Reznor CAUA Users Manual - Manual (Page 5)

Form O-CAUA, P/N 164772 R7, Page 5
Excessive dirt buildup on and inside the ports on a burner could cause fuel gas to spill
out of the back of the burner tube. Fuel gas spilling out of the back of a burner tube will
cause gas odor inside the building, and if not corrected, could eventually cause a fire/
explosion hazard. To prevent fuel gas spilling from the back of a burner tube, check
the burner ports at least annually and clean if necessary. Remove any soot deposits
from the burners with a wire brush. Clean the ports with an aerosol degreaser and/
or compressed air. Wipe the inside of the burner tubes clean. (Cleaning the burners
with an aerosol degreaser is highly recommended as the degreaser will retard future
buildup of dirt.)
Inspect the cleaned burner rack for any damage or deterioration. If a burner has any
damage or signs of deterioration, replace it.
Clean the burner orifices with air pressure. Do not ream orifices.
Re-assemble the heater and test for proper operation.
CAUTION: Use of eye protection is recommended.
1. Shut the gas supply off upstream of the combination
valve.
2. Turn off the electric supply.
3. Remove the burner compartment door.
4. Disconnect the union and remove the gas pipe from
the inlet of the gas valve.
5. Mark and disconnect the electrical wires to the gas
valve. Disconnect the flame sensor wire, the flame
rollout switch wires, and the ignitor wire at the burner
box cover. Mark and disconnect the ignitor ground wire
at the terminal board.
6. Disconnect the silicone tubing from the static tap on
the burner box cover.
7. Remove all burner cover sections. Depending on when
the unit was manufactured, there will be either two
or three sections. If two, there will be a right and left
section which extend over the front. If three, there will
be right, left, and a separate front section.
8. Remove the screws that attach the manifold to the
burner rack. Slide the manifold from the burner rack.
Remove the screws at the ends of the burner rack that
attach it to the cabinet. Carefully pull the burner rack
away from the heater.
Clean the Burner Rack
and Manifold
(requires a wire brush,
cleaning cloth, an
automotive type aerosol
degreaser or refrigerant
coil cleaner, and
compressed air)
2.2.5 Ignition System
R
This heater is equipped with a direct spark integrated control system. The ignition
board monitors the safety devices and controls the operation of the blower and venter
motors and the gas valve.
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 ignite the main burner gas. Burner flame is electronically
sensed by the control (minimum 1.0 microamps) upon carryover of all burners. (A sep-
arate 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 blower motor is energized 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 blower motor remains
energized for an additional 135 seconds.
NOTE: This is a three trial system. The unit will lockout for one hour before initiating
another trial for ignition. If the unit fails after one recycle interval, the unit will go into
hard lockout and must be reset by interrupting power or resetting the thermostat. To
initiate another trial for ignition before the one hour interval, either reset the thermostat
or interrupt power to the unit for 30 seconds.
Maintenance: To access the ignition system, follow Steps 1-3 in Paragraph 2.2.4.
Ignitor - On the right side of the burner rack, locate the ignitor. Disconnect the wire;
remove the screw and the ignitor. Clean the ignitor assembly with an emery cloth.
Spark gap must be maintained to 1/8". See FIGURE 6, page 9 .
IMPORTANT: When re-assembling, the brown ground wire must remain attached to
the ignitor.