Reznor SFT Unit Installation Manual - Manual (Page 15)

Form RZ -NA-I-SFT, Page 14
Figure 9 - Electrical Connections on the Integrated
Ignition Control Module in the Control Compartment
Ignition Control Module LED Codes
Slow Flash ..... Normal Operation, No call for heat
Fast Flash ...... Normal Operation, Call for heat
2 Flashes ......... System Lockout, Failed to detect or sustain flame
3 Flashes ......... Pressure Switch Open or Closed
4 Flashes ......... High Limit or Flame Rollout Switch Open
5 Flashes ......... Flame Sensed and Gas Valve not energized
Steady On ....... Internal Failure - Replace the ignition control module
Ignitor
Connection
24-volt Terminal Strip
for Thermostat
Connections
Line Voltage
Connection
Fan Delay to OFF Switch (DIP Switch Settings)
(selected prior to call for heat)
SW1 Fan Delay
1 2 To OFF (seconds)
OFF OFF 90
OFF ON 120 (Factory Preset)
ON OFF 180
ON ON 240
15. Gas Valve
The main operating gas valve is powered by the 24-volt control circuit
through the thermostat and safety controls. The main control valve is
of the diaphragm type providing regulated gas flow preset at the fac-
tory.
14. Combustion Air Proving
Switch
The combustion air proving switch is a pressure sensitive switch that
monitors air pressure to ensure that proper combustion air flow is avail-
able. The switch is single pole/double throw with the normally open
contacts closing when a decreasing pressure is sensed in the system.
On start-up when the heater is cold, the sensing pressure is at the most
negative level, and as the heater and flue system warm up, the sensing
pressure becomes less negative. After the system has reached equilib-
rium (about 20 minutes), the sensing pressure levels off.
If a restriction or excessive flue length or turns cause the sensing pres-
sure to be outside the switch setpoint, the pressure switch will function
to shut off the main burners. The main burners will remain off until the
system has cooled and/or the flue system resistance is reduced. The
Table below lists the approximate water column negative pressure read-
ings and switch setpoints for sea level operating conditions.
Model Start-Up Equilibrium Set Point Set Point
Sizes Cold “OFF” “ON”
45, 60, 75 -1.20 -0.75 -0.60 -0.70
100, 125 -1.10 -0.70 -0.40 -0.50
150, 200 -1.50 -0.90 -0.65 -0.75
250, 300
DANGER: Safe operation of this unit requires
proper venting flow. NEVER bypass combustion
air proving switch or attempt to operate the unit
without the venter running and the proper flow
in the vent system. Hazardous conditions could
result. See Hazard Levels, page 2.
WARNING: The operating valve is the prime safety
shutoff. All gas supply lines must be free of dirt or
scale before connecting the unit to ensure positive
closure. See Hazard Levels, page 2.
16. Ignition System
This heater is equipped with a direct spark integrated control system.
The system monitors the safety devices and controls the operation of
the fan and venter motors and the gas valve between heat cycles.
Ignition System Operating Sequence -- On a call for heat from the
thermostat, the system energizes the venter motor and goes through a
10-second prepurge. The system verifies that the pressure switch has
changed states closing the normally open contactor and that the high
limit is in the closed state. The gas valve is then energized and the
ignition system provides the high voltage spark to the electrode to ig-
nite the main burner gas. Burner flame is electronically sensed by the
control upon carryover of all burners. (A separate solid metal probe is
used as the flame sensing function. A low voltage electrical signal is
imposed on the metal probe which is electrically isolated from ground.
When the flame impinges on the flame sensing probe, the flame acts as
a conduction path to ground. The flame rectifies and completes the DC
circuit, and the ignition system acknowledges the flame.) The fan mo-
tor is energized by the system after 30 seconds of flame sensing.
After the thermostat has been satisfied, the system de-energizes the gas
valve, the venter motor goes through a 45-second post-purge, and the
fan motor remains energized for an additional 120 seconds.
NOTE: This is a three trial system, should the unit not sense burner
flame, the unit will lockout for one hour before initiating another trial
for ignition. To initiate another trial for ignition before the one hour,
requires that either the thermostat be reset or the power to the unit be
interrupted for 30 seconds.
17. Burners
This unit heater has inshot burners designed to provide controlled flame
stability without lifting or flashback with either natural or propane gas.
The burners are lightweight and factory mounted in an assembly which
permits them to be removed as a unit for inspection or service.