47
8.6 -
Operating limits for changeover between
modes
From cooling only to heat reclaim and vice versa.
Condenser water & ambient temperatures
Minimum Maximum
Entering water temperature
°C
125
(1)
57,5
Ambient operating temperature
°C
-20
45
(1) The entering water temperature must not be lower than 12.5°C. For installations
with a lower temperature, a three-way valve must be used.
NOTE:
if the temperature at the evaporator is below 4 °C, a glycol/water solution or the
frost protection option must be used.
8.7 -
Flow control
The water flow switch supplied needs to be installed at the heat
reclaim condenser water inlet and protects the condenser 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
4
6
5
10
11
9
8
10
7
3
4
6
5
10
11
9
8
10
7
12
12
1
2
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
8.8 - 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
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.
A
B
C
D
E
+2,5 K
+1,25 K
-1,25 K
-2,5 K
T
Setpoint, °C
Condenser water entering
temperature
Deadband
E
A
B
C
D
-1.25 K
-2.5 K
+2.5 K
+1.25 K
The deadband of 5 K is controlled by default.
For more details on the heat reclaim operation logic, please refer
to the SmartVu
TM
control manual.
8.9 - Condenser pump selection
Heat reclaim condenser water flow rate / pressure drop
characteristic curves are shown in the following graphs.
Option 50: heat reclaim condenser pressure drop in
water flow function
0
10
20
30
40
50
60
70
0
10
20
30
40
Pressure drop, kPa
Water flow rate, l/s
1 Condenser 10” (water volume = 38 litres)
2 Condenser 12” (water volume = 55 litres)
3 Condenser 14” (water volume = 68 litres)
Option 50C: heat reclaim condenser pressure drop in
water flow function
0
10
20
30
40
50
0
10
20
30
40
Pressure drop, kPa
Water flow rate, l/s
Condenser 14’’ (water volume = 82 litres)
8.10 - Frost protection
The heat reclaim condenser is equippped with electric heaters to
protect the condenser against frost. These are activated if the
condenser entering and leaving water temperatures are below 3
°C and deactivated, if they are higher than 4.3 °C.
8 - HEAT RECLAIM CONDENSER OPTIONS (OPTIONS 50 & 50C)
