We reserve the right to make changes without prior notice
37
6.3.5 Manual operation
Manual operation may be selected as an alternative to the air flow control system. This is how it is possible to
directly set, within the expected limits, the value of the command signal to be sent to the fans, as an alternative
to setting the air flow value.
The controller displays the unit air flow without controlling it, however.
Manual operation is selected at the time of unit start-up to run some tests concerning the air flow in the system.
6.3.6 Fan overload switch alarm
The controller checks that the digital input of the fan overload switch in both the delivery and return (where
provided) lines is closed.
If it is not, the fans are stopped after a delay of a few seconds. If the fans on the delivery line are alarmed, the
entire unit is stopped following an overload switch alarm of the fans in the delivery line. If the alarm affects the
fans in the return line (where provided), the overload switch alarm of the fans in the return line is activated, but
the unit is not stopped.
6.3.7 Air flow alarm
The controller checks that the digital input connected to the air flow switch of the fans in the delivery line is
closed.
If it is not, the fans are stopped after a delay of a few seconds and the entire unit is stopped too following an
air flow alarm.
6.4 Temperature regulation system
One of the major purposes for which a roof top unit is designed is to safeguard the preset temperature and
humidity conditions in the cooled/heated location. To fulfil this purpose, the unit is supplied with devices (fans,
compressors, dampers, ancillary batteries, electric heaters, heat recovery unit) based on its configuration.
Below is a brief list of the primary functions of the temperature regulation system in a roof top unit.
The ambient temperature and its setpoint are displayed in the main controller screen. If an ambient humidity
probe is fitted, the main screen also shows the humidity value and its setpoint.
6.4.1 Air cooling
The units cool the air using compressors or a free cooling system - this applies to units featuring a damper
module.
6.4.1.1 Compressor cooling
The compressors used for the cooling cycle are activated proportionally as the ambient temperature (Ta) rises
with respect to the summer setpoint (SPc) and within the cooling differential (DTc), which is divided in equal
parts depending on the number of compressors fitted in the unit. A “dead zone” (ZN) may be envisaged within
which the controller does not activate the compressors. The software manages the dead zone in such way
that half of the dead zone value (1/2 ZN) is between the summer setpoint and the beginning of the cooling
differential.
C2
C1
DTc
1/2
ZN
C1
C2
C3
C4
SpC
Ta