Evaporator Water Pump Control; Control Interlock Contact; Evaporator Antifreeze Protection; Control Point - Carrier 30RQ Operation And Maintenance Instructions

5.2.2 - Heating/cooling/auto selection
The table below summarises the unit heating/cooling
operation, based on the following parameters:
• Control type: indicates whether the unit operates in
local, remote or CCN mode. See section 5.1.
Unit on/off status: indicates whether the unit is shut
•
down (not authorised to start) or in operation (or
authorised to start).
• Heating/cooling/auto selection in local mode:
operating mode selected via the user interface. See
Information menu.
Parameter status
On/off status Control type
Off -
On Local
On Local
On Local
On Local
On Local
On Remote
On Remote
On Remote
On Remote
On Remote
On CCN
On CCN
On CCN
On CCN
On CCN
* Does not apply to cooling only units that do not control a boiler.

5.3 - Evaporator water pump control

The unit can control one or two evaporator water pumps.
The evaporator water pump is turned on when this option
is configured (see User configuration) and when the unit is
in one of the on modes described above or in delay mode.
Since the minimum value for the delay at start-up is 1 minute
(configurable between 1 and 15 minutes), the pump will run
for at least one minute before the first compressor starts.
The pump is kept running for 20 seconds after the unit goes to
stop mode. The pump keeps working when the unit switches
from heating to cooling mode or vice-versa. It is turned off
if the unit is shut down due to an alarm unless the fault is a
frost protection error. The pump can be started in particular
operating conditions when the evaporator heater is active (see
section 5.5). See section 5.14 for the particular evaporator
pump control for the follower unit (master/slave assembly).
If two pumps are controlled and the reversing function has
been selected (see User 1 configuration), the control tries to
limit the pump run time delta to the configured pump change-
over delay. If this delay has elapsed, the pump reversing
function is activated, when the unit is running. During the
reversing function both pumps run together for two seconds.
If a pump has failed and a secondary pump is available, the
unit is stopped and started again with this pump.
The control provides a means to automatically start the
pump each day at 14.00 hours for 2 seconds when the unit
is off. If the unit is fitted with two pumps, the first pump is
started on odd days and the second pump is started on
even days. Starting the pump periodically for few seconds
increases the life-time of the pump bearings and the
tightness of the pump seal.
Heating/cooling selection Remote heating/
in local mode cooling contacts
- -
Cooling -
Heating -
Auto -
Auto -
Auto -
- Cooling mode
- Heating mode
- Auto mode
- Auto mode
- Auto mode
- -
- -
- -
- -
- -
Remote heating/cooling contacts: these contacts are
•
only active if the unit is under remote control. See
sections 3.6.2 and 3.6.3.
• HC_seL: this network command permits heating/
cooling/auto control, if the unit is in CCN operating
mode.
Outdoor temperature: determines the operation, if
•
the unit is in automatic heating/cooling/standby
changeover mode.
HC_SEL Outdoor temperature
- -
- -
- -
- > Cooling threshold
- < Heating threshold
- Between cooling and heating thresholds
- -
- -
- > Cooling threshold
- < Heating threshold
- Between cooling and heating thresholds
Cooling -
Heating -
Auto > Cooling threshold
Auto < Heating threshold
Auto Between cooling and heating thresholds

5.4 - Control interlock contact

This contact checks the status of a loop (water flow switch
and customer safety loop, see section 3.6). It prevents the
unit from starting if it is open when the delay at start-up has
expired. This open contact leads to an alarm shut-down, if
the unit is running.

5.5 - Evaporator antifreeze protection

The heater for the evaporator and water pump (for units
with a pump) can be energised to protect the evaporator, if
it can be damaged by freezing, when the unit is shut down
for a long time at low outdoor temperature.
NOTE: Evaporator heater control parameters can be
modified, using the Service configuration.

5.6 - Control point

The control point represents the water temperature that
the unit must produce. The inlet water is controlled by
default, but the outlet water can also be controlled
(requires a Service configuration modification).
Control point = active setpoint + reset
5.6.1 - Active setpoint
Two setpoints can be selected as active in cooling mode and
two in heating mode. Usually, the second cooling setpoint
is used for unoccupied periods. The second setpoint in
heating mode is used for unoccupied periods.
Operating mode
Cooling
Cooling
Heating
Cooling
Heating*
Standby
Cooling
Heating
Cooling
Heating*
Standby
Cooling
Heating
Cooling
Heating*
Standby
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