Heil Furnace Limit Switch Boiler Safety Controls & Aquastats

The Heil furnace limit switch (also called a furnace high limit switch, limit control or thermal safety switch) is a replacement safety control for Heil heating equipment. It monitors temperature inside the furnace or boiler. If the temperature rises above its safe operating point, it interrupts the heating cycle to help protect the system from overheating.

Key Features:

• Temperature-sensing safety control that helps prevent overheating of the heat exchanger and surrounding components
• Works as a boiler safety control or aquastat-style limit device in the heating system
• Calibrated to open at a specific temperature, which varies by model
• Direct replacement for the matching Heil OEM part number, so no modification is needed
• Helps restore reliable burner shutoff and normal heating cycles when the original limit has failed or become unreliable

Common signs of a failing limit switch include a furnace that short-cycles, shuts down unexpectedly, or won't start a heating cycle. Replacing it with the correct Heil part helps keep the safety circuit working as designed. Choose the variant whose part number matches your original control. Turn off power to the furnace before servicing, and have the work done by a qualified technician.