Moving towards continuous
(written for Water, Energy & Environment)
Re-commissioning traditional fan coil and chilled beam systems to optimise
performance can be disruptive and expensive. Martin Lowe, Technical Manager with
Marflow Hydronics, explains how new valve and control technologies are enabling
a system of ‘continuous commissioning’.
Over the last few years the workplace has become considerably more flexible and
this is a phenomenon that is likely to continue. Unfortunately, where there is a
fan coil or chilled beam air conditioning system, the likelihood is that the
system will not be adjusted in relation to the changes in the conditioned space
– potentially compromising both energy performance and comfort.
In addition, the historic inflexibility of such systems makes it more difficult
to incorporate low or zero carbon heat sources, such as heat pumps. However, as
discussed in more detail below, this situation is now changing and energy
managers need to be aware of the potential arising from new valve and control
The dynamic nature of the workplace is driven by a number of factors including
routine churn, the increased popularity of flexible working practices such as
hot desking and the rationalisation of space usage. These factors can often have
the effect of creating denser populations of staff in one area of a building,
while other areas are used less.
All of which means that the heating and cooling demands in a particular space
can vary considerably and, while local controls may provide some coarse
adjustment of such systems, this will be limited by the way the system was
configured during commissioning. Clearly, the ideal response is to re-commission
the system in line with the new requirements but with conventionally designed
systems this is disruptive, time-consuming and expensive. Little wonder, then,
that many organisations choose compromise as the path of least resistance.
In the last couple of years, however, new technologies have been applied to fan
coil systems that allow systems to be re-commissioned from a remote PC, thus
minimising the disruption of accessing the ceiling void and facilitating a
system of ‘continuous commissioning’. Potentially, this creates a system that is
as dynamic as the space it is serving.
One of the key factors in this respect has been the development of addressable
pressure independent two-port control valves (PICVs) that can be precisely
adjusted through a building management system (BMS) or BACnet system.
This approach opens the doors for a whole new approach for the design and
operation of fan coil and chilled beam systems as the valves are no longer
‘fixed’ and difficult to adjust. On the contrary, they can be quickly and easily
adjusted to suit different circumstances, creating a dynamic regime that gives
building and energy managers far greater control of both energy optimisation and
For example, such a system enables water flows to be quickly and easily adjusted
in relation to increasing or decreasing heat loads in a workspace, without the
need for specialist commissioning skills. Similarly, in a situation where
heating and cooling are provided by a heat pump, use of an addressable valve
will enable water volumes to be adjusted in direct response to changes in
heating and cooling loads throughout the year. In this way, the same coil can be
used for heating or cooling for most of the year, adjusting water volumes to
compensate for the varying outputs of the heat pump.
This enhanced flexibility can also help to reduce maintenance requirements. For
instance, when valves are fixed at a minimal position, the orifice may be so
small that dirt and air can become trapped.
Conventionally, the only way to free any dirt particles larger than the set
orifice is to manually open the valves to allow the dirt through. However, with
a dynamic system the simple expedient of setting valves to open fully for a few
seconds once a week will eliminate blockage problems by flushing through any
accumulated dirt particles.
These are just some examples of the potential for addressable pressure
independent valves to bring about a real sea-change in how we operate fan coil
and chilled beam systems. The key is for building operators to recognise the
potential and take advantage of it.
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