Schwank STSp-CANADA - Manual (Page 27)

SP-MSTP-AC-15A
STS-p Manual
RD: DEC, 2003
RL:15
KH
Page 23
CA Series: The STS-p Burner with direct spark ignition, sequence is as follows :
1. Upon a call for heat by the line voltage
Thermostat or "ON/OFF" switch, the Blower
and the 120/24 volt Transformer are powered
simultaneously with 115 volts.
1a. Field installed 24 volt option:
The 120 volt supply to heater will power the
120v/24v Transformer and the 120V side of the
Blower switching relay simultaneously.
A call for heat by the 24 volt Thermostat
energizes the 24 volt control circuit and the
24v/120 volt relay powering the Blower.
2. The 24 volt control circuit powers the DSI con
trol in series through the normally open Air
Pressure Switch (APS) and the normally closed
Blocked Flue Switch (BFS).
3. The Blower creates a positive pressure and
closes a normally open contact inside the (APS).
4. 24 volts supplied to the DSI control initiates
the 30 second pre-purge cycle.
19. CA SERIES SEQUENCE OF OPERATION - HONEYWELL S87J-1034
5. After completing the 30 second pre-purge
cycle the DSI control generates high voltage
to the Spark Igniter, and 24 volts to energize
the Gas Valve.
6. The Burner will light and establish a steady
flame.
7. Once the flame sensor determines there is a
steady flame established, the spark igniter is
then de-energized.
8. In the event ignition does not occur, the
safety circuit will function to interrupt gas
flow after approximately 21 seconds and
lock the system out. No further gas will
flow until the power has been manually
interrupted for a period of 30 seconds.
This will reset the ignition module and the
operating sequence will restart at step #1
9. If the blower does not run, the blower air
pressure switch (normally open contact)
does not close and power is not supplied
to the ignition control.