Commissioning Code A: Air Distribution Systems

43 Pages·1996·0.894 MB·English

by  CIBSE

Air distribution systems
CIBSE Commissioning Code A: 1996 (2004)
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Nopart of this publication may be reproduced, stored in a
retrieval system or transmitted in any form or by any means
without the prior permission of the Institution.
This edition first published August 1996; reviewed and
confirmed August 2004.
©August 2004 The Chartered Institution of Building Services
Engineers London
ISBN0 900953 73 X
This document is based on the best knowledge available at
the time of publication. However no responsibility of any
kind for any injury, death, loss, damage or delay however
caused resulting from the use of these recommendations can
be accepted by the Chartered Institution of Building Services
Engineers, the authors or others involved in its publication.
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Typeset by CIBSE Publications Department
Printed in Great Britain by Hobbs the Printers Ltd., Totton,
Hampshire, SO40 3WX
Note from the publisher
This publication is primarily intended to provide guidance to those responsible for the
design, installation, commissioning, operation and maintenance of building services. It is
not intended to be exhaustive or definitive and it will be necessary for users of the guidance
given to exercise their own professional judgement when deciding whether to abide by or
depart from it.
Appendices 19
AA1 Design implications 19
AA1.1 Introduction 19
AA1.2 Design requirement 19
AA1.3 Design information 20
AA1.4 Design development considerations 20
AA2 Installation 22
AA2.1 Introduction 22
AA2.2 Requirements 22
AA2.3 Cleanliness 22
AA2.4 Inspections 22
AA2.5 Ductwork leakage testing 22
AA2.6 Static completion certificate 23
AA3 Measurement of air flow and calibration of instrumentation 23
AA3.1 Equipment, instruments and measuring techniques for 23
typical procedures
AA3.2 Instrument calibration 23
AA3.3 Comparison of two or more methods of measurement 23
AA3.4 Tolerances for regulation of air flow 23
AA4 Health and safety arrangements 24
AA4.1 Introduction 24
AA4.2 Contractor’s duties 24
Index 26
List of figures and table
Figure 1Key stages involved in the commissioning of air 1
distribution systems
Figure 2Flow chart for activities prior to proportional balancing 6
Figure 3Air distribution junction 7
Figure 4A typical branch duct configuration 7
Figure 5A typical air distribution system 8
Figure 6Flow chart for proportional balancing and testing of 12
air systems
Figure 7Flow chart for commissioning of VAVsystems 14
Figure 8Flow chart for commissioning of typical ventilation systems 17
designed to produce pressure regimes within a space
Table A1Cumulative tolerance limits for regulation of air flow 24
Contents
A0 Introduction 1
A0.1 Scope 1
A0.2 Definitions 1
A0.3 Commissioning method statements 2
A0.4 Specification 3
A0.5 Inspection and testing 3
A0.6 Commissioning records 3
A0.7 Responsibility 3
A0.8 Practical considerations 3
A1 Preliminary checks 3
A1.1 Objective 3
A1.2 State of the building and system 3
A1.3 System cleanliness 3
A1.4 Air regulating devices and other components within airways 4
A1.5 Visual checks for air tightness 4
A1.6 Fan checks 4
A1.7 Electrical checks 4
A2 Setting to work 5
A2.1 Procedure 5
A2.2 Preliminary checks 5
A2.3 Precautions against airborne detritus 5
A2.4 Precautions against frost 5
A2.5 Initial running of fan set 5
A3 Regulation of air flow 6
A3.1 Principles 6
A3.2 Procedures 7
A3.3 Techniques 10
A3.4 Variable air volume systems 13
A3.5 Pressure regimes 16
A4 Commissioning documentation 17
A4.1 Content 17
A4.2 Format 18
A5 Witnessing 18
A5.1 Introduction 18
A5.2 Objective 18
A5.3 Selection of the witnessing authority 18
A5.4 Programme 18
A5.5 General 18
A5.6 Witnessing arrangements 19
A5.7 Air distribution system acceptance 19
Appendices 19
AA1 Design implications 19
AA1.1 Introduction 19
AA1.2 Design requirement 19
AA1.3 Design information 20
AA1.4 Design development considerations 20
AA2 Installation 22
AA2.1 Introduction 22
AA2.2 Requirements 22
AA2.3 Cleanliness 22
AA2.4 Inspections 22
AA2.5 Ductwork leakage testing 22
AA2.6 Static completion certificate 23
AA3 Measurement of air flow and calibration of instrumentation 23
AA3.1 Equipment, instruments and measuring techniques for 23
typical procedures
AA3.2 Instrument calibration 23
AA3.3 Comparison of two or more methods of measurement 23
AA3.4 Tolerances for regulation of air flow 23
AA4 Health and safety arrangements 24
AA4.1 Introduction 24
AA4.2 Contractor’s duties 24
Index 26
List of figures and table
Figure 1Key stages involved in the commissioning of air 1
distribution systems
Figure 2Flow chart for activities prior to proportional balancing 6
Figure 3Air distribution junction 7
Figure 4A typical branch duct configuration 7
Figure 5A typical air distribution system 8
Figure 6Flow chart for proportional balancing and testing of 12
air systems
Figure 7Flow chart for commissioning of VAVsystems 14
Figure 8Flow chart for commissioning of typical ventilation systems 17
designed to produce pressure regimes within a space
Table A1Cumulative tolerance limits for regulation of air flow 24
1
Air distribution systems
A0 Introduction A0.2 Definitions
For the purpose of this Code the following definitions
A0.1 Scope apply.
This Code deals with the work stages required to commis-
Accuracy
sion typical air distribution systems. The procedures
represent a standard of good practice generally accepted in
the building engineering services industry and are, there- Accuracy is a compounding of the following factors:
fore, presented in the form of recommendations and instrument accuracy, flow measuring device accuracy and
guidance. operator accuracy. Refer to the BSRIA Application Guide
3/89.1: The commissioning of air systems in buildings(1) for
The Code sets out generally to inform on ‘what should be further information.
done’. Manuals published by the Building Services
Research and Information Association (BSRIA) inform on
Accuracy — flow measuring device
‘how it should be done’.
The flow chart in Figure 1 illustrates the key stages invol- Variations in the reading arising from manufacturing
ved in the commissioning of air distribution systems tolerances of the flow measuring device.
covered by this Code. Attention is drawn to the fact that
there are other, subsequent stages that do not form part of
Accuracy — instrument
this Code.
Variations in the reading arising from manufacturing
tolerances in the instrument.
Planning and programme
Accuracy — operator
Method statements
Any error introduced by the operator such as parallax in
Static completion certified the reading of instruments or test points not ideally
positioned.
Setting to work
Commissionable system
Air volume flow rate regulation
A system designed, installed and prepared to specified
requirements in such a manner as to enable
commissioning to be carried out.
Fan performance testing
Commissioning
Witnessing
The advancement of an installation from the state of static
Air distribution system acceptance End of code A completion to full working order to specified require-
ments. It includes the setting to work of an installation
and regulation of the system flow rates.
Systems proving
Commissioning management
Systems acceptance
The planning, organisation, coordination and control of
Environmental assessment commissioning activities.
Commissioning manager
Figure 1 Key stages involved in the commissioning of air distribution The firm or person appointed to manage the commission-
systems ing process.
2 Air distribution systems
Commissioning specialist Scan— final
The firm or person appointed to carry out specified duties The final set of recorded measurements taken of a system
in connection with commissioning. upon completion of the regulation process.
Definitive air volume flow rate Scan — initial
The inferred volume flow rate derived from measurements The first set of recorded measurements taken of a system
taken using a pitot tube in accordance with defined tech- with all regulation devices in the fully open position prior
niques. to any regulaton.
Setting to work
Design criteria
The process of putting a static system into dynamic opera-
The specified environmental conditions, fluid flow rates
tion.
and equipment outputs required to meet a particular
design performance.
Specification
Diversity
The document that prescribes the requirements for com-
missioning by reference to drawings, information sche-
A hypothetical aggregate simultaneous air volume flow
dules and relevant codes, manuals, guides and standards.
rate at design maximum system performance, compared
with the summation of the design maximum air volume
output of all terminal units. The diversity ratio is often Static completion
quoted as a percentage.
The state of a system installed in accordance with the
specification, ready for ‘setting to work’. This includes
Fine tuning
cleaning and pressure leakage testing of the distribution
system (where required).
Local adjustment to the system where usage and system
proving have shown a need for it. This may also include
the re-assessment of control set points and values to System
achieve optimum performance.
A set of connected components for heating, cooling, venti-
lation or air conditioning consisting of plant, distribution
Hood ducting and terminal units together with arrangements to
control their operation.
A proprietary or custom-made device used to capture air
flow from an air distribution terminal for the purposes of
System proving
measurement (flow or velocity).
Measuring, recording, evaluating and reporting on the
Index (terminal/sub-branch/branch) seasonal performance of a system against specified design
criteria.
The terminal/sub-branch/branch in a distribution system
which, prior to regulation of air flow, receives the lowest
Testing
indicated percentage of design fluid flow rate.
The measurement and recording of system parameters to
Indicated air volume flow rate assess specification compliance.
The inferred volume flow rate derived from
Tolerance
measurements, typically at terminal outlets, taken using
proprietary instrumentation and devices (e.g. terminal air
Permissible deviation from a specified design
collection hoods).
requirement.
Pressure and leakage testing
A0.3 Commissioning method
The process of measuring and recording specified pressure statements
retention or permitted rate of leakage in an air
distribution system or component part thereof. To ensure that all technicians work to the same
procedures and sequences, the commissioning specialist
should compile a commissioning method statement
Regulation
particular to the project. This method statement should
include particulars, in principle or in detail as appropriate,
The process of adjusting volume flow rates of a fluid in a
of the following:
distribution system to achieve specified values (within
tolerances). (a) equipment and instrumentation to be used
Introduction 3
(b) preliminary checks to be applied (e.g. sections A0.8 Practical considerations
A1.2 to A1.7)
The measuring, regulating and apportioning of air flow in
(c) commissioning procedures to be followed (e.g.
a distribution system as applied in the commissioning
sections A2 and A3)
procedures described in this Code is a means to an end.
The primary objective is to ensure that the performance of
(d) tolerancesto be applied in air flow regulation
the commissioned installation is adequate to maintain the
specified space environmental conditions with optimum
(e) arrangements, where appropriate, for witnessing
efficiency.
(e.g. the advance notice to be given).
It should be borne in mind that flow rate apportionment
In some instances, the commissioning specification may
to unnecessarily close tolerances will result in high com-
require the commissioning specialist to submit a method
missioning costs, with little or no practical advantage.
statement for approval. Where this is not a requirement, the
Also, the use of additive tolerances (e.g. –0% +10%) could
commissioning specialist may nonetheless wish to make a
result in running cost penalties throughout the life of the
formal submission of a particular method statement to the
installation. It is the responsibility of the designer to
contractor/client. By this means, interested parties would
specify flow rate tolerances and to ensure that these are
be informed of the commissioning intent, thus providing
appropriate to the particular design, installation and
scope for any concerns regarding methods or procedures to
application.
be addressed before commissioning is commenced.
A0.4 Specification A1 Preliminary checks
The Code assumes that the installation is complete and
properly constructed to an agreed specification. The speci- A1.1 Objective
fication should state permissible tolerances within which
the system should operate. The purpose of the procedure given in this section is to
check that the system is in a satisfactory and safe
condition before starting up. All the following checks
A0.5 Inspectionand testing should be carried out in the sequence given before the
initial running of fans.
The requirements of this Code do not replace the need for
regular inspection of the installation which should be
A1.2 State of the building and system
carried out during construction. All ductwork and mech-
anical and electrical plant should be tested as required by
Before starting regulation it is essential that the following
the specification and the test results recorded and docu-
conditions are fulfilled:
mented. Testing carried out in accordance with the
requirements of the specification, both on and off site, (a) the building is complete and windows and doors
should be recorded and the documents made available to are open or shut consistent with their normal state
the commissioning specialist prior to the commencement (see section A3.5 when dealing with pressure
of their works. related areas e.g. laboratories, operating theatres
etc.)
(b) the air distribution system is complete and, where
A0.6 Commissioning records
required by the specification, leakage testing is
satisfactorily concluded, inclusive of builders’
It is essential that all checks and measurements are work ducts and shafts
recorded in writing at the time they are made. Breaks in
the continuity of commissioning operations are likely, and (c) the requirements of this section, sections A1.3–
proper records will show the state of progress at any stage. A1.7 and A2.2–A2.5 have been met
It is most important that commissioning records are
(d) all main and branch heaters and coolers on supply
provided as part of the ‘hand-over’ documentation. It is
systems are shut off to maintain consistent air den-
recommended that a standardised format be agreed for
sity during testing. However, in cold weather and
recording the necessary commissioning performance data
particularly on full outside air systems, some heat-
for a particular project.
ing may be applied to the main airstream (which
handles the total air flow) in order to temper the
air delivered by the system (see also section A2.4).
A0.7 Responsibility
A1.3 System cleanliness
The responsibility for commissioning is a contractual
matter outside the scope of this Code. Nevertheless, it is
recommended that the managementof the whole commis- Note: it is important to ensure a reasonable standard of
sioning process be under the guidance and control of a system cleanliness before start-up. Debris may be
single authority. Total commissioning management may entrained by air flow on start-up, significantly reducing
be considered as an option. the life of the filter media and other system components.
Introduction 3
(b) preliminary checks to be applied (e.g. sections A0.8 Practical considerations
A1.2 to A1.7)
The measuring, regulating and apportioning of air flow in
(c) commissioning procedures to be followed (e.g.
a distribution system as applied in the commissioning
sections A2 and A3)
procedures described in this Code is a means to an end.
The primary objective is to ensure that the performance of
(d) tolerancesto be applied in air flow regulation
the commissioned installation is adequate to maintain the
specified space environmental conditions with optimum
(e) arrangements, where appropriate, for witnessing
efficiency.
(e.g. the advance notice to be given).
It should be borne in mind that flow rate apportionment
In some instances, the commissioning specification may
to unnecessarily close tolerances will result in high com-
require the commissioning specialist to submit a method
missioning costs, with little or no practical advantage.
statement for approval. Where this is not a requirement, the
Also, the use of additive tolerances (e.g. –0% +10%) could
commissioning specialist may nonetheless wish to make a
result in running cost penalties throughout the life of the
formal submission of a particular method statement to the
installation. It is the responsibility of the designer to
contractor/client. By this means, interested parties would
specify flow rate tolerances and to ensure that these are
be informed of the commissioning intent, thus providing
appropriate to the particular design, installation and
scope for any concerns regarding methods or procedures to
application.
be addressed before commissioning is commenced.
A0.4 Specification A1 Preliminary checks
The Code assumes that the installation is complete and
properly constructed to an agreed specification. The speci- A1.1 Objective
fication should state permissible tolerances within which
the system should operate. The purpose of the procedure given in this section is to
check that the system is in a satisfactory and safe
condition before starting up. All the following checks
A0.5 Inspectionand testing should be carried out in the sequence given before the
initial running of fans.
The requirements of this Code do not replace the need for
regular inspection of the installation which should be
A1.2 State of the building and system
carried out during construction. All ductwork and mech-
anical and electrical plant should be tested as required by
Before starting regulation it is essential that the following
the specification and the test results recorded and docu-
conditions are fulfilled:
mented. Testing carried out in accordance with the
requirements of the specification, both on and off site, (a) the building is complete and windows and doors
should be recorded and the documents made available to are open or shut consistent with their normal state
the commissioning specialist prior to the commencement (see section A3.5 when dealing with pressure
of their works. related areas e.g. laboratories, operating theatres
etc.)
(b) the air distribution system is complete and, where
A0.6 Commissioning records
required by the specification, leakage testing is
satisfactorily concluded, inclusive of builders’
It is essential that all checks and measurements are work ducts and shafts
recorded in writing at the time they are made. Breaks in
the continuity of commissioning operations are likely, and (c) the requirements of this section, sections A1.3–
proper records will show the state of progress at any stage. A1.7 and A2.2–A2.5 have been met
It is most important that commissioning records are
(d) all main and branch heaters and coolers on supply
provided as part of the ‘hand-over’ documentation. It is
systems are shut off to maintain consistent air den-
recommended that a standardised format be agreed for
sity during testing. However, in cold weather and
recording the necessary commissioning performance data
particularly on full outside air systems, some heat-
for a particular project.
ing may be applied to the main airstream (which
handles the total air flow) in order to temper the
air delivered by the system (see also section A2.4).
A0.7 Responsibility
A1.3 System cleanliness
The responsibility for commissioning is a contractual
matter outside the scope of this Code. Nevertheless, it is
recommended that the managementof the whole commis- Note: it is important to ensure a reasonable standard of
sioning process be under the guidance and control of a system cleanliness before start-up. Debris may be
single authority. Total commissioning management may entrained by air flow on start-up, significantly reducing
be considered as an option. the life of the filter media and other system components.
4 Air distribution systems
Prior to the fitting of filters, check the following for clean- (c) ductwork joints, including flexible couplings, are
liness: air tight
(a) air intake screens (d) inspection covers are fitted
(b) fanand other equipment chambers (e) drainage trap water seals are intact
(c) fan internals (f) plugs or covers for test holes are fitted.
(d) heater and cooler batteries
(e) cooling coil condensate trays A1.6 Fanchecks
(f) condensate drainage traps
The following should be checked:
(g) eliminators
(a) internal and external cleanliness
(h) humidifiers
(b) all components, bolts, fixings etc. are secure
(i) volume control dampers and linkages
(c) impeller secured, free to rotate, of correct handing
(j) fire dampers and correct clearances
(k) ducting and other airways (d) axial-flow-type fans installed for correct air flow
direction and, where compounded, in correct order
(l) sensing elements
(e) anti-vibration mountings and the removal of tran-
(m) terminal units.
sit bolts and packing materials
The commissioning specialist should formally report any (f) correct drive is fitted
instances of unsatisfactory cleanliness to the appropriate
(g) securing and alignment of pulleys and couplings
level in the project management.
(h) belt tension and match
(i) where necessary, lubrication has been applied in
A1.4 Air regulating devicesand other
accordance with manufacturer’s requirements
components within airways
(j) drive guards fitted, access for speed measurement
provided
The following checks should be made:
(k) where appropriate, satisfactory operation of inlet
(a) turning vanes, thermal insulation, acoustic linings,
guide vanes and variable pitch fans over full range
battery fins and sensing elements have been fitted
of movement.
and are undamaged
(b) heater and cooler batteries, humidifiers, filters, sil-
A1.7 Electricalchecks
encers etc. are installed correctly in relation to air
flow
Prior to the initial running of any electrically driven fan,
(c) volume control dampers are operating
electric air heater or automatically advancing filter, the
(d) there is freedom of movement, throughout range, following procedures should be adopted:
on motorised damper control linkages
(e) dampers throughout the system are secured in the A1.7.1 With all electrical supplies isolated
fully open position (except where other require-
ments may be specified) Check:
(f) there is free movement of fire dampers, together (a) local isolation of motorand control circuits
with the location of, access to and fitting of fusible
(b) no unshrouded live components within panels
link assemblies; all fire dampers are finally secured
in the open position (c) panels and switchgear clean
(g) all adjustable louvres set without deflection, i.e. (d) motor and surrounding area clean; air heaters clean
normal to face of grille; adjustable cones on dif-
(e) transit packing removed from contactors and other
fusers set either all in the fully up or all in the fully
equipment
down position
(f) no mechanical damage to switchgear or air heaters
(h) test holes are provided at strategic points for the
measurement of branch and total air volume flow (g) all mechanical checks on fan, motor and automatic
rates. filter complete (see section A1.6)
(h) all connections tight on busbars and wiring
A1.5 Visual checks for air tightness (i) internal links on starter correct
(j) all power and control wiring completed in detail to
Check to ensure that:
the circuit diagram (special attention to circuits for
(a) builders’ work ducts and shafts are sealed star-delta connected or specially wound motors)
(b) plant access doors are sealed around whole periphery (k) fuse ratings correct