with hard wired systems, which must be disconnected, relocated and reconnected by an electrician, the flex and plug solution allows unqualified personnel to simply unplug a luminaire, shift it and plug back in. This method is becoming the accepted norm for all commercial interiors.
Similarly, active wiring is taken to all lights rather than merely switchwires. This approach enables switching modifications with only minor rearrangement of wiring in the event of refurbishment or rearrangement.
Access control consists, as the name implies, of means of limiting entry to a facility or portions of the facility. This may be achieved by manual key locking or electric locking. Over the past decade, increases to the perceived threat to facilities due to vandalism, theft, espionage and other nefarious reasons has led to far greater use of electric locking. Control may be achieved by the use of cipher key pads or a variety of different styles of card readers, with different access codes issued for different users, time frames or areas.
The design of any access control system, from the simplest single door controller to the most complex multi level multi user system, must be carefully designed, not only to provide a level of security appropriate to the threat assessment but to ensure that authorised movements through a facility are not unduly impeded. This requires consideration of every controlled point to determine the components and controls needed to best achieve the necessary functions.
Loosely related to access control, intruder detection is provided to generate alarms should unauthorised persons be within or adjacent the secured facility. Devices include movement detectors (passive infrared, ultrasonic, microwave), trip wires, photo-electric beams, glass break detectors and pressure mats. Perimeter door lock tongue sense switches and reed switches. if provided, may be incorporated into the intruder detection system. Control is most commonly by the use of either key switches or cipher key pads. However, interface control with an access control system may also be incorporated if required.
The most recent innovation in intruder detection is the use of closed circuit television video motion detection. Such systems are used for surveillance of selected areas and are configured to record the detection of a change in the field of view, using either video cassette recorders, computer hard disks or both. However, the cost of such systems generally restricts their use to installations with perceived high risk and must be carefully designed to attain maximum cost effectiveness.
At Port Adelaide, access control is achieved by the use of keypad controlled electronically locked doors at focal entries, with other entries being manually locked and alarmed. All spaces with external windows, or accessible from an uncontrolled space, are provided with passive infrared motion detection to detect unauthorised entry. The system as a whole is capable of local configuration for authorised personnel and is remotely monitored.
Project development must include an early phase for design team consultation to ensure that the final product incorporates sufficient capacity, flexibility and reliability to meet user requirements for many years, thereby avoiding premature obsolescence.
Data cabling was also of copper conductor, but used a variety of different constructions, the most common of which are coaxial ethernet and IBM Type I Token Ring. Other vendor specific wiring systems abound, the most important limiting factor being that none was compatible with any other. A further limiting factor was the use of a "plug in" bus system which resulted in protracted total loss of all communications in the event of a breakdown anywhere in the backbone system. A block diagram of a typical bus based system illustrating the effect of cable breakdown is shown at figure C1.
Figure C1: Bus communications cabling
In order to address these problems, the American Electronic Industry Association (EIA) developed the TSB 40 standard which allowed transmission of token ring ethernet, ISDN, video and voice traffic over the same type of cable. This standard has now been adopted by Australian Standards and International Standards Organisation, and being based on a radial or "star" configuration, allows all workstations to operate independently. A block diagram of a typical system of this type is shown at figure C2.
Figure C2: Star communications cabling
This type of medium is now becoming the standard for workstation cabling. Being only a relatively recent innovation, it is unlikely that any existing buildings in excess of 5 years old would be able to meet current standards.
Whether in copper or fibre optic cable. transmission links are installed as radial lines, or in a star topology, from the voice and/or data Communications Centre to communications closets strategically located in work areas. These closets house the active equipment necessary for communication with the workstations and also plug in patch panels to enable allocation of any workstation outlet to any Communications Centre port. This equipment is generally rack mounted to facilitate additions and alterations.
In the case of South Australian Colleges, the use of Synoptics Hubs and Cisco Routers has been adopted as being best suited to the operating environment of the user groups. This equipment has proven to be both reliable and cost effective over time and copes well for a system which is distributed both within campus areas and across the state using Telecom land lines.
Data traffic for Administration and Educational functions has been deliberately separated over the backbone cabling and hubs to minimise congestion and increase security. However, by the use of patch panels, any communications workstation outlet can be assigned to either Administration or Educational use.
Facilities are also available for access to centralised data processing facilities by remote or "home station" users by use of a personnel computer and modem link. This allows students (and staff) access to data from any location provided correct access codes are utilised. With the trend toward student learning independence, use of such facilities will almost certainly accelerate in the future.
With advances in cable technology. UTP cables are now available which will operate at speeds up to 100 MHz, known as category 5 grade cables. The cost of this level of cable has now reduced to the point where the use of lower grade cables is not considered cost effective, particularly with respect to the capacity to cater for advances in computer technology.
Similarly, the initial cost to install a dense system of communications outlets is low compared with retrofitting of additional outlets in a facility. Consequently, the technique of "flood wiring" which provides at least 2 outlets to each potential workstation is becoming accepted practice, and has been generally adopted at both Port Adelaide and Onkaparinga campuses.
Development of infrared and radio communications to replace the need to plug in to wall outlets is proceeding, particularly for use with portable laptop computers. However, the number of devices which can simultaneously use such systems is currently limited due to interference problems. In addition, there are Occupational Health Safety and Welfare concerns associated with the use of radio frequency interfaces, similar to those presently being investigated with mobile telephones. It is therefore unlikely that any significant changes to present procedures will occur within at least the next 10 years with the exception of limited, special purpose applications.
An illustration of the power and communications facilities in a typical open plan room is shown at figure C3.
Figure C3: Typical room power and communications arrangement
Present operating systems at Onkaparinga require 4 fibre optic cores for each of the Administration and Educational networks. Accordingly, 12 core fibre optic cables have been installed initially to provide 50% redundancy to cater tor expansion. Backbone cabling is installed on dedicated cable trays on well defined accessible routes between cable centres to facilitate the future installation of additional cabling if required. At least 100% spare cable tray capacity has been provided in each location.
Similarly, spare space is provided within the communications closets where the networking equipment and patch panels are housed. Initially, only one 18 inch rack, with an overall width of approximately 590 mm, is required at each location. The use of 1400 mm wide communications closets is now encouraged to enable future installation of an additional rack or system support equipment such as uninterruptible power supplies and line conditioners to enhance power supply reliability.
With respect to workstation cabling, which is necessarily hard wired from the communications centres, flood wiring is generally adopted to maximise flexibility. Nevertheless, if changes are required, replacement of portions of the workstation cabling will be necessary. Although unavoidable, the effect of this work on the building fabric will be minimised by adopting maximum use of ceiling space, demountable partitions, service columns, workstation ducts and skirting ducts to achieve simple, accessible wiring paths as described more fully in the Electrical Services portion of this paper.
Maximum accessibility for additional wiring and the initial provision of redundancy will ensure the installation of additional and modification of existing cabling without undue imposition.
This trend will allow the installation of system independent cabling which will remain valid for at least the next 15-20 years.
|Author: Henrique J Harding, Bestec Pty Ltd. 144 Gawler Place, Adelaide SA 5000.
Please cite as: Harding, H. J. (1994). The built technology of the learning environment. In J. Steele and J. G. Hedberg (eds), Learning Environment Technology: Selected papers from LETA 94, 81-91. Canberra: AJET Publications. http://www.aset.org.au/confs/edtech94/ak/harding.html