Mitsubishi Electric MXZ-18NV Service Manual page 33

No. Item
LEV opening correction by suction superheat
(Suction superheat) = (Suction temperature) - (Evaporation temperature)
The LEV opening is corrected as shown in the following table.
Suction superheat (S.H.)
10 < S.H
8 < S.H [ 10
7 < S.H [ 8
5 < S.H [ 7
4 < S.H [ 5
2 < S.H [ 4
0 < S.H [ 2
S.H [ 0
LEV opening correction by discharge temperature
The LEV opening is corrected to 55 pulse when it has been corrected consecutively 20 times
due to the discharge temperature (Td) of
below 35°C. When such a status has continued for 10 minutes, the compressor stops and
enters the 3 - minute time delay.
If the compressor stops five times during a continuous operation, the unit stops due to
abnormality.
MXZ-18NV-
E1 E2
Discharge
Cooling Heating
temperature (:)
100 < Td
5 20
95 < Td [ 100
5 20
90 < Td [ 95
5 20
85 < Td [ 90
1 20
80 < Td [ 85
0 20
75 < Td [ 80
-2 2
70 < Td [ 75
-2 0
65 < Td [ 70
-2 -3
60 < Td [ 65
-2 -3
Td [ 60
-5 -12
For capacity class 12(13) or 18 in single-unit operation, the stabilized range shifts to the next
higher level.
(
I. e. Cooling : 85<Td <
=
Heating : 80<Td
<
=
LEV opening correction by gas pipe temperature (effective in cooling operation only.)
(1) Maximum correction width : +14 pulse
(2) Single correction width : 1, 2, or 3 pulse
(3) Control details
1) S.H. HEX of each operating unit is calculated by using the following formula.
S.H. HEX (i) = (Gas pipe temperature (i)) - (Evaporation temperature)
2) The minimum valve is selected from each S. H. HEX.
3) From S. H. HEX (i) calculated in step 1) and the minimum value obtained in step 2), the
difference of each S. H. HEX (∆S. H. HEX (i)) is calculated as follows.
∆S. H. HEX (i) = (S. H. HEX (i) - S. H. HEX (min))
4) Each LEV opening is controlled based on ∆S. H. HEX (i) obtained in step 4).
∆S. H. HEX (i) and LEV control width
Range of ∆S. H. HEX (i)
∆S. H. HEX (i)
3<∆S. H. HEX (i)
6<∆S. H. HEX (i)
9<∆S. H. HEX (i)
Details
LEV opening correction (pulse)
MXZ-18NV- MXZ-18NV-
E1
Cooling Heating Cooling
20
15 40
15
10 30
15
10 30
8
5 16
4
3 8
0
0 0
0
0 0
0
0 0
60; or below, or when the discharge temperature falls
LEV opening correction (pulse)
Two units or more
Discharge
Cooling Heating
temperature (:)
10
100 < Td
95 < Td [ 100
5
90 < Td [ 95
0
85 < Td [ 90
-2
80 < Td [ 85
-2
75 < Td [ 80
-5
70 < Td [ 75
-5
65 < Td [ 70
-5
Td [ 65
-5
-
-
)
92
91
3 deg
<
=
< 6 deg
=
< 9 deg
=
MXZ-32NV-
E2 E1 E2
Heating Cooling Heating
15 20 10
10 15 10
10 15 10
5 7 5
3 0 0
0 0 0
0 0 0
0 0 0
MXZ-32NV-
E1 E2
For capacity class 07 or 09 in single unit operation
Discharge
Cooling
temperature (:)
100 < Td 100 < Td
10 10
95 < Td [ 100
10 10
92 < Td [ 95
5 10
85 < Td [ 92
5 5
80 < Td [ 85
0 0
75 < Td [ 80
0 -2
70 < Td [ 75
-2 -2
60 < Td [ 70
-2 -5
Td [ 60
-2 -5
-
- -
LEV variation for corresponding unit
0
+1
+2
+3
Discharge
Heating
temperature (:)
10
95 < Td [ 100
10
90 < Td [ 95
10
85 < Td [ 90
5
80 < Td [ 85
5
73 < Td [ 80
0
65 < Td [ 73
-2
60 < Td [ 65
-5
Td [ 60
-5
-
-
33