Troubleshooting, Position, Control | Lennox Hearth MPD35ST-NM

TROUBLESHOOTING

Note: Before troubleshooting the gas control system, Ensure external gas shut off valve, located at gas supply inlet, (and wall switch, iff applicable), is in the “ON” position.

Important: Valve system troubleshooting should only be accomplished by a qualiﬁed service technician.

TROUBLESHOOTING GUIDE - MILLIVOLT GAS CONTROL SYSTEM

	SYMPTOM	POSSIBLE CAUSES	CORRECTIVE ACTION
1.	Spark igniter will not light pilot after	A. Defective igniter	Check for spark at electrode and pilot; if no spark and
	repeated triggering of igniter button.	(no spark at electrode).	electrode wire is properly connected, replace igniter.
		B. Defective or misaligned electrode at pilot	Using a match, light pilot. If pilot lights, turn off pilot
		(spark at electrode).	and trigger the igniter button again. If pilot lights, an
			improper gas mixture caused the bad lighting and
			a longer purge period is recommended. If pilot will
			not light – check gap at electrode and pilot – should
			be 1/8" to have a strong spark. If gap measures 1/8",
			replace pilot (see Figure 15 on Page 10).
		C. Gas supply pressure errant.	Check inlet gas pressure. It should be within the limits
			as marked on the rating plate.
		D. Pilot oriﬁce plugged.	Clean or replace pilot oriﬁce.

2.	Pilot will not stay lit after	A. Defective pilot generator	Check pilot ﬂame, it must impinge on thermocouple
	carefully following the lighting	(thermocouple).	(see Figure 15 on Page 10). Clean and/or adjust pilot
	instructions.		for maximum ﬂame impingement on thermocouple.
			Ensure that the connection between the valve and
			thermocouple are tight and secure.
3.	Pilot burning, no gas to burner, Valve	A. Wall switch or wires defective.	Check wall switch and wires for proper connections.
	knob “ON,” and the (standard) burner		Jumper wire across terminals at wall switch, if burner
	OFF/ON switch is “ON." Read impor-		comes on, replace defective wall switch. If okay, jumper
	tant note below.		wires across wall switch wires at valve, if burner comes
			on, wires are faulty or connections are bad.
	IMPORTANT NOTE: If an optional	B. Thermopile may not be generating suf-	Check thermopile with millivolt meter. Take reading
	IMPORTANT NOTE: If an optional	ﬁcient millivolts.	at thermopile terminals of gas valve. Should read
	*remote switch is used for burner	ﬁcient millivolts.	at thermopile terminals of gas valve. Should read
	*remote switch is used for burner		325 millivolts minimum with optional wall switch
	operation, if the standard burner		325 millivolts minimum with optional wall switch
	operation, if the standard burner		“OFF.” Replace faulty thermopile if reading is below
	OFF/ON switch is still installed on		“OFF.” Replace faulty thermopile if reading is below
	OFF/ON switch is still installed on		speciﬁed minimum.
	appliance it must be in the "OFF"		speciﬁed minimum.
	position.	C. Plugged burner oriﬁce.	Check burner oriﬁce for blockage and remove.
		C. Plugged burner oriﬁce.	Check burner oriﬁce for blockage and remove.
	*Optional remote switch kits - wall
	*Optional remote switch kits - wall	D. OFF/ON Switch & *Remote Switch are in	When turning on the burner using a *remote switch,
	switch, wall thermostat or remote	the "ON" position resulting in excessive	ensure that the standard OFF/ON switch is in the "OFF"
	control.	resistance.	position. If both switches are in the ON position, it
			may result in excessive resistance (& millivolt drain-
			age) and the burner may not come on.
4.	Frequent pilot/burner outage prob-	A. Pilot ﬂame may be too low or blowing (high)	Clean and/or adjust pilot ﬂame for maximum ﬂame
	lem.	causing the pilot/valve safety to drop out.	impingement on thermocouple (see Figure 15 on
			Page 10).

TROUBLESHOOTING GUIDE - ELECTRONIC IGNITION SYSTEM

	SYMPTOM	POSSIBLE CAUSES	CORRECTIVE ACTION

1.	Burner will not light.	A. Faulty Valve System.	See Below.

		B. “OFF/ON” or wall switch defective.	Disconnect the two black wires from the wire nuts.
			Test switch(s) for continuity with a multimeter. If
			continuity is not indicated, switch(s) is defective and
			must be replaced.
			Note: Before replacing “OFF/ON” switch, Ensure to
			check wiring for loose connections or broken wires
			and repair as needed.
2.	Burners come “ON,” then turns “OFF.”	A. Burner oriﬁce plugged.	Check main burner oriﬁce(s) for blockage. Clean
			or replace.
		B. Obstructed vent system.	Check vent system for obstructions.

NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.

MPD35ST-NE, MPD35ST-PM, MPD35ST-NM specifications

The Lennox Hearth MPD35ST series, which includes the MPD35ST-NM, MPD35ST-PM, and MPD35ST-NE models, is designed for homeowners seeking superior heating solutions with aesthetic appeal. These multi-position direct vent gas fireplaces combine efficiency with advanced technology, ensuring that both performance and style are prioritized in any living space.

One of the standout features of the MPD35ST series is its innovative Direct Vent technology. This system draws air from the outside for combustion, eliminating the need for indoor air and thereby reducing energy consumption and improving indoor air quality. This feature not only enhances efficiency but also provides a safe and comfortable environment for your home.

The MPD35ST fireplaces come with a variety of design options to suit different decor styles. With a variety of front options, including sleek and modern designs or classic and rustic looks, homeowners can customize their fireplace to match their aesthetic preferences. The 'No Media' (NM) style offers a clean and minimalist contemporary design, while the 'Panel Media' (PM) and 'Enhanced Media' (NE) styles feature options for adding decorative media, such as pebbles or logs, that enhance the visual ambiance of the fire.

These units also incorporate advanced heating technologies, featuring high-efficiency burners that produce significant heat output with minimal energy consumption. With adjustable flame settings, users can control the intensity of the heat while enjoying the mesmerizing flicker of the flames. This flexibility allows homeowners to create a cozy environment tailored to their comfort needs.

In addition, the Lennox MPD35ST series is designed with user-friendly controls that simplify operation. Integrated remote controls allow for easy adjustment of the temperature and flame settings from the comfort of your seat. Safety is a paramount consideration; these fireplaces are equipped with built-in safety shut-off systems that ensure worry-free operation.

Furthermore, the construction of the MPD35ST series focuses on durability and longevity. Made from high-quality materials, these fireplaces are built to withstand the test of time, providing both reliable performance and an attractive focal point in any room.

In summary, the Lennox Hearth MPD35ST-NM, MPD35ST-PM, and MPD35ST-NE models epitomize modern fireplace design. With their energy-efficient technologies, customizable aesthetic options, and user-friendly features, they are an excellent choice for homeowners looking to enhance their living spaces with both comfort and style.