Water Tank - AERMEC NRA 2000 Manual Tecnico

The versions with accumulation offer
different set-ups that vary on the basis
of the effective pressure that you want to
obtain, the characteristics of the pumping
unit, and the presence or absence of holes
for integrative resistance. The following
tables show the main characteristics of
the components of the hydraulic circuit,
while the graphs on these pages show
the relative pressures. The accumulation
tanks with holes for heaters are equipped
with plastic, temporary closing plugs.
WARNING
Before start-up, the installer must
assemble the heaters. If these heaters
are not immediately necessary, the
plastic plugs must be replaced with
suitable metal plugs.
10. 1 MAXIMUM WATER CONTENT
IN THE SYSTEM
The table below indicates the maximum
water content, in litres, of the hydraulic
system, compatible with the capacity
of the expansion tank supplied as
standard. The values shown in the table
refer to three conditions of maximum
and minimum water temperature. If the
effective water content of the hydraulic
system (including the accumulation
tank) is greater than that shown in the
operational conditions table, another,
additional expansion tank must be
installed, measured (using the common
criteria) with reference to the additional
volume of water. From the following
tables, it is possible to obtain the values of
maximum system content, also for other
operational conditions with glycol water.
The values are obtained by multiplying
the reference value by the correction
coefficient.
10. 1 . 1 Calibration of expansion tank
The standard value of pre-charge
pressure of the two expansion tanks is
1.5 bar, while their volume is 24 litres,
maximum value 6 bar.
The calibration of the tanks must be
regulated on the basis of the maximum
difference of level (H) of the user (see
figure), according to the formula:
p (calibration) [bar] = H [m] / 10.2 +
0.3.
For example, if the level difference H is
20m, the calibration value of the tank will
be 2.3 bar.
If the calibration value obtained from
the calculation is lower than 1.5 bar (i.e.
for H < 12.25), maintain the standard
calibration.

WATER TANK

10
Hydraulic height
Calibration of expansion tank
Water content reference value
Water content reference value
Water content reference value
Glycol water Water temp. °C
max.
10% 40
10% 60
10% 85
20% 40
20% 60
20% 85
35% 40
35% 60
35% 85
Working reference conditions:
(1) Cooling: max water temp. = 40°C, min water temp. = 4°C.
(2) Heating (heat pump): max water temp. = 60°C, min water temp. = 4°C.
(3) Heating (boiler): max water temp. = 85°C, min water temp. = 4°C.
H max (1) = 55 m
H = 12.25 m
H = 0 m
H min (2)
H m 30 25 20
bar 3.2 2.8 2.3
l (1)
2. 1 74 2.646 3. 1 18
l (2)
978 1190 1404
l (3)
510 622 732
Correction
coefficient
min.
-2 0,507
-2 0,686
-2 0,809
-6 0,434
-6 0,604
-6 0,729
-6 0,393
-6 0,555
-6 0,677
KEY
(1) Check that the highest user does
not exceed a level difference of 55
metres.
(2) Check that the lowest user can
sustain the global pressure acting
at that point.
15 ≥ 12.25
1.8 1.5
3590 3852
1616 1732
844 904
Reference
condition
(1)
(2)
(3)
(1)
(2)
(3)
(1)
(2)
(3)
H
23