Schwank STR-USA - Manual (Page 21)

SP-MSTR-AU-05A
STR Manual
RD: NOV, 2003
RL: 5
KH
Page 17
The voltage at the spark ignition control is
24V. Note that proper functioning of the heater will be adversely affected if the input
voltage varies by more than +/-10%.
WARNING: The heater must be electrically grounded in accordance
with the current Electrical Code.
12. OPERATING SEQUENCE
a) Heat Mode
1. On call for heat, relay is energized closing
contacts to power up the combustion air
fan motor. When the fan is up to speed,
and enough pressure is built up, the
pressure switch contacts close, energizing
the ignition module. The ignition module
incorporates a 30-second pre-purge pe-
riod. Following pre-purge, the gas valve
is energized and spark commences for the
trial for ignition period of 21 seconds.
2. When a flame is detected during the trial for
ignition, the spark is shut off immediately
and the gas valve remains energized. When
the thermostat is satisfied and the demand
for heat ends, the blower, ignition module
and gas valve are all de-energized.
b) Failure To Light – Lockout
1. Should the main burner fail to light or
flame is not detected during the trial for
ignition period, the control will lockout
and the gas valve will immediately be de-
energized. The combustion blower will
continue to purge the heater.
2. Recovery from lockout requires a manual
reset by either resetting the thermostat
or setting the line voltage switch power
ing the heater to the OFF position for a
minimum of 30 seconds. .