Particular Specification - Part 36
Particular Specification
for Air-conditioning Installation
1.General Requirements
1.1The scope of this installations includes the design, supply, installation, commissioning, testing and maintenance of the entire air-conditioning installation as listed in the Works Orders under this Contract and described in this Particular Specification unless otherwise specified.
1.2The Contractor shall employ a specialist sub-contractor from "List of Approved Suppliers of Materials and Specialist Contractors for Public Works: Air-conditioning Installations (Group II - Contracts of Any Value)" (hereinafter referred to as Specialist Air-conditioning Sub-contractor) to carry out the Air-conditioning Installations as described in this Particular Specification.
1.3All materials and workmanship for the air-conditioning installation shall comply with this Particular Specification, General Specification for Air Conditioning, Refrigeration, Ventilation and Central Monitoring and Control System Installation in Government Buildings of the Hong Kong Special Administration Region (hereinafter referred as A/C General Specification or A/C GS), and all relevant sections of the following specifications, and code of practice and all current amendments thereto issued.
Unless otherwise specified, all design shall be in accordance with the recommendations in the Guides and Standards published by the Chartered Institution of Building Services Engineers, (U.K.) and the American Society of Heating, Refrigerating and Air Conditioning Engineers (U.S.A.) and the Code of Practice for Energy Efficiency of Air Conditioning Installations issued by EMSD.
1.4Sample Board
Within 4 weeks after award of the Contract, the Contractor shall submit a common sample board containing samples of general items for the Architect’s approval.
The Contractor shall also submit sample board containing samples of specific items other than those in the common sample board for individual Works Order as required by the Architect for approval before the commencement of installation work.
1.5 Testing Equipment
The Contractor shall provide the calibrated equipment and the associated calibration records with validate period not less than 10 months, and as stated in the Particular Specification for Supply of Inspection, Measurement and Test Equipment in the Contract.
1.6Commissioning and Testing
The Contractor shall commission and test the Air Conditioning and Mechanical Ventilation Installation in compliance with Section A9 of the Air Conditioning General Specification and the Testing and Commissioning Procedures No. 1, 2 and 6 for Air Conditioning, Refrigeration, Ventilation and Control Systems, Electrical Installation and Low Voltage Cubicle Switchboard Installation issued by the Building Services Branch, Architectural Services Department. The Contractor shall follow the manufacturer’s recommendation for the commissioning and testing of any proprietary system and product included in the installation.
All submissions as required under these procedures are to be submitted to the Architect for approval at least 28 days prior to the commencement of testing and commissioning work.
2.Specific Requirements
2.1Date Compliance
No value for current or future date/time will cause any interruption to operation which will affect the performance or functionality of all or part of the systems and/or equipment (including any supplied or supported embedded systems, hardware, software, firmware, microcode and programmes).
2.2Air-conditioning Installation Design Conditions
Unless otherwise specified, design conditions for all air-conditioned areas shall be :
Summer Design ConditionsWinter Design Conditions
Outdoor33oC db., 66% Sat.10oC db., 40% Sat.
Indoor25.5oC db., 54% Sat.20oC db., 50% Sat.
Unless otherwise specified, individual control of air-conditioning shall be provided for each room/compartment of the building/site wherever possible.
The Contractor shall base on the air conditioning loading of the accommodation for selection of the equipment. The selected equipment shall have a 10% spare capacity for future need.
2.3 Refrigerant Used
The refrigerant used for the air-conditioning equipment shall be zero Ozone Depletion Potential (zero ODP) unless otherwise specified.
2.4Ventilation Installation
Mechanical ventilation system shall be provided as specified in the Works Order and in the specified drawings. The equipment selected shall meet the recommended rates of air change in the international standards such as those guides and standards from CIBSE and ASHRAE.
Exhaust air grilles shall be kept away from any air intake louvers or at different orientations.
2.5Selection of Equipment
Selection of equipment shall be based on information & design criteria given in this Specification and the information given in the A/C General Specification. The Contractor shall ensure that the space provided in each site/building shall be adequate for installing and maintaining the offered equipment.
2.6Noise Level
Noise emitted from all air-conditioning and ventilation equipment to the exterior of the building shall be within the acceptable noise levels in compliance with the Noise Control Ordinance, or acoustic treatment shall be provided to achieve the compliance.
The noise levels inside the accommodation shall meet with the recommendations in the CIBSE Guide.
2.7Vibration Isolation
The Contractor shall supply and install anti-vibration mountings, flexible connectors and mounting framework as shown on the drawings and in accordance with Sections B8 and C8 of the relevant clauses in the A/C General Specification where applicable. Anti-vibration mountings and flexible connectors shall be provided for all chillers, heat pumps, water pumps, air handling units, fan coils, fans, unitary air conditioner and elsewhere when necessary.
The Contractor shall ensure that the locations of vibration isolators for the equipment are properly designed and selected such that the equipment will be in level and the required static deflection can be obtained.
The Contractor shall select isolators based on the actual equipment offered and shall submit the design calculation for approval.
All floor-standing equipment shall be completed with 6 mm thick neoprene acoustical friction pad between the base-plate and the support.
Flexible pipe connectors and duct connectors shall be provided at both inlets and outlets of the air handling units, fan coil units and ventilation fans where applicable
3. Additional Requirements
3.1Kitchen Exhaust System
The kitchen exhaust system shall be in compliance with the requirements of the Air Pollution Control (Furnaces, Ovens and Chimneys) (Installation and Alteration) Regulations under the Air Pollution Control Ordinance.
(A)Grease Filter Type Kitchen Exhaust Hood
1)The exhaust hood shall be made of 316 stainless steel sheet of hairline finish and shall comply with Clause B2.7 of the relevant clauses in the Air Conditioning General Specification.
2)The exhaust hood shall be constructed of not less than 1.2 mm thick stainless steel sheets with flushed fluorescent lighting fittings having heat resistant wired glass diffusers. All joints and seams shall be welded for grease and water-tight with exposed welds ground and polished.
3)Grease filters shall be washable and shall be generally as specified in Sections B1 & C1of Air Conditioning General Specification.
4)Washing facilities including one set of duplicating cleaning tanks and cleaning detergent shall be provided as specified in Clause 12.08 of the relevant clauses in the AirAir Conditioning General Specification.
(B)Water Scrubbing Type Kitchen Exhaust Hood System
1)The exhaust hood shall be designed to effectively remove the hot, grease-laden air, lint, odors, vapour, smoke, etc. from the cooking equipment through an air inlet opening above, and parallel to the top of each cooking equipment item being ventilated.
2)The exhaust hood system shall be provided with rotary baffles, inspection door, non-return valve, suction line strainer, stop valve and by-pass valve.
3)The exhaust hood system shall be complete with one supply water tank, one control panel with two built-in circulating pumps (i.e. one duty and one standby), discharge pressure gauges, non-return valves, valves, oil filter, filling water strainer, pressure reducing valve, detergent injection valve; filling water pressure gauge, safety pressure switch, solenoid valve, pressure by-pass valves, thermal cutout and grease removing liquid detergent.
4)The control panel shall be of electronic type and complete with ON-OFF switch, line protection fuse, operation timer and starting switch, procedure signal lamps (for water detergent and pump) and fault indication lamps (for circulation water pressure and temperature and detergent). The supply and exhaust fan shall also be interconnected with the system so that the system will operate when the fans are switched on. A delay timer shall be incorporated to allow the supply and exhaust fans to continue running up to five minutes after the circulating pump is switched off. A key switch should also be provided to by-pass the system when the water recirculation system is at fault.
5)The hot, grease-laden air, lint, odors, smoke, etc., in the air stream shall enter the ventilator slot opening at a high velocity. The air shall travel through a jet-spray of cool water and detergent, emulsifying the grease and contaminates in the air drawn into the lower plenum, then up into the rotating baffles. The baffles shall remove the grease, moisture, and other impurities by centrifugal action allowing the clean, cool air to be exhausted through the upper plenum, duct system, and into the outside atmosphere.
6)A balance shall be maintained between the movement of air into the lower plenum and through the rotating baffles above to provide a uniform flow along the entire length of the ventilator.
7)The functions of the unit shall be automatically controlled by a self-contained control panel. The control panel shall continuously recirculate the detergent saturated cool water to provide a constant water spray mist and add water as needed and shall automatically cycle at present intervals to flush the system and refill detergent laden new water, with thermo-switch safeguard, to provide a constant supply of water in the event of the water temperature rise above 80º in the reservoir.
8)The self-contained unit shall consist of stainless steel exhaust hood with first main inlet and second inlet with duct collar, the automatic control panel, water recirculating system, rotating baffles, manifold and jet nozzles.
9)Stainless steel exhaust hood shall be of the following construction :-
Construction
Exhaust hoods shall be constructed of not less than 1.2 mm thick 316 stainless steel sheet of hairline finish. All joints and seams shall be welded for grease and water-tight with exposed welds ground and polished.
Control panel
The automatic control panel made of ANSI 316 stainless steel shall effectively control all of the functions of the unit. The body of the control panel shall be completely removable for access. The overall dimensions of the self-contained control unit and pump and fittings shall be completely assembled and shall be secured within the cabinet ready to receive plumbing and electrical field connections. The internal electrical wiring shall be brought to one common terminal block.
10)The control unit shall perform the following functions automatically :-
a)Continuously recirculate the water contained with the ventilator at a fixed, constant pressure.
b)Flush soiled water and refill with fresh water and detergent at fixed intervals.
c)Compensate for any loss of water and evaporation. A pressure switch shall de-energize the pumping unit should serious loss of water occur.
d)Automatic Water Recirculating
The exhaust unit shall be engineered to have a supply of water suitable for the particular model and length of the ventilator, circulated by means of a pumping unit at a fixed pressure, through a closed system complete with a stainless steel water supply tank suitably sized. A line strainer and filter unit shall be located between the pumping unit and the ventilator on the return side. The strainer and filter unit shall be positioned for easy access and cleaning. Particular care shall be taken in the design of nozzle to form mist, eliminate water splash over or excessive carry over.
e)Rotation Baffles
The baffles rotating through the force of the passing air shall, by centrifugal action, catch and hurl the emulsified droplets of grease and moisture laterally from the air stream. The baffles shall be constructed of an aluminum alloy especially selected for this application and telfon coated. They shall be balanced to spin freely on stainless steel ball bearings. The baffle units shall be removable without tools.
f)Manifold & Jet Spray Nozzles
The manifold shall be constructed of stainless steel, type 316, brass nozzles and copper purge line and shall be provided to effectively produce a blanket of detergent-charged water in a heavy spray mist in the lower plenum area, so that all the exhausted grease-leaden hot air, lint, smoke, odors, etc. in the air stream must pass through the spray mist. The manifold shall extend the entire length of the exhaust hood. The nozzle shall be spaced to provide even water curtain and shall be removable without use of tools.
g)Lighting
Adequate flushed fluorescent lighting fittings having heat resistant wired glass diffusers shall be provided inside the hood for illumination of cooking.
h)Air requirements
The average throat velocity shall be 5 m/s, requiring 380 l/s per linear metre of intake throat opening.
i)Static pressure
The statistic pressure at duct take-off collar shall not be less than 25 mm water gauge.
3.2Water Scrubber System
(A)General
(a)Horizontal Cross Flow Fibreglass Reinforced Polyester (FRP) Foul Air Water Scrubber System shall be provided to the exhaust systems for central air treatment of odour, gas, liquid and solid contaminants prior discharge to outside of the building. Three of the major components in the RCP application are hydrogen sulphide, mercaptans and aldehydes. Oil mist will be present in the foul air source of the Cooked Food Centre. The specification requirements as shown on Clause A5.5.6 of shall refer to relevant clauses in the A/C GS.
The arrangement of the combined exhaust and scrubbing systems shall be as shown on Drawings.
Other alternative construction material with equivalent or better corrosion resistance, mechanical strength and crucial properties such as the UV stabilization may be proposed for approval by the Architect subject to full substantiation by providing technical information, test certificates of recognised authorities or testing organisations, international standards, etc. together with the tender.
(b)Allow for splitting the whole water scrubber system into two parts, as required by the Works Order, with chemical tank and feed pumps to be located at different location from the water scrubbing fan unit. The rates in the Schedule of Rates for whole water scrubber system unit will still apply but with the interconnecting pipeworks between the two parts to be measured separately.
(c)Performance Specification
i)Application - removal of odour, gas, liquid and solid contaminants of foul air sources at the Refuse Collection Point, Poultry and Cooked Food Stalls through water scrubbing, absorption and chemical oxidation of malodorous compounds in the exhausted air.
ii)Odour Removal Efficiency - 98% based on hydrogen sulphide at 25 ppm. Removal efficiency of mercaptans and aldehydes shall be given by the Contractor with substantiation.
iii)Oil Mist Elimination Efficiency - for Cooked Food Stall scrubber - 98% based on oil mist of 4 microns or larger in size.
iv)Scrubber System Data
Design for local outdoor weather conditions.
Design air flow rate - from 5.5 to 14.5 m3/s
Maximum static pressure loss at design flow rate - 500 Pa
Mist eliminator efficiency - 99% of the entrained moisture in exhaust air
v)Chemical Selected for Operation
- sodium hydroxide and sodium hypochlorite
(d)A detail design report on the offered water scrubber system shall be submitted together with the tender for assessment and approval by the Architect. Full technical details shall be provided including at least the followings :-
i)Certificates and documentary evidence of excellent chemical resistance of all material, component and equipments adopted for the operation with the selected chemicals and specified application.
ii)Detail information and calculations on :-
-chemical reaction formulation and design criteria;
-selection of the type and depth of packing, mist eliminators, nozzles, etc. with manufacturer's test data or recognised standards;
-scrubber overall height & dimensions, packing depth, mist eliminators depth, etc.;
-selection of water recycle pump head and flow rate in accordance to the system design and configuration to meet specified performance;
-design of maximum air velocity at specified air flow rate and selection of fan duties with respect to the design flow and pressure drop in ductworks, fittings, silencers, scrubber section, etc.;