Carrier AquaSnap 30RB Series Installation, Operation And Maintenance Instructions page 42

11.2.4 - operating limits
Heat reclaim condenser
Entering water temperature at start-up
Leaving water temperature during operation
Condenser (air)
Outdoor ambient operating temperature
Available static pressure
* The minimum outside temperature for heat reclaim mode is 0°C in cooling
mode and -20°C with the 'winter operation' option.
The water entering temperature at start-up must not fall
below 15°C. for installations with a lower temperature
an accessory 3-way valve must be installed.
legend
1 Evaporator
2 Heat reclaim condenser
3 Air condenser (coils)
4 Compressor
5 Expansion device (EXV)
6 Solenoid valve: heat reclaim mode
7 Solenoid valve: cooling mode
8 Solenoid valve: charge recovery in heat reclaim mode
9 Solenoid valve: charge recovery in cooling mode
10 Check valve
11 Pressure and temperature measurement to calculate the liquid subcooling to
optimise the charge recovery
11.2.5 - Flow control
A flow switch on the condenser is factory-installed. The
condenser loop is protected against a flow rate that is too
low. Output 16 of the additional board of this option
allows control of the condenser pump operation that will
start up after the unit has started.
If the flow rate is too low:
- changeover to the heat reclaim mode is not permitted,
- immediate changeover to cooling mode when the flow
rate is too low and the unit operates in heat reclaim
mode.
42
Minimum Maximum
°C 15 55
°C 20 55
Minimum Maximum
°C 0* 46
Pa 0 0
11.2.6 - heat reclaim operation
The heat reclaim condenser option is only available on
units with two circuits. It was designed with a shell-and-
tube two-circuit heat exchanger with the coils in parallel.
The two circuits are independently controlled. This means
that one circuit can be in cooling mode and the other in heat
reclaim mode. This permits two stable control stages (100% if
the circuits are in heat reclaim mode, and approximately
50% based on the size of the circuit in operation). The
intermediate stages are obtained by cycling between the
air condenser mode and the heat reclaim mode.
HR stopped
°C
HR
setpoint
HR = Heat reclaim mode
This cycling will lead to a water temperature change in the
condenser loop of the heat reclaim condenser. Based on
the stability required, the water loop must be more or less
significant.
Stability volume
2°C 40 l/kW*
3°C 30 l/kW*
4°C 20 l/kW*
5°C 15 l/kW*
* kW: cooling mode capacity
The number of cycles is limited to 4 per hour
Please refer to the 30RB controls manual for more
information on the control logic of the condenser loop.
11.2.7 - Frost protection
The water condenser is protected by electric heaters. The
algorithm is based on the outside temperature. However, the
condenser connection pipes are not protected. It is recom-
mended to add pipe protection at the time of installation
(glycol, heat insulation, heaters etc.). If the pumps are
ordered by unit, the water condenser is also protected by a
pump control algorithm that ensures water flow at water
temperatures that are too low. If the pumps are not ordered
by unit, it is recommended to ensure water flow at outside
temperatures that are too low.
Cycling time
HR operating
Dead band
Condenser
water
temperature