Water Pump Control; Heat Exchanger Anti-Freeze Protection - Carrier SmartVu 61AF 030-105 Manual

6 - STANDARD CONTROL OPERATIONS AND OPTIONS

6.4 - Water pump control

The unit can control one water exchanger pump which can be
either a fixed speed pump or a variable speed pump.
The pump can be factory-installed ("internal pump") or it can be
supplied by the customer ("external pump").
Pump control logic Internal pump
Constant speed control yes
Variable speed control yes
The pump is normally turned on when the unit is running in Heating
mode. The pump control method may vary depending on the type
of the pump (internal or external) and the pump control logic set
by service technicians. When the unit is "Off", the pump is stopped;
however, the pump can be started in particular operating conditions
when freeze protection of the heat exchanger is active (see
section 6.5).
6.4.1 - Constant speed control
Fixed speed pump can be controlled through the "Pump 1 Output"
parameter in the Outputs menu. Fixed speed pump control applies
only to internal pumps.
6.4.2 - Variable speed control
The water flow is controlled based on Delta T (differential
temperature) on the water exchanger; however, the control logic
may differ depending on the type of the pump (internal/external).
Variable speed control Internal pump
LEN drive yes
0-10V drive: Step control -
0-10V drive: PID control
6.4.2.1 - Internal pump control
The speed of the internal pump may vary depending on the current
unit capacity and service configuration. For example, in defrost
mode higher pump speed equals better efficiency; therefore, during
defrost the pump speed will be set to the maximum speed that is
allowed. At the same time, when the unit is running, but there is
no heating demand, the pump speed will be low. Under normal
operating conditions, the unit's nominal water flow should
correspond to the minimum pump speed.
Depending on factory installation, the internal pump can be
controlled either through the standard LEN drive or the optional
0-10V drive. The internal pump control can be set only by service
technicians.
When controlled through the LEN drive:
■ The status of the internal pump is displayed in the Pump Status
menu under "Drive pump status".
■ "External Pump Output" (PUMP_EXT, Pump Status menu) and
"External Pump Output" (PUMP_EXT, Outputs menu) will be
set to '0'.
When controlled through the 0-10V drive:
■ The drive output is controlled through 0-10V output, i.e.
"External Pump Output" (PUMP_EXT, Outputs menu).
■ "External Pump Output" (PUMP_EXT, Pump Status menu)
displays its value in %.
■ The output is controlled by a PID to satisfy the Water Delta T
Setpoint defined by service technicians. When the unit is ready,
the pump speed is set to pump saving speed (minimum pump
speed). When the unit is running, water pump speed is clamped
between the minimum and maximum pump speed.
34
External pump
-
yes
External pump
-
yes
optional yes
6.4.2.2 - External (customer) pump control
The control allows for managing the external 0-10V pump via the
0-10V Pump Config menu (FLOWCONF).
When controlled through the 0-10V drive:
■ The pump is controlled through 0-10V output, i.e. "External
Pump Output" (PUMP_EXT, Outputs menu).
■ "External Pump Output" (PUMP_EXT, Pump Status menu)
displays its value in %.
The customer pump can be controlled by:
■ Step control logic.
- a step value is added to the output each time the "Reschedule
timer" has elapsed and Delta T > Water Delta T Setpoint
[dt_stp] + Deadband
- a step value is removed from the output each time the
"Reschedule timer" has elapsed and Delta T < Water Delta
T Setpoint [dt_stp] - Deadband
■ PID control logic. The output is controlled by a PID to satisfy
Water Delta T Setpoint.
To set 0-10V pump control method
1. Navigate to the Configuration menu.
2. Select 0-10V Pump Config (FLOWCONF).
3. Set the pump control logic [logictyp].
Logic: 0=No,1=STEP,2=PID [logictyp]
0 = no (no external pump)
1 = Step control logic
2 = PID control logic
6.4.3 - Pump protection (pump anti-stick function)
The control provides a means to automatically start the pump each
day at 14:00 for 2 seconds when the unit is off.
Starting the pump periodically for a few seconds extends the
lifetime of the pump bearings and the tightness of the pump seal.
To set pump sticking protection
1. Navigate to the Configuration menu.
2. Select Pump Configuration (PUMPCONF).
3. Set Pump Sticking Protection [pump_per] to "yes".
Pump Sticking Protection [pump_per]
no/yes

6.5 - Heat exchanger anti-freeze protection

When the outside air temperature is low, the risk of heat exchanger
freezing is increased. In systems without the anti-freeze protection,
the water inside the heat exchanger would freeze and cause heat
exchanger damage.
The control system comes with two solutions to protect the heat
exchanger from freezing:
■ Quick pump start algorithm
As standard, the automatic pump start-up algorithm protects
the heat exchanger and the hydraulic module piping from
freezing when the outside air temperature is down to -10°C.
Forcing water circulation will protect the water from freezing.
- No additional configuration is required.
■ Electric heater (optional) + quick pump start algorithm
The installation of this optional electric heater will protect the
heat exchanger and the hydraulic module piping from freezing
when the outdoor temperature goes down to -20°C.
- The cooler heater option requires service configuration.
- The status of the electric heater "Cooler Heater Active" can
be verified by the user (MODES, m_cooler).
yes