Carrier 38QF - Manual (Page 8)

To check and/or adjust charging during cooling
season, use correct Cooling Cycle Charging Chart
(Fig. 7, 9, 11, 13, 15, 17, 19) and follow Charging
Chart Method below. The charging chart may also
be used as an alternate method of recharging system.
To check system operation during heating cycle,
use correct Heating Cycle Operation Check Chart
(Fig. 8, 10, 12, 14, 16, 18, 20).These charts indicate
whether a correct relationship exists between system
operating pressures and air temperatures entering
indoor and outdoor units. If pressure and tempera­
ture lines do not intersect on chart, the system re­
frigerant charge may not be correct or other system
abnormalities may exist. Do not use Operation
Check Charts to adjust refrigerant charge. Weigh
charge into system.
COOLING CYCLE CHARGING CHART
METHOD
1. Operate unit a minimum of 10 minutes before
checking charge, and after each charge
adjustment.
2. Measure suction pressure by attaching a gage to
outdoor unit suction service port. (See Fig. 6 for
correct service port location on cooling cycle.)
3. Measure outdoor (coil inlet) air dry-bulb tem­
perature with service thermometer.
4. Using a sling psychrometer, measure wet-bulb
temperature of air entering indoor unit.
5. Refer to correct Charging Chart. Locate on
curves where outdoor air dry-bulb and indoor
air wet-bulb temperature lines intersect.
6. From intersect point, project vertically down­
ward to chart suction pressure line. Compare
chart suction pressure to unit suction pressure
(Step 2).
7. If unit suction pressure is lower than chart pres­
sure, add refrigerant to system until chart
pressure is reached. If unit suction pressure is
higher than chart pressure, remove refrigerant
until chart pressure is reached.
Unit Single-Phase Compressors
COMPRESSORS OF THE SPLIT CAPACITOR
(PSC) TYPE require an equalized system pressure
to start. When supply voltage is within nameplate
limit and compressor does not start, give com­
pressor a temporary capacitance boost. See Carrier
Standard Service Techniques Manual, Chapter 2,
for details.
W A R N I N G : C’apacilance boost or installation
of start capacitor and slaii relay should be per­
formed b\ trained personnel. Improper pro­
cedure could cause personal injur\ or equipment
CHARGING AND PRESSURE CHECK CHARTS
160
66 68 70 72 74 76 78 80 82 84 86 88
PRESSURE AT SUCTION SERVICE VALVE (PSIG)
Fig. 7 — 38QF018 with 40AQ018,024,
28HQ,VQ018 or 024, 40FS075 with
28HQ,VQ042 Cooling Cycle Charging Chart
Fig. 8 — 38QF018 with 40AQ018,024,
28HQ,VQ018 or 024, 40FS075 with 28HQ,
VQ042 Heating Cycle Operation Check Chart