Resideo L4008E1040 High-Limit Aquastat 130-270°F Manual Reset

The Resideo L4008E1040 is a high-limit aquastat with remote bulb sensing, designed for boiler and tank temperature control in hydronic heating systems. It features a 130–270°F adjustable range, SPST switch action, and a manual reset high-limit function that shuts the system down on overtemperature conditions requiring manual intervention to restore operation. The 66-inch capillary tube allows the remote bulb to be positioned in the boiler well or tank for accurate temperature sensing. Rated to 270°F, it is intended for residential and commercial hydronic and boiler applications. This control is an OEM replacement for Resideo systems and is compatible with Resideo equipment only. Installation is rated intermediate, requiring basic hand tools, and a thermowell is recommended for proper bulb immersion, along with insulation tape and a mounting bracket as needed. It addresses common failure symptoms such as repeated high-limit trips, unexpected shutdowns, boiler overheating, or failure to reach setpoint temperature. No display or programmable features are included; it operates as a non-programmable, manual reset control.