14
RG66002124 - Rev 05
MCA
All copying, even partial, of this manual is strictly forbidden
8
HEAT RECOVERY OPTIONS
In air-conditioning applications it is useful and often indispensable to have
heat available for heating sanitary water or controlling post-heating in air-
handling units where independent temperature and humidity control is
required. All the units belonging to the MCA-C series can be equipped (on
request) with a desuperheater for recovering heating power corresponding to
20% of the available heating capacity. All units equipped with a heat recovery
kit have modulating condensation control as a standard feature. To prevent
unbalances from occurring in the cooling circuit in the event of start-ups with
very low water temperatures at the recuperator inlet, the recovery system
water circuit should be configured as shown in the figure.
A low recuperator inlet water temperature would cause low condensation
temperatures and thus an insufficient pressure differential on the expansion
valve with the consequent risk of tripping the safety devices.
The sensor of the 3-way mixing valve shoul be situated at the recuperator
inlet and mixing the hot water produced with colder water from the inertial
storage reservoir makes it possible to bring the system to optimal operating
conditions in a few instants. Given that the demand for heat and the
availability of heat do not coincide, since the latter is dependent on the
compressors running, it is essential to install an inertial storage reservoir
between the unit and the user.
9
CALCULATION FACTORS
9.1
WATER TEMPERATURE DROP/RISE DIFFERENT THAN 5°C
Find the performances of the unit as a function of the water outlet temperature
and multiply them with the factor reported in the table below.
D
T
W
C
PF/PT
C
PA
C
Qw
C
Dpw1
3
0,975
1
1,63
2,64
4
0,99
1
1,24
1,53
5
1
1
1
1
6
1,015
1
0,85
0,72
7
1,03
1
0,74
0,54
8
1,04
1
0,65
0,42
9.2
GLYCOL AND WATER SOLUTION
With the minimum water outlet temperature find the glicol percentage and the
calculation factors using the table below..
Percentage of glycol
0%
10%
20%
30%
40%
Minimum water outlet temperature
5°C
2°C
-5°C
-10°C
-15°C
Mixture freezing temperature
0°C
-4°C
-14°C
-18°C
-24°C
Capacity correction factor
1,000
0,998
0,994
0,989
0,983
Water flow correction factor
1,000
1,047
1,094
1,140
1,199
Water pressure drop correction factor 1,000
1,157
1,352
1,585
1,860
7
OPERATING LIMITS
Supply voltage: ± 10% of rated voltage.
The operating limits shown in the diagrams are valid for thermal differentials
of water between 3 and 8°C
Legend:
RH
Relative humidity of outdoor air
Tbs
1
Outdoor temperature (dry bulb)
Tw
2
Outlet water temperature
7.1 COOLING MODE
In order to work with outdoor temperatures below 20 °C it is essential to install
a condensation control device (optional). The control works by modulating
the fan speed with a potentiometer and allows the unit to operated in the
cooling mode with outdoor temperatures (Tbs1) as low as -15 °C
7.2 HEATING MODE
3
-15
0
10
20
30
40
45
5
7
9 11 13 15 17 19
42
Tw2
(°C)
Tbs1
(°C)
Condensation
control device
25
-5 / 90%
0 / 90%
5 / 90%
10 / 80%
15 / 80%
20 / 70%
30 35 40 45 50 55
Tw2
(°C)
Tbs1 / RH
(°C) / %
heat recovery
exchanger
Heat recovery
users
