Electric wall heaters: how they work and when to service them

How a fan-forced wall heater works

The fan-forced wall heaters in the manuals we read are mounted in a box the makers call the back box. One manual says the back box may be recessed into the wall or surface mounted. One manufacturer's instructions place the back box between two wall studs.

The front cover is called the grille.

One manual says that turning the power on and rotating the thermostat knob fully clockwise should energize the heating elements and the fan. That causes air to flow out of the openings in the bottom of the grille. The manuals call these fan-forced wall heaters.

On the heater in that manual, the thermostat is a knob on the unit itself. The manual says to wait until the air coming out has become warm, then turn the knob to a comfortable setting.

It also says the heater works best left on all through the heating season. A properly set thermostat will then hold the temperature, the manual explains.

The FZL Series manual says all wiring must follow national and local electrical codes. It also says the heater must be grounded as a precaution against possible electric shock.

Built-in safety controls

The wall heater manual we read describes two layers of protection against overheating. The first is what the maker calls a manual reset thermal limit safety control.

The manual says this control will automatically turn the heater off to prevent a fire if the heater overheats. It sits inside the heater, between the element and the fan blade.

The manual explains how that control is reset once the heater has cooled. It also gives a firm warning, in capital letters. It says not to continue to attempt to use the heater if the safety control repeatedly operates after being reset. Doing so could permanently damage the heater or create a fire or safety hazard, it says.

The second layer is a backup part called a thermal fuse. The manual says the thermal fuse will permanently shut the heater off if the main over-temperature control does not work as intended.

If that thermal fuse activates, the manual says the heater will not reset and must be repaired by a qualified repair person. It also says, in capital letters, not to tamper with or bypass any safety limits inside the heater.

For other heating problems, see our guide on a heater that is not working.

Everyday safety: space, airflow and location

Heating is a real fire risk in homes. The U.S. Fire Administration (USFA), part of the Federal Emergency Management Agency (FEMA), says heating fires remained the second leading cause of home fires in 2021.

The USFA says to keep anything that can burn at least 3 feet from all heat sources, including space heaters. One wall heater manual gives the same distance. It says to keep furniture, pillows, bedding, papers, clothes and curtains at least 3 feet from the front of the heater.

A second manual from the same maker says not to install the heater behind doors, furniture, towels, or boxes. Both manuals say not to block the air intake or exhaust in any manner, to prevent a possible fire.

Keep objects out of the openings, too. The K Series manual warns that foreign objects in a ventilation opening may cause an electric shock, fire, or damage to the heater.

The manual says a heater has hot and arcing or sparking parts inside. For that reason, it says not to use the heater where gasoline, paint, or flammable liquids are used or stored.

The same manual says not to use the heater in damp or wet locations. It also says not to use the heater for dry out. Paint, plaster, sawdust and drywall sanding dust will permanently damage the heater, the manual says.

It adds that the heater should not be run without the grille installed. Extreme caution is necessary when any heater is used by or near children, the manual says. The same goes whenever a heater is left running and unattended.

When to have a wall heater serviced

One maker's K Series wall heater manual says it is important to keep the heater clean. It calls for the power to be off at the main service panel and the element to be cool first.

The manual draws a clear line after that. It says all servicing beyond simple cleaning that requires taking the heater apart should be done by qualified service personnel.

For that deeper cleaning, the manual sets a schedule. It says that at least annually, the heater should be cleaned and serviced by a qualified service person to assure safe and efficient operation.

That visit should include removing the grille and, as needed, taking the heater out of its back box to clean residue from the unit. Afterward, the manual says the heater should be fully reassembled and checked for proper operation.

The USFA gives similar advice for heating equipment in general. It says to have heating equipment cleaned and inspected each year by a professional.

Some signs mean you should stop using the heater right away. The manual says not to operate any heater after it malfunctions. It says to disconnect power at the service panel and have the heater inspected by a reputable electrician before using it again.

A heater that keeps tripping its safety control after a reset is another reason to stop, as the built-in safety controls section explains. For what a seasonal heating visit covers on other kinds of systems, see our heating tune-up guide.

Recalls worth checking

Wall heaters have been recalled before, so it is worth knowing whether yours is one of them.

On September 12, 2024, Glen Dimplex Americas announced a recall of Cadet-branded Apex72 high wall electric heaters. The notice says the fan can fail to turn on, causing the unit to overheat and ignite internally, posing a fire hazard. The notice says these heaters were sold through electrical distributors nationwide.

The notice says these fan-forced heaters have a white dust cover and are installed at least six feet off the ground. It says the brand name, model number and manufacturing date appear on a rating label. That label is visible through the bottom of the air outlet grill. The notice tells owners to stop using recalled heaters immediately and contact the company about a free replacement.

Older recalls involved in-wall heaters too. A 1997 notice said limit switches within certain heaters could emit sparks, presenting a fire hazard. A 2002 notice said some replacement heaters could run continuously, regardless of thermostat settings or room temperature. It said this could cause the heater to overheat and catch nearby combustibles on fire.

Those older recalls centered on western states. The 1997 notice listed homes in Oregon, Washington, California, Idaho, Montana and Wyoming. The 2002 notice said the heaters were distributed mainly in California, Idaho, Montana, Oregon and Washington.

If a heater is part of a recall, the 2002 notice says to stop using it by turning it off at the electrical panel. That means the circuit breaker or fuse box. Leave anything beyond that to the manufacturer or a qualified service person.

Electric wall heaters in Florida

We found no source that counts how many Florida homes use electric wall heaters.

The U.S. Energy Information Administration (EIA) says Florida residents use space heating equipment much less than those in other states.

The EIA also says that despite the warm climate, most Florida households still use some heating equipment during the winter. Most of those households use electric furnaces or heat pumps, it says. A heat pump is a system that moves heat from one place to another, the University of Maryland Extension explains. In summer, it works like an air conditioner. These EIA statements come from its 2009 survey, so treat them as older data.

One manufacturer's K Series manual calls for cleaning and service by a qualified person at least once a year. It also says to keep things that can burn at least 3 feet from the front of the heater.

Our guide to central heating in Florida explains how whole-home heat works here, including heat pumps. Our guide to gas furnace vs electric strip heat explains what strip heat is and how it compares.