Operating Limits For Changeover Between Modes; Flow Control; Heat Reclaim Operation; Condenser Pump Selection - Carrier AquaForce 30XBE 250 Installation, Operation And Maintenance Instructions

9 - HEAT RECLAIM CONDENSER OPTION (OPTION 50)
9.6 - Operating limits for changeover between
modes
From cooling only to heat reclaim and vice versa.
Heat reclaim condenser water temperature
Water entering temperature
Ambient operating
temperature
(1) -20 °C with winter operation option (option 28)

9.7 - Flow control

The water flow switch supplied needs to be installed at the heat
reclaim condenser water inlet and protects the conden-ser loop
against low water flow conditions. When the heat reclaim mode is
required, a signal from the additional board output activates the
system pump. Once the pump is started, flow detection takes place
for one minute. If no flow is detected by the end of this time:
1. Changeover to the heat reclaim mode is not permitted
2. Mode is changed to cooling only mode when the water flow
rate is low, accompanied by a water flow detection alarm.
3
6
12
10
7
11
8
10
5
4
Legend
1 Evaporator
2 Heat reclaim condenser
3 Air condenser (coils)
4 Compressor
5 Expansion device (EXV)
6 Motorised valve - heat reclaim mode
7 Motorised valve - cooling only mode
8 Solenoid valve - charge recovery in heat reclaim mode
9 Solenoid valve - charge recovery in cooling only mode
10 Check valve
11 Pressure and temperature measurement to calculate the liquid sub-cooling to
optimise the charge recovery
12 Check valve with capillary

9.8 - Heat reclaim operation

The heat reclaim condenser option is only available on units with
two circuits. It has been designed with one or two single or two-circuit
shell-and-tube heat exchangers, depending on the unit size.
The two circuits are independently controlled. One circuit can be
in cooling only and the other in heat reclaim mode.
Changeover from one mode to the other (changeover from heat
exchange at the air condenser to heat exchange at the water
condenser and vice versa) is ensured by motorised two-way valves
located upstream of the air and water condensers.
ATTENTION: Mode changes may lead to higher sound levels
than the levels at stable operation.
Depending on the mode selected (heat reclaim or cooling), the
logic compares the water entering temperature required with the
°C Minimum Maximum
12,5 57,5
-10 (1) 45
2
3
12
9 9
10
7
11
8
10
5
4
1
setpoint. Depending on this difference the unit circuits are either
activated or deactivated in heat reclaim mode (one or two together),
as shown in the following diagram and table.
E
D
C
B
A
The deadband of 5 K is controlled by default.
Selection of the
Case
heat reclaim mode
- NO
A YES
B YES
6
C YES
D YES
E YES
For more details on the heat reclaim operation logic please refer
to the SmartVu TM
reclaim module".

9.9 - Condenser pump selection

Heat reclaim condenser water flow rate/pressure drop
Heat reclaim condenser pressure drop in water flow
70
60
50
40
30
20
10
0
0
1 Condenser 10" (water volume = 38 litres)
2 Condenser 12" (water volume = 55 litres)
3 Condenser 14" (water volume = 68 litres)
For units with a water condenser please refer to chapter 9.1 - "Technical data, 30XB
units with heat reclaim condenser option".
E
D
C
B
A
Number of circuits
in heat reclaim mode
0
Whatever the number
0
1
2
Whatever the number
1
2
Whatever the number
control manual, chapter 6.15 - "Optional heat
rate function
10 20
Water flow rate, l/s
+2,5 K
+2.5 K
+1.25 K
+1,25 K
Setpoint, °C
-1,25 K
-1.25 K
-2.5 K
-2,5 K
T
Action
+ 2 circuits in
cooling mode
+ 2 circuits in heat
reclaim mode
+ 1 circuit in heat
reclaim mode
No change
No change
No change
No change
- 1 circuit in heat
reclaim mode
- 2 circuits in heat
reclaim mode
30 40
67