Field Controls 1170004 FTS-4 Thermal Safety Switch 120/240V 140°F Manual Reset Spill Switch

The Field Controls FTS-4 (Part No. 1170004) is a 120/240V thermal safety switch — also known as a spill switch — designed to protect gas-fired and oil-fired heating systems from dangerous flue gas spillage. Rated to trip at 140°F, this single-pole single-throw (SPST) switch is an essential safety component for residential furnaces and boilers.

How It Works:

The FTS-4 is wired in series with the burner circuit. When it detects the elevated heat caused by flue gas spillage — resulting from a blocked flue, continuous down-drafting, or inadequate draft conditions — it automatically de-energizes the system's burner or burner control. Once tripped, the burner will not restart until the switch has been manually reset, ensuring the root cause is addressed before resuming operation.

Key Features:

• Trip Temperature: 140°F (opens on temperature rise)
• Voltage Rating: 120/240V AC
• Current Rating: 12A at 120V / 6A at 240V
• Switch Type: Single Pole Single Throw (SPST), Normally Closed
• Reset Type: Manual reset — burner cannot restart until manually reset
• Compatible Applications: Gas-fired and oil-fired furnaces and boilers
• Mounting: Mounts on draft hood or double-acting barometric draft control (mounting brackets included)
• Also Known As: Spill switch, flue gas spillage switch, thermal safety cutout

The Field Controls FTS-4 1170004 provides reliable, passive protection for heating systems by detecting dangerous flue gas conditions before they become hazardous. Its manual reset design ensures a technician or homeowner must consciously acknowledge and clear the fault condition before restoring heat — a critical safeguard for home safety.