7
START-UP
PRELIMINARY CHECKS:
1) Check that all internal wiring connections are tight and
all barriers, covers and panels are in place.
2) Field electrical power source must agree with unit
name plate rating.
3) All service valves must be opened.
INITIAL CHARGE
1. Have charging manifold and refrigerant bottle properly
connected to Schrader valve.
2. Add charge to approximately 448kPa back pressure.
This is not full charge, but it is enough to start the system.
START SYSTEM
1. Check that field disconnect is closed.
2. Set room thermostat to below room temperature, and
unit compressor will start after 5 minutes delay.
3. Check back pressure when compressor runs. Add
charge to keep back pressure at approximately 448kPa.
AIR PURGE
Air does not function as refrigerant because it cannot be
condensed in the condenser. Air and moisture remaining
in the system have undesirable effects. Therefore, they
must be purged out completely.
AIR PURGING PROCEDURE
1.) Remove the blind caps of the three-way valves.
2.) Loosen the valve stem of the three-way liquid valve by
90
°
for 5 seconds with a hex key wrench, then close
the valve stem quickly.
3.) Push the valve core of the three-way suction valve.
4.) Stop pushing as soon as the hissing stop.
5.) Open the three-way liquid valve for about 3 seconds,
then close quickly to check for gas leak.
6.) After checking for gas leak, open both three-way
valves all the way.
7.) Re-install the blind caps.
FIG. 12 SERVICES VALVE
CAUTION
STEM VALVE MUST BE FULLY SEATED TO CLOSE SERVICE
PORT. THERE IS NO SCHRADER VALVE AT THE SERVICE
PORT AND FAILURE TO BACKSEAT THE VALVE COULD
RESULT IN LOSS OF SYSTEM CHARGE
OR PERSONAL INJURY.
REFRIGERANT CHARGING
CAUTION
TO PREVENT PERSONAL INJURY, WEAR SAFETY
G L A S S E S A N D G L O V E S W H E N H A N D L I N G
REFRIGERANT. DO NOT OVERCHARGE SYSTEM.
THIS CAN CAUSE COMPRESSOR FAILURE.
IMPORTANT
For accurate system performance, charge by superheat
method as shown in Tables 4 and 5.
To check and adjust charge, follow the following procedures:-
1) Operate unit for a minimum of 15 minutes before
checking charge.
2) Measure suction pressure by attaching a gauge to
suction valve service port.
3) Measure suction line temperature by attaching a service
thermometer to unit suction line near suction valve.
Insulate thermometer for accurate readings.
4) Measure outdoor coil air inlet dry-bulb temperature
with a second thermometer.
5) Measure indoor coil air inlet wet-bulb temperature
with a sling psychrometer.
6) Refer to Table 4. Find air temperature entering outdoor
coil & wet-bulb temperature entering
indoor coil. At this intersection, note the superheat.
7) Refer to Table 5. Find superheat temperature and
suction pressure, note suction line temperature.
8) If unit has higher suction line temperature than charted
temperature add refrigerant until charted temperature
is reached.
9) If unit has lower suction line temperature than charted
temperature, bleed refrigerant until charted temperature
is reached.
10) If air temperature entering outdoor coil or pressure
at suction line changes, charge to new suction line
temperature indicated on chart.
11) This procedure is valid independent of indoor air quantity.
Summary of Contents for 38VTA040
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