Communications wiring
Unit Ventilator
CARRIER CORPORATION ©2019
Integration Guide
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20
OAT is greater than the
Cooling Lockout Temperature
If occupied, the SPT is greater than the
Occupied Cooling
setpoint
If unoccupied, the SPT is greater than the
Unoccupied Cooling
setpoint
If all the above conditions are met, cooling is energized as required, otherwise it is disabled. If cooling is active
and the SAT approaches the minimum SAT limit, the cooling valve modulates closed. (For DX cooling, if the SAT
drops below the configured minimum SAT value, the fan is indexed to a higher speed. If this is insufficient and if
the SAT falls below the minimum limit minus 5 °F (2.7 °C), the DX cooling will be disabled.)
The configuration screens contain
Min Cooling SAT
and
Cooling Lockout
based on outdoor air temperature (OAT).
Both can be adjusted to meet various specifications.
For DX cooling, after the compressor is staged off, it may be restarted again after the supply air temperature has
increased above the minimum supply air temperature limit. There is a 5 minute minimum off-time for the
compressor as well as a 2 minute minimum on-time to prevent oil migration.
Modulating Chilled Water
- The control can operate a modulating (0-10 Vdc or 2-10 Vdc) type, NO or NC, chilled
water valve connected to the cooling coil of the unit in order to maintain the desired cooling setpoint. The valve
modulates to maintain the SAT at the calculated
Cooling Control Setpoint
. The control will also prevent the SAT
from exceeding the
Minimum Cooling SAT
limit.
Face & Bypass Chilled Water
- The control can operate a modulating (0-10 Vdc or 2-10 Vdc) type F&B damper and
an optional 2-position NO or NC chilled water valve to maintain the desired cooling setpoint. The damper
modulates to maintain the SAT at the calculated
Cooling Control Setpoint
. The valve opens when cooling is
required (and the water is suitable if 2-pipe changeover). The control will prevent the SAT from exceeding the
Minimum Cooling SAT
limit.
Single Stage Direct Expansion (DX)
- The control can operate a single stage of DX cooling in order to maintain the
desired cooling setpoint. The DX stage is controlled to prevent the SAT from exceeding the
Minimum Cooling SAT
minus 5 °F (2.7 °C) and also subject to a 2 minute minimum on-time. The compressor output is not energized
unless SAT >
Minimum Cooling SAT
limit plus 10 °F (5.5 °C). Once disabled, the compressor cannot be
restarted for at least 5 minutes.
Heating
The Unit Vent operates mechanical heating (staged electric heat, a modulating hot water/steal valve, or a F&B
damper plus a 2-position heating valve, or a combination) to maintain the desired heating setpoint. The heating is
controlled by the PI (Proportional-integral) heating algorithm and the heating stage capacity algorithm for electric
heat. The desired
Heating Control Setpoint
is calculated by the controller. This setpoint is compared to the actual
supply air temperature and determines valve or damper operation and staging control for electric heat.
The following conditions must be true in order for the heating algorithm to run:
Heat Enable
is set to
Enable
Space temperature reading is valid
Supply Fan
must not be in alarm
For 2-pipe systems, the water temperature is suitable for heating
Cool mode is not active
For electric heat, the minimum off timers have expired
