Midco J121A-3 - Manual (Page 7)

FIGURE 3 Control Components -7-
■ Check that the electrode ends are positioned and that the
gap between the end of each electrode and the ground
barrier is spaced per Figure 5.
■ Check that the Ignitor Air Deflector is at the correct angle
(45°). See Figure 4.
■ Inspect the electrode wire insulation for cracks or worn
areas, or any contact with the burner frame. Dampness will
facilitate electrical leakage to ground, which will cause
ignition or flame signal failure.
SPARK TEST—Main Manual Shut-Off Valve must be off.
Place the Ignitor Assembly on top of the burner with the
electrode ends visible and good metal to metal contact
between the Ignitor Mounting Plate and the burner chassis.
■ Connect the high voltage wire to the spark electrode.
Spark should be visible during trial for ignition period and
arc from the electrode end to the Ground Barrier. It should
be audible and visible, though it is rather thin and difficult to
see in bright light.
■ If the spark is not audible or visible it is leaking directly to
ground. Before removing electrodes, check to make sure
voltage is available by positioning the spark wire 1/8" from
the end of the electrode. If necessary, press relay reset
button to recycle ignition sequence.
■ Disconnect Flame Electrode wire and switch the high
voltage wire to the flame electrode and repeat test for
insulator leakage.
CAUTION: Do not indiscriminately change the
ignitor gas orifice size as ignition troubles are rarely
cured in this manner. The ignitor utilizes a premixed
gas/air mixture and, as the air input is relatively fixed,
any adjustment to the gas/air ratio that might be
required for a specific application should be made by
careful adjustment of the ignitor regulator to vary its
outlet gas pressure. Pressure adjustments must be
made when the gas is flowing. If cleaning and electrode
adjustment does not eliminate an ignition problem,
further checks are required. Refer to Trouble Chart.
IX IGNITOR GAS/AIR ADJUSTMENT (J121A-
3 ONLY)
The ignitor assembly as shipped is pre-set during factory
fire-testing and normally needs no adjustment except in
installations where the air shutter is full open. The ignitor
should not be adjusted until it is confirmed that good light-
offs are not possible with ignitor gas pressure adjustments
only as described in Section VIII.
■ The Air adjustment screw is located under a plug button
in the Ignitor Block about 1⁄2 inch behind the Ignitor Orifice
(refer to Figure 4). A 5⁄64 (.078) inch hexagon wrench is
required for adjustment. Pry up the plug button to expose
air adjustment screw. Adjust the screw up or down to find
the best Flame Signal or until repeatable and stable light-
offs are achieved. Ignitor airflow is decreased as the screw
is turned clockwise, and increased as it is turned counter-
clockwise. Generally 3 to 5 turns up from full closed (screw
bottomed out) works best.
■ When adjustments are completed, replace plug button to
protect adjustment screw
X FLAME SAFEGUARD
WARNING: Explosion hazard. Do not use this device
if it gets wet. It can malfunction and cause serious
injury or death. Replace any device that has been wet.
Standard Incinomite J Series burners are equipped with a
Honeywell RM7890 microprocessor based burner control
employing a flame rectification system of flame detection.
Burner construction for special codes and/or insurance
requirements such as Factory Mutual or Industrial Risk
Insurers (IRI) may require alternate controls. (Refer to
Section XI SPECIAL EQUIPMENT). A safe start and run
control sequence is provided with instantaneous response
to presence or loss of flame signal. Flame failure response
time is .8 seconds. Pilot Flame Establishing Period (PFEP)
is field selectable from 4 or 10 seconds. The RM7890
features a plug in amplifier. Five LED’s (light emitting
diodes) are provided to display sequence information.
Refer to the Honeywell RM7890 literature for detailed
operating information, configuration requirements, testing,
and service.