Furnace High Limit Switch Open

So to put it simply the limit switch tells the furnace fan when to turn on and when to shut off and it tells the furnace to shut down if it is overheating.

Furnace high limit switch open.

Once the plenum reaches a specific temperature the limit switch sends a signal to the air handler to begin running and delivering warm air to your home. Some furnaces provide extra safety features by wiring two or three high limit switches in a series that check the temperature in the furnace at different points. A fault will appear when it s open or if it doesn t reset within a specified period of time during which the blower is expected to circulate enough air to cool the heat exchanger to. Attempting to reset the furnace limit switch while the power is connected may result in electrical shock.

Rollout switches and high temperature fuses are different from limit switches in that when they open they will not close again unless reset as in the case of the rollout switch or replaced as in the case of the high temperature fuse. A limit switch is a device that s located under your furnace s supply plenum. Depending on your furnace model the switch will be surrounded by a silver or white cover. Founded in 1982 goodman manufacturing is an american company that produces heating and air conditioning equipment for residential and commercial customers.

Locate the white limit switch. Some of these parts are shown on the left. It reads the temperature of the plenum and waits until it gets appropriately warm. I have the the amana air command 80 high eff gas furnace and the unit works for 3 4 hrs cycling on and off normally then will shut down and won t start again until the unit is powered off reset.

The high temperature limit switch is an important device used in forced air furnaces powered by gas or heating oil. It s also known as a fan limit switch or simply a limit switch. Goodman residential furnaces contain multiple limit switches to ensure safe operation. I have a 1994 lennox 80 mgf series furnace and there is a 4 ligh flashing which say high limit or rollout switch open.

The switch makes sure the furnace is operating safely and at its desired settings. The limit switch will open periodically to prevent over heating. It will be located at the top of the panel.