Midco RE32 - Manual (Page 8)

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TROUBLE CHART
Make sure the thermostat and operating controls are calling for heat. Defective wiring or loose connections can simulate the
component defects outlined below. Check associated wiring before replacing a component.
ELECTRICAL AND FLAME CHECKS MUST BE MADE IN THE ORDER LISTED.
Shut off the manual gas control to the gas utilization equipment.
Do not shut off the control switch to the pump or blower.
I. MOTOR WILL NOT RUN OR MOTOR RUNS IN
REPEATED CYCLES.
A. Confirm 120V between strip terminals 1 and 2 and
verify the circuit polarity and electrical ground
between strip terminal 1 and burner chassis metal.
B. Check 24V* operating control circuit:
1. Between left strip terminal T and GND.
a. No voltage, transformer defective.
b. Very low voltage,* circuit is overloaded or
transformer defective.
2. Between right strip terminal T and GND.
a. No voltage, circuit between T and T is open.
C. Confirm 120V between strip terminal 2 and motor relay
terminal 4:
1. No voltage, motor relay is defective.
2. Voltage present, motor is defective.
II. MOTOR RUNS CONTINUOUSLY, BUT NO FLAME.
A. Confirm that both Main Manual Shut-Off and
combination gas shut-off valves are in the ON
position.
B. If the pilot flame is not proven within 90 seconds, or if
the proof of flame is lost during the burner run and the
pilot is not re-established within 90 seconds, the
Electronic Control will lock out. To reset the control for
restart, de-energize the Electronic Control by setting
the operating control to OFF or thermostat below room
temperature for at least 60 seconds.
1. No pilot flame.
a. Check for 24V* between Electronic Control
terminal 24V and strip terminal GND. No
voltage, Blower Motor Interlock Switch is
defective.
C. For each of the following tests, reset the Electronic
Control per step II.B. TESTS ARE VALID ONLY
DURING THE 90 SECOND TRIAL FOR IGNITION.
1. TURN MANUAL GAS COCK KNOB OFF. Check
for 24V* between Electronic Control terminal PV
and strip terminal GND. No voltage, Electronic
Control is defective.
2. Check for 24V* between pilot valve terminal PV on the
combination valve and terminal strip GND. No
voltage, defective valve wire harness. Voltage
present, pilot valve operator is defective; replace
valve.
3. Connect manometer to pilot flame gas pressure tap.
TURN MANUAL GAS COCK KNOB ON. Separate
main valve wire at harness splice. During trial for pilot
ignition period, check gas pressure.
a. No pressure, confirm that both Main Manual
Shut-Off and combination gas shut-off valves
and pilot adjustment screw are full open.
Repeat step 3, and if still no pressure, pilot valve
operator is defective.
b. Pilot flame pressure is 3.0" to 4.0" W.C., continue
with step 4.
c. Refer to Standby Gas Pressure requirements in
Section IX and adjust or regulate the pilot gas
pressure as indicated.
4. Check for ignition spark (spark gap is approx. 5/32
±1/32) Since this is a capacitor discharge system,
observe closely when visually checking the spark as it
is faint and thread-like and may be overlooked in
bright light.
a. Between Electronic Control high voltage
terminal and strip terminal GND. No spark,
defective Electronic Control.
b. Check for ignition spark at electrode tip. No
spark, defective electrode or cable.
c. Check for gas flow at pilot tip. No flow, clogged
pilot spud or pilot tube.
III. FLAME ON ONLY DURING TRIAL FOR IGNITION
PERIOD.
A. With motor running and flame off, check line voltage
terminals for voltage as follows:
1. Between strip terminals 1 and 2 - 120V; voltage
OK.
2. Between strip terminals 1 and GND - 120V; ground
OK.
3. Between strip terminals 2 and GND - "0" V; no
backfeed OK.
B. Follow reset procedure as specified in step II.B.
1. Check sensor wire for continuity.
2. Separate main valve wire at harness splice. Connect
DC microamp meter in series with sensor wire and
Electronic Control. With pilot only burning, flame
signal should not be less than 2 microamps. Adjust
pilot flame gas pressure per Section IX to obtain
acceptable signal and note gas pressure and
resultant signal for future reference.
3. Reconnect separated main valve wire at harness.
After main flame comes on, flame signal should
increase. If signal does not increase, a rich flame is
indicated. Refer to Table 3 for approximate air shutter
and/or manifold gas pressure settings (see step VI).
C. IMPORTANT: If changes are made in the main
spud orifice size, manifold gas pressure or primary air
adjustment, change the installation data tag
accordingly.
IV. PILOT FLAME ON BUT NO MAIN FLAME.
A. Check for 24V* between Electronic Control terminal
MV and strip terminal GND. No voltage, Electronic
Control is defective.
B. Check for 24V* between main valve terminal MV on
combination valve and strip terminal GND. No voltage,
defective valve wire harness. Voltage present, main gas
valve operator is defective.
V. SHORT FLAME.
A. Low gas pressure.
B. Primary air adjustment open too far.
C. Main spud orifice too small.
VI. LONG HAZY FLAME.
A. High gas pressure.
B. Primary air adjustment closed too far.
C. Dirty blower wheel.
D. Main spud orifice too large.
VII. GAS FAILS TO SHUT OFF.
A. Defective combination valve.
* Normal low voltage: Burner in standby - 24V min.
Burner running (main gas valve
energized) - 21V min.