Description Of Control - Software Strategy - NuAire XBOXER XBC Series Installation, Operating And Maintenance Instructions

XBOXER XBC ECOSMART ADAPT (TREND) CONTROL (AT)

14.0 Description of Control - Software Strategy

The system incorporates a web enabled Trend IQ422/12/LAN/BAC/230
controller.
14.1 Unit Contains The Following Controllable Items:
•Inlet damper (if fitted).
•Extract damper (if fitted).
•Heat recovery & bypass damper.
•Heating coil.
•Cooling Coil
•Supply fan speed.
•Extract fan speed.
14.2 Enable Signal
The unit can be enabled via the following methods:
• Software switch (ENABLE) via SDU, IQView4, IQView8 or network.
• Switched live (230VAC) input, PIR etc.
• Low voltage contact.
• Night cooling / summer free-cooling strategy.
• Scheduled via weekly calendar.
When the enable signal is removed, the unit will run on for a time defined by the
run-on set-point. If an electric heater is fitted, the fans will automatically run-on
for an extra 2 minutes, without heating, in order to dissipate residual heat.
14.3 Occupancy Control
When a Trend occupancy sensor is selected via UI4 & 5 software module, the
control will look for a Trend OCC-U sensor in the appropriate input.
An occupied signal will give an enable signal.
0V = Occupied
14V = Unoccupied
14.4 Boost
When the control receives a boost signal the fans will run at boost speed. Once
the signal is removed the fans will run on for a time defined by the boost run-on
set-point.
14.5 Trickle Mode
When trickle mode is active, the fans will run at their minimum speed even when
there is no enable signal. Heating and cooling will also function in this mode if
available.
14.6 CO Control
When a CO2 sensor is selected via UI4 & 5 function knobs, and an enable signal
is received, ventilation will increase to reduce CO2 concentration the target
CO2 set-point. The target CO2 sensor set-point can be changed as one of the
commissioning set-points.
14.7 Supply Temperature Control
While an enable signal is present, this mode modulates heating, cooling &
heat exchanger bypass dampers with the aim of the supply air reaching the
temperature set-point. Please note that heating and cooling outputs will only
function if the HeatingType or CoolingType set-points are set to heating or
cooling options.
14.8 Frost Protection
Should the internal temperature of the unit fall below a value defined in the
commissioning variables, the control will override all heating/cooling logic to
open the LPHW or CW control valves, if fitted. This is to allow any protective
flow through the heating/cooling coils. The supply fan will also stop and the
appropriate frost protection software module will enter an alarm state. This
period will last for a minimum of 5 minutes by default. The fault relay will also
open. Heat and cool demand relays will not operate but digital inputs "Frost
Protecting LPHW" or "Frost protecting CW" will enter an alarm state. Please
note that frost protection will only function if the HeatingType or CoolingType
set-points are set to LPHW or CW.
14.9 Night Cooling / Summer Free Cooling
Once enabled in software, this routine uses an individual time schedule to cool
the fabric of the building at night using only the external air. This mode only
functions if the daytime temperature is above the set-point, cooling is possible
and if the cooling air is not too cold.
14.10 Alarms
14.10.1 CRITICAL ALARM (LATCHING)
Once in critical alarm state the unit will drive all heating and cooling outputs
to 0V. Other functions continue as normal. The critical alarm is latched and
required manual reset to clear.
Causes of critical alarm:
• Fan fail via alarm circuit 1.
• Heater overtemp via alarm circuit 1.
Maintenance Alarms (Non-Latching)
14.10.3
Once in maintenance alarm state the only action taken is de-energising of the
fault relay. Once the trigger is removed, the alarm will reset automatically.
Causes of maintenance alarm:
•Condensate pump fault via alarm circuit 2 (This bypasses the heater
exchanger automatically).
•Sensor failure.
•Low supply temperature, default 8°C.
•Frost protection routine active, default 4°C (Only runs if water valves are
selected as fitted).
•Excessively high supply temperature reading (this will stop heating).
•Filter fault
All alarms have a hold off period set by the set-point "Alarm delay".
Thermal Trip
14.10.2
In case of software failure, as a final resort, the electric heater is protected by a
fail-safe thermal overload switch. This switch disables the heater controller once
the temperature reaches 80°C. When this occurs, the critical alarm will latch in
software.
Once the unit cools, the contactor will re-engage but the heater signal will
remain at 0V until the critical fault is reset in software or by power cycle.
22. 01. 18. Leaflet Number 671730
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