Module 30: Commissioning processes for heating and cooling water distribution in buildings

The latest regulations emphasise the need to commission building services appropriately. So, when should commissioning start and what should it involve? This CPD gives an overview of the process and focuses on specific examples.

The complexity of building services solutions frequently expands to meet the demands of the increasingly stringent requirements of regulations and of local authorities. Building systems are proved in concept and their theoretical performance marked by their asset rating (in the UK by the Energy Performance Certificate, EPC) as calculated during the design process. However, the key measure is their effectiveness in use, as might be measured by an operational rating (and demonstrated by a Display Energy Certificate, DEC, in the UK).

The operational effectiveness will depend not only on the ingenuity and skill of the design and installation but, importantly, on the ability to set the systems to work properly. This commissioning activity provides an important link between the aspiration of the EPC and the actuality of the DEC. So important is the need for suitable commissioning that the Approved Documents for the 2010 revisions to the Building Regulations require that building services be appropriately commissioned, and that this should be done in a planned way and formally recorded, so that there is evidence that the systems operate in line with the design intent.

This CPD article will look at the required commissioning processes of the one service that is included in virtually every building: water distribution for heating and cooling circuits.

The formalisation of the need for commissioning

The Building Regulations require that it must be properly demonstrated to the BCB (building control body, a local authority or approved inspector) that the heating and hot water systems have been adequately commissioned. The term ‘commissioning’ includes the processes of bringing the systems into operation; their regulation; the setting up of associated control systems; plus the recording of the final settings and the state of the final system performance.

The actual commissioning process should start well before the building systems are installed, with a commissioning plan submitted at the design stage at the same time as the Target Emission Rate (TER)/Building Emission Rate (BER) calculations are produced. As well as ensuring that commissioning is properly integrated into the process, this will allow the BCB to check that commissioning is being undertaken as work proceeds. It will also help to ensure that provisions specifically included for commissioning purposes do not fall foul of value engineering exercises, and are not neglected due to poor understanding of the commissioning needs by site personnel.

At the end of the commissioning process the BCB must be formally advised (within a prescribed time period) that the commissioning plan has been followed and that the results of tests confirm that the performance is reasonably in accordance with the actual building design. If the installed systems deviate from what was proposed at the time of design, then the alterations must be detailed in the report to the BCB. And until this commissioning notice is received, the building cannot be signed off as complying with the Building Regulations, so a delay in the formal commissioning processes may have significant implications on the issuing of a final completion certificate.

The approved document to the England and Wales regulations notes that it would be ‘helpful’ if the notifications made to the BCB were signed by a suitably qualified person as from the Commissioning Specialists Association or the commissioning group of the Heating and Ventilating Contractors Association (HVCA).

The use of templates as outlined in the Model Commissioning Plan (BSRIA BG 8/2009) is recommended for documenting the process in an appropriate way. Not only do the templates provide a checklist of the required stages of activity, but they also ensure that the responsibility for that activity is clearly identified and signed off by the appropriate building professional. The principal stages identified are preparation, design, preconstruction, construction, commissioning of engineering services, pre-handover, initial occupation and post-occupancy (with each being subdivided into a number of activities). An example of one of the stages, pre-construction, is given in Figure 1.

Figure 1: Pre-construction stage activities from BSRIA Model Commissioning Plan.

CIBSE Commissioning Code M

Whether by a sub-contractor or a specialist firm, the actual commissioning must be carried out in accordance with approved procedures in CIBSE Commissioning Code M: Commissioning Management. This Code provides an overview of the management arrangements required to ensure that building services systems are commissioned to meet the objectives of the relevant parts of UK Building Regulations (as described in AD Part L for UK and Wales). The Code is intended as a guide to good practice to enable the development of appropriate procedures and specifications aimed at developing a whole team approach to project commissioning. It does not contain specific detail on procedures for particular types of installations; these are provided in the CIBSE Commissioning Codes specific to the technology. (These are Code A: Air distribution systems; Code B: Boilers; Code C: Automatic Controls; Code L: Lighting ; Code R: Refrigerating Systems and Code W: Water Distribution Systems).

And although much of the content of Code M is generic, it lays out an underlying structure for the commissioning cycle that is then contextualised in the detailed technology codes. It provides some clarity by defining terms used in this work in an attempt to avoid misunderstandings. Fairly commonly interpreted terms such as ‘balancing’ and ‘regulation’ are succinctly defined. Potentially more contentious terms that may not be universally understood by professionals are also given. One example of this is ‘static completion’, defined as: ‘The state of a system when it is installed in accordance with the specification, i.e. clean and ready for setting to work. In the case of water systems this includes flushing, cleaning, pressure testing, filling and venting.’

Code M outlines the management of the whole process, from the need to set up the commissioning systems, programmes and teams early in the project; through the design and co-ordination of commissioning; the actual commissioning and proving of the systems; and the need for proper recording, certification and handover. A particularly helpful appendix, ‘Example responsibility matrix’, provides guidance on the responsibilities that are likely to be taken by the various building professionals. (Four of the 17 example responsibilities are shown in Figure 2.)

Figure 2: Part of example responsibility matrix. (Source: CIBSE Commissioning Code M)

The practices and delineation of responsibilities in a building project may well have shifted in the eight years since Code M was published. However, the core underlying requirement for the activities remains.

Commissioning Code W for Water Distribution Systems 2010

CIBSE updated its Commissioning Code W for Water Distribution Systems only a few months ago. This code describes the requirements for balancing and commissioning water distribution systems, and is complemented by BSRIA Guide BG2/2010 Commissioning Water Systems, which gives the more detailed procedures in a step-by-step format. (Both documents potentially are needed to properly plan and execute the commissioning process.) The scope of both documents relates to the circulatory systems associated with heating and cooling systems.

Code W 2010 replaces the 2003 edition of the code, but maintains the same principal numbering systems to broadly accommodate any existing standard specifications that make explicit reference to sections of the code. The 2010 version contains guidance that has been updated to reflect the changes in practices and equipment. The revision was particularly prompted by the need to clarify and consolidate the guidance for variable flow systems that, as variable speed pumping control has dropped in capital cost, have become increasingly frequently applied in commercial applications. The difficulties of commissioning systems operating at very low flow rates (such as fan coil units) are also tackled in the revised edition.

Code W provides context to the generic guidance from Code M, although many of these areas (including definitions and process management tasks) are common across the different building services systems. Although most of the detailed practical advice is also provided by BG2/2010, there are particularly notable specific areas of detail covered in Code W, such as ‘pre-commissioning checks’, ‘setting pumps to work’, ‘balancing and regulating water flow rates’ and ‘commissioning documentation’. However, much of the detailed guidance that is contained in the main text and the practical insight into the equipment given in the appendices, is also available in BG2/2010 (together with more informative illustrations and photographs).

BSRIA Guide BG2/2010 Commissioning Water Systems

This is an excellent guide and provides upto-date information on the commissioning needs of contemporary (circulatory) water distribution systems. Designed to be used in conjunction with CIBSE Commissioning Code W, this joint BSRIA/ CIBSE document shares much material (as well as its principal author) with Code W

One of the key statements at the beginning of the guide is that: ‘Unless commissioning is properly considered during both the design and installation stages of the project it may not be possible to meet the requirements of CIBSE Code W.’ It then goes on to provide detailed guidance on aspects of design that are essential to enable the systems to be commissioned, noting that: ‘The ease with which the flow rates in a pipework system can be regulated is often dependent on the level of planning that occurs at the design stage.’

Following a comprehensive outline of the information needs for a commissioning specification, the guide goes on to include practical design provisions. These include guidance on design parameters such as acceptable water velocities; overcoming the challenges of setting up systems with low flow rates; and the outline requirements for venting excessive air and deaeration. The guide also includes the suggested tolerances of balance for the various heating and cooling systems – an example is given in Figure 3.

Figure 3: Partial excerpt of suggested tolerances when commissioning heating systems

The Guide has particularly useful sections on the application of various commissioning instruments, valves and devices, including clear illustrations and matrices to assist in their appropriate selection, application, location and identification. An example of one of the tables that provides an application summary for different valves is given in Figure 4. There are several examples given of commonly applied commissioning designs that include detailed schematic representations, together with the associated balancing procedures.

Figure 4: Partial excerpt of table showing application notes for commissioning devices

The future for commissioning of water distribution systems

As new buildings are required to be more sustainable than their predecessors, the need for a rigorous commissioning process has never been greater. The term ‘whole life commissioning’ is sometimes used to emphasise the need for a life-cycle approach to maintaining building systems so that they perform most effectively. Concepts such as the Soft Landings promote a formalised process stretching some years into the occupation period. The increased adoption of building information modelling looks set to change the whole approach to both maintaining a more coherent picture of the building’s services and driving a more integrated commissioning process.

There are many stories of how systems still do not perform adequately after handover to the client; there is a view that it is only by following some postoccupation commissioning activity that a building is brought into useful operation. In many instances there will be a need to ‘(re-)commission’ some time after the building is in use and has experienced the full impact of seasonal changes. But this need should be properly identified and scheduled.

The lack of appropriate commissioning may surface when highlighted by activity associated with providing a DEC in public buildings, but for many other buildings the lack of proper commissioning might remain undetected for many years, causing unknown consequences to operational efficiencies and the impact on the environment. Hopefully the more stringent planning and reporting requirements under the 2010 Building Regulations will ensure that key parts of the commissioning process do not suffer from inadvertent neglect.

© Tim Dwyer