Furnace Diagram


Our AC coverage is for the main source of heat to the home, so it covers residential ducted units up to 5-ton capacity and below 21 SEER. Forced air, Heat pumps, Ducted Built-in Heater Boiler (Gas or Steam) are all eligible for coverage. Our Platinum and Gold plans cover up to two units, so larger homes with multiple systems will have both units covered.


The pilot light is a gas ignition source for the furnace, and the thermocouple is a safety feature that closes the gas line if the pilot light goes out. Furnaces are either ignited with a pilot light or with an electric igniter.
The power switch controls power to the furnace.
The wire terminal provides connections for wires from other parts of the system, such as the thermostat.
The blower motor powers the fan which moves air throughout the ducts in the home.
The main control board is an electronic circuit board that controls all of the major electronic functions of the HVAC system. Without it, the different mechanical components would not function together to make the system fulfill its purpose.
Some heating units have a separate control board for the thermostat that is separate from the thermostat. We cover those, too.

This is a solenoid that opens and closes the gas supply valve.

The transformer raises or lowers the voltage of electricity to meet the demand of different parts of the system such as the thermostat or blower motor.
This is an electrical junction box specific to HVAC systems.
The fan control is a circuit board that controls the function of either of the fan motors.
Bearings facilitate the motion of moving parts on the compressor and motors.
On boilers, this is a valve to release water from the system.
Fuses protect the system against spikes in electrical current.
The relays manage the flow of high-voltage electricity in the system, controlling when the cooling system turns on and off.
The limit control, also called the limit switch, ensures that the furnace is at the appropriate temperature before the air handler begins moving heated air through the ducts. It also acts as a safety shut-off in case the temperature inside the unit gets too high.
The flame spreader does just you would expect: it spreads out the burner’s flame to provide more even heat distribution to the head exchanger.
A straight metal tube that runs from the main gas valve to the burners. It distributes gas evenly across the burners.
The igniter provides an electric ignition source to the furnace. Furnaces are either ignited with a pilot light or with an electric igniter.
Any sensor that is part of the heating assembly. An example would be the flame sensor, which is part of a fail-safe system that shuts down the gas supply when the pilot light goes out.
A power pack converts power for low-voltage parts of the system.
Pulleys are part of the blower motor assembly and work with a belt to keep the motor operating smoothly.
On a boiler, this shuts the system down when the water level drops below safe operating levels. When the water returns to safe levels, the boiler will resume operation.
A motor coupling connection
For electronic furnaces, this is basically for emergency heat in case the heat pump fails.

Not Covered

Systems that are oversized or undersized for your home do not operate as intended and experience increased wear and tear, leading to premature failure. In addition, oversized units often get stuck short-cycling, meaning that they do not run long enough cycles to maintain the right humidity in the home.
This refers to air conditioning systems with a mismatched condensing unit and evaporator coil. Any licensed HVAC technician will recommend against installing or running a mismatched system. These systems have less efficiency and longevity.
Geothermal heating consists of pipes that run several feet underground, where the earth maintains a relatively constant temperature throughout the year. Most HVAC technicians do not perform repairs on geothermal systems, and the repairs involved are substantially different from regular HVAC repairs.
These connect to a nearby body of water and are exposed to all sorts of weathering and temperature extremes. They are uncommon and often require heavy equipment to repair.
Radiant heating relies on a series of wires or pipes that run through the walls and floors and provide heat via infrared radiation. This system is separate from standard heating systems, consists of few mechanical components, and are generally not the main source of heat to the home.
Solar heating systems require solar panels to function, which most HVAC technicians are not qualified to repair.
Portable units, also known as space heaters, are often cheaper than a service call and do not require installation.
Heat lamps are not intended to heat a home, but to keep food warm before serving or occasionally in a terrarium for a lizard or other cold-blooded animal.
A zone system refers to the use of dampers in the ductwork to control how air is routed through the home. While they are convenient, a zone system is not part of the heating system itself and often requires a separate technician to make repairs.
This refers to air conditioning systems with a mismatched condensing unit and evaporator coil. Any licensed HVAC technician will recommend against installing or running a mismatched system. These systems have less efficiency and longevity.
Whole-house humidifiers are added on to heating systems. They are a separate appliance and can actually reduce the operational life of the heating system.
Strainers are an add-on for the condensate drain. They are installed when the drain has frequent problems with clogs, which is something maintenance can prevent.
these are installed on the plumbing supply line to a boiler, and it prevents water in the boiler system from flowing back into the houses plumbing supply lines.
These tanks are placed outside and provide a fuel source such as propane or natural gas for the home. These are present when the gas supply is not directly piped into the home by a utility company. It is a separate system from the HVAC system.
Leak searches are exploratory work that is separate from the repair process. Also, if you believe you are experiencing a gas leak, call your local gas utility or the fire department immediately.
Maintenance is the homeowner’s responsibility. No coverage can replace preventative measures, and having a warranty does not mean that homeowners do not have to care for their appliances and systems. Read more about the benefits of HVAC maintenance here.
Valves are mostly used for servicing and diagnosing unit and should be replaced if they fail during maintenance. They don’t fail mechanically and are cheap to replace.
Just like drain-line stoppages and noise, Water leaks can be easily prevented by routine maintenance. Changing filters regularly and having annual maintenance can completely eliminate these issues.
Drain lines coming from an HVAC system should only contain water, so if these lines are clogged by algae or dirt, it’s a sign of improper installation or lack of maintenance. Unclogging these stoppages is generally cheaper than the cost of a service fee, and it’s easy to do yourself.
While a noisy air conditioner is not ideal, it’s an issue that is easily addressed by routine maintenance. During maintenance, technicians will lubricate and clean parts, minimizing or eliminating unnecessary noises.
Filters are made to be cleaned or replaced regularly and contain no moving or mechanical parts.
Heat exchangers are a closed system and are built to last. Most come with a 20-30 year guarantee, while others come with a lifetime guarantee. They only fail when they crack from water coming down the flue, which is something HVAC technicians monitor during routine maintenance.
These are part of the closed system and are usually changed when changing compressor coils or modifying the system.
Flue piping carries exhaust gases to the exterior of your home. It contains no mechanical parts and fail only if improperly installed or exposed to the elements.
Catches condensation coming off the evaporator coils. This is a pan that contains no mechanical parts.
These pans catch overflows under the coils. They contain no mechanical parts, and if maintenance is performed, the pans will drain properly.
These are the grills that are on the walls, floors, and ceilings of the home. They require nothing more than a screwdriver to replace and are much less than the cost of a service fee. Most do not contain moving mechanical parts.
These components are subject to extreme temperature changes and weather, and so may fail prematurely.

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