Water Treatment for Closed Heating & Cooling Systems – BSRIA BG 50/2013

BSRIA Guide BG 50/2013 – Water Treatment for Closed Heating and Cooling Systems was published in October 2013 and was written to replace (in part) AG 2/93 Water Treatment for Building Services Systems in relation to closed water system applications.

BSRIA BG 50/2013

BSRIA BG 50/2013 gives detailed guidance to design engineers, installing contractors and facilities managers with responsibility for the management of low temperature hot water and cooling systems, and how to select the most appropriate water treatment programmes for their closed circuit water systems to ensure they operate effectively.

The guidance given in BSRIA BG50/2013 is consistent with:

• BG 29/2012 – Pre-Commission Cleaning of Pipework Systems.
• BS 8552:2012 – Sampling and monitoring of water from building services closed systems.
• European Biocidal Products Regulation (528/2012, commonly known as BPR).

Water Treatment for Closed Heating & Cooling Systems

Effective water treatment practices for modern building services installations, including closed circuit heating and cooling systems is becoming more important than ever, helping to control microbiological fouling (biofouling), corrosion and scale.

Unwanted biofouling, system corrosion and the accumulation of scale in such closed systems can result in poor thermal transfer efficiencies, increased energy usage and the accelerated deterioration of plant and system components. Such problems can be detrimental to system performance and often be expensive to remedy.

BG 50 /2013 was written to highlight to engineers, contractors and facilities managers the importance of effective water treatment programmes in the management of closed circuit heating and cooling systems, why they are required and the serious consequences an ineffective treatment programme can cause.

Water Treatment Programme Design

A well designed water treatment programme for a closed heating or cooling system should focus on maintaining system efficiency, overall cleanliness and extend the life of the closed system. BG 50/2013 explains how to achieve this through:

• Good closed heating and cooling system design.
• Correct system installation, testing and pre-commission cleaning prior to start-up.
• Design and implementation of a suitable water treatment programme
• Managing the performance of the water treatment programme to ensure it is effective at all times.

Managing Closed Heating & Cooling Systems

BG 50/2013 provides clarification on a number of issues that have previously caused confusion for facilities managers and water treatment companies responsible for the management of closed heating and cooling water systems, these include:

• The minimum re-circulation time for heating and cooling circuits is one hour daily.
• Any chemical dosing pots used should remain open with continuous flow to minimise potential dead-legs and biofouling issues.
• Designers should consider permanent monitoring equipment, including corrosion coupons, on-line sensors etc. to manage system conditions more effectively.
• Sampling points should be introduced at key locations throughout the system to ensure monitoring is possible.
• BG 50/2013 identifies when remedial flushing may be necessary.
• For remedial flushing of an existing system the guide states that it may not be possible to achieve the recommendations outlined in BG 29/2012.
• Contact time for any chemical cleaners used in the closed circuit system should allow sufficient time to be effective. This is unlikely to be achieved in a limited time frame, e.g. up to 4 hours.
• Full and accurate record keeping of all activity is essential.
• The use of chemical biocides should be considered during seasonal shut downs (summer months) to control bacteria. The system should also be recirculated for at least one hour each day.
• The introduction of side stream filters should be carefully considered to allow for the removal of accumulated suspended solids, this is an alternative to remedial flushing.
• Guidance is given on the interpretation of samples taken from the system, in accordance (BS8552:2012).

Good Design, Pre-Commission Cleaning & Effective Water Treatment

What is clear from BG 50/2013 is that good closed system design, together with correct installation, testing and pre-commission cleaning prior to hand-over are all essential.

Additionally, facilities managers and maintenance staff should take a holistic approach to the water treatment and on-going maintenance management of low temperature closed circuit hot water and cooling systems.

Maintenance activities should take account of all analysis results, additional evidence and data trends to guide the successful water treatment of such closed systems.

Finally, always remember that it is typically more cost effective to take a proactive approach to the maintenance of a closed circuit system than to deal with extensive biofouling, corrosion or scaling issues.

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Further Reading…

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