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505023M 04/06
may be on) is turned off and continuous fan runs (if the
demand for heat remains) until the air temperature
falls below 130ºF and the minimum timed−off delay ex-
pires.
S
If the heat pump goes into defrost mode, the zone con-
trol energizes all stages of compressor and the first
stage of electric heat. If the defrost process lasts lon-
ger than 20 minutes, the zone control, presuming a de-
frost board failure, de−energizes the heat pump and
instructs electric heat to service the remainder of the
current heating call. (The heat pump will be tried again
on the next heating call.)
Dual Fuel−Heat Pump with Gas Furnace
In this sys-
tem, when it receives a thermostat heating call, the zone
control responds in one of two ways:
1.
Outdoor temperature below balance point
(bal-
ance point sensor
closed
): the zone control unit sends
a W1 signal to the furnace to satisfy heat demands,
staging the furnace to maintain discharge air tempera-
tures between 110ºF and 130ºF.
2.
Outdoor temperature above balance point
(bal-
ance point sensor
open
): the heat pump is first used
to satisfy the demand. If, after 20 minutes, the heat
pump fails to maintain the required discharge air tem-
perature, the zone control will discontinue using the
heat pump and initiates furnace heating. (A five−min-
ute delay exists between stopping the heat pump and
starting the furnace.) In this mode, all heating calls for
the next three hours are serviced with the gas furnace.
Also, diagnostic lights 2, 3, and 4 blink to indicate that
the board is operating within this 3−hour furnace lock−in
time. During this time, the zone control stages the fur-
nace to maintain discharge air temperatures between
110ºF and 130ºF. After the 3−hour delay expires, the
heat pump will again be tried on the next heating call.
Emergency heat mode
When the unit is setup for heat pump and the emergency
heat switch is turned on, the unit will satisfy all heating de-
mands with electric backup heat or, in a dual mode system,
the heat demand is satisfied by the gas furnace.
Operation & Troubleshooting Indicators
Zone Control Board LEDs
The zone control system operation is indicated by light
emitting diodes (LEDs) located on the zone control board.
In addition to operating condition, the LEDs provide valu-
able information system troubleshooting. The LEDs
(shown in figure 22) are thermostat, diagnostic, and output
status.
1. Thermostat LEDslocated along the upper edge of
the zone control board board. Each zone has three
LEDs to indicate a call for heating or cooling: green (in-
dicates a Y / compressor demand), red (indicates a W
/ heating demand) and amber (indicates a G / indoor
blower demand). These LEDs are labeled according
to the zone and demand.
System Indicators/Troubleshooting Devices
Figure 22
THERMOSTAT
LEDs
OUTPUT STATUS LEDs
DIAGNOSTIC
LEDs
TIME DELAY
OVERRIDE
FAULT
RECALL
EQUIPMENT
OUTPUT LEDs
2. Diagnostic LEDsDiags 1, 2, 3, 4located near the
bottom center of the the zone control board board.
These LEDs aid the technician in troubleshooting
problems. When an error is detected, LEDs illuminate
in a pattern. See
Fault Recall and Time Delay Override
on page18.
3. Output LEDslocated along the bottom of the zone
control board and near connection terminals. These
red LEDs indicate the output status of dampers, fur-
nace, outdoor unit, etc. When an output is powered or
active, the corresponding LED is illuminated.
The LEDs are labeled according to output and func-
tion. For example, if Damper 1 LED is illuminated, it’s
damper has been signaled to close; when the LED is
extinguished, it’s damper has been signaled to open,
allowing air flow to that zone.
Fault Recall & Time Delay Override
When the Time Delay Override is pressed and held, the in-
ternal clock speeds up by a factor of 60. This overrides the
current time delay and permits the next event to occur.
Table 9 identifies the time delays used by the system.
When the Fault Recall button is pressed and released
(clicked), the fault codes are displayed (10 most recent).
When the fault recall button is pressed and held, the fault
codes are erased. Each code will be displayed for 10 sec-