Unit installation

19
Thermostat Control
For the unit to enter heating mode, three additional things must be
true: the indoor fan must be ok to use, the mode changeover time
guard must be expired, and there must be a heating demand (W1,
W2). The unit will remain in heating until the heating demand is
dropped or if any of the above conditions turn false. The heating
mode can not officially end until all heat stages are off and the IGC
fan request (IGC.F) is dropped.
Space Sensor Control
For the unit to enter heating mode, five things must be true: the
indoor fan must be ok to use, the mode changeover time guard
must be expired, the unit must have a valid space temperature, the
W1 jumper must be installed, and there must be a heating demand.
The unit will remain in heating for at least one minute and until the
demand is dropped or if any of the above conditions turn false. The
heating mode can not officially end until all heat stages are off and
the IGC fan request (IGC.F) is dropped.
Staging Control
Once the unit is in a heating mode, it must decide what the demand
is and how to satisfy. Based on the unit control configuration,
requested heating stages (Run Status →HEAT →REQ.H) will be
determined then passed to heat control to actually add the heating
stages.
Thermostat Control
There are two ways of requesting stages when thermostat control is
enabled, Traditional Thermostat control or Adaptive control.
Traditional Thermostat control is used if the Thermostat Control
Type (T.CTL) is set to 1, 2, or 3. Adaptive control is used if
Thermostat Control (T.CTL) is set for 0.
T.CTL = 0 (Adaptive Control)
Stage timers and supply air temperature limits apply when
determining the request for stages. The first request (REQ.C=1)
comes immediately when the W1 input is active. The Heat Stage
Increase Time (Configuration →HEAT →H.INC) or the Heat
Stage Decrease Time (Configuration →HEAT →H.DEC) has to
expire before another stage can be added or a stage can be
subtracted. If at any time the Supply-Air Temperature (SAT) falls
below the Maximum Supply Air Temperature Lower Level
(Configuration →HEAT →SAT →SAM.L), the requested stages
will not be allowed to increase. If at any time the SAT falls below
the Maximum Supply Air Temperature Upper Level
(Configuration →HEAT →SAT →SAM.U), the requested stages
will be reduced by one without honoring H.DEC.
T.CTL = 1, 2 or 3 (Traditional thermostat control)
Stage timers and supply air temperature limits do not apply when
determining the request for stages. Request staging will follow the
thermostat inputs directly. W1 will request one stage. W2 will
request all stages.
Space Sensor Control
Space sensor staging control is an adaptive anticipation control that
weighs the actual space demand against the trend of that demand. It
also honors stage time guards and supply air limits. The demand
for heating in the space is displayed as the Heating Demand (Run
Status →HEAT →DMD.H). The control tries to anticipate the
change in the space because of its current stage status. This
anticipation is based on the Heat Demand Trend (Operating
Modes →HEAT →TRD.H). This trend will show the control how
the space is reacting to the current running conditions and help it
decide when to add or remove one stage from the requested stages.
The Heat Stage Increase Time (Configuration →HEAT →H.INC)
or the Heat Stage Decrease Time (Configuration →HEAT
→H.DEC) has to expire before another stage can be added or a
stage can be subtracted. . If at any time the Supply-Air
Temperature (SAT) falls below the Maximum Supply Air
Temperature Lower Level (Configuration →HEAT
→SAT
→SAM.L), the requested stages will not be allowed to increase. If
at any time the SAT falls below the Maximum Supply Air
Temperature Upper Level (Configuration →HEAT →SAT
→SAM.U), the requested stages will be reduced by one without
honoring H.DEC.
Heat Relay Control
The heat relay control is responsible for energizing or
de-energizing the heat stage relays and works hand and hand with
the staging control. As the staging control requests stages, the heat
relay control determines what actual heat relays are available or
energized and tries to provide stages for what is requested. The
availability of a heat relays depends on the heat installed, how
many stages, and time guards. The type of Heat Installed
(Configuration →HEAT →HT.TY) must be set for gas or electric
for any stages to be available. The Number of Heat Stages
(Configuration →HEAT →N.HTR) configuration tells the control
how many heat relays can be used. Heat Stage 1Timeguard (Run
Status →HEAT →TG.H1) and Heat Stage 2 Timeguard (Run
Status →HEAT →TG.H2) display the time a respective heat relay
has before it is available for use. The available stages at any given
time are displayed as Available Heating Stages (Run Status
→HEAT →AVL.H). The actual heat relays on at any given time
are displayed as Actual Heating Stages (Operating Modes
→HEAT →ACT.H). Heat Stage 1 Relay (Run Status →HEAT
→HT.1) and Heat Stage 2 Relay (Run Status →HEAT →HT.2)
are displayed on when the respective relay is energized. There are
time guards to protect from short cycling, Heat Minimum On Time
(Configuration →HEAT →MRT.H) and Heat Minimum Off
Time (Configuration →HEAT →MOT.H) apply before a heat
relay can be turned back on or turned off.
Integrated Gas Controller (IGC) – 48LC Units Only
The heat staging is determined as described above and the
Integrated Gas Controller (IGC) initiates the gas heat module
start-up. The Integrated Gas Controller (IGC) minimum on-time of
1 minute will be followed even if Heat Minimum On Time
(Configuration →HEAT →MRT.H) is lower and during Service
Test. If the IGC temperature limit switch opens within 10 minutes
of the end of the gas heat cycle, the next fan off delay will be
extended by 15 seconds. The maximum delay is 3 minutes. Once
modified by the IGC, the fan off delay will not change back to the
configured Fan-off Delay, Gas Heat (Configuration →HEAT
→FOD.G)
unless power is reset to the control. A light emitting
diode (LED) is provided on the IGC to indicate status. During
normal operation the LED is continuously on. See the
Troubleshooting section if the LED is off or flashing. The IGC is
located above the gas section in the control box.
When the control energizes Heat Stage 1 Relay (Run Status
→HEAT →HT.1), power is sent to the W terminal on the IGC
board. A check is made to ensure that the rollout switch and limit
switch are closed. The induced-draft motor is then energized, and
when speed is proven with the Hall Effect sensor on the motor, the
ignition activation period begins. The burners will ignite within 5
seconds. If the burners do not light, there is a 22-second delay
before another 5-second attempt. If the burners still do not light,
this sequence is repeated for 15 minutes. After the 15 minutes have
elapsed, if the burners still have not lit, heating is locked out. The
control will reset when the request for heat is temporarily removed.
When ignition occurs the IGC board will continue to monitor the
condition of the rollout switch, limit switches, the Hall Effect
sensor, as well as the flame sensor. If the unit is controlled through
a room thermostat or space sensor set for fan auto and 45 seconds
after ignition occurs, the indoor-fan request IGC Fan Request
(Inputs →GEN.I →IGC.F) will be energized. If for some reason
the over temperature limit opens prior to the start of the indoor fan
blower, on the next attempt, the 45-second delay will be shortened
to 5 seconds less than the time from initiation of heat to when the
limit tripped. Gas will not be interrupted to the burners and heating
will continue. Once modified, the fan on delay will not change
back to 45 seconds unless power is reset to the control. When the
control energizes Heat Stage 2 Relay (Run Status →HEAT
48/50LC