Loading ...
Loading ...
Loading ...
If the indoor temperature is above 80°F (27°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 (27°C) before
attempting to check system charge by subcooling
method as described above.
If the indoor temperature is below 70°F (21°C), or the
outdoor temperature is not in the favorable range, adjust
charge for line set length above or below 15 feet (4.6 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 feet (24.4 m) or greater
than 20 feet (6.1 m) vertical separation, See Long Line
Guideline for special charging requirements.
A. UNITS WITH COOLING MODE TXV
Units installed with cooling mode TXV require charging
by the subcooling method.
1. Operate unit a minimum of 15 minutes before
checking charge.
NOTE: If outdoor unit has a 2-speed fan motor,
motor will operate in low speed when outdoor
ambient temperature is below 82°F. Pull one of
the yellow low voltage wires off the fan control and
the unit will default to high speed fan for servicing.
Reconnect wire after servicing.
2. Measure liquid service valve pressure by
attaching an accurate 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
temperature.
5. Refer to Figure 13. Find the point where required
subcooling temperature intersects measured
liquid service valve pressure.
6. To obtain required subcooling temperature at a
specific liquid 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 (+ 1.7°C).
B. UNITS WITH INDOOR PISTON
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 15 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 thermistor type or electronic
thermometer to suction line at service valve.
4.
5.
6.
7.
.
.
10.
11.
12.
Measure outdoor air dry-bulb temperature with
thermometer.
Measure indoor air (entering indoor coil) wet-bulb
temperature with a sling psychrometer.
Find outdoor temperature and evaporator
entering air wet-bulb temperature. At this
intersection, note superheat. Where a dash (--)
appears on the table, do not attempt to charge
system under these conditions or refrigerant
slugging may occur. Charge must be weighted in,
adding or removing 0.6 oz/ft of 3/8 liquid line
above or below 15 feet (4.6 m) respectively.
Find superheat temperature (from #6 above) and
suction pressure. At this intersection, note suction
line temperature.
If unit has a higher suction line temperature than
charted temperature, add refrigerant until charted
temperature is reached.
If unit has a lower suction line temperature than
charted temperature, reclaim refrigerant until
charted temperature is reached.
When adding refrigerant, charge in liquid form into
suction service port using a flow-restricting
device.
If outdoor air temperature or pressure at suction
valve changes, charge to new suction line
temperature indicated on chart.
Optimum performance will be achieved when
the operating charge produces 10°F suction
superheat at suction service valve with 95°F
(35°C) outdoor ambient and 80°F (27°C) dry
bulb (67°F / 19°C) wet bulb) indoor
temperature (DOE "A" test conditions) at
rated airflow.
10 421 01 5103 02
Loading ...
Loading ...
Loading ...