Technical Chilled
Beyond its usual working range,
the valve can be scheduled to
fully open for a few seconds every
month to ‘self-clean’
> maximum opening to achieve design flow. Limiting the Remote access
amount by which the pressure-independent, two-port “What makes the remote commissioning concept
Prefabrication
control valve opens allows for further design increases, if possible is the ability to program the valve characteristics
is no longer required. or the valve performance curve into the fan coil unit
just a way of
A major benefit of this on very low flows is to allow the controller,” Lowe says.
pressure-independent valve to be cycled to fully open once a “Once the performance curve is in the controller,
transferring site
week, for a few seconds, to allow the flushing of air and dirt design flow values can be entered on the front end
work to another particles. Moving to an intelligent approach also gives control [PC] and downloaded to the appropriate controller. The
location
of variable speed fan motors, providing a highly energy- processor-controlled valve actuator ensures that the disc
efficient system. It also provides the opportunity to remotely moves to the correct position. Any discrepancies between
change parameters without entering the ceiling void. the design flow and actual flow can be made by entering
In parallel, the company has developed a spreadsheet the percentage adjustment calculated remotely.
package that brings all valve information and hydronic “However, having remote access means that further
performance data into a single location, so any changes adjustments can be made when the building is occupied
can be quickly distributed to all relevant parties. and the environmental conditions are known. The most
important issue at commissioning time is that more
flow is available if required.”
The BMS/BACnet controller, housed in its own case,
can be wired to the actuator via pluggable leads and
sockets within the assembly to reduce installation time
and the risk of connection errors. A power plug socket is
provided for mains power to the controller, and to allow
switched power to the fan on the fan coil unit. A plugged
cable is also provided from the controller to the fan coil
unit supplying power and the temperature sensor. The
communication cable to the BMS is also a pluggable
connection.
“The controller used by the system provides two
accurately time controlled outputs to control the valve
actuators within 1/900th of a second,” explains Lowe.
“It communicates with other controllers via a BACnet
MS/TP network, which also enables communications
with a PC, so that system software can be configured and
updated without directly accessing the controller.”
Balancing
The remote commissioning approach uses what Lowe
refers to as a single station balancing (SSB) method of
Characterised curved programmed into FCU controller commissioning.
68 CIBSE Journal February 2009
www.cibsejournal.com
CIBSEfeb09pp66-69 chilledV2•.indd 68 5/2/09 14:39:37
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