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26. 01. 22. Document Number 671829
Nuaire | Western Industrial Estate | Caerphilly | CF83 1NA | nuaire.co.uk
BPS H-AT
Installation Manual
8.11 Supply Air 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 setpoint. Please note that heating and
cooling outputs will only function if the HeatingType or CoolingType
setpoints are set to heating or cooling options.
8.12 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 setpoints are set to LPHW or CW.
8.13 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
setpoint, cooling is possible and if the cooling air is not too cold.
8.14 Mitsubishi Reverse Cycle DX (Optional)
For units for use with Mitsubishi reverse cycle condenser units, one or
more PACIF012B-E Interface boards are fitted inside the control panel.
The controller interacts with this board in the following ways:
•
Digital Output Heat/Cool selection from iQ4E relay 8. Another
relay is used to split output over multiple boards.
•
0-10v Heat/Cool demand from iQ4E OUT14.
•
Faults are monitored via iQ4E IN8 (Alarm circuit 2). A relay is
fitted to reverse the fault action.
•
The defrost status relay is connected to the enable input of the
controller to start the fans when the condenser enters defrost
mode.
When Mitsubishi Reverse Cycle DX is fitted, this is selected in software
by setting the cooling type “3-Reverse Cycle”. A heating type is not
required unless another heating type is fitted (eg LPHW).
Once this is selected cooling and heating demand will share iQ4E
OUT14 and heat/cool is decided on the state of iQ4E relay 8.
(Energised = Cool Demand)
For the cases where Reverse Cycle DX and another heating type are
both fitted, a schedule module is provided in the Trend strategy. When
the schedule is on, the heating output reverts to LPHW/Electric heating.
The enable run-on time must be set to 3 minutes for reverse cycle
units. This is required in order to keep the compressor running for at
least 3 minutes for each period.
A minimum-on module is connected to the heat/cool relay in order to
stop frequent mode switching.
Although the controller outputs a variable 0-10v heating/cooling
voltage, the Mitsubishi condenser can only run at 7 discrete levels and
so cannot supply an accurate supply air temperature.
The PAC boards are powered from the BPS control so the only
connections required to the Outdoor condenser are S2 & S3. For the
same reason, SW8-3 must be set to “ON” on the outdoor unit.
8.15 Partial Recirculation Damper (Optional)
If a partial recirculation module is fitted, the recirculation damper will
open/close via iQ4-8DO Relay 6 according to the following strategy.
If the room temperature is more than 5°C(adjustable) from the
setpoint and free-cooling or free-heating is not available then partially
recirculate the air.
This aids heating and cooling elements and also avoids thermal loss
from the room.
8.16 Alarms
8.16.1 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 or power cycle to clear.
Causes of critical alarm:
•
Fan fail via fault circuit 1.
•
Heater overtemp via fault circuit 1.
8.16.2 Maintenance Alarm
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 critical alarm:
•
Condensate pump fault via alarm circuit 2
•
dp Filter fault via alarm circuit 2.
•
IO damper fault via alarm circuit 2.
•
Thermal Wheel fault via alarm circuit 2.
•
Sensor failure
•
Low supply temperature, default 8°C (Can be set to stop fans if
required).
•
Frost protection routine active, deafult 4°C (Only runs if water
valves are selected as fitted)
•
Excessively high supply temperature reading (Will stop heating).
If pump fault circuit is broken two additional events occur in order to
stop condensate production.
•
The heat exchanger will enter bypass mode.
•
Alarm 2 circuit will break, stopping cooling functions.
All alarms have a hold off period set by the setpoint “Alarm delay”.
8.16.3 Thermal Trip
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 via a contactor once the temperature reaches
80°C. When this occurs, the critical alarm will latch in software and the
supply contactor will latch in the off position.
Once the unit cools, the contactor will remain latched off until power
cycle.
