McQuay MDS030AR Applications Manual page 56

Design & installation Guide For McQuay MDS Multi System
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3.3.7 Actual Capacity Calculation
Based on the model and combination rate of the outdoor unit, select an appropriate door
unit capacity table. Then find out the capacity of the outdoor unit (kW) and that of each
indoor unit (kW) according to the related temperatures of the indoor and outdoor units.
The formula is as follows:
Where,
I is the actual capacity of each indoor unit.
UC
O is the capacity of the outdoor unit. unit: kW.
UC
I is the capacity index of each indoor unit.
NX
T is the total capacity index.
NX
The capacity of indoor units changes with the length of the refrigerant pipe. If the
capacity after change is less than the load, replace the unit with one with larger capacity
and calculate
and select the model again.
3.3.8 Change of Cooling Capacity (3-30HP)
50
40
30
20
98.5%
10
100%
100%
0
-10
-20
-30
-40
0 10
3.3.9 Change of Heating Capacity (3-30HP)
50
40
30
99.0%
20
100%
10
100%
0
-10
-20
-30
-40
0 10
Read the performance correction factor of the refrigerant pipe length and height drop from the
figure. When the height drop is negative, the outdoor unit is installed below the indoor unit.
If there is snow on the heat exchanger or the outdoor temperature drops to 7
the air conditioning system is heating, frosting occurs. As this will reduce the heating
performance, the air conditioner will automatically defrost once every 40 min to 70 min. During
the defrosting, the air conditioner will stop heating and the fan of the indoor unit will also stop
for three to ten minutes.
The heating capacity tables of outdoor and indoor units do not reflect the reduction of performance
caused by defrosting.
I =O
UC UC
92.5% 91.0%
94.0%
95.5%
97.0%
97.5% 94.0%
20 30 40 50 60
96.0% 95.0%
97.0%
98.0%
98.0% 96.0%
20 30 40 50 60
x (I /T )
NX NX
89.5% 88.0% 86.5% 85.0% 83.5%
91.0% 88.0% 85.0%
70 80 90 100 110
Pipe length (m)
94.0% 93.0% 92.0% 90.0% 89.0%
94.0% 92.0% 90.0%
70 80 90 100 110
Pipe length (m)
82.0% 80.5% 79.0%
82.0% 79.0%
120 130 140 150
88.0% 87.0% 86.0% 85.0%
88.0% 86.0%
120 130 140 150
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when