Thomas & Betts LDAP 1200 - Manual (Page 39)

Form RZ-NA-I-LDAP, P/N 207733 (Rev 2), Page 39
Trial for
Ignition
Call for Heat
Is there a
spark across gap at
ignitor?
Does gas
ignite?
Is there minimum
flame current at the flame
sensor?
Is there
minimum flame current
at the control
module?
Replace control
module.
Check connections to
flame sensor or
moisture in bulkhead
connector.
Is the flame sensor
corroded?
Clean
flame
sensor.
Is the sensor
located in flame
correctly?
Replace flame
sesnsor.
Repositon flame
sensor.
Is gas flowing?
Is the ignitor
position correct in the
gas flow?
Check gas pressure and
supply voltage. If either
are low, correct and
repeat startup.
Reposition spark
ignitor.
Is there
24VAC at the gas
valve?
Is there 24VAC from
gas valve output on control
module to chassis?
Check wiring and
connections to gas
valve.
Replace ignition
control module.
Replace gas valve.
Is there
spark voltage at
control?
Check high
voltage wire
continuity.
Is there
24V P1-2 to power
control?
Replace control
module.
Check wiring and/or
24VAC transformer
output.
YES
NO
YES NO
YES
NO
YES
NO
YES
NO
YES
NO
YES NO
YES
NO
NO
YES
YES
NO
YES
NO
YES NO
DSI Integrated
Control Module
(Circuit Board) Trial
Troubleshooting
Flowchart
PROBLEM PROBABLE CAUSE REMEDY
1. No power to unit. 1. Turn on power; check supply fuses or main circuit breaker.
2. No 24 volt power to integrated circuit board. 2. Turn up thermostat; check control transformer output.
3. Integrated circuit board fuse blown. 3. Correct cause. Replace fuse (type ATC or ATO, 32VDC, 3A).
4. No power to venter motor. 4. Tighten connections at circuit board and/or motor terminals.
5. Integrated circuit board defective. 5. Replace intergrated circuit board.
6. Defective venter motor. 6. Replace venter motor. See Paragraph 32.
Burner will 1. Manual valve not open. 1. Open manual valve.
not light 2. Air in the gas line. 2. Bleed gas line (initial startup only).
3. Gas pressure too high or too low. 3. Supply pressure should be 5" - 14" w.c. for natural gas or 11" - 14"
w.c. for propane gas.
4. No Spark: 4.
a) Loose wire connections. a) Be certain all wire connections are solid.
b) Transformer failure. b) Be sure 24 volts is available.
c) Incorrect spark gap. c) Maintain spark gap at 1/8".
d) Spark cable shorted to ground. d) Replace worn or grounded spark cable.
e) Spark electrode shorted to ground. e) Replace if ceramic spark electrode is cracked or grounded.
f) Burner not grounded. f) Make certain integrated circuit board is grounded to ignitor.
g) Circuit board not grounded. g) Make certain integrated circuit board is grounded to furnace chassis.
h.) Unit not properly grounded. h.) Make certain unit is properly field grounded to earth ground and
properly phased (L1 to hot lead L2 to neutral).
i) Integrated circuit board fuse blown. i) Correct cause. Replace fuse (type ATC or ATO, 32VDC, 3A).
j.) Faulty intergrated circuit board. j) If 24 volt is available to the integrated circuit board and all other causes
have been eliminated, replace board.
5. Lockout device interrupting control circuit by above causes. 5. Reset lockout by interrupting control at the thermostat or main power.
6. Combustion air proving switch
6.
not closing. a) Make sure unit is properly vented.
b) Remove obstructions from vent.
c) Replace faulty tubing to pressure switch.
7. Faulty combustion air proving switch. 7. Replace combustion air proving switch.
8. Main valve not operating. 8.
a) Defective valve. a) If 24 volt is measured at the valve connections and valve remains
closed, replace valve.
b) Loose wire connections b) Check and tighten all wiring connections.
9. Integrated circuit board does not power main valve. 9.
a) Loose wire connections. a) Check and tighten all wiring connections.
b) Flame sensor grounded. b) Be certain flame sensor lead is not grounded or insulation or ceramic is
not cracked. Replace as required.
c) Incorrect gas pressure. c) Supply pressure should be 5" - 14" w.c. for natural gas or 11" - 14"
w.c. for propane gas.
d) Cracked ceramic at sensor. d) Replace sensor.
Venter motor will
not start
General Troubleshooting