Specifications

Iftheindoortancontrolisconfiguredtocyclewiththeheat-
ing demand((bnfiguration---_UNIr_OC.FN= No) the
thn will stop after a conligured delay, (bnfiguration---_
HEAT---_FOD.G Factory dethutt value is 45 seconds. If the
IGC temperature limit switch opens within 10 minutes of the
end of the gas heating, the next thn off delay wilt be extended
by 15 seconds. The maximum delay is 3 minutes. Once modi-
fied by the IGC, the thn off delay will not change back to
FOD.G unless power is reset to the control.
A light-emitting-diode (LED) is provided on the It_R2
(intemated gas controller) to indicate its status. During normal
operation the LED is continuously on. See the Troubleshooting
section if the LED is offor flashing. The IGC is located behind
gas section access panel. See Fig. 5 for location.
THERMOSTAT CONTROL When the thermostat calls
for heating, the MBB senses that W1 is On and closes the HT.1
relay. When the relay is closed, it sends power to W on the It_R2
(intemated gas unit controller) board. An LED (light-emitting
diode) on the IGC board will be on during normal operation.
A check is made to ensure that the rollout switch and limit
switch are closed. The induced-draft motor is then energized.
When speed is proven with the Hall Effect sensor on the motor,
the imlition activation period begins.
The burners will i_ite within 5 seconds. If the burners do
not light, there is a 22-second delay betbre another 5-second
attempt. If the burners still do not light, this sequence is repeated
for 15minutes. After the 15minutes have elapsed, ffthe burners
still have not imlited, heating is locked out. The control wilt
reset when the request for heat is temporarily removed.
When ignition occurs, the IGC board wilt continue to moni-
tor the coMition of the rotlout switch, limit switches, Hall
Effect sensor, and the flame sensor. If the unit is controlled
through a room thermostat set for tan auto, 45 seconds after
ignition occurs the indoor-fan motor wilt be eneNized (and the
outdoor-air dampers wilt open to their minilnum position). If
for some reason the overtelnperamre limit opens prior to the
start of the indoor tan blower, on the next attempt, the
45-second delay will be shortened to 5 seconds less than the
time fiom initiation of heat to when the limit tripped. Gas will
not be interrupted to the burners and heating wilt continue.
Once modNed, the thn on delay will not change back to
45 secoMs unless power is reset to the control.
When additional heat is required and the MBB senses that
W2 is On, the MBB will turn on the HT.2 relay which sends
power to the second stage of the main gas valve. If the thenno-
star relnoves the call for W2, the unit wilt turn offHT.2. If W1
is satisfied, the MBB will mm off HT. 1 which will turn off gas
to the main burners.
If the user has selected Adaptive (see Cooling section) for
its thermostat mode, the algorithin will follow the configurable
delays for adding and relnoving stages. When adding addition-
al heat stages, the delay is measured ftom when the last stage
was added (Configumtion---_HEAT---_H.IN(). When relnov-
ing stages, the delay is measured ftom when the last stage was
removed (Configuration--_HEAT--_H.DEO. Therefore, if
W1 and W2 turn on simultaneously, the second stage wilt turn
on after a H.INC delay.
NOTE: ff the mode is not Adaptive, then there are no delays
tbr adding and relnoving stages.
SPACE SENSOR CONTROL To operate the unit in
Space Sensor 1node, set the Unit Control Type to 3 (Configura-
tion--+U?ClT--+U.CTL 3). To enable heating during space
temperature control, a jumper wire must be added between R
and W1 on the field connection terminal strip (see Major
System Components section tbr wiring diam'ams).
Because Space Sensor mode is an "Auto" mode, the control
will switch between cooling and heating to maintain space
temperature. However, to lninimize unnecessary changes, there
is a 10-minute mode select tilne_ard (Operating Modes---_
HEAT--+MS.TG) after the last stage of cool rams off before
heating is allowed.
The unit tries to maintain the space temperature at the Occu-
pied Heat Set Point (Setpoints_OHSP) or the Unoccupied
Heat Set Point (Setpoints--+UHSP). See the Occupancy Deter-
mination section for thctors that affect the Occupied stares
(Run Status---_VIEW_'OC O. Heating Demand (Operating
Modes--+HEAT---_qPT---_DMD.H) is equal to the occupied or
unoccupied set point minus the Space Temperature (Operating
Modes -+HEA T---_gP T---_gP I).
DMD.H setpoint SPT
Two lnethods are used to add and relnove stages of heating
for units with lnore than one heat stage. The first method caus-
es the unit to operate around its steady-state number of stages.
For example, if the correct number of stages is between 0
and 1, this method will cause the first stage to cycle. If the cor-
rect number of stages is between 1 and 2, this method will
cause the second stage to cycle. The second method causes the
unit to find the steady-state number of stages. Details of these
methods are provided below.
SCREEN
(HIDDEN)
PEM 1
CONTROLBOX
OUTLET
CO2SENSOR
FI_ER ACCESS
RETURNSMOKE DOOR
DETECTOR
SMOKECONTROL
MODULE
GAS SECTION
Fig. 5 -- Panel and Filter Locations (48PG Unit Shown)
43