Carrier 38VH - Manual (Page 8)

Fig. 7 — Charging Chart (Non TXV Systems)*
*Not to be used for 28VH applications See "Weight Method —
28VH Applications "
CHARGING CHART METHOD — Use Charging
Chart, Fig. 7 and the following procedure.
1. Operate unit a minimum of 10 minutes before
checking charge.
2. Measure suction pressure by attaching a gage
to suction valve service port.
3. Measure suction line temperature by attaching
a service thermometer to unit suction line near
compressor. (Insulate thermometer for accurate
readings.)
4. Measure outdoor (condenser inlet) air dry-bulb
temperature with a second thermometer.
5. Refer to Charging Chart (Fig. 7). Find air Tem­
perature Entering Condenser and project
horizontally to curve showing suction pressures
(psig at Suction Valve).
6. From this intersection, project vertically down­
ward to Suction Line Temperature.
7. If unit has a higher suction line temperature
than charted temperature, add refrigerant until
charted temperature is reached.
8. If unit has a lower suction line temperature than
charted temperature, bleed refrigerant until
charted temperature is reached.
9. If air temperature entering condenser or pressure
at suction valve changes, charge to new suction
line temperature indicated on chart.
CHARGEMASTER® METHOD — Operate unit
for 10 minutes before using Chargemaster (Carrier
part No. 38GC680004).
1. Tape Chargemaster feeler bulb to suction line
close to condensing unit. Insulate bulb. Ensure
suction line is clean for good contact with bulb.
(Uninsulated bulb or dirty suction line will
seriously
affect accuracy of temperature
readings.)
2. Connect refrigerant drum to Chargemaster inlet
port keeping drum in position for vapor
charging.
3. Connect Chargemaster outlet port to unit suction
valve service port.
4. Crack valves on refrigerant drum and Charge-
master to purge lines from drum to suction valve.
After purging lines, close valve on Chargemaster
only.
5. Measure outdoor air dry-bulb temperature.
6. Crack unit suction valve and read evaporator
temperature at red needle position on Charge-
master temperature gage and suction line tem­
perature at black needle position.
- , v ' - - ;
7. Enter Chargemaster Charging Chart, Table 8, at
Outdoor Air Temperature (step 5) and Evap­
orator Temperature (step 6). Find the Suction
Line Temperature required for correct system
charge. If actual suction line temperature (step 6)
is higher than table value, the system is under­
charged. If suction line temperature is lower than
table value, system is overcharged.
EXAMPLE: At outdoor air temperature of 85 F
and evaporator temperature of 44 F, the system
will be correctly charged at 71 F ± 2 F suction
line temperature. See Table 8.
Table 8 — Chargemaster Charging Chart
(Non TXV Systems)t
Example
^Saturated evaporator temperature which is the equivalent tem­
perature of pressure taken at the condensing unit suction
service valve
fNot to be used for 28VH applications See "Weight Method —
28VH Applications "