Desa DNV40NB, DNV25NB installation manual Ignition Failures

DYNAVENT®

DIRECT-VENT NATURAL GAS HEATER

TROUBLESHOOTING

Continued

OBSERVED PROBLEM	POSSIBLE CAUSE		REMEDY
No heat (continued)	7.	Blower not operating	7.	A. Check power supply to furnace
				B. Check electrical connections at furnace
				C. With thermostat points closed, check for cir-
				cuit completion at motor. If voltage is present,
				replace motor. If no voltage is present at mo-
				tor, check for:
				• 24 volts on secondary coil or transformer. If
				no voltage, replace transformer.
				• If 24 volt transformer okay, check for circuit
				completion across contacts on time delay
				relay. Allow three to five seconds for con-
				tact to close
				• If circuit across contacts okay, check conti-
				nuity of wiring in motor circuit
	8.	Short cycling (motor goes on and off)	8.	A. Check thermostat. Contacts should remain
				closed. If contacts are breaking:

• Check thermostat anticipator setting. It should be between .75 and 1.0

• If anticipator setting okay, check amp draw across thermostat. If amp draw exceeds .65, check amp draw across coil of valve and time delay relay. Note: On initial operation of glo bar, there is a momentary surge of approxi- mately 4.0 amps

• If amp draw is within limits, check for shorts in thermostat wiring

• If wiring is okay, replace thermostat

IGNITION FAILURES

WARNINGS:

•Never connect unit or ignition circuit to 230 volts.

•Never operate unit with glo bar touching burner or any other ground. Damage to ignition control will occur.

•Be sure sensor probe never touches glo bar. This will dam- age ignition control.

•If the ignition control is defec- tive, it must be replaced. It is not field-repairable.

The electronic system is made up of two parts: the ignition control and the glo bar. The ignition control is the brain of the elec- tronic system. It has several functions:

1.When the blower reaches full r.p.m., a 24-volt circuit is completed to the ig- nition control. (Check across yellow and orange wires.)

2.The red and blue wires at the ignition control are the 120-volt input for the glo-bar circuit. When the 24-volt cir- cuit is completed, the ignition control will complete the 120-volt circuit to the glo bar and it begins to glow. (Check this circuit across the two white wires at the ignition control.)

nition control to a neutral ground.) This circuit opens the valve, gas flows to the burner and is ignited by the heat from the glo bar. Note: Glo bar remains on.

4.When the burner flame is established, the sensing probe will sense the pres- ence of burner flame and open the glo- bar circuit. The glo bar will then stop glowing.

It is important to determine the type of problem being experienced. Then the proper checkout procedure can be made. The fol- lowing is a list of problems, how to identify in which area the problem is located, and how to correct it.

CAUTION: Do not attempt to repair the ignition control. This may alter it and cause it to oper- ate incorrectly.

3.After approximately 20 seconds, a 24- volt circuit is completed through the ig- nition control to the gas valve. (This cir- cuit is checked from brown wire at ig-

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