Resideo L4008E1156 Aquastat Controller 130-270°F 66

The Resideo L4008E1156 is a high-limit manual reset aquastat controller for boiler and hydronic heating systems, using a remote bulb sensing element with a 66-inch capillary for immersion well mounting. It operates over a 130°F to 270°F range with an SPST-NC switch that breaks on temperature rise above setpoint, requiring manual reset once tripped. Rated for 240V line voltage service with a 5-30A contact rating, it mounts horizontally or vertically and includes heat-conductive compound for proper thermal transfer at the immersion well. This is a hardwired, non-programmable control intended for professional installation. As an OEM replacement, this unit is compatible with L4008E1040, L4008E1248, and L4008E1321 controllers, making it suitable for servicing existing residential or commercial hydronic systems using those models. It is commonly applied where boiler overheating, high-limit lockout, or burner cycling issues indicate a failing high-limit control. Installation requires an immersion well or thermowell, and use of the supplied heat-conductive compound is recommended to ensure accurate bulb temperature sensing.