AERMEC NRGI-H - Minimum System Water Content; Expansion Vessel Setting

28 21.01  5723611_01
MINIMUM SYSTEM WATER CONTENT
For correct unit operation, there must be a suitable amount of water in the system.
A sucient quantity of water not only ensures machine stability, but also helps
avoid a high number of hourly compressor start-ups.
To calculate it, use the formula: Unit rated cooling capacity (kW) x table value (l/kW)
= Minimum system content (l).
Size 151 201 281 302 332 352 382 502 552 602
Minimum system water content (1)
Application for ambient comfort A,E l/kW 5,0 5,0 5,0 2,5 2,5 2,5 2,5 2,5 2,5 2,5
Process chiller application A,E l/kW 10,0 10,0 10,0 5,0 5,0 5,0 5,0 5,0 5,0 5,0
(1) Calculated with a minimum load factor 15%
Units with the hydronic kit mounted come standard with the expansion vessel set
at 1.5 bar, the pressure relief valve, the ow switch and the water lter mounted.
The maximum system water content depends on the capacity of the expansion ves-
sel and on the calibration of the pressure relief valve.
Size 151 201 281 302 332 352 382 502 552 602
Hydronic kit
Expansion vessel number A,E no. 1
Expansion vessel capacity A,E l 24
The table gives an example of the maximum water content calculated at the indi-
cated operating conditions and only to protect the unit.
If the volume of water in the system is higher, add another expansion vessel of the
correct size.
System water temperature max/min °C 40/4
Hydraulic height M 30 25 20 15 ≤12,25
Expansion vessel pre-load bar 3,2 2,8 2,3 1,8 1,5
Water content maximum l 2174 2646 3118 3590 3852
System water temperature max/min °C 60/4
Expansion vessel pre-load bar 3,2 2,8 2,3 1,8 1,5
Water content maximum l 978 1190 1404 1616 1732
System water temperature max/min °C 85/4
Expansion vessel pre-load bar 3,2 2,8 2,3 1,8 1,5
Water content maximum l 510 622 732 844 904
The data in the table refer to units with a 24 l expansion vessel.
EXPANSION VESSEL SETTING
The expansion tank volume is 24l. The standard value of the expansion tank pre-
charge pressure is 1.5 bar, but this can be calibrated up to a maximum of 6 bar.
The expansion tank pressure setting has to be adjusted based on the dierence in
height (H) of the installation (see gure) according to the formula:
p (rating) [bar] = H [m] / 10.2 + 0.3.
For example, if the dierence in height H is 20 m then the value of the expansion
tank pressure setting is 2.3 bar.
If the calculated pressure setting value is less than 1.5 bar (when H < 12.25), main-
tain the standard pressure setting.
Key
A Expansion vessel
1 Check that highest utility is
not higher than 55 metres
2 Ensure that lowest utility can
withstand global pressure in
that position
H max
(1)
= 55 m
H = 0 m
H = 12.25 m
Ptar = H / 10.2 + 0.3
Ptar = 1.5 barPtar = 1.5 bar
H min
(2)
A