What causes high limit switch open?
If the supply air is too hot, the interior of the furnace overheats, which can cause damage to components. The limit switch trips when temperatures are too hot, effectively shutting down the system and locking furnace operation until the unit cools.
Are high limit switches normally open?
The fan limit switch is normally open and closes when the temperature reaches its preset value, whereas the high limit switch is normally closed and opens when the temperature reaches its threshold value.
What does an open high temperature switch code mean?
Limit switch codes If the furnace failure code indicates an “open limit” or “open high temperature switch” or “open rollout switch”, it is probable that the furnace has overheated. Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace.
Can a high temp limit switch be reset?
The high temp limit switches usually have a manual reset button that needs to be pressed to reset. I would try a reset it may have been a fluke that it tripped, if the reset dosent trip again it is probably fine.
What to do if your furnace has an open high temperature switch?
If the furnace failure code indicates an “open limit” or “open high temperature switch” or “open rollout switch”, it is probable that the furnace has overheated. Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace.
When does a furnace have a high temperature limit?
High temperature limit problems on gas furnaces When troubleshooting, understand you are working with potentially lethal voltages and a highly flammable gas. If the furnace failure code indicates an “open limit” or “open high temperature switch” or “open rollout switch”, it is probable that the furnace has overheated.
Why does the limit switch stuck open?
If the furnace overheats, then a limit switch will open. That will cause the burners or heat source to shut off and the fan to run until the limit switch closes again. In some cases, the limit switch will stick open, and this will cause the fan to run continuously.
How do you reset the limit switch on a furnace?
Press and hold the red “Reset” button in the center of the rollout limit switch component. Hold the button for one to two seconds before releasing it.
How does the limit switch work in a furnace?
The limit switch is a safety control switch located on the furnace just below the plenum. If the plenum gets too hot, the limit switch shuts off the burner. It also shuts off the blower when the temperature drops to a certain level after the burner has shut off.
What is a high-temperature limit switch on a furnace?
A high-temperature limit switch, also called a fan limit switch or simply a limit switch, is an important device used in forced-air furnaces powered by gas or heating oil. Simply put, it senses the temperature of the furnace and tells the blower fan to turn on and off at the appropriate times.
