Why a furnace or air handler trips the circuit breaker, and who should fix it

What a tripped breaker is telling you

OSHA explains what breakers are for. It says circuit protection devices limit or stop the flow of current automatically in the event of a ground fault, overload, or short circuit.

OSHA says fuses and circuit breakers open or break the circuit automatically when too much current flows through them. It says they are designed to protect conductors and equipment. OSHA adds that breakers prevent wires and other components from overheating.

Why your heating system has its own breaker

Daikin Comfort Technologies is an equipment maker. Its installation manual for one line of air handlers says every installation must include an NEC (USA) or CEC (Canada) approved overcurrent protection device.

The manual says the unit's Series and Rating Plate provides the maximum overcurrent device permissible. It also lists the Minimum Circuit Ampacity (MCA), which is the least current the wiring must be able to carry. The manual says fuses or breakers are to be sized larger than the MCA but not over that maximum.

The same manual covers air handlers fitted with an electric heat kit. A heat kit is an optional electric heater for the air handler. Some heat kits come with their own circuit breaker mounted in the air handler.

The manual says that where a license is required to service this equipment, only licensed personnel should service it.

For more on the indoor unit and its parts, see air handler repair and replacement.

The Florida picture: most homes here heat with electricity

In Florida, most homes use electricity, not gas, as their main heating fuel.

The U.S. Energy Information Administration (EIA) runs a national survey of home energy use. For 2020, it counted 8.06 million Florida housing units. Of those, 5.35 million used electricity as the main heating fuel. Only 0.42 million used natural gas.

The EIA table does not say which electric equipment those homes use. The Daikin manual describes one kind of electric heat, a heat kit in the air handler. The HVAC detail in this guide comes from an air handler manual. If you have a gas furnace, check its own manual.

For more, see auxiliary heat. For a wider look at heating trouble here, see heater not working in Florida.

What the manufacturer tells owners to check first

The Daikin manual has a short list titled "Before you call your servicer." It says to check the thermostat to confirm that it is properly set.

The same manual warns against filter neglect. It says never to run the unit without a filter, because dust and lint build up on internal parts, with possible fire. It says to check filters at least once a month.

The manual's own troubleshooting chart lists a blown fuse or circuit breaker among its possible causes. The chart also says "Turn power OFF prior to repair."

If the whole system is dead, our guide to an AC not turning on covers other power checks.

When a breaker keeps tripping

The Daikin manual gives owners a clear limit. If the breaker or fuse opens again within thirty days, it says to contact a qualified servicer to correct the problem.

It also says that if you repeatedly reset the breaker without having the problem corrected, you run the risk of severe equipment damage.

The U.S. Consumer Product Safety Commission (CPSC) lists warning signs of electrical system hazards. They include dimming or flickering lights, sizzle or buzzing sounds, an odor of overheated plastic, and hot switch plates. The list also includes circuit breakers that need resetting frequently. For these signs, the CPSC says to have a licensed electrician check your home's electrical system.

OSHA notes that arcs that result from short circuits can cause injury or start a fire.

Who is licensed to fix it in Florida

Florida Statutes section 489.105 defines a Class A air-conditioning contractor. One part of its scope covers repairing or replacing power wiring, disconnects, breakers, or fuses for dedicated HVAC circuits. The statute words this as work done "with proper use of a circuit breaker lock." The same definition says the scope "does not include any work such as ... electrical power wiring."

Section 489.505 defines an electrical contractor in part as "a person who conducts business in the electrical trade field and who has the experience, knowledge, and skill to install, repair, alter, add to, or design, in compliance with law, electrical wiring, fixtures, appliances, apparatus ..."