A new approach to commissioning of fan coil units and chilled beam systems, which includes remote positioning of control of valves, is said to offer a number of advantages. Paul Haddlesey spoke to the people behind the concept.
It’s often said that, with the exception of a few high profile projects, building services engineering is a conservative discipline that is slow to adopt new methodologies over more familiar approaches. While this is clearly an exaggeration, there are certainly many instances where new developments have yet to be fully exploited.
A case in point is the commissioning of variable volume chilled and hot water systems. Here, it appears, a novel approach using new pressure independent valves and remote control technologies could simplify installation and commissioning, reduce costs and improve system performance. At least, that’s the view of Martin Lowe, technical manager with Marflow Hydronics. “We have to recognise that design, installation and commissioning practices in many projects have failed to keep pace with key developments in the industry,” he suggests. “These developments include the growth of design and build, skills shortages and the increased use of multi-national labour forces, as well as the opportunities provided by modern valve technologies. As a result, this outdated approach is failing to deliver the best result for the end client in many projects,” he adds.
One key reason for this is that the installation of hydronic air conditioning systems is characterised by a fragmented approach, with a range of components being sourced from different suppliers and arriving on site at different times for unpacking, assembly and installation. This is in contrast to VRF systems, often chosen as an alternative, where a single supplier takes responsibility for developing the system as a whole and taking it forward. These issues have led Lowe and his colleagues to introduce what they call the ‘remote commissioning concept’, following several years of development, experimentation and field testing. It is based on several key ideas. Firstly, there is the suggestion that proportional balancing methods developed for commissioning constant volume water systems are not suitable for increasingly popular variable volume systems. The current CIBSE Commissioning code does not take in account the ‘remote commissioning concept’ and as a result the consultant will automatically demand Tolerances that have become less important as the ability to alter the flow remotely is achieved without entry into the ceiling.
Secondly, Lowe points to the increasing sophistication of pre-fabrication techniques. “Pre-fabrication is no longer just a way of transferring site work to another location. It has evolved into an engineered solution where assemblies are produced under controlled conditions bringing many trades together under one roof to produce something that is far more effective when installed on site. Plus everything required is delivered to site at the same time ready for installation, complete with pictorial instructions so language isn’t an issue,” he explains.
Thirdly, Lowe promotes the adoption of an intelligent approach to valve regulation which uses the Fan Coil Unit controller (soft regulation) for example to set the maximum opening to achieve design flow. Limiting the amount the Pressure Independent Two Port control valve opens allows for further design increases if required. A major benefit on very low flows is to allow the Pressure independent valve to be regular cycled fully opened once a week to allow the flushing of air and dirt particles. Moving to an intelligent approach also gives control to variable speed Fan motors giving a very energy efficient system and to remote change parameters without entering the ceiling void.
Thirdly, Lowe promotes the adoption of manifold systems, where each manifold houses all of the valves for a group of, typically up to six, terminal units in a single, pre-insulated box – rather than installing individual valve assemblies at each terminal unit. “Instead of taking measurements at each fan coil the commissioning engineer can access up to six fan coils in one space,” Lowe suggests. “Clearly this brings enormous time savings, simply from not having to move from one fan coil to another and complying with the Working at Height Regulations at each location. With a properly considered control solution the need to revisit each manifold more than once is unnecessary, often reducing the commissioning process to a ‘read and record’ exercise,” he asserts.
A further advantage is that a centralised manifold box provides the ideal location for information about the local system that can be accessed by the building operator beyond commissioning.
In parallel, the company has developed a spreadsheet package that brings all valve information and hydronic performance data into a single location, so any changes can be quickly distributed to all relevant parties.