Vermont Casting DVHVAC36 Troubleshooting the Gas Control System, SIT Nova 825 Millivolt Valve

DVHVAC36

Troubleshooting the Gas Control System

SIT NOVA 825 Millivolt Valve

NOTE: Before troubleshooting the gas control system, be sure external gas shut off is in the "ON" position.

SYMPTOM	POSSIBLE CAUSES	CORRECTIVE ACTION
1. Spark ignitor will not light	A. Defective or misaligned	Using a match, light pilot. If pilot lights, turn off
	electrode at pilot.	pilot and push the red button again. If pilot will not
		light - check gap at electrode and pilot-should be
		1/8" to have a strong spark.
	B. Defective ignitor (Push Button)	Push Piezo Ignitor Button. Check for spark at
		electrode and pilot. If no spark to pilot, and elec
		trode wire is properly connected, replace ignitor.
2. Pilot will not stay lit after	A. Defective pilot generator	Check pilot flame. Must impinge on thermo-
carefully following lighting	(thermocouple)	couple/thermopile. Note: this pilot burner assem
instructions.		bly utilizes both-a thermocouple and a thermopile.
		The thermocouple operates the main valve
		operation (On and Off). Clean and or adjust pilot for
		maximum flame impingement on thermopile and
		thermocouple.
	B. Defective automatic valve	Turn valve knob to “Pilot”. Maintain flow to pilot;
		millivolt meter should read greater than 10 mV. If
		the reading is okay and the pilot does not stay on,
		replace the gas valve. Note: An interrupter block
		(not supplied) must be used to conduct this test.
3. Pilot burning, no gas to	A. Thermostat or wires defective	Check wall switch and wires for proper connections.
main burner, Valve knob
"ON", thermostat "ON"	B. Thermopile may not be	1. Be sure wire connections from thermopile at
	generating sufficient	gas valve terminals are tight and thermopile is
	millivoltage.	fully inserted into pilot bracket.
		2. One of the wall switch wires may be grounded.
		Remove wall switch wires from valve terminals if
		pilot now stays lit, trace wall switch wiring for
		ground. May be grounded to fireplace or gas
		supply.
		3. Check thermopile with millivolt meter. Take
		reading at thermopile terminals of gas valve.
		Should read 325 millivolts while holding valve
		knob depressed in pilot position and wall switch
		“Off”. Replace faulty thermopile if reading is below
		specified minimum.
	C. Plugged burner orifice.	Check burner orifices for debris and remove.
	D. Defective automatic valve	Turn valve knob to “On”, place wall switch to “On”
	operator.	millivolt meter should read greater than 100 mV. If
		the reading is okay and the burner does not come
	E. Transformer defective.	on, replace the gas valve.
	F. Power Not ON.
	G. heat demand satisfied.
4. Frequent pilot outage	A. Pilot flame may be too low	Clean and/or adjust pilot flame for maximum flame
problem.	or blowing (high) causing the	impingement on thermopile and thermocouple.
	pilot safety to drop out.
	B. Possible blockage of the vent	Check the vent terminal for blockage
	terminal.

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