Variable Flow Evaporator; System Minimum Water Volume; Maximum System Water Volume; Evaporator Water Flow Rate - Carrier Aqua Force 30XA Installation, Operation And Maintenance Instructions

6.4 - Variable flow evaporator

Variable evaporator flow can be used in standard 30XA
chillers. The chillers maintain a constant leaving water tem-
perature under all flow conditions. For this to happen, the
minimum flow rate must be higher than the minimum flow
given in the table of permissible flow rates and must not
vary by more than 10% per minute.
If the flow rate changes more rapidly, the system should
contain a minimum of 6.5 litres of water per kW instead of
3.25 l/kW.

6.5 - system minimum water volume

Whichever the system, the water loop minimum capacity is
given by the formula:
Capacity = Cap (kW) x N litres
application
Normal air conditioning
Process type cooling
Where Cap is the nominal system cooling capacity (kW) at
the nominal operating conditions of the installation.
This volume is necessary for stable operation and accurate
temperature control.
It is often necessary to add a buffer water tank to the circuit
in order to achieve the required volume. The tank must
itself be internally baffled in order to ensure proper mixing
of the liquid (water or brine). Refer to the examples below.
Connection to a buffer tank
Bad
Bad
24
N
3.25
6.5
Good
Good

6.6 - Maximum system water volume

Units with hydronic module incorporate an expansion
tank that limits the water volume. The table below gives
the maximum loop volume for pure water or ethylene
glycol with various system concentrations, as well as the
static pressures. If the maximum volume is insufficient,
compared to the minimum system water loop volume, an
additional expansion tank must be added to the system.
30XA
static pressure bar
Maximum water loop volume l
Pure water
Ethylene glycol 10%
Ethylene glycol 20%
Ethylene glycol 30%
Ethylene glycol 40%

6.7 - Evaporator water flow rate

30Xa Evaporator water flow rate, l/s
Min. flow rate
252 3.6
302 4.0
352 4.3
402 5.3
452 6.0
502 6.7
602 8.1
702 8.9
752 9.6
802 10.4
852 11.0
902 11.8
1002 13.1
1102 15.1
1202 16.4
1302 17.5
1352 18.8
1402 19.3
1502 19.9
1702 22.0
* The maximum water flow rate corresponds to a pressure drop of 100 kPa.
252-452 502
1 2 2.5 1 2
2400 1600 1200 3960 2640 1980
1800 1200 900 2940 1960 1470
1320 880 660 2100 1400 1050
1080 720 540 1740 1160 870
900 600 450 1500 1000 750
Max. flow rate*
37.5
40.5
40.5
34.1
36.9
42.0
45.0
56.1
59.1
67.1
67.1
73.9
83.9
87.8
92.9
96.1
107.4
107.4
109.4
107.4
2.5