Page 93
CAUTION
Failure to use properly sized wiring and circuit
breaker may result in property damage. Size wiring
and circuit breaker(s) per Product Specifications
bulletin (EHB) and unit rating plate.
WARNING
Fire Hazard. Use of aluminum wire with this product
may result in a fire, causing property damage,
severe injury or death. Use copper wire only with
this product.
WARNING
Electric Shock Hazard. Can cause injury
or death. Unit must be properly grounded
in accordance with national and local
codes.
Electronic Ignition
The two-stage, variable speed integrated control used
in EL296UHV units has an added feature of an internal
Watchguard control. The feature serves as an automatic
reset device for ignition control lockout caused by ignition
failure. After one hour of continuous thermostat demand
for heat, the Watchguard will break and remake thermo
-
stat demand to the furnace and automatically reset the
control to begin the ignition sequence.
NOTE -
The ignition control thermostat selection DIP
switch is factory-set in the “TWO-STAGE” position.
Applications Using a Two-Stage Thermostat
See FIGURE 59 for ignition control sequence
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 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 low
pressure switch has closed, the combustion air
inducer begins a 15-second pre-purge in low speed.
NOTE -
If the low fire pressure switch does not close
the combustion air inducer will switch to high fire.
After a 15 second pre-purge the high fire pressure
switch will close and the unit will begin operation on
high fire. After 10 to 20 seconds of high fire operation
the unit will switch to low fire.
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, 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.
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.
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).
6 - At the end of the recognition delay, the integrated
control energizes the combustion air inducer at high
speed. The control also checks the high fire (second
stage) pressure switch to make sure it is closed. The
high fire (second stage) gas valve is energized and
the indoor blower motor is energized for operation at
the high fire heating speed.
7 - When the demand for high fire (second stage) heat
is satisfied, the combustion air inducer is switched to
the low-fire heating speed and the high-fire (second
stage) gas valve is de-energized. The low-fire (first
stage) gas valve continues operation. The indoor
blower motor is switched to the low-fire heating
speed.
8 - When the thermostat demand for low-fire (first stage)
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.
Содержание EL296UH045XV36B
Страница 89: ...Page 89 VII Wiring and Sequence of Operation Ignition Control 103130 05 EL296 Schematic Diagram...
Страница 90: ...Page 90 Ignition Control 103130 05 and Blower Drive EL296 Units With Blower Drive...
Страница 91: ...Page 91 Ignition Control 107045 01...
Страница 92: ...Page 92 Ignition Control 107045 01 and Blower Drive...