Check Charge
Factory charge amount and desired subcooling are shown on unit rating plate. Charging method is shown on information plate inside unit. To properly check or adjust charge, conditions must be favorable for subcooling charging. Favorable conditions exist when the outdoor temperature is between 70_F and 100_F (21.11_C and 37.78_C), and the indoor temperature is between 70_F and 80_F (21.11_C and 26.67_C). Follow the procedure below:
Unit is factory charged for 15ft (4.57 m) of lineset. Adjust charge by adding or removing 0.6 oz/ft (.018 kg/m) of 3/8 liquid line above or below 15ft (4.57 m) respectively.
For standard refrigerant line lengths (80 ft/24.38 m or less), allow system to operate in cooling mode at least 15 minutes. If conditions are favorable, check system charge by subcooling method. If any adjustment is necessary, adjust charge slowly and allow system to operate for 15 minutes to stabilize before declaring a properly charged system.
If the indoor temperature is above 80_F (26.67_C), and the outdoor temperature is in the favorable range, adjust system charge by weight based on line length and allow the indoor temperature to drop to 80_F (26.67_C) before attempting to check system charge by subcooling method as described above.
If the indoor temperature is below 70_F (21.11_C), or the outdoor temperature is not in the favorable range, adjust charge for line set length above or below 15ft (4.57 m) only. Charge level should then be appropriate for the system to achieve rated capacity. The charge level could then be checked at another time when the both indoor and outdoor temperatures are in a more favorable range.
NOTE: If line length is beyond 80 ft (24.38 m) or greater than 20 ft (6.10 m) vertical separation, See Long Line Guideline for special charging requirements.
Units with Cooling Mode TXV
Units installed with cooling mode TXV require charging by the subcooling method.
1.Operate unit a minimum of 10 minutes before checking charge.
2.Measure liquid service valve pressure by attaching an accur- ate gage to service port.
3.Measure liquid line temperature by attaching an accurate thermistor type or electronic thermometer to liquid line near outdoor coil.
4.Refer to unit rating plate for required subcooling temperat- ure.
5.Refer to Table 3. Find the point where required subcooling temperature intersects measured liquid service valve pres- sure.
6.To obtain required subcooling temperature at a specific li- quid line pressure, add refrigerant if liquid line temperature is higher than indicated or reclaim refrigerant if temperature is lower. Allow a tolerance of 3_F.
Units with Indoor Pistons
Units installed with indoor pistons require charging by the superheat method.
The following procedure is valid when indoor airflow is within 21 percent of its rated CFM.
1.Operate unit a minimum of 10 minutes before checking charge.
2.Measure suction pressure by attaching an accurate gage to suction valve service port.
3.Measure suction temperature by attaching an accurate ther- mistor type or electronic thermometer to suction line at ser- vice valve.
4.Measure outdoor air
5.Measure indoor air (entering indoor coil)
6.Refer to Table 4. Find outdoor temperature and evaporator entering air
7.Refer to Table 5. Find superheat temperature located in item 6 and suction pressure. At this intersection, note suction line temperature.
8.If unit has a higher suction line temperature than charted temperature, add refrigerant until charted temperature is reached.
9.If unit has a lower suction line temperature than charted temperature, reclaim refrigerant until charted temperature is reached.
10.When adding refrigerant, charge in liquid form into suction service port using a
11.If outdoor air temperature or pressure at suction valve changes, charge to new suction line temperature indicated on chart.
12.Optimum performance will be achieved when the operating charge produces 5_ to 6_F suction superheat at suction service valve with 82_F outdoor ambient and 80_F (26.7_C) dry bulb (67_F / 19.4_C) wet bulb) indoor temperature (DOE “B” test conditions) at rated airflow.
Heating Check Chart Procedure
To check system operation during heating cycle, refer to the Heating Check Chart on outdoor unit. This chart indicates whether a correct relationship exists between system operating pressure and air temperature entering indoor and outdoor units. If pressure and temperature do not match on chart, system refrigerant charge may not be correct. Do not use chart to adjust refrigerant charge.
223A / 225B
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