Table of Contents
Advertisement
Applications Using a Two-Stage Thermostat
A - Heating Sequence -- Integrated Control Thermostat
Selection DIP Switch 1 OFF in "Two-Stage" Position
(Factory Setting)
1. On a call for heat, thermostat first-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 fire 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 fire heating speed, the HUM contacts close
energizing the humidifier and 120V ACC terminal is
energized. The furnace will continue this operation
as long as the thermostat has a first-stage heating
demand.
NOTE: If the indoor thermostat is set on CONTINUOUS
FAN ON mode, the furnace will light on high fire
(second-stage) for 60 seconds to improve heat
exchanger warm up. After 60 second warm-up period,
furnace will switch to low fire (first-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 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 fire and the
indoor blower motor is energized for operation at the
high fire heating speed.
7.
When the demand for high fire heat is satisfied, the
combustion air inducer is switched to the low-fire
heating speed and the gas valve reduces to low fire.
The low-fire gas valve continues operation. The indoor
blower motor is switched to the low-fire heating speed.
8.
When the thermostat demand for low-fire heat is
satisfied, the gas valve is de-energized and the
field-selected indoor blower off 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 off delay.
31-5000734 Rev. 0
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
initiated by the integrated control if heating demand has
not been satisfied after the field adjustable period (7 or 12
minutes).
1. On a call for heat, thermostat first-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 fire (first 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 fire 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
secondstage on delay, the integrated control energizes
the combustion air inducer at high speed. The gas
valve is energized on high fire and the indoor blower
motor is energized for operation at the high fire heating
speed.
6.
When the thermostat heating demand is satisfied, the
combustion air inducer begins a 5-second low speed
post-purge. The field-selected indoor blower off delay
begins. The indoor blower operates at the low-fire
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 off delay.
Page 37
Advertisement
Table of Contents
