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System Component; Selection Of The Heat Exchanger (Air Handling Unit) - Mitsubishi Electric PAC-AH125 Installation Manual

Air handling unit controller
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3. System component

[Fig. 3.0.1] (P.2)
A Air handling unit controller (PAC-AH
B Air handling unit (field supply)
C Controller (field supply)
D Outdoor unit
E Heat exchanger (field supply)
F Gas pipe
G Liquid pipe
H LEV-kit
I Thermistor (gas pipe)
J Thermistor (liquid pipe)
K Thermistor (suction air)
L Thermistor (discharge air)
3.1. Selection of the heat exchanger (air
handling unit)
3.1.1 Compressive strength
The design pressure of this system is 4.15MPa. The compressive strength of the
evaporator and of other pipes must exceed 12.45MPa (=4.15 × 3).
3.1.2 Contamination control
Control the contamination to keep proper quality of the models using HFC refrig-
erant.
Contamination
Residual water content
The content shall be less than [10 mg/lit.].
Residual oil content
The low residual oil pipe [0.5 mg/m or less] shall
be used for heat exchangers.
For long piping connected or piping tended to be
stagnated with oil, the content shall be less than
[3 mg/m]. For other piping, [9 mg/m or less] shall
be applied.
Residual foreign substance
The content shall be less than [25 mg/m
(including residual machining
oil content)
Others
No chlorine content shall be found inside the
refrigerant circuit.
3.1.3 Specifications of the heat exchanger
Select the heat exchanger (field supply) according to the table below.
Caution:
If not, malfunction of the outdoor unit may be caused.
Model name
Unit capacity
Reference air flow rate in case
of connection without standard
indoor units (m
/h)
3
Max. air flow rate in case of
connection with standard
indoor units, except cooling
only (m
/h)
3
Min. volume inside heat
exchanger tube (cm
)
3
Max. volume inside heat
exchanger tube (cm
)
3
Max. capacity (kW)
Min. capacity (kW)
Standard number of paths
(Heat exchanger tube size
(ø9.52))
Pressure drop of the refrigerant
in heat exchanger
LEV inlet temperature
Evaporating temperature
8.5 ˚C
SH
Evaporator outlet Temperature 13.5 ˚C
Evaporator suction air temper-
ature
8
·
M-J)
Content
2
PAC-M-J
AH125
AH140
AH250
AH500
100
125
140
200
250
400
2000 2500 3000 4000 5000 8000 10000
800 1000 1120 1600 2000 3200 4000
1500 1900 2150 3000 3750 6000 7500
2850 3550 4050 5700 7100 11400 14200
11.2 14.0 16.0 22.4 28.0 45.0 56.0
9.0
11.2 14.0 16.0 22.4 36.0 45.0
4~5
4~5
5~6 6~10 8~10 16~20 16~20
Max. 0.03MPa
25 ˚C
5K
27 ˚CDB/19 ˚CWB
Max. capacity (kW)
Min. capacity (kW)
Condensing temperature =TC
Outdoor temperture 0 ˚CDB / -2.9 ˚CWB (Water temp. 20 ˚C in PQHY/PQRY)
55
50
45
40
35
30
25
P100
P125
1000
P140
1120
P200
1600
P250
2000
P400
3200
P500
4000
Unit
capacity
HEX inlet temperature
].
80
75
70
65
60
55
50
45
40
25
500
SC
Condensor outlet temperature TC-15
Condensor suction air temper-
ature
Caution:
The heat exchanger must be used within the following temperature range.
Inlet air temperature range of the air handling unit: 15-24 ˚CWB (cool-
ing), –10 - +15 ˚CDB (heating)
12.5 16.0 18.0 25.0 31.5 50.0 63.0
10.0 12.5 16.0 18.0 25.0 40.0 50.0
Choose TC satisfying a condenser design
condition among chart below depending on
unit size. In the case of using a heat
recovery, choose TC=49 ˚C as the suction
temperature of heat exchanger may
become 10 ˚C or more even if outdoor
temperature is 0 ˚C.
Available
800
1200
1600
2000
1500
2000
2500
1680
2240
2800
2400
3200
4000
3000
4000
5000
4800
6400
8000
6000
8000
10000
Air flow rate (CMH)
Choose HEX inlet temperature from chart
below depending on TC.
30
35
40
TC (˚C)
15K
0 ˚CDB / –2.9 ˚CWB
2400
3000
3360
4800
6000
9600
12000
45
50

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