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INSTALLING ISOLATION GROMMETS
Locate the isolation grommets (provided). Slide grommets
onto vapor and liquid lines. Insert grommets into piping
panel to isolate refrigerant lines from sheet metal edges.
SUCTION LINE
LIQUID LINE
TWO ISOLATION GROMMETS ARE
PROVIDE FOR THE LIQUID AND
SUCTION LINE PIPE PANEL PASS
THROUGH.
REAR VIEW OF UNIT EXTERIOR
Figure 23. Isolation Grommets
System Operations
The outdoor unit and indoor blower cycle on demand from
the room thermostat. When the thermostat blower switch
is in the ON position, the indoor blower operates
continuously.
ROOM THERMOSTAT EMERGENCY HEAT
FUNCTION
®
ComfortSense
5000 and 7000 thermostats have an
emergency heat function. This feature is applicable when
isolation of the outdoor unit is required.
Emergency heat is usually used during an outdoor unit
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 (10°C). The system
should be left in the emergency heat mode at least six
hours to allow the crankcase heater sufficient time to
prevent compressor slugging.
FILTER DRIER
The unit is equipped with a large−capacity biflow filter drier
which keeps the system clean and dry. If replacement is
necessary, order another of like design and capacity.
Defrost System
The demand defrost control (A108) provides a demand
defrost algorithm, field−selectable defrost termination
temperatures, compressor anti−short−cycle timing, and
internal switching of outputs. Additionally, the software
provides a inactive mode that shuts the heat pump off
when
icing
conditions
second−stage heating (gas heat) is desired.
The
demand
defrost
temperature, outdoor coil temperature and total run time to
determine when a power or natural defrost cycle is
required. The coil temperature probe has a spring clip to
allow mounting to the outside coil tubing. The location of
the coil sensor is important for proper defrost operation.
See figure 2 for proper coil sensor location.
506212−01 11/10
PIPING PANEL
are
detected
and
when
control
monitors
ambient
DIAGNOSTIC LIGHT−EMITTING DIODES
The state (Off, On, Flashing) of two light−emitting diodes
on the demand defrost control [DS1 (Red) and DS2
(Green)] indicate diagnostic conditions that are described
in table 9.
DEMAND DEFROST CONTROL (A108) PRESSURE
SWITCH CONNECTIONS
The unit's pressure switches (LO PS − S87 and HI PS − S4)
are factory−wired into the demand defrost control on the
LO−PS and HI−PS terminals, respectively.
Low Pressure Switch (LO−PS)
switch trips, the demand defrost control will cycle off the
compressor, and the strike counter in the demand defrost
control will count one strike. The low pressure switch is
ignored under the following conditions:
S
During the defrost cycle and 90 seconds after the
termination of defrost.
S
For 90 seconds following the compressor start−up.
S
During TEST mode.
High Pressure Switch (HI−PS) When the high pressure
switch trips, the demand defrost control will cycle off the
compressor, and the strike counter in the demand defrost
control will count one strike.
DEMAND DEFROST CONTROL PRESSURE SWITCH
EVENT SETTINGS
The following pressures are the auto reset event value
triggers for low and high pressure thresholds:
S
High Pressure (auto reset) − trip at 590 psig; reset at
418.
S
Low Pressure (auto reset) − trip at 25 psig; reset at 40.
FIVE−STRIKE LOCKOUT SAFETY FUNCTION
The five−strike lockout safety function is designed to
protect the unit's compressor from damage. The demand
defrost control looks for 24VAC on its Y1 terminal. When
the Y1 input detects 24VAC, the demand defrost control
internal control logic will do the following:
S
Count any HI−PS and LO−PS pressure switch trips
(open and close). Individual HI−PS and LO−PS trips
are totaled by the demand defrost control.
S
Up to four pressure switch trips are allowed in a single
thermostat demand without locking out the demand
defrost control. If the thermostat demand is satisfied
before a fifth pressure switch trip, the control will reset
the five−strike counter to zero.
S
If either pressure switch opens for a fifth time during
a single Y1 demand, the demand defrost control will
enter a lockout condition.
The system will require servicing to determine the cause of
the pressure switch condition. Once the condition has
been rectified, power to the demand defrost control's R
terminal must be cycled OFF, or jumper placed on the
TEST pins between 1 to 2 seconds to reset the demand
defrost control.
Page 36
When the low pressure
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