Gas wall heaters: how they work and when to repair them

What federal rules call a gas wall heater

Part 430 of Title 10 of the Code of Federal Regulations (CFR) holds the Department of Energy's energy conservation program for consumer products. Section 430.2 of Title 10 of the CFR uses the term vented wall furnace. The section defines it as a self-contained vented heater complete with grilles or the equivalent, designed for incorporation in, or permanent attachment to, a wall of a residence.

The same definition says it furnishes heated air circulated by gravity or by a fan directly into the space to be heated through openings in the casing.

The rules group wall furnaces with floor furnaces and room heaters as vented home heating equipment. The rule defines that class as home heating equipment, not including furnaces, "designed to furnish heated air to a space proximate to such heater, directly from the heater, without inlet duct connections (except that boots not to exceed 10 inches beyond the casing may be permitted) and with exhaust venting." Unvented heaters are a separate class; one of its criteria is that they have no exhaust venting.

How a wall heater gets air and sends out exhaust

Wall heaters differ in where they get combustion air and where the exhaust goes.

Direct vent. One Williams manual for its Cozy brand describes a sealed combustion system. It draws combustion air directly from outdoors into the combustion chamber. Exhaust leaves directly outdoors through tubes on the rear of the furnace. The manual says this furnace must be installed on an outside wall for proper venting of flue gases.

Top vent. A Williams manual for a top vent model says combustion air is drawn in from the room. Exhaust goes up through vent piping inside the wall to a vent top on the roof. That manual adds that most homes will require outside air be supplied to the heated area through grilles or ducts.

Gravity or fan. The Cozy direct vent gravity model needs no electric power unless an optional blower accessory is added. The Williams high efficiency direct vent model is certified as a fan-type unit.

How a wall heater runs, step by step

The Cozy manual lists the operating sequence. First, the thermostat turns on the main burner.

Next, heat builds up in the furnace and starts the fan, if the unit has one. The heated air comes out the panel louvers. When the thermostat setting is reached, it shuts off the main burner. The fan runs until the heat is removed from the furnace, then it turns off.

The Cozy model has a pilot, which must be lit by hand. The Cozy manual says its safety pilot will shut off the gas valve if the pilot is not burning or working properly. The Williams high efficiency manual says that appliance is equipped with an ignition device that automatically lights the burner.

The Williams top vent manual describes a vent safety shutoff system. It is designed to protect against improper venting of combustion products.

Signs a wall heater needs repair

The Cozy and top vent troubleshooting tables are headed "For qualified service technicians."

The pilot will not stay lit. The Cozy table lists possible causes such as a weak or faulty generator. The manual says the pilot flame must touch the generator, and a generator not making enough millivolts may not open the valve. It also lists loose or dirty generator connections at the gas valve, and a defective gas valve.

The pilot burns but the main burner never lights. Listed causes include a plugged burner opening, broken thermostat wires and, on the top vent model, a tripped vent safety switch.

The heater shuts off before the room warms. The top vent table lists thermostat location as one cause. It says the thermostat should not be in the path of the heater's warm air, near a lamp or above a TV.

The flame looks wrong. The Williams high efficiency manual says the flame must be stable and have blue colour. The Cozy manual says dust in the room air can make the flame look yellow, and it should then change to blue.

The unit got wet. The high efficiency and Cozy manuals both say not to use the heater if any part has been under water. They say to immediately call a service technician to inspect it and replace any part of the control system and any gas control that was under water.

Yearly inspection, cleaning and carbon monoxide

All three Williams manuals say the heater should be inspected before use and at least annually by a qualified service technician or professional service person. The high efficiency manual goes further: the home owner may not service the furnace.

Lint matters. The Cozy manual says cold air is drawn to the flame, so lint from carpeting, bedding and dust builds up in the burner area. It warns that failing to keep the burner and control area clean can cause dangerous conditions. The high efficiency manual says all servicing must be done by a qualified service technician or a service agency. Our guide to a heating tune-up covers what a yearly visit is for.

The Centers for Disease Control and Prevention (CDC) says gas and oil furnaces produce carbon monoxide (CO). It calls CO an invisible, odorless, poison gas that kills without warning. The Consumer Product Safety Commission (CPSC) says the heating system inspection should also check flues for blockages, corrosion and disconnections.

In 2008 the CPSC announced a recall of two Rinnai direct vent wall furnace models. The CPSC said a gasket in the unit can fail, risking carbon monoxide leaking into the home. Owners were told to stop using the furnace immediately and contact the firm to arrange installation of a free repair kit.

What we found for Florida

We found no count of gas wall heaters in Florida homes. The 2020 Residential Energy Consumption Survey by the U.S. Energy Information Administration (EIA) estimated about 8.06 million primary occupied Florida homes in 2020. Natural gas was the main heating fuel in about 0.42 million of them. Electricity was the main heating fuel in about 5.35 million.

We cannot say how many Tampa Bay homes have one.

Florida Statutes section 553.885 covers buildings and additions built on or after July 1, 2008, that have a feature that emits carbon monoxide as a byproduct of combustion. One listed feature is a fossil-fuel-burning heater or appliance. The sleeping-room alarm rule does not cover hospitals, inpatient hospice facilities or nursing home facilities licensed by the Agency for Health Care Administration; the same subsection sets a separate detector rule for a new hospital, an inpatient hospice facility, a nursing home facility licensed by that agency or a new state correctional institution. Covered buildings need an approved operational carbon monoxide alarm within 10 feet of each room used for sleeping purposes in the new building or addition, or at such other locations as required by the Florida Building Code. The statute says a hard-wired or battery-powered alarm, or a combined carbon monoxide and smoke alarm, may satisfy this. The statute says, "This subsection does not apply to existing buildings that are undergoing alterations or repairs unless the alteration is an addition as defined in subsection (3)." Our guide to carbon monoxide detector placement covers where alarms go.