Variable Flow Water Heat Exchanger; Minimum System Water Volume; Maximum System Water Volume; Water Heat Exchanger Flow Rate - Carrier AQUASNAP 30RQ Installation, Operation And Maintenance Instructions

6.4 - variable flow water heat exchanger

Variable water heat exchanger flow can be used in standard
heat pumps. The 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 2.5 l/kW.

6.5 - Minimum system 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.
It can be 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
14
N
2.5
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.
Maximum water loop volume, litres
30RQ
static pressure bar
Pure water
EG 10%
EG 20%
EG 30%
EG 40%
EG - Ethylene glycol

6.7 - Water heat exchanger flow rate

30RQ Water flow rate, l/s
Minimum
262 3.5
302 3.9
342 4.4
372
4.9
402 5.2
432
5.8
462 6.1
522 6.9
* The maximum flow rate corresponds to a pressure loss of 100 kPa (heat
exchanger without hydronic module).
Water heat exchanger pressure drop curves,
standard units
100
90
80
70
60
50
40
30
20
10
10
Water flow rate l/s
legend
1 30RQ 262-302
2 30RQ 342
3 30RQ 372-522
262 302-522
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
Maximum*
26.7
26.7
29.4
31.1
31.1
31.1
31.1
31.1
3
20 30
2.5
40