WEIGH IN (RFC AND TXV)
CALCULATING SYSTEM CHARGE FOR OUTDOOR UNIT VOID OF CHARGE
If the system is void of refrigerant, first, locate and repair any leaks and then weigh in the refrigerant charge into the unit. To calculate the total refrigerant charge:
Amount specified on nameplate
Adjust amount. for variation in line set length listed on line set length table below.
Total charge
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| Refrigerant Charge per Line Set Length | ||||||
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| Liquid Line | Ounces per 5 feet (g per 1.5 m) |
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| adjust from 15 feet (4.6 m) line set* |
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| Set Diameter |
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| 3/8" (9.5 mm) | 3 ounce per 5’ (85 g per 1.5 m) |
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| *If line length is greater than 15 ft. (4.6 m), add this amount. If | ||||||
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| line length is less than 15 ft. (4.6 m), subtract this amount. | |||||||
NOTE | Insulate liquid line when it is routed through areas where the surrounding ambient temperature could become higher than the | |||||||||
temperature of the liquid line or when pressure drop is equal to or greater than 20 psig. | ||||||||||
NOTE | The above nameplate is for illustration purposes only. Go to actual nameplate on outdoor unit for charge information. | |||||||||
Figure 21. Using HFC−410A Weigh In Method
| USE | 65ºF (18.3ºC) | ||
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based upon line length |
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| 64ºF | ABOVE or | ||
| BELOW | |||
| (17.7ºC) and | |||
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| Below |
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| If value is greater than shown (high |
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| approach), add refrigerant; if less |
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| than shown (liquid temperature too |
| If refrigerant is added or | |
| close to ambient temperature, low |
| removed, retest to confirm | |
| approach), remove refrigerant. |
| that unit is properly charged. | |
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APPº (Approach) Values(F:+/−1.0° [C: +/−0.6°])
1.Confirm proper airflow across coil using figure 19.
2.Compare unit pressures with table 4, Normal Operating Pressures.
3.Set thermostat to call for heat (must have a cooling load between
4.Connect gauge set.
5.When heat demand is satisfied, set thermostat to call for cooling.
6.Allow temperatures and pressures to stabilize.
7.Record outdoor ambient temperature: AMBº =_________
8.Record liquid line temperature: LIQº = __________
9.Subtract to determine approach (APPº): LIQº_____ − AMBº _____ = APPº_____
10.Compare results with table below.
ºF (ºC)* | −018 | −024 | −030 | −036 | −041 | −042 | −047 | −048 | −059/−060 |
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65 (18) | 4 (2.2) | 2 (1.1) | 2 (1.1) | 2 (1.1) | 3 (1.7) | 6 (3.3) | 9 (5.0) | 7 (3.9) | 8 (4.4) |
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75 (24) | 5 (2.8) | 4 (2.2) | 4 (2.2) | 5 (2.8) | 3 (1.7) | 6 (3.3) | 9 (5.0) | 8 (4.4) | 9 (5.0) |
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85 (29) | 6 (3.3) | 4 (2.2) | 6 (3.3) | 8 (4.4) | 4 (2.2) | 8 (4.4) | 8 (4.4) | 8 (4.4) | 9 (5.0) |
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95 (35) | 5 (2,8) | 4 (2.2) | 5 (2.8) | 7 (3.9) | 4 (2.2) | 8 (4.4) | 8 (4.4) | 8 (4.4) | 9 (5.0) |
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105 (41) | 3 (1.7) | 4 (2.2) | 5 (2.8) | 6 (3.3) | 4 (2.2) | 8 (4.4) | 8 (4.4) | 8 (4.4) | 9 (5.0) |
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115 (45) | 3 (1.7) | 3 (1.7) | 4 (2.2) | 6 (3.3) | 5 (2.8) | 8 (4.4) | 8 (4.4) | 9 (5.0) | 9 (5.0) |
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*Temperature of air entering outdoor coil.
Figure 22. HFC−410A Approach TXV Charge
Page 24
506645−01
