10
Midco
International
Inc.
8470 70
Service
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 diffi cult 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 fl ame electrode and
repeat test for insulator leakage.
CAUTION: Do not indiscriminately change the ignitor gas orifi ce 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 fi xed, any adjustment to the gas/air ratio that might be required for a
specifi c 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 fl owing. If
cleaning and electrode adjustment does not eliminate an ignition problem, further checks are
required. Refer to Trouble Chart.
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The ignitor assembly as shipped is pre-set during factory fi re-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 confi rmed that good lightoff s 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 Orifi ce (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 fi nd the best
Flame Signal or until repeatable and stable lightoff s are achieved. Ignitor airfl ow is decreased as the
screw is turned clockwise, and increased as it is turned counterclockwise. 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
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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 fl ame rectifi cation system of fl ame 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 fl ame signal.
Flame failure response time is .8 seconds. Pilot Flame Establishing Period (PFEP) is fi eld selectable
from 4 or 10 seconds. The RM7890 features a plug in amplifi er. Five LED’s (light emitting diodes)
are provided to display sequence information. Refer to the Honeywell RM7890 literature for detailed
operating information, confi guration requirements, testing, and service.
Initiate (“Power” LED is lit)
The RM7890 enters the INITIATE sequence when it is powered. The INITIATE sequence lasts for
ten seconds unless the voltage or frequency tolerances are not met (refer to Honeywell RM7890
literature for criteria). When tolerances are met, the INITIATE sequence will restart. If the condition
is not corrected and the hold condition exists for four minutes, the RM7890 will lock-out. Causes for
hold conditions in the INITIATE sequence are in the Honeywell RM7890 literature.
Standby (“Power” LED is lit)
The RM7890 is idle in this state of sequencing. When the burner switch, limits, operating limit
controls, and all microprocessor monitored circuits are in the correct state for RM7890 to continue,
sequencing will advance to
IGNITION TRIAL
.
VIII Ignitor and
Regulator Assembly
Continued
!
IX Ignitor Gas / Air
Adjustment (J121A-3 Only)
X Flame Safeguard
!
