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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 operatein 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 orbelow 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.
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.
Verify 226A units for proper switching between
low & high stages
Check the suction pressures at the service valves. Suction pressure
should be reduced by 3--10% when switching from low to high
capacity.
Compressor current should increase 20--45% when switching from
low to high stage. The compressor solenoid when energized in
high stage, should measure 24vac.
When the compressor is operating in low stage the 24v DC
compressor solenoid coil is de--energized. When the compressor is
operating in high stage, the 24v DC solenoid coil is energized. The
solenoid plug harness that is connected to the compressor HAS an
internal rectifier that converts the 24v DC signal to 24v AC. DO
NOT INSTALL A PLUG WITHOUT AN INTERNAL
RECTIFIER.
Unloader Test Procedure
The unloader is the compressor internal mechanism, controlled by
the DC solenoid, that modulates between high and low stage. If it
is suspected that the unloader is not working, the following
methods may be used to verify operation.
1. Operate the system and measure compressor amperage.
Cycle the unloader on and off at 30 second plus intervals at
the thermostat (from low to high stage and back to low
stage). Wait 5 seconds after staging to high before taking a
reading. The compressor amperage should go up or down
at least 20 percent.
2. If the expected result is not achieved, remove the solenoid
plug from the compressor and with the unit running and the
thermostat calling for high stage, test the voltage output at
the plug with a DC voltmeter. The reading should be 24
volts DC.
3. If the correct DC voltage is at the control circuit molded
plug, measure the compressor unloader coil resistance. The
resistance should be 32 to 60 ohms depending on com-
pressor temperature. If the coil resistance is infinite, much
lower than 32 ohms, or is grounded, the compressor must
be replaced.