Operation - Allied Air 4SHP13 series Installation Instructions Manual

3. Compare stabilized pressures with those provided on
pressure chart on control box cover. Minor variations in
these pressures may be expected due to differences in
installations. Significant differences could mean that
the system is not properly charged or that a problem
exists with some component in the system.
Pressures higher than those listed indicate that the
system is overcharged. Pressures lower than those
listed indicate that the system is undercharged. Verify
adjusted charge using the approach method.
4. Use the same digital thermometer to check liquid line
temperature.
5. Subtract the outdoor ambient temperature from the liquid
line temperature to determine the approach temperature.
_____ ° Liquid Line Temperature ° F
–
_____ ° Outdoor Ambient Temperature ° F
=
_____ ° Approach Temperature ° F
6. Compare the approach value with those shown in
charge chart mounted on inside of control box cover. If
the values to do not agree with those provided, add
refrigerant to lower the approach temperature or recover
refrigerant from the system to increase the approach
temperature.
Check Charge Using Normal Operating Pressures
For maintenance check, check operating pressures &
temperatures with the charge chart mounted on inside of
control box cover. Minor variations in these pressures may
be due to differences in installations. Significant deviations
could mean that the system is not properly charged or that a
problem exists with some component in the system.
506762-01
Outdoor unit and indoor blower cycle on demand from the
room thermostat. When the thermostat blower switch is
moved to the ON position, the indoor blower operates
continuously.
Filter Drier
The unit is equipped with a large campacity bi-flow filter which
keeps the system clean and dry. If replacement is necessary,
replace with one of similar design capacity. The replacement
filter drier must be suitable for use with R-410A refrigerant.
Crankcase Heater
If unit is equipped with a crankcase heater, it should be
energized 24 hours before unit start-up to prevent
compressor damage as a result of slugging.
Emergency Heat Function (Room Thermostat)
An emergency heat function is designed into some room
thermostats. This feature is applicable when isolation of
outdoor unit is required or when auxiliary electric heat is
stage by outdoor thermostats. When the room thermostat
is placed in the emergency heat position, the outdoor unit
control circuit is isolated from power and the field-supplied
relays bypass the outdoor thermostats. An amber indicating
light simultaneously comes on to remind the homeowner
that the unit is operating in the emergency heat mode.
Emergency heat is usually used during an outdoor shutdown,
but it should also be used following a power outage if power
has been off for over an hour and the outdoor temperature
is below 50° F. System should be left in the emergency heat
mode at least 6 hours to allow the crankcase heater sufficient
time to prevent compressor slugging.
Defrost System
The defrost system includes two components: the defrost
thermostat and the defrost control.
Defrost Thermostat
The defrost thermostat is located on the liquid line between
the check/expansion valve and the distributor. When the
defrost thermostat senses 42° F or cooler, the thermostat
contacts close and send a signal to the defrost control board
to start the defrost timing. It also terminates defrost when
the liquid line warms up to 70° F.
Defrost Control
The defrost control board includes the combined functions
of time/temperature defrost control, defrost relay, diagnostic
LEDs and terminal strip for field wiring connections (see
Figure 3).
Issue 1143

OPERATION

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