CPD PROGRAMME Component


Forced convection (fan driven) heating coils where flow rate is ≥ 0.015 l/s and < 0.1 l/s: Heating water ∆T ≤ 11˚C Heating water ∆T > 11˚C


Forced convection (fan driven) heating coils where flow rate is > 0.1 l/s: Heating water ∆T ≤ 11˚C Heating water ∆T > 11˚C


Tolerance


± 15% ± 10%


± 10% ± 7.5%


Figure 3: Partial excerpt of suggested tolerances when commissioning heating systems. (Source BSRIA Guide BG2/2010; CIBSE Code W)


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 up- to-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


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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. 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.


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


Valve type


Lockshield radiator valves


Double regulating valve (DRV)


Application notes


SUITABLE for radiator, radiant panel, natural convector and underfloor heating circuit connections.


SUITABLE for system branches, sub-branches and terminal branches where manual balancing of flow rate is required (usually installed as part of a FODRV)


USUALLY REQUIRED on three-port control valve by-passes in order to balance the by-pass. (NOT REQUIRED if the circuit flow is held constant by a CFR).


NOT USUALLY REQUIRED on the same branches as DPCVs, CFRs, or PICVs, nor on any of the branches feeding to sub-branches containing these devices.


NOT REQUIRED on the mainreturn to the pump, unless the pump is a constant feed pump. For variable speed pumps, pump speed should be set using the pump speed controller.


Figure 4: Partial excerpt of table showing application notes for commissioning devices Source BSRIA Guide BG2/2010


July 2011 CIBSE Journal 53


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 post- occupation commissioning activity that a building is brought into useful operation. In many instances there will be a need


The term ‘whole life commissioning’ is sometimes used to emphasise the need for a life-cycle approach


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


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