7 
OPERATING PRESSURES / SUPERHEAT
SYSTEM CHARGE
The factory charge in the outdoor unit includes enough charge for the unit and the smallest matched evaporator and 25 feet of line. Some evaporator matches may require some additional charge. See Tabular Data sheet provided in unit lit- erature packet.
The “TOTAL SYSTEM CHARGE” must be permanently stamped on the unit data plate.
Total system charge is determined as follows:
1.Determine outdoor unit charge for the selected evapora- tor from the corresponding table on Pages
2.If using line length other than 25 feet, calculate the line charge from the tables on Page 24.
MEASUREMENT METHOD
If a calibrated charging cylinder or accurate weighing device is available, add refrigerant accordingly.
Compressor damage will occur if system is improperly charged. On new system installations charge system per
Check flare caps on service ports to be sure they are leak tight. DO NOT OVER TIGHTEN (between 40 and 60 inch - lbs. maximum).
NOTE: The line charge over 25 feet should be included on the data plate and must be added to the system.
3.Total system charge = item 1 + item 2.
4.Permanently stamp the unit data plate with the total amount of refrigerant in the system.
Use one of the following charging methods whenever addi- tional refrigerant is required for the system charge.
Refrigerant charging should only be carried out by a qualified air conditioning contractor.
Table 1: SUPERHEAT VALUE
SUPERHEAT CHARGING METHOD
NOTE: Use this method only during system maintenance and repair.
1.Operate system until temperatures and pressures stabi- lize (minimum of 10 minutes).
2.Measure and record indoor wet bulb (WB) temperature using a sling psychrometer and the outdoor dry bulb (DB) temperature using a thermometer.
INDOOR WB |
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| OUTDOOR DB°F |
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°F1 |
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55 | 60 | 65 | 70 | 75 | 80 | 85 | 90 | 95 | 100 | 105 | 110 | 115 | |
50 | 9 | 7 |
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52 | 12 | 10 | 6 |
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54 | 14 | 12 | 10 | 7 |
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56 | 17 | 15 | 14 | 10 | 6 |
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58 | 20 | 18 | 16 | 13 | 9 | 5 |
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60 | 23 | 21 | 19 | 16 | 12 | 8 | 6 |
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62 | 26 | 24 | 22 | 19 | 16 | 12 | 8 | 5 |
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64 | 29 | 27 | 24 | 21 | 18 | 15 | 11 | 9 | 6 |
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66 | 32 | 31 | 30 | 24 | 23 | 18 | 15 | 11 | 9 | 6 |
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68 | 35 | 33 | 30 | 27 | 24 | 21 | 19 | 16 | 14 | 12 | 9 | 6 |
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70 |
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72 |
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| 35 | 33 | 30 | 28 | 26 | 24 | 20 | 20 | 17 | 15 | 14 |
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74 |
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| 34 | 31 | 30 | 27 | 25 | 23 | 22 | 20 | 18 |
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76 |
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1. Evaporator Entering Air °F
24 | Mitsubishi Electronics 2003 |