Thomas & Betts LDAP 1200 warranty General Troubleshooting, Problem Probablecause Remedy

DSI Integrated

Control Module

(Circuit Board) Trial

Troubleshooting

Flowchart

Trial for	Is there a	NO		Is there	YES
Ignition	spark across gap at			spark voltage at
Call for Heat	ignitor?			control?
	YES			NO
		Check wiring and/or	NO	Is there	YES
		24VAC transformer		24V P1-2 to power
		output.		control?

Check high voltage wire continuity.

Replace control module.

Is there minimum	Is there
	YES minimum flame current
flame current at the flame
sensor?	at the control
	module?

YES	Does gas	NO
	ignite?
YES	Replace control	YES Is gas flowing? NO
	module.

		NO	NO
	YES		Check connections to	Check gas pressure and		YES
Clean		Is the flame sensor	flame sensor or	supply voltage. If either YES	Is the ignitor		Is there
flame		corroded?	moisture in bulkhead	are low, correct and	position correct in the	Replace gas valve.	24VAC at the gas
sensor.					gas flow?		valve?
			connector.	repeat startup.

NO

Is the sensor	YES
located in flame
correctly?

	NO			NO
Replace flame	Reposition spark	Check wiring and	YES	Is there 24VAC from
sesnsor.	ignitor.	connections to gas		gas valve output on control
		valve.		module to chassis?

NO	NO
Repositon flame	Replace ignition
sensor.	control module.

General Troubleshooting

PROBLEM	PROBABLECAUSE		REMEDY
Venter motor will	1. No power to unit.		1. Turn on power; check supply fuses or main circuit breaker.
not start	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"
	d) Cracked ceramic at sensor.		w.c. for propane gas.
			d) Replace sensor.

Form RZ-NA-I-LDAP, P/N 207733 (Rev 2), Page 39