Page 47
IMPORTANT
Failure to use properly sized wiring and circuit
breaker may result in property damage. Size wiring
and circuit breaker(s) per Product Specications
bulletin (EHB) and unit rating plate.
Applications Using a Two-Stage Thermostat
A - Heating Sequence -- Integrated Control Thermo-
stat Selection DIP Switch 1 OFF in “Two-Stage” Posi-
tion (Factory Setting)
1 - On a call for heat, thermostat rst-stage contacts
close sending a signal to the integrated control. The
integrated control runs a self-diagnostic program
and checks high temperature limit for normally
closed contacts and pressure switch for normally
open contacts. The combustion air inducer is
energized at low speed.
2 - Once the control receives a signal that the pressure
switch has closed, the combustion air inducer
begins a 15-second pre-purge in low speed.
3 - After the pre-purge is complete, a 20-second initial
ignitor warm-up period begins. The combustion air
inducer continues to operate at low speed.
4 - After the 20-second warm-up period has ended,
the gas valve is energized on low re and ignition
occurs. At the same time, the control module sends
a signal to begin an indoor blower 30-second ON-
delay. When the delay ends, the indoor blower
motor is energized on the low re heating speed,
the HUM contacts close energizing the humidier
and 120V ACC terminal is energized. The furnace
will continue this operation as long as the thermostat
has a rst-stage heating demand.
NOTE - If the indoor thermostat is set on
CONTINUOUS FAN ON mode, the furnace will
light on high re (second-stage) for 60 seconds to
improve heat exchanger warm up. After 60 second
warm-up period, furnace will switch to low re (rst-
stage).
5 - If second-stage heat is required, the thermostat
second- stage heat contacts close and send a signal
to the integrated control. The integrated control
initiates a 30-second-stage recognition delay.
6 - At the end of the recognition delay, the integrated
control energizes the combustion air inducer at high
speed. The gas valve is energized on high re and
the indoor blower motor is energized for operation
at the high re heating speed.
7 - When the demand for high re heat is satised, the
combustion air inducer is switched to the low-re
heating speed and the gas valve reduces to low
re. The low-re gas valve continues operation.
The indoor blower motor is switched to the low-re
heating speed.
8 - When the thermostat demand for low-re heat
is satised, the gas valve is de-energized and the
eld-selected indoor blower o delay begins. The
combustion air inducer begins a 5-second post-purge
period.
9 - When the combustion air post-purge period is
complete, the inducer, the HUM contacts as well
as the 120V ACC terminals are de-energized. The
indoor blower is de-energized at the end of the o
delay.
Applications Using A Single-Stage Thermostat
B - Heating Sequence -- Integrated Control Thermostat
Selection DIP Switch 1 ON in “Single-Stage” Position
NOTE - In these applications, two-stage heat will be initi-
ated by the integrated control if heating demand has not
been satised after the eld adjustable period (7 or 12
minutes).
1 - On a call for heat, thermostat rst-stage contacts
close sending a signal to the integrated control. The
integrated control runs a self-diagnostic program
and checks high temperature limit switches for
normally closed contacts and pressure switches for
normally open contacts. The combustion air inducer
is energized at low speed.
2 - Once the control receives a signal that the pressure
switch has closed, the combustion air inducer
begins a 15-second pre-purge in low speed.
3 - After the pre-purge is complete, a 20-second initial
ignitor warm-up period begins. The combustion air
inducer continues to operate at low speed.
4 - After the 20-second warm-up period has ended,
the gas valve is energized on low re (rst stage)
and ignition occurs. At the same time, the control
module sends a signal to begin an indoor blower
30-second ON-delay. When the delay ends, the
indoor blower motor is energized on the low re
heating speed and the HUM contacts are energized.
The integrated control also initiates a second-stage
on delay (factory-set at 7 minutes; adjustable to 12
minutes).
5 - If the heating demand continues beyond the second-
stage on delay, the integrated control energizes
the combustion air inducer at high speed. The
gas valve is energized on high re and the indoor
blower motor is energized for operation at the high
re heating speed.
6 - When the thermostat heating demand is satised,
the combustion air inducer begins a 5-second low
speed post-purge. The eld-selected indoor blower
o delay begins. The indoor blower operates at the
low-re heating speed.
7 - When the combustion air post-purge period is
complete, the inducer, the HUM contacts as well
as the 120V ACC terminals are de-energized. The
indoor blower is de-energized at the end of the o
delay.
To Next Page
Loading...
