Refurbishment of Jessie Street Centre

Transcription

1 Refurbishment of Jessie Street Centre 2 12 Macquarie Street, Parramatta, New South Wales Dalton Veitch, mechanical services engineer, Wood & Grieve Engineers, Sydney PROJECT OVERVIEW Commencement Jessie Street Centre (JSC) is an office complex situated in the Parramatta business district. It was completed in 1987, is currently owned and managed by Brookfield Multiplex (BM), and had the original services until this refurbishment. At the commencement of this refurbishment project, the client engaged Wood & Grieve Engineers (WGE) to provide a Life Cycle Upgrade Report to identify actions required to meet their objectives for the building. These objectives were: Efficiency and quality improvements to achieve a NABERS design rating of 4.5 Stars, a Green Star design rating of 4 Stars, and the provision of an environment for tenants which was considered high quality, while minimising energy, water, and gas usage. Services upgrades commensurate with the Property Council of Australia A Grade level for type and location of existing building. Refurbishment for a 20-year plant life. Plant redundancy as far as practicable. Upgrade of particular essential services, including conversion of the original smoke purge system to a zone pressurisation system, and re-commissioning of the stair pressurisation systems. To address these aims, BM engaged WGE s Environmentally Sustainable Design (ESD) Department to carry out energy modelling of the existing building and systems to provide a strategy for achieving the functional objectives. JSC is a multi-storey office complex with reinforced concrete structure and facades predominantly of glazed curtain wall construction. It has the following characteristics: single-level belowground car park (300-plus spaces) plus loading dock; above-ground entry foyer with a six-storey atrium (not open to the floors); South Wing with five office floors; North Wing with seven office floors; main tower with 20 office floors; varying floor plates with podium levels around 5,500 sq m each and tower levels around 1,800 sq m each. There is gross lettable area of around 55,000 sq m. Jessie Street Centre external facade. The new calculated cooling load for central plant is 6000 kwr and there are currently three x 2,200 kwr chillers installed. The system comprised four main AHU plant rooms serving North Wing, South 30 Eco li b r i u m OC TO B E R

2 Wing, and Main Tower, including a major plantroom on level two (L2) also housing the chillers and pumps, while cooling towers and heating water boilers were situated at the top of the building (main tower L21), with duct and pipe risers within the building cores. The air conditioning was conventional multi-storey design, using chillers, cooling towers, and built-up variable air volume (VAV) air handling units (AHUs) with ducted supply air and an older type building monitoring and control system (BMCS). The floor air conditioning supply used fan-assisted VAV boxes for the centre zones, and non-fan VAV boxes for the perimeter zones, supplying via light air troffers. The AHUs are zoned North, West, South, East, and Centre, with vertical risers connecting zones of similar orientation and solar load characteristics. Various office tenancies on Level 1 (entry level) were air conditioned by fan coil units using chilled and hot water. These systems did not have variable air volume or outside air economy cycle. A number of specific areas that could require cooling beyond normal office hours had air conditioning via fan coil Energy modelling was carried out on the existing building. units connected to the base building chilled water system, requiring operation of a reasonably large low load chiller, plus pumps and cooling tower, after hours. These included lift motor rooms, and various electrical rooms. Flowtech AIR CONDITIONING Independent Commissioning Agents Commissioning Management Air & Water Balancing Surveys of Existing Plant & Buildings Dilapidation & Performance Reports Retro-Commissioning Existing Buildings AS1851 Essential Services Maintenance NEBB Certification Preventative Maintenance Pressure Testing: Clean Rooms & Ducting International Projects Unit 1/54 Nealdon Drive Meadowbrook Brisbane Qld 4131 Tel: Fax: admin@f lowtech.com.au markgilby@f lowtech.com.au lowtechac.com.au OC TO B E R Eco li b r i u m 31

3 The building had been maintained to a standard considered well above average, and existing systems were generally in excellent condition. Where systems or components could be reused without sacrifice of efficiency they were retained. The client was well informed, with experienced and knowledgeable personnel providing design direction and decisions throughout the design and construction process. Services contractors were well suited to the nature of the project, and were flexible, cooperative, communicative and resourceful. REFURBISHMENT WORKS To achieve the desired Green Star rating, many works were undertaken involving all building services. Various parts of the building were refurbished, and a comprehensive BMCS installed to monitor and control building operation. The focus in the following section of this article is on some of the air conditioning works and the approach taken. Challenges There were two significant challenges for the project. One was that the building was existing. Many aspects could not be changed or designed to suit current objectives as a new building could be (e.g. orientation, structure, glazing, plant locations, car parking and other amenities). This provided significant limitations compared to green field designs. Second, the building was tenanted, a status the client wished to retain. Therefore, JSC needed to remain fully occupied with services functioning to an acceptable level throughout the refurbishment. The challenges posed limitations on which facets could be amended, as well The centre was fully occupied throughout the refurbishment. as restraints on feasibility of works, while keeping the building operational. All challenges were met and overcome. Strengths In addition to some challenges, the project had much going for it. The building had an original design that could be considered reasonably good for the date of construction in terms of architecture (appearance and suitability for purpose), provision of tenant services, and energy efficiency. It incorporated well zoned air conditioning with economy cycles, provision of tenant condenser water and tenant supplementary outside air. The building was double glazed, with internal blinds. Air conditioning system refurbishment The approach to achieve the desired efficiency and high-quality refurbishment for the air conditioning systems was determined by the mechanical services consultants and implemented. This involved an extensive replacement and refurbishment program. Old full-load and part-load chiller sets were replaced with new, high-efficiency chiller sets supplying chilled water at lower than typical temperature. Modelling showed that over one year it would be more efficient for the building to save on fan power by using lower supply air volumes at lower temperature, driving efficient chillers and cooling towers slightly harder instead. AHU cooling coils were replaced with new cooling coils matched to low temperature chilled water (4.5 C entering the coil) and providing low temperature supply air (8.5 C leaving the air handling unit). AHU heating coils were single row (minimal air resistance, which would reduce further as air flows were lowered) and typically in excellent condition, so were retained, with new control valves. 32 Eco li b r i u m OC TO B E R

4 VAV boxes were replaced with all new boxes suitably insulated for the low supply air temperature (without any fan-assisted boxes) and sized to handle final lower supply air flows (at low temperature) but able to handle interim higher air flows while refurbishment was in process. On any given AHU system, changeover was staged such that floors were changed over one at a time, so there was an interim mix. New swirl diffusers were installed in ceilings, providing adequate air mixing and thermal comfort with the VAV system and low temperature supply air. Additionally, the new T5 light fittings being installed would not perform well with low temperature supply air troffers fitted to them. New main stainless steel cooling towers were installed on a new steel support structure on top of the south wing, Level 6. This installation allowed room for four towers (three duty/one standby) and new risers down to the Level 2 chillers and pumps, with a minimal final changeover period. The existing old main cooling towers were in excellent condition and were retained on Level 21 for provision of tenant condenser water. All cooling tower fans have new variable speed drives. All fans were specified as being replaced with new fans, selected for efficiency, also having high-efficiency electric motors (refer to additional comments below). All pumps were replaced with new pumps to suit the required duties, with redundancy in most cases (e.g. four for three) with high-efficiency motors. The existing collection of variable speed drives of varying age and capability was replaced with new, higher efficiency drives, and almost all fans and pumps were powered via new drives complete with high level interface to the building monitoring and control system (BMCS). For the air distribution system, new motorised smoke dampers were added at the cores for both supply air take-offs and return air/smoke spill sub-ducts, to facilitate zone pressurisation. Damper control panels were installed on the floors to allow the smoke control logic to override the normal hours/after hours damper operation, in the event of a fire situation. New manual supply air balancing dampers were also added to supply take-offs for commissioning balancing of the risers. A new BMCS was installed throughout. It handles all services and requirements except security and lifts, which have dedicated control systems. This included all new sensors, new damper motors, new VAV box drives, and new control valves. Particular attention was paid to insulation of supply air ductwork, considering the low temperatures now involved. All existing thermal insulation in AHUs was checked to ensure good condition, with repairs/ replacement occurring where necessary. Exposed ductwork in plant rooms was clad with additional external insulation. It would have been difficult to replace the ductwork, with new ductwork having thicker internal insulation, and the NEW & IMPROVED EVAPODRY TRAY the complete solution The probe senses condensate that has accumulated in the tray and energises the heating element. When the probe senses the liquid has evaporated, the heating element is turned off. For information or a free quote, call us on or visit our website at Probe COFFS HARBOUR - HEAD OFFICE SYDNEY - MELBOURNE - BRISBANE ABN Pro Pipe Supplies Pty Ltd, Main Street, Beverly, SA5009 t: enquiries@propipesupplies.com.au OC TO B E R Eco li b r i u m 33

5 The six-storey atrium. duct runs were generally at heights that would avoid accidental damage to the added external insulation. The external insulation to ducts within the core shafts was practically inaccessible, and calculations showed heat gain in these areas to be tolerable, so duct insulation within the cores remained untouched. Specialist duct cleaning contractors were engaged to clean ductwork interiors as part of the refurbishment process. In the larger duct risers this sometimes necessitated abseiling down inside the duct from a top access panel. The existing mechanical services switchboards were either replaced or rebuilt using modern switchgear. The two existing heating water boilers were replaced with two new boilers of similar capacity to the old ones and boiler room ventilation upgraded. A new Fire Fan Control Panel with controls and indication for essential services (zone pressurisation, stair pressurisation, etc.) was integrated into the new FIB for the building. Note regarding AHU supply fans It should be noted that AHU supply fans (20 +) were specified to be replaced with smaller fans. However, as these are large centrifugal fans, removal and replacement from the multiple AHUs within the plant rooms would in many cases involve demolition of large areas of AHUs and leave patching afterwards. Additionally, these fans were assessed as being of high-quality manufacture and in excellent condition due to the maintenance regime. Therefore gross replacement could be counter-productive. A series of tests were run to check on the stability and performance of these fans at lower air quantities (i.e. VAV, but turning down from a lower maximum). Results were positive, and after fan curves were examined for individual fan efficiencies in their respective new operating regions, the outcome was that supply fans were generally retained. They were, however, refurbished with new bearings, new belt drives, new highefficiency motors, new spring mounts, and painted as necessary. Associated mechanical services elements Various other elements were integrated into the refurbishment. Outside air economy cycles were placed on all AHUs, using enthalpy control. CO 2 monitoring was allowed for on office floors, with a sensor placed in approximately every second temperature sensor. Floor shut-off provision for unoccupied floors, or after-hours operation of limited areas. Small cooling systems that would be used after hours, such as lift motor room cooling, or security room cooling, were taken off the main chilled water and changed to individual package units using tenant condenser water. This avoids chiller operation after hours for minor loads. Car park exhaust systems were made variable speed (new axial fans with VSDs), controlled via BMCS using input from CO and NO 2 sensors throughout the parking level. Side-stream filtration and automatic water treatment systems were added to the condenser water system to minimise bleed requirements and water usage. Tenant condenser water provision was increased to Property Council of Australia A Grade level. Motorised dampers on mechanical services plant, including smoke dampers, were replaced, bearing in mind the 20-year refurbishment aim, and were fitted with new drive motors to match the BMCS. The air conditioning infrastructure tender documentation was prepared by the mechanical services engineers as a number of self-contained separate packages. These individual packages included chilled water system, air handling units, essential services (stair pressurisation and smoke exhaust), tenant condenser water upgrade, BMCS, and heating water plant. Efficiency improvements At the commencement of the investigation, reporting, modelling, and design process in 2007, a full year s data (late 2004 to late 2005) was obtained on electrical and gas energy usage for Jessie Street Centre. With input on the building s floor area and hours of use, this equated to total energy consumption of 557MJ/m 2 or emissions of 110kgCO 2 /m 2. The simulation modeling estimated that after the proposed upgrade works the total energy usage would be 343MJ/ m 2 (reduced by 38% from 2004/2005) or 72kgCO 2 /m 2 (reduced by 34% from 2004/2005). The actual energy usage, to date, has indicated that the building performance is close to these predicted improvements. Points of interest for this refurbishment With an existing building, particular restrictions occur, sometimes requiring more lateral approaches. It would have been difficult, disruptive, and expensive to install new chilled water risers, from Level 2 chillers/pumps up to Level 21 plant room. Existing risers were 300mm diameter mild steel pipe, with chilled water running at about the maximum allowable velocity (based on tables of acceptable velocities re pipe erosion for the pipe material). Slightly more capacity was needed in the upgrade, so existing risers were assessed for corrosion (in situ) and appeared to be in excellent condition due, presumably, to effective water treatment. The decision was made to retain them, and the chilled water temperature split was increased to deliver the required capacity at the same flow rate. Pumps, chillers, and coils were then selected to suit the temperature split. Existing main cooling towers were situated in a notch in the side of the 34 Eco li b r i u m OC TO B E R

6 roof plantroom. They were constructed of stainless steel and were in excellent condition, so all options for achieving the required increased capacity (plus redundancy) using these existing towers were explored. However, this could not be achieved without serious disruption to the existing plant room, with many negative consequences. Therefore, an alternative location was found at a lower level (Level 6) on the roof of the south wing, and a full steel A typical ceiling, with swirl diffusers. platform erected above a concrete and membrane roof to handle the transfer of structural loads. This required a DA submission to Council, and surveying of another piping riser down the south wing from Level 6 to the car park, across the car park, down the southern driveway, and up into the Level 2 chiller plant room. This route was determined, and new piping installed as two 300 dia. pipes for flow, and two for return, to make handling the piping in limited spaces easier. Mild steel was used. The Jessie St Centre refurbishment at a glance Building details Owner/manager: Brookfield Multiplex Mechanical services engineers: Wood & Grieve Engineers ESD: Wood & Grieve Engineers Duct-cleaning: Clean Air Technologies Services contractors: Triple M Mechanical Services Equipment BMCS: Johnson Controls Chiller sets: Powerpax Swirl diffusers: Krantz Cooling towers: BAC VXT Compressors: Turbocor