Recently, on a large commercial office project, WT Consultancy, in its capacity as the ICA (Independent Commissioning Agent) pressed the mechanical services contractor for their backflush cleaning procedures of chilled water terminal units. Their response was ‘there is no need for back-flushing as the system is filled and emptied quite a few times during the course of pressure testing and chemical treatment’. The contractor also stated ‘that the main branches are where all the major works took place and they will flush and submit samples for testing for these areas only’. On top of this, it was claimed that the units would generally be clean from the factory,and as a consequence they were adamant that back-flushing would be a waste of everyone’s time.
We begged to differ… a guide produced by BSRIA (Building Services Research and Information Association based in the UK) and referenced by WT Consultancy in the project commission clauses noted: “ the purpose of back-flushing is to remove the small amounts of loose debris which might collect in the units. Although the amount of debris likely to be found in any one terminal unit is not great, the accumulation of the deposits from a large number of units can cause problems” (BG29, clause 5.2.7).
The contractor highlighted the not insignificant time and cost implications of the cleaning, emphasising again ‘there would be no real benefit’, but in this instance, we insisted the back-flushing take place.
The results and discovery for the contractor were a shock! Not only did the back-flushing dislocate dirt, but it dislodged so much excess, that extended back-flushing was required, and this in a system that was new, supposedly very clean, and that had been previously flushed on more than one occasion.
With the works now complete, all parties are pleased that WT Consultancy were so insistent. Both the mechanical services and main contractors have recognised the improvement in their defects liability position, the building owner admits they have potentially dodged a performance and reliability claim, and the consultant responsible for energy modelling is satisfied that one of the potential performance hurdles has been resolved from the outset.
The role of the ICA is often misunderstood. Some building owners engage an ICA simply to tick the Green Star credits box and are comfortable to pay low fees. It’s a shame, because a competent and experienced ICA, that is empowered to do a full and comprehensive job, could save the client from a lifetime of reduced performance.
For further insight, please don’t hesitate to contact Steve Hennessy, National Manager Sustainability.