BUILDING SERVICES BRANCH
TESTING AND COMMISSIONING
PROCEDURE NO. 1
FOR
AIR-CONDITIONING, REFRIGERATION,
VENTILATION AND CONTROL SYSTEMS
IN
GOVERNMENT BUILDINGS
HONG KONG
? HONG KONG SPECIAL ADMINISTRATIVE REGION GOVERNMENT
Building Services Branch
Architectural Services Department (2000 Edition)
COPYRIGHT
1. This Testing and Commissioning Procedure is solely compiled for use on Air-conditioning, Refrigeration, Ventilation and Control Systems in Government Buildings of the Hong Kong Special Administrative Region.
2. This Testing and Commissioning Procedure is copyrighted and all rights (including subsequent amendment) are reserved.
3. It is hereby declared that the procedure contained therein may not be pertinent or fully cover the Air-conditioning, Refrigeration, Ventilation and Control Systems carried out by other Government Departments or private sectors. Prior consent by the Director of Architectural Services must be obtained for adoption of this testing and commissioning procedure for Air-conditioning, Refrigeration, Ventilation and Control Systems of other nature or locations.
TABLE OF CONTENT
Page
1. Introduction 1
2. General Requirements 1
3. Testing and Inspection 2
4. Statutory Inspection/Commissioning 3
5. Calibrated Equipment 93
Appendix A Page
Testing and Commissioning Certificate on Air-conditioning, Refrigeration, Ventilation and Control Systems
Part 1 : Details of Project 1
Part 2 : Declaration 1
Part 3 : Items Inspected and Tested 2
3.1 The General Requirements as indicated in the T & C procedure have been complied with.
2
3.2 Precommissioning Checks 2
3.3 Setting to Work & Balancing 2
3.4 Comments 6
Part 4 : Test Record attached to the Test Certificate 7
4.1 General 7
4.2 Packaged Water Chillers 7
4.3 Air-Cooled Condensing Sets 8
4.4 Cooling Towers 9
4.5 Pumps (Medium) 10
4.6 Air Handling Units 11
TABLE OF CONTENT
Page
4.8 Ducts, Grilles, Diffusers etc. 13
4.9 Testing Equipment 14
Appendix B Page
Testing and Commissioning progress chart for Air-conditioning, Refrigeration, Ventilation and Control Systems
1
Appendix C Page
Flow Chart for Testing and Commissioning Procedure on Air-conditioning, Refrigeration, Ventilation and Control Systems
1
Figure 1 Example of Water Distribution System 2
Figure 2 Example of Air Distribution System 3
Figure 3 Example of Air Distribution Branch 3
Figure 4 Example of Low Velocity Supply Air System 4
B.S.B. Testing and Commissioning Procedure No. 1
Air-conditioning, Refrigeration, Ventilation and Control Systems
1. Introduction
1.1 This procedure is intended to lay down the minimum testing and commissioning requirements to be carried out by the Contractor on a new Air-conditioning, Refrigeration, Ventilation and Control Systems upon completion or on an existing Air-conditioning, Refrigeration, Ventilation and Control Systems after a major alteration. Additional testing and commissioning (T & C) requirements may be proposed by the Contractor as appropriate and agreed by the Project Building Services Engineer (PBSE), e.g. for special equipment supplied and/or installed by the Contractor.
1.2 This procedure is also written to facilitate the PBSE and Project Building Services Inspector (PBSI) in carrying out the following aspects of work with respect to T & C.
(i) To vet and approve the T & C procedures proposed and submitted by the Contractor.
(ii) To witness those T & C procedures as specified.
(iii) To receive the T & C certificate and other supporting data.
2. General Requirements
2.1 The Contractor shall submit the T&C procedures to the PBSE for approval. The submission shall be made at least one month before the commencement of T&C.
2.2 Where tests are required to be witnessed by the PBSE/PBSI, the Contractor shall give due advance notice (usually not less than three days) and provide details of date, time and type of tests to be performed.
2.3 Upon completion of such T & C procedure, the Contractor shall complete and sign a testing and commissioning certificate as Appendix A, to the effect that agreed T & C procedures have been duly carried out.
2.4 Before carrying out any test, the Contractor shall ensure that the installations comply with the statutory requirements and regulations.
2.5 Part of the testing & commissioning may be required to be carried out in Supplier’s premises in accordance with the provisions in the General/Particular Specification.
required to be carried out in parts or as a whole depending upon the status of the progress of work or as dictated by the requirements of the Contract. 2.7 It must be ensured that the personnel carrying out the tests are trained,
experienced commissioning engineers and for specialised items such as refrigeration plants, control equipment etc., these may be carried out by the manufacturers’ own T & C engineers if necessary.
3. Testing and Inspection
3.1 The requirements are in general as specified in the latest General Specification for Air-conditioning, Refrigeration, Ventilation and Control Systems issued by Building Services Branch of Architectural Services Department, herein after described as General Specification. If there is any discrepancy between this procedure and the General Specification, the General Specification shall take precedence.
3.2 The Contractor shall carry out the tests and inspections as shown in Part 3 and record the test results on Part 4 of Appendix A and as agreed between the Project BSE and the Contractor.
3.3 The Contractor shall provide all the necessary staff, labour, materials and equipment for a thorough test and examination of the installation.
3.4 The purpose of this T & C procedure is to provide the Contractor a guideline which would ensure that the building environmental systems produce the design objectives. It includes :
(i) The balance of air and water distribution.
(ii) The adjustment of total system to provide design quantities. (iii) The electrical measurement.
(iv) The verification of performance of all equipment and automatic controls.
(v) The sound and vibration measurement.
3.5 The objectives as outlined above can be accomplished by : (i) Checking installations for conformity to design.
(ii) Measurement and establishment of fluid quantities of the system as required to meet design specification.
(iii) Recording and reporting the results.
3.6 The procedure covers the following sections of testing & commissioning : (i) Preliminary checks
(ii) Setting to work and balancing the systems (iii) Recording of test data
4. Statutory Inspection/Commissioning
4.1 After the proper testing and commissioning of the Air-conditioning, Refrigeration, Ventilation and Control Systems, the Contractor shall notify the appropriate Authority, through the PBSE, on the completion of the installation and its readiness for inspection and testing.
4.2 Before operating the system to carry out T & C, the following steps should be followed :
(i) Obtain design drawings and specifications and to be thoroughly acquainted with the design intent.
(ii) Obtain copies of approved shop drawings of all air handling equipment, outlets (supply, return and exhaust) and temperature control diagrams.
(iii) Compare design to installed equipment and field installation.
(iv) Check the system from the air handling equipment to terminal units to determine variations of installation from design.
(v) Check filters and dampers (for both volume control and fire protection) for correct and locked position, and temperature control for completeness of installation before starting fans.
(vi) Obtain manufacturer’s outlet factors and recommended procedure of testing. Summation of required outlet volumes permits a crosscheck with required fan volumes.
(vii) Obtain schematic diagrams of system as-built ductwork and piping layouts to facilitate reporting.
4.3 During construction certain tests will have been carried out on the installations to ensure their suitability for operating at the design conditions. Such test certificates have to be issued together with certificates of any works tests.
4.3.1 Works Tests
a) Works tests shall be carried out in accordance with the type normally associated with the specified item of equipment and to the standards as laid down in the Specification and the Conditions of Contract.
b) Works static pressure tests will be carried out on such items of plant and equipment as pressure vessels, water coils, heat exchangers and plate exchangers, radiators and convector
elements, and all items of plant or equipment handling refrigerant, as laid down in the Specification and the Conditions of Contract.
c) Dynamic rotation tests will be carried out on such items as fan impellers and drives, compressor, pump impellers and drives. Tests shall be conducted through the entire rotational speed range up to a maximum of 150% design operating speed if the provision have been made in the Conditions of Contract. When items of plant are purchased ex-stock, manufacturer’s test certificate will suffice.
d) Rotational test on electric motors will not be carried out if the equipment is constructed to the requisite current British Standard or any other approved standards.
4.3.2 Welds in Piped Services
a) The welds shall be inspected by means of cutting. The total number of welds to be inspected should be limited to 2.5% of the total. If any of the welds are found to be of sub-standard, equal number of further welds shall be cut out.
b) At least two welds per operative shall be inspected. Each welder employed on the works shall be allocated an identification number and each site weld shall be stamped with the appropriate identification number to identify the operative. c) Where required by the Particular Specification, some welds on
large bore or high pressure mains may be subject to testing by radiographic or ultrasonic methods. Such non-destructive testing should be carried out by specialized laboratories who both perform the tests and analyse the results.
4.3.3 Pressure Testing of Piped Services
a) Pressure testing of piped services systems, or any section of a completed system, shall be completed prior to the application of any thermal insulation to the cleaned pipe surfaces.
b) Ensure that all plugs, caps, tees and drain fittings required to enable the tests to be carried out have been provided.
c) Before hydraulic tests are carried out, all safety valves, gauges etc. shall be effectively isolated or removed. For all non-destructive safety equipment, these shall be effectively tested at their design working pressure during commissioning of the installation.
d) Tests on lengths of pipe or portions of systems shall be applied by filling the section to be tested with water and raising its pressure to the figure quoted in the Specification.
e) The section shall then be left fully isolated without further strokes of the pump and all joints must remain watertight for a period of at least two hours. As to whether or not the section is sound shall be governed by the rate at which the pressure falls. f) Any fault discovered during such tests shall be at once
remedied and the test reapplied until the section under test is considered sound. Remedial work shall conform with all the requirements of the General and Particular Specification for materials and standards of workmanship.
g) Upon completion of the test, the water shall be released and drained away as rapidly as possible, the section being then thoroughly sluiced through to ensure the removal of as much dirt and dross as possible before being refilled and put into service.
4.3.4 Air Leakage Test for Ductwork
a) Where required by the Specification, all air-conditioning supply ductwork connected to central air handling units shall be tested for air leakage in accordance with - HVCA (V12) Specification for Sheet Metal Ductwork (DW series).
b) For preliminary and visual test, the method will include using chemical ‘white’ smoke generators. All openings in the ductwork shall be properly sealed followed by the introduction of smoke.
4.4 The flow-chart in Appendix C provides the sequence, responsibilities and guidelines for the testing and commissioning procedure.
4.5 Precommissioning Checks 4.5.1 Water Distribution System
4.5.1.1 System Cleanliness
Irrespective of the precautions taken during the construction stage to keep the internal surfaces of pipework clean, it should be assumed that it has not been done so and one of the following procedures shall be used to clean the system.
4.5.1.1.1 Flushing
a) Divide the pipework system into self-draining sections so that the maximum possible flushing rate is achieved.
b) Isolate items which are particularly sensitive to dirt, such as pumps, small bore coils and tubes, including induction and other room unit coils and spray nozzles. Washers, cooling
tower basins, feed and other tanks which may have accumulated with deposits during manufacturing or installation should also be isolated and flushed independently.
c) Where make-up or feed tanks are used for flushing, ensure that the maximum possible pressure is sustained on the system during the flushing process. This may necessitate the provision of a temporary parallel feed of mains water into the tank where the ball valve has limited capacity. This procedure assumes that the connection of the section from the tank is at a high point in the section being flushed.
d) Ensure :
(i) that flushing is carried out from the upper to the lower sections of a multi-section system, finishing with the lowest point; initial flushing should always be from small bore to large bore pipe. Particular care is required on reverse return systems and systems with roof-top chiller or boiler plant;
(ii) that the large bore outlet is not opened until the section being flushed is fully primed;
(iii) that the maximum possible flow rates are used; (iv) that flushing continues until the outflow runs clear. 4.5.1.1.2. Cleaning by Forced Circulation
Where facilities exist, final cleaning of systems can be achieved by circulation of the medium in order to collect dirt at filters or other selected points in the system. Where circulation is achieved by the use of a pump, this action shall be deferred until the pump has been set to work in accordance with para. 4.6.1.4.
4.5.1.1.3 Chemical Cleaning & Corrosion Inhibiting
Chemical cleaning, if required, shall be carried out as specified by the specialist. Corrosion inhibiting, where specified, should be carried out after flushing.
4.5.1.2 State of System Check :
(i) that where special valve packing is required, e.g. grease in medium or high temperature system, this shall be in accordance with manufacturer’s instructions;
(iii) that the system has been cleaned in accordance with para. 4.5.1.1;
(iv) that permanent water connections have been made; (v) that water treatment is available if specified. 4.5.1.3 Check of System before Filling
Check :
(i) that probes, pockets, pressure gauges, siphons, orifice plates and taps, and air vents are installed;
(ii) that drains and overflows are connected and free from blockage;
(iii) that connections to heating and cooling coils and all other heat exchangers are correct in relation to the design water flow direction;
(iv) that control and non-return valves are installed the right way round;
(v) that relief valves are installed as specified and are free to operate;
(vi) that relief valve outlets are piped away to suitable drain points;
(vii) the expansion devices for alignment and freedom from obstruction;
(viii) the presence of special pump priming devices where specified;
(ix) that the strainer mesh is of the correct grade and material; (x) that the changeover devices for duplex strainers are operative and that there are means of isolation for single strainers;
(xi) that washers, tanks, nozzles and filters are clean; (xii) that tank covers are provided where specified;
(xiii) that drain cocks are closed and other valves are left open or closed according to the plan for filling (see para. 4.5.1.5 below);
(xv) that all pipework and fittings are adequately supported, guided and/or anchored where applicable.
4.5.1.4 Mechanical Checks 4.5.1.4.1. Pumps
Check :
(i) the external cleanliness of the pumps; (ii) that the flow direction is correct;
(iii) that all components, bolts, fixings, etc., are secured; (iv) that the impeller is free to rotate;
(v) the level and plumb of pump and motor shaft and slide rails; direct drive pumps require particular attention in this respect;
(vi) the anti-vibration mountings for correct deflection; (vii) that the correct drive is fitted;
(viii) that the pipework imposes no strain at the pump connections;
(ix) the securing and alignment of pulleys and couplings; (x) the belt tension and match;
(xi) the cleanliness of the bearing;
(xii) that the lubricant is fresh and of the correct grade;
(xiii) that the coolant is available at the bearings when specified;
(xiv) that glands are correctly packed and the gland nuts are finger-tight only, pending adjustment to correct drip rate after start-up;
(xv) that drive guards are fitted and the access for speed measurement is provided.
4.5.1.4.2. Motorized Valves and Float Switches Check :
(ii) that the valve spindles are free to move; (iii) for freedom from excessive looseness; (iv) the fit of pins;
(v) the rigidity of the mountings;
(vi) the stiffness of the linkage members; (vii) the tightness of locking devices; (viii) the bearing lubrication.
4.5.1.5 System Filling
Charge the system with water (treated, if so specified) to a prepared plan, the object of the plan being successful venting by filling from the bottom upwards forcing the air to high points - for venting to atmosphere. Careful consideration should be given to the stage of valves and air vents before and during filling to avoid air-locks and excessive spillage. Take care not to exceed the working pressure of the system when filling from a high pressure source. When the whole system is filled, disconnect the filling source, open the permanent supply and adjust the tank levels.
4.5.1.6. Electrical Checks
Prior to the initial running of any electrically driven pump, valve or electric water heater, the following procedures should be adopted.
4.5.1.6.1. With all Electrical Supplies Isolated Check :
(i) the local isolation of motor and control circuits;
(ii) that there are no unshrouded live components within the panels;
(iii) that the panels and switchgears are clean;
(iv) that the motor and surrounding areas are clean and dry; (v) that the transit packing has been removed from contactors
and other equipment;
(vi) that there is no mechanical damage to switchgears and that thermostats are of a suitable range to operate at
ambient temperature (see para. 4.6.1.2);
(vii) that all mechanical checks on the pump and motor or valve are completed (see para. 4.5.1.4);
(viii) that all connections are tight on busbars and wirings; (ix) that the internal links on the starter are correct;
(x) that all power and control wirings have been completed in detail to the circuit diagram (paying special attention to circuits for star-delta connected or specially wound motors);
(xi) that the fuse ratings are correct;
(xii) that the starter overloads are set correctly in relation to the motor name-plate full load current;
(xiii) that the dashpots are charged with the correct fluid and the time adjustments and levels are identical;
(xiv) that insulation tests on the motor have been performed satisfactorily;
(xv) that the adjustable thermal cut-outs are set correctly (check manufacturers’ test certificates);
(xvi) that all cover plates are fitted.
4.5.1.6.2 With the Electrical Supply Available
(i) Check that the declared voltage is available on all supply phases.
(ii) Where motor powers are substantial or reduced voltage starting or complex interlocks are involved, the control circuit logic and the starter operation should be tested before the motor is rotated. The supply should first be isolated by the withdrawal of the two power fuses not associated with the control circuit or the disconnection of cables. The “red” phase shall be used for control circuit normally. The control circuit fuse must be checked to ensure that it is rated to give the correct discriminatory protection to the control circuit cables. The control circuit should be activated and the starter operation observed. Adjust the timers. Check for positive operation of all contactors, relays and interlocks. Finally, open the isolators, reinstate the power connections and close the isolators.
simple control circuits, the starter operation, etc., should be checked when first starting the motor.
(iv) Never energize electric valve motors until the checks (para. 4.5.1.4.2), have been completed.
4.5.2 Air Distribution System
4.5.2.1 System Cleanliness
Prior to the fitting of filters and washer elements, ensure that the environment is clean and then proceed to check the following for cleanliness :
(i) air intake screens;
(ii) fan and other equipment chambers; (iii) floor gulley and all drainage traps; (iv) fan internals;
(v) heater and cooler batteries; (vi) cooling coil trays;
(vii) washer tanks; (viii) humidifiers; (ix) eliminators; (x) dampers;
(xi) ducting and other airways; (xii) sensing elements;
(xiii) terminal units;
4.5.2.2 Air Regulating Devices and Other Components Within Airways
Checks :
(i) that turning vanes, thermal insulation, acoustic linings, battery fins and sensing elements have been fitted and are undamaged;
(ii) that heater and cooler batteries, humidifiers, filters, silencers, fire dampers, sail switches, volume control dampers etc., are installed correctly in relation to air
flow;
(iii) the damper free-movement, clearances seating pining to damper spindles, position of blades with respect to quadrant indication, relative positions of blades in multi-leaf dampers;
(iv) the control linkages on motorized dampers for alignment, rigidity, lubrication and free movement without slackness;
(v) that dampers throughout the system are secured in open position with damper actuators disconnected;
(vi) the free movement of fire dampers together with the location of, access to and fitting of, fusible link assembly; all fire dampers are finally secured in open position; (vii) that all adjustable louvres are set without deflection, i.e.
normal to face of grille. Adjustable cones on diffusers are set either all in the fully up or all in the fully down position;
(viii) that test holes are provided for measurement of total air flow.
4.5.2.3 Visual Checks for Air tightness
It is assumed that pressure testing of high velocity system ductwork is carried out during construction. This is essential on all high velocity systems and is widely required for low velocity systems.
Check :
(i) the builder’s work ducts and shafts seals;
(ii) that access doors to plant equipment are sealed around the whole periphery;
(iii) the ductwork joints, including flexible couplings; (iv) that inspection covers are fitted;
(v) that drain water seals are fitted;
(vi) that plugs or covers for test holes are fitted. 4.5.2.4 Mechanical Checks
Check :
(i) the external cleanliness of fans;
(ii) that all components, bolts, fixing, etc., are secured;
(iii) that the impeller is secured, free to rotate, of correct handing and correct clearances;
(iv) that axial-flow-type fans are installed for correct air flow direction and, where compounded, in correct order; (v) the level and plumb of fan and motor shaft and slide rails; (vi) the anti-vibration mountings for correct deflection; (vii) the static balance;
(viii) that the correct drive is fitted;
(ix) the securing and alignment of pulleys and couplings; (x) the belt tension and match;
(xi) the cleanliness of the bearing;
(xii) that the lubricant is fresh and of the correct grade; (xiii) that the coolant is available at bearings when specified; (xiv) that drive guards are fitted and the access for speed
measurement is provided;
(xv) for satisfactory operation of inlet guide vanes over full range of movement;
(xvi) that fan casings to be earthed are correctly and soundly bonded.
4.5.2.4.2 Automatic Fabric Filters Check :
(i) the level mounting;
(ii) the alignment, clearances and free movement of spools, drives and limit switches;
(iii) the lubrication of spool drive motor, gearbox and spool bearings.
Prior to the initial running of any electrical driven fan, electric air heater or automatically advancing filter, the following procedures shall be adopted :
4.5.2.5.1. With all Electrical Supplies Isolated Check :
(i) the local isolation of motor and control circuits;
(ii) that there are no unshrouded live components within the panels;
(iii) that panels and switchgears are clean;
(iv) that the motor and surrounding areas are clean; air heaters are clean;
(v) that the transit packing has been removed from contactors and other equipment;
(vi) that there is no mechanical damage to switchgears or air heaters;
(vii) that all mechanical checks on fan, motor and automatic filter are completed (see para. 4.5.2.4);
(viii) that all connections are tight on busbars and wirings; (ix) that the internal links on the starter are correct;
(x) that all power and control wirings have been completed in detail to the circuit diagram. (paying special attention to circuits for star-delta connected, or specially wounded motors);
(xi) that fuse ratings are correct;
(xii) that starter overloads are set correctly in relation to motor name-plate full load current.
(xiii) that the dashpots are charged with the correct fluid and the time adjustments and levels are identical;
(xiv) that insulation tests on motor have been performed satisfactorily;
(xv) that the adjustable thermal cut-outs are set correctly; (xvi) that all cover plates are fitted.
4.5.2.5.2. With Electrical Supply Available
a) Check that the declared voltage is available on all supply phases;
b) Where motor powers are substantial or reduced voltage starting or complex interlocks are involved, the control circuit logic and the starter operation should be tested before the motor is rotated. The supply should first be isolated; then by the withdrawal of two power fuses or the disconnection of cables followed by the reinstatement of supply to the control circuit alone, the control circuit shall be activated and starter operation observed. Adjust the timers. Check for proper operation of all contactors, relays and interlocks. Finally open the isolators, reinstate power connections and close the isolators;
c) Where small motors have direct-on-line starting and simple control circuits, the starter operation, etc., should be checked when first starting motor.
4.5.2.6 Electrostatic Precipitators
4.5.2.6.1 Before Approaching the Precipitator : Establish :
(i) what isolators must be opened and fuses withdrawn to completely disconnect the precipitator plant from the low voltage supply. Beware of interlocking circuits which are energized from elsewhere and where cannot be isolated local to the precipitator;
(ii) the arrangements for preventing access to any high voltage component until it is at zero potential;
(iii) adequatelabels for instructions / precautions / warnings to be deployed at the entrance access to the precipitator. 4.5.2.6.2 Low Voltage Electrical System
With all low voltage supplies isolated, check : (i) the local isolation of all low voltage circuits; (ii) that switchgears are clean and undamaged;
(iii) that the transit packing has been removed from contactors and other equipment;
(v) that all wirings have been completed in detail to circuit diagram;
(vi) that all cover plates are fitted. 4.5.2.6.3. High Voltage Electrical System
Only a skilled and experienced person should be allowed to enter the precipitator casing; he should have with him the interlock key which controls the opening of the access door to the section of precipitator which he is entering or a fuse link or other item to prevent the precipitator being energized; a second person should be stationed outside the door as an observer and he will normally also be in control of the operation of the power pack from this position. Before working on any precipitator system, any residual High Tension (H.T.) charge must be removed using an earthing tool with insulated handle. Where the power pack is remote from the precipitator, a shorting bar should be securely fixed between earth and each H.T. feed to the precipitator.
The inbuilt features which prevent access to high voltage components until at zero potential shall, without fail, be checked as follows :
(i) no access to precipitator section via inlet or outlet ductwork connections. Where equipment is being used as a barrier, beware of items which are demountable without tools such as pre-filter cells. Such items should always be supplemented by safety screens as should dampers with blade width exceeding 100 mm;
(ii) any mechanical interlock correctly links H.T. circuits to earth before access door can be opened and simultaneously de-energizes the H.T. primary circuit to prevent overload caused by the earth link;
(iii) no duplicate keys on site for the mechanical interlock system;
(iv) any safety switches fitted to access doors break the Low Tension (L.T.) interlock circuit and destroy H.T. potential before the door is open wide enough to allow an arm or leg to reach a H.T. component within the precipitator casing; also check that switches are held positively open to prevent manual closure or closure by spring failure whilst access door is open;
(v) check that H.T. potentials are reduced to a safe level within the time it takes to open the door and reaches any H.T. component. This will be of particular importance when door safety switches do not merely augment a
mechanical interlock earthing system but are also the sole safety interlock, the value of bleed resistors connected across each capacitor holding H.T. charge will be critical; (vi) a solid copper or aluminium bond connects the H.T.
power pack and filter frame to the building main earthing system.
4.5.2.6.4 Cleanliness and Mechanical Condition
With all electrical supplies isolated, H.T. circuits earthed and precautions for staff adopted in accordance with para. 4.5.2.6.3. Check :
(i) for unsafe ladders, walkways or dangerous projections; (ii) the internal cleanliness of casing, components, including
insulators and ductwork connections;
(iii) that all components are in place and correctly connected. No damage or distortion to ionizer and collector sections. No obvious foreign items in the precipitator cells. Ionizer wires of the correct diameter and type to be provided and to be correctly tensioned. Displacement of these wires from the centres between neutral electrodes should not exceed 5% of the distance between the neutral electrodes. No distortion of collector plates and gaps between plates shall not vary by more than 10%;
(iv) that the wash water and fluid coating systems are completed, reservoir is charged with correct fluid and drainage systems are completed and free from blockage. Connection is provided for manual wash;
(v) that fabric filter sections are loaded with media; if automatic advancing then checks listed in para. 4.5.2.4.2 shall be carried out.
4.5.2.6.5 Interlock Sequence and Alarm Systems With electrical supply available check :
(i) that the precipitator interlock sequence is correct;
(ii) that all safety and failure alarm systems are functioned correctly.
4.6 Setting to Work & Balancing 4.6.1 Water Distribution System
4.6.1.1 General
a) It is not possible in a document of this nature to embody every type of plant layout that the commissioning engineer is likely to encounter in the field. The system as detailed in Fig. 1 at the Appendix C includes only those plant items necessary for clarification of the regulation method described. The procedure given here may have to be adapted to suit the particular arrangement.
b) The method of manual regulation detailed below is applicable to the following systems :
(i) Constant volume, variable temperature primary circuits. (ii) Constant volume, variable temperature secondary
circuits.
(iii) The maximum flow situation in a variable volume system designed without diversity.
4.6.1.2 Procedures
This section defines the procedures to be carried out in order to achieve a water distribution system which is working satisfactorily and regulated appropriately. These works should normally be carried out with the medium at ambient temperature and therefore there is no need for heated or chilled water to be available. It is unwise, in any event, to allow the commissioning of heating or refrigeration plant (particular if of low thermal capacity) unless design primary circulation flow rates have been established and any likelihood of primary flow rate variations due to modulation of unbalanced secondary systems have been eliminated.
4.6.1.3 Checks Prior to Pump Start-Up
a) Check that all normally open isolating and regulating valves are fully open and that all normally close valves are closed. In the case of thermostatic valves it is essential that provision for fully opening of the valves is available. Most electric motorised valves have either provision for manual override of normal control using a switch on the main control box or a facility to position the valves seat mechanically. Pneumatically operated 3-way valves rarely have this facility. It is, therefore, necessary to ensure that the control pneumatics are commissioned to the extent that the controller set point can be adjusted to its extremes, to position the valve fully open or fully closed. Space temperature at the sensing point of the controller in the dynamic mode must be considered at this point, i.e. reducing the control set point
of a chilled water valve controller which is already sensing a low temperature, will not have the desired effect; provision of a local form of valve heat pressurisation must then be considered, such as a portable air compressor.
b) Open all control valves to full flow to heat exchangers of branch circuits.
c) Fully open the return and close the flow valve on the pump, close valves on standby pump. Closing the flow valve on the duty pump will limit the initial starting current, which is usually excessive at the first time a pump is running due to bearing stiffness.
4.6.1.4 Initial Running of Electrically Driven Centrifugal Pump Set
4.6.1.4.1 Initial Start
On activating the motor starter, Check :
(i) that the direction and speed of rotation of the motor shaft are correct;
(ii) that the motor, pump and drive are free from vibration and undue noise;
(iii) the motor starting current for sequence timing adjustment;
(iv) the motor running current on all phases to ensure that they are balanced between phases. The flow valve can be opened at this point to raise the running current to say 50 per cent of the name-plate full load current;
(v) that there is no sparking at the commutator or slip rings; (vi) that there is no overheating of the motor (see BS 587 and
BS 5000, Part II);
(vii) that there is no seepage of lubricant from the housing; (viii) that the water flow to water-cooled bearings is sufficient; (ix) the reduced speed and motor running current on
multi-speed motors. 4.6.1.4.2 Initial Run
a) A light load should be sustained until the commissioning engineer is satisfied from the checks listed in para. 4.6.1.4.1 and from motor insulation test readings that further load may be applied. Repetitive starting of the motor should be avoided to prevent over-stressing of the fuses, switchgear and motor.
b) Gradually open the discharge valve until the motor current reaches either the design value or the motor full load current, whichever is the lower.
c) Check the pump pressure developed by means of the pump altitude gauges against the design pressure. If excessive pressure is developed at this stage, the cause should be investigated.
d) Adjust the discharge valve so that the flow as determined roughly from the pump characteristic is between 100 and 110 per cent of the design value. Note that the motor full load current is not exceeded.
4.6.1.4.3 Running-in Period
a) The pump should be run in accordance with the manufacturer’s recommendations and should be under fairly continuous observation. It should not be left running outside normal working hours unless attended. During this time check that the bearings and motor temperature remain steady, that no noise or vibration develops and that no bolts or fixing works loose. Observations may then become less frequent, but it is advisable while later commissioning other parts of the system, to check the pump from time to time. During the first part of the running-in period :
(i) Vent all high points from time to time. When possible the medium should be heated to maximum permissible levels to assist in removing air from the heating system. (ii) Adjust the gland nuts of the pump glands to give the
correct drip rate. (Not applicable to mechanical seals.) b) After eight hours of running, check all strainers. If these
are clean, regulation can commence. If they are dirty, clean the strainers, and run again for at least eight hours and then re-check.
4.6.1.4.4 Standby Pump
On installations with a standby pump, this standby pump should also be commissioned. This pump can be checked against the other and in the unlikely event of failure of the first
pump, commissioning can continue using the second pump. However, a full diagnosis of the reasons for the failure of the duty pump must be made before energizing the standby pump to ensure that any contributory causes are remedied.
4.6.1.4.5 Secondary Pump
In systems with primary and secondary pumps, starting procedures for the primary pumps should be dealt with first. Isolate the secondary system during this period to prevent any accumulated deposits not removed during the flushing process being carried over into the secondary services. After the final check of strainers referred to in para. 4.6.1.4.3.b, the secondary system can be opened up and the starting procedure for the secondary pumps initiated. Only after a final check of both primary and secondary strainers should actual regulation commence.
4.6.1.5 Regulation of Water Flow
4.6.1.5.1 The procedures described in this section are a guide to the principles of regulation by proportional balance. Regulation is achieved by measuring the pressure drop across a device with a constant flow coefficient capacity index. Balance is obtained by varying the water flow across the device so that the ratio of actual water flow rate to the design water flow rate (as calculated from the square law relationship of water flow rate to pressure drop) is the same (or within designer’s tolerance) across devices. The device may be a venturi-meter, an orifice-plate, a control valve with a known calibrated flow characteristic, a calibrated regulation valve or any device with a constant flow coefficient and a calibrated characteristic reliable as to accuracy and repeatability. Where valves are used they are used in the fully open position, i.e. as a form of fixed orifice. For greater accuracy of absolute flow measurement, only devices covered by British Standard BS 1042 (Measurement of fluid flow in pipes) should be used.
4.6.1.5.2 For the purposes of illustration of the procedures, the system as shown in Fig. 1 of Appendix C will be used. Although the procedures are equally applicable to heating and condensing water circuitry, a chilled water system will be used to illustrate the method. In the heat exchange processes in chilled water systems, temperature differences between the two fluids are generally very small by comparison with heating systems and for this reason the performance of terminal plant is considerably more sensitive to any deviations from the design water flow rate. Hence, the T & C procedure requires more exacting tolerances when balancing this type of system.
A series of branch circuits each with several loads have been indicated, flow to each load being controlled by a three-way control valve. Three-way valves in both mixing and diverting applications plus a ‘wild’ non-controlled coil have been included in the diagram to demonstrate the flexibility of the regulation procedures. In the system illustrated at Fig. 1 of Appendix C, the flow line to each terminal unit is fitted with a regulating/isolating valve which has in-built pressure tappings. This valve is used in its fully open position as a fixed orifice device for water flow rate measurement. The flow measurement may be made anywhere in the branch circuit. A fixed orifice is sometimes incorporated into the regulating valve in the return line. The principle of the balancing method remains the same. The return line from each terminal unit is fitted with a double regulating/isolating valve which is regulated and locked in position during the balancing procedure. Where there-way valve is fitted, a double regulating/isolating valve is installed in the bypass, e.g. across the heat exchanger to balance the bypass with the coil.
4.6.1.5.3 Initial Check of System Water Flow Rates
a) Check the pressure drop across the associated flow regulating valve of each terminal unit by connecting a manometer between points a and b. (Refer to terminal unit “A1” in Fig. 1 of Appendix C) It should be remembered that the reading obtained is related to the design water flow rate by a square law, not a linear relationship. This can be represented by the following expression : P1 Q12 P2 = Q22 . .. .. .. . W.1 Where :
P1 = Actual pressure drop .. .. kPa P2 = Design pressure drop .. .. kPa Q1 = Actual water flow rate.. .. m3/s Q2 = Design water flow rate.. .. m3/s
Hence the actual percentage of design water flow rate obtained can be deduced from the following calculation :
√P1 =
√P2
x 100.. .. .. .. ..W.2
b) Inspection of the percentages of obtained water flow rate to design water flow rate will indicate which is the least favoured (index) branch and which is the most favoured branch.
c) At this stage manually set the three-way valve to the bypass position and regulate the bypass valve S so that the pressure drop between a and b equals the reading previously obtained with the three-way valve in the full flow position. Lock the bypass double regulating valve. This procedure is not part of the balancing of the main water distribution system but is the local commissioning of the water flow control of the three-way valve.
4.6.1.5.4 Balancing of Terminals
Start to balance the most favoured branch. The water flow rate of each terminal unit should be balanced to the water flow rate of the index terminal unit in that branch. Each branch is dealt with independently. (The main branch valves A, A’, B, B’, C, C’ in Fig. 1 of Appendix C are all fully open at this stage). Assume branch A-A’ has the highest unit A1 (remote in hydraulic terms relative to the circulating pump) is the least favoured. If it is not, connect one manometer across valve No. 1 and a second manometer across the regulating valve associated with the least favoured terminal unit. Regulate the down-steam double regulating valve No. 2 until the percentage of design water flow rate across the two valves are equal (or within the designer’s tolerances). Leaving the first manometer connected across valve No. 1 (a and b) while the rest of the branch A-A’ is balanced. Connect the second manometer across valve No. 3. Regulate valve No. 4 until the percentage of design water flow rate is the same (or within the designer’s tolerances) as valve No. 1. Repeat this procedure for all valves on branch A-A’. Remove both manometers and start on the next most favoured branch. Carry on until the water flow rates of all terminal units on all branches are balanced within each branch.
4.6.1.5.5 Balancing of Complete Branches
For this stage, the branch regulation valves (A’, B’ and C’) will be the measuring stations. Check the percentage of design water flow rate across each branch regulating valve. It will then be apparent that which is the index branch (say A-A’). Set the first manometer across valve No. A’ and the second manometer across valve B’ until the percentage of design water flow rates across the valves A’ and B’ are equal (or within the designer’s tolerances for branch balance). Leaving the first
manometer connected across valve A’, repeat this procedure for all branches (in this example for branch C-C’) working back from the most remote branch to the branch nearest the pump. (Where, at the start of branch balancing, if the most remote branch is not the index or least favoured branch, it should be made so, in the manner described for terminal balance.)
4.6.1.5.6 Secondary Mixing Set Regulating
For the purpose of illustration it is assumed that the design water flow rate as delivered by the secondary circulating pump is in excess of the design water flow rate of the secondary mixing three-way valve. The first manometer is connected across valve No. 11 and the second manometer across valve No. 14. With valve No. 13 fully open and the secondary three-way valve in the full flow position, the percentage of design water flow rate through valve No. 11 should be in excess of the percentage through valve No. 14. (Regulate valve No. 13 until the percentage of design water flow rate are equal (or within the designer’s tolerances). Manually set the secondary three-way valve to the bypass position and regulate valve No. 12 until the percentage of water flow rate through valve No. 11 equals the percentage obtained with the three-way valve in the full flow position.
4.6.1.5.7 Secondary and Primary Final Regulation
Total water flow is measured by connecting a manometer (or other accurate measuring device) across the total flow measuring device such as an orifice plate or venturi meter. The secondary total water flow rate is regulated first by adjustment of valve No. 15 until the pressure drop across the total flow device equals the design pressure drop. This procedure is repeated finally on the primary circuit with the manometer connected across the primary total flow measuring device and adjusting the double regulating valve No. 16. At this stage re-scan all the measuring stations for record purposes including the pump differential pressures and the evaporator pressure drop and, where possible, check against the manufacturer’s data.
4.6.1.5.8. Other Regulating Valves
Valves incorporating an integral orifice plate, double regulating facility and metering station as a single unit, or double regulating valve plus separate orifice plate and metering station are also available, this eliminate the need for a regulating valve with in-built pressure tappings. The T & C procedures would be similar but check with the manufacturer.
4.6.2.1 Precautions Against Airborne Dirt
The system should have been cleaned internally in accordance with para. 4.5.2.1 but further precautions shall be taken before starting the fans for the first time :
(i) disconnect final flexible connections to terminal units such as induction units and blender boxes which are susceptible to faulty operation through dirtiness;
(ii) preferably remove all high efficiency terminal filters which are susceptible to rapid choking;
(iii) check that suitable temporary protection has been provided for anything within spaces served by the system which could be damaged by initial discharge of dust from supply outlets at first start-up;
(iv) install main inlet filter cells, properly coated as necessary, to avoid introducing additional dirt into the ductwork system after start-up. Check seating of cells for airtightness. Commission automatic fabric and electrostatic filters in accordance with para. 4.6.2.2 and 4.6.2.3;
4.6.2.2 Automatic Fabric Filters
a) Preliminary checks in accordance with para. 4.5.2.4.b and 4.5.2.5 shall have been completed.
b) Install filter media in accordance with manufacturer’s instructions.
c) Energize the filter without air flow. With the differential pressure control device looped out, close the isolator controlling supply to filter and test operation by the manual advance switch. Leave the filter on manual advance until the correct total air flow is established through the filter.
d) The correct total air flow through the filter shall be established as part of the procedure for regulation of air flow (see para. 4.6.2.5 below).
e) Commission the differential pressure controller after establishment of correct air flow as described in para. 4.6.2.5.7 for which the clean filter condition will normally have been manually selected. An inclined manometer with pressure sampling points adjacent to the filter fabric will be used to measure the prevailing static pressure drop across the clean filter and this will be recorded. The filter may then be progressively blanked
off (e.g. with cardboard) until the manometer indicates the design ‘dirty filter’ pressure drop. The differential pressure control will be adjusted to start advancing the filter at this ‘dirty filter’ pressure drop and to stop advancing the filter at the design clean filter pressure drop.
4.6.2.3 Electrostatic Precipitators
Only a skilled and experienced person should be allowed to enter the precipitator casing; he should have with him the mechanical interlock key which controls the opening of the access door to the section of precipitator which he is entering or a fuse link or other item to prevent the precipitator being energized; a second person should be stationed outside the door as an observer and he will normally also be in control of the operation of the power pack from this position. Before working on any precipitator system, any residual H.T. charge must be removed using an earthing tool with insulated handle. Where the power pack is remote from the precipitator a shorting bar should be securely fixed between earth and each H.T. feed to the precipitator.
4.6.2.3.1 Preliminary Checks
Under no circumstance shall commissioning proceed until all checks listed in para. 4.5.2.6 have been completed.
4.6.2.3.2 Water Wash and Fluid Coating Systems
a) Commission the wash and coating systems in accordance with para. 4.5.1 and 4.6.1 Adjust sequence timers.
b) The precipitator should be washed prior to initial energizing and if specified coated with fluid, allowing correct drainage periods to elapse. (Note : This may be a matter of hours.)
4.6.2.3.3 Automatic Fabric Filter Sections
Commission any automatic fabric filter sections in accordance with para. 4.5.2.4.2, 4.5.2.5 and 4.6.2.2.
4.6.2.3.4 Initial Energizing of Precipitator Without Air Flow (i) Check that no one is inside precipitator casing, that
access doors are closed and that no entry can otherwise be made to the precipitator interior.
(ii) Cancel and lock out any remote control system for precipitator.
(iii) Switch on precipitator.
(iv) Check that there is no flash-over problem and that indications from meters and lamps on precipitator control panel are normal. Faulty operation at this stage will probably indicate that a preliminary check has been missed or that water is still present from the initial wash. All safety measures listed in para. 4.5.2.6.3 must be implemented before entry to the precipitator casing. (v) Restore full automatic control sequence ready for the
establishment of air flow through the precipitator. 4.6.2.3.5 Application of Air Flow to Precipitator
When air flow is established through the precipitator (see. 4.6.2.4.5) :
a) check that there is no excessive flash-over (say, an average of over five per minute per square metre of the face area). This may be caused, for example, by the lack of correct pre-filtration, no lint screen etc., in main or recirculation ducts, presence of water, incorrect air velocity or excessive H.T. voltage;
b) an inspection should be made of the de-energized precipitator after a few hours operation with air flow established (see para, 4.6.2.4.5). Absence of dirt staining on any ionizer neutrals, etc., may indicate H.T. disconnection;
c) the H.T. voltage shall be checked at ionizer and collector sections. Unless otherwise specified the H.T. voltage should be within +3% of the nominal figure specified at the mean declared L.T. voltage. Polarity should normally place positive voltage on the ionizer section to limit ozone generation. Measurement of H.T. voltage shall be by means of an instrument comprising high stability resistance chain with high sensitivity milliammeter in series, or electrostatic voltmeter across one section of the chain. Only a skilled and experienced operator should attempt measurement of H.T. voltage. Great care is necessary to avoid contact with live parts of the meter and no part of the meter or its connections should be touched when it is connected to H.T. components; any such connections should normally be in special H.T. cable to avoid current leakage. Readings should normally be made with the meter placed within the precipitator casing and observed from the outside through the observation window;
established as part of the procedure for regulation of total air flow (see para. 4.6.2.5.7);
e) the uniformity of air velocity distribution across the face of the de-energized precipitator bank should be checked using an anemometer, after the regulation of total air flow (see para. 4.6.2.5.7);
To do this, it will be necessary to override the interlock with the supply fan. It is important to ensure that the precipitator is cleaned and washed before operating the fan with the precipitator de-energized;
f) single point measurements of indicated velocity should be made at the centre of each 300 mm square of the face area, and where appropriate instrument correction factors shall be applied to each of the readings. The mean indicated velocity is then calculated and each of the point readings is expressed as a percentage of this mean. The percentage variations of velocity must be within the tolerances specified. Upper limits will always be critical and lower limits also in the case of agglomerator/storage type units. Any failure to meet the specified tolerances must be rectified.
4.6.2.4 Initial Running of Electrically Driven Fan Set 4.6.2.4.1 Limit the Load
Wherever possible the first start of any motor should be on light load. With centrifugal fan sets this will normally be achieved by limiting the mass flow by operation of the main damper; a knowledge of the fan characteristic is required so that excessive suction or delivery pressures are not applied to the ductwork system.
4.6.2.4.2 Initial Start
On activating the motor starter, check :
(i) that the direction and speed of rotation of motor shaft are correct;
(ii) that the motor, drive and fan are free from vibration or undue noise;
(iii) the motor starting current for sequence timing adjustment;
(iv) the motor running current on all phases;
(vi) that there is no overheating of motor (see BS 587 and BS 170);
(vii) that there is no seepage of lubricant from the housing; (viii) that there is no overheating of the bearings;
(ix) that oil rings are running freely;
(x) the reduced speed rev/s and the motor running current on multi-speed motors;
(xi) the rev/s of fan and motor;
(xii) the performance of fan belts in case of abnormal vibration.
4.6.2.4.3 Initial Run
A light load run shall be sustained until the commissioning engineer is satisfied from the checks listed in para. 4.6.2.4.2 above and from motor insulation test readings that further load may be applied. Repetitive starting of the motor should be avoided to prevent over-stressing of fuses, switchgear and motor.
4.6.2.4.4 Start at Normal Load
Subsequent to the satisfactory conclusion of the initial light load run, the machine shall be stopped and restarted at normal starting load, and the checks listed in para. 4.6.2.4.2 repeated. Again avoid repetitive starting.
4.6.2.4.5 Running-in Period
After a short run at normal load (a few minutes’ run will normally suffice) flexible connections to terminal units, etc., and terminal filters (which were removed in para. 4.6.2.1) shall be restored to position. Subsequently a running-in period shall be sustained until the fan set is in a reliable continuous running condition that can safely be placed under the normal operation and maintenance regime. The regulation of the air distribution system shall be delayed until the running-in period (which may last some days) is completed satisfactorily. During the running-in period the following work shall be conducted; a) the dynamic balance of the fan and motor shall be
investigated and correct if necessary;
b) the performance of electrostatic precipitators shall be checked (see para. 4.6.2.3).
4.6.2.5 Regulation of Air Flow
Regulation of air flow shall be carried out in accordance with the following procedure. It is applicable to all air distribution systems which require manual regulation, including induction unit systems. Only the method of measurement of air flow at the terminals is particular to the type of system involved.
4.6.2.5.1 Principles
The method consists essentially of working back to the fan from the remote branches by setting the correct proportional air flow at each junction of the system in turn (without regard for absolute values of air flow) and so balancing the system. This done, the absolute valves of air flow throughout the system are then brought to their design values simply by adjusting the main damper only (next to the fan) until the design total air flow rate is established at the fan.
This theme is illustrated by consideration of air flow at the junction PQR in a system AZ as shown in Fig. 2 Appendix C. Q is a dampered branch on the duct RP and the required design volumetric air flow rates are shown. With damper Q fully open we may find by measurement that P handles 1.7 m3/s, Q handles 1.3 m3/s; 50% and 75% of their design air flow rates respectively. To balance this junction we would close damper Q until P and Q handle the same proportion of their respective design air flow rates : this may result in a balance of P handling 2.0 m3/s (60% of its design) and Q handling 1.0 m3/s (60% of its design). It follows that B will now be handling 60% of its design rate also, i.e. 3.0 m3/s.
Now that damper Q is set, provided that we do not alter any dampers in the system QB downstream of Q or in the system PA downstream of P, we know that whatever the absolute value of air flow at R, this air flow will be divided into the correct design proportions between P and Q at this junction PQR, i.e. two-thirds to P and one-third to Q.
As we work back up the system towards the fan, adjusting dampers at other junctions between R and the fan, we will be changing the absolute values of flows in R, P and Q but not the ratios of those flows which remain 3:2:1. Ultimately, when all the junctions have been balanced, we will adjust the main damper to obtain the design absolute air flow rate in the main duct from the fan. The correct total air flow will not be divided by the system as set in the correct proportions at each succeeding junction, until R is reached where 5.0 m3/s will be flowing; this will now divided into 3.3 m3/s in P and 1.7 m3/s in Q exactly as required by the design.
One final point to note is that in practice, when balancing successive junctions, a particular routine is adopted both to avoid accumulative errors and to avoid the need for test points and dampers in ducts between junctions. Referring to Fig. 3 of Appendix C, when A, B have been balanced, A, B and C are all handling the same proportion of their respective design air flow rates. Thus when we come to balance the junction CDE, D can be balanced against A or B and not only against C. In practice A is usually selected as the reference point and the air flows in B, D and F are in turn balanced against the air flow in A.
Adjusting the distribution dampers to obtain a proportional balance only, has the important implication that a knowledge is not required at this stage of the absolute values of air flow rate in any part of the system. Hence, the instrument used for measuring the air flow at the terminals or branches of a distribution system needs not necessarily indicate the true value of air velocity or pressure. Therefore, inherent errors in the instrument causing a consistently higher or lower velocity reading than the true value can be ignored; also provided that the same method of measurement is used, factors such as those for effective grille areas are usually self-cancelling and can be disregarded.
Not until the entire distribution system has been proportionally balanced will it be necessary to establish the absolute value of the system total air flow rate.
4.6.2.5.2 State of the System and Building
Before starting the regulation of air flow, it is essential that the following conditions are fulfilled :
(i) the building is completed and windows and doors are opened or shut consistent with their normal state; (refer to para. 4.6.2.5.2.v);
(ii) the duct system is complete and leak-free and in the case of high velocity systems pressure testing is satisfactory; (iii) the requirements of checks listed in para. 4.5.2 have been
met;
(iv) normally all main and branch heaters and coolers on supply systems shall be shut off but on all fresh air systems, some heating or cooling may be applied to the main duct only (which handles the total air flow) in order to temper the air delivered to the spaces. Heat gains and losses to the ductwork can be minimized by restricting the difference between duct air temperatures and ambient temperatures;
(v) any associated air supply or extract systems which have not been regulated should normally be shut down. For balanced systems it may be necessary to balance supply and exhaust individually against atmosphere (i.e. with doors open), then operates them together for regulation of total system air flow.
4.6.2.5.3 Preliminaries to Regulation
To illustrate the regulation procedure a diagram (Fig. 4 in Appendix C) of a typical low velocity supply air system is provided. Note, however, that the procedure for other types of system, including extract systems, is identical to that described here :
a) Check that the dampers on all terminal grilles or diffusers 1, 2, 3, 4 etc., are fully open; also that sub-branch dampers AA, AB, etc., branch dampers A, B, C and main damper M are fully open. All adjustable louvres should be set without deflection, i.e. normal to face of grille. All adjustable cones on diffusers should be set either all in the fully up or all in the fully down position. Set automatic plant mixing dampers FA and RC to one extreme position, i.e. normally either full fresh air or full recirculation.
b) Measure fan motor amps. Throttle main damper M if necessary.
c) Measure the indicated air flow rates at all terminal grilles or diffusers 1, 2, 3, 4, etc., preferably using one instrument. Express these initial measurements as ‘Indicated percentages of design air flow’. It is important that the design air flow rates (with which the measured air flow rates are compared) are all based on a common datum of density, usually that of Standard Air or occasionally that of air at design density at fan inlet; during these initial measurements air must be of constant temperature throughout the distribution system (see para. 4.6.2.5.2.iv) although this temperature datum need not necessarily equate with the density datum adopted for the design values of air flow. Note also that variations in wind, stack effect, fan motor voltage, filter resistance, etc., will all have some effect on the performance of the system; for this reason these initial measurements (and also the final measurements, see para. 4.6.2.5.3.d) will be made in one quick, continuous operation so that the readings will normally be truly comparable.
The principal points of interest are :
(i) If the indications are that the total air flow rate handled by the system is less than 100% of the design then physical changes to the air handling system will probably be necessary before regulation can begin. The fan performance curve and a measurement of fan motor current will assist in assessment of the total air flow. (ii) Are there any obvious faults such as design errors,
blockages or leakages indicated, for example, by large differences of air flow readings between apparently similar branches and terminals? Such faults will required correction.
(iii) What are the indicated values of air flow in each branch A, B, C and each sub-branch AA, AB, etc., of the system? (obtainable by totalling appropriate sub-branch values). This will usually determine the order in which branches and groups of terminals are tackled in the regulation procedure.
(iv) What is the location of the least favoured terminal (i.e. the terminal with the lowest percentage of design air flow) on which sub-branch AA, AB, etc., of the system? This information is necessary for the regulation of terminals.
4.6.2.5.4 Regulation Procedure
a) On any one branch, A, B, or C of the system, the first task is to regulate the terminal dampers on that branch. The order in which this work is tackled will normally be decided from the initial readings described in para. 4.6.2.5.3. The branch A, B or C which has the highest indicated percentage of design air flow will be identified as, say, C and normally tackled first; on that chosen branch C, the Sub-branch with the highest indicated percentage of design air flow will be identified as, say CE and the group of terminals No. 101 to No. 107 on that sub-branch CE will normally be regulated first. Next the group of terminals on the sub-branch with the second highest indicated percentage of design air flow, say, CD, will normally be regulated and so on working towards the sub-branch of the branch C which had the lowest indicated percentage of design air flow during the initial readings. By working in this order measurements of air flow at terminals will be made usually at values which are as near as possible to the design values of air flow. Also, this order of work will give the earliest possible indication that any branch with low initial flow is not going to reach ultimately the design performance
required; thus, if necessary, the designer can define physical changes to the system or revise tolerances on air flow without delay.
b) For the regulation of terminal dampers, the group of terminals on each sub-branch of the system will be treated independently of groups of terminals on their sub-branches. Thus on sub-branch CE, dampers on terminals No.101 to No.107 will be adjusted to obtain the same indicated percentage of design air flow at each of the terminals within this group No.101 to No.107. (This percentage could be, say, 130%.) On sub-branch CD the dampers on terminals No.94 to No.100 will be adjusted to obtain the same indicated percentage of design air flow at each of the terminals within this group No.94 to No.100. (But this percentage could be, say, 110%). During the regulation of groups of terminals, all the sub-branch dampers (and the sub-branch dampers) will be left untouched in the original fully open position.
c) When all the groups of terminals on this chosen branch C have been adjusted in this way, the next task is to regulate the groups of sub-branch dampers CA to CE on this one branch C only. The sub-branch dampers CA to CE will be adjusted to obtain the same indicated percentage of design air flow at each sub-branch within this group CA to CE. Now for the first time each terminal on branch C will be handling the same percentage of design air flow as every other terminal, in whatever group, on branch C. d) When the regulation of both terminals and sub-branch
dampers on branch C has been completed, the branch with the second highest indicated percentage of design air flow will be identified from the initial readings as, say, B and the procedure described in para. 4.6.2.5.4.a and 4.6.2.5.4.b repeated for this branch and so on for any other branches leaving the branch with the lowest initial indicated percentage of design air flow (in our case branch A) to the last. Note that through out this procedure branch dampers A, B and C are all left untouched in the fully open position.
e) When the regulation of terminal and sub-branch dampers has been completed on all branches, the next task is to regulate the branch dampers A, B and C to obtain the same indicated percentage of design air flow in each branch (this could be, say, 115%). Now for the first time each terminal on the entire system will be handling the same percentage of design air flow as every other terminal in the entire system, i.e. 115% throughout. f) Finally, when the regulation of all branch dampers has
