Resideo L8148E1299 Aquastat Relay

The Resideo L8148E1299 is a technical-grade high-limit Aquastat relay designed for immersion-type hydronic systems. This 120Vac controller effectively combines system safety with operational switching, managing both the burner and circulator motors. Engineered with a vertical mount configuration, it provides a high-limit operating range of 180°F to 240°F with a 15-degree fixed differential. This ensures consistent thermal cycling and reliable system protection for forced hot water applications. As the direct replacement for the L8148E1299/U, this model includes a built-in 50VA transformer to power low-voltage control circuits and comes standard with heat conductive compound for optimized thermal response.

For service technicians, the L8148E1299 relay simplifies field installations with its SPST switching action and 4-1/2" capillary. It is rated for 0-95% RH humidity, making it suitable for standard mechanical room environments. Whether you are performing a boiler aquastat troubleshooting task or a full system upgrade, this immersion-type controller provides the durable high-limit protection and circulator control needed to maintain peak boiler performance and prevent short-cycling in residential and light commercial hydronic systems.

• Enhanced Power Capacity: Features an integrated 50VA transformer, offering more overhead than the 40VA found in older 1265 models.
• Precise Safety Control: The fixed 15°F differential prevents rapid cycling while maintaining the high-limit safety threshold.
• Universal Replacement: Serves as the modern standard for the L8148E1299/U, ensuring a direct footprint match for existing service calls.
• Complete Setup: Includes heat conductive compound to ensure the sensing bulb maintains accurate thermal contact with the immersion well.
• Durable Switching: Reliable SPST relay contacts designed for standard 120V circulator loads and low-voltage burner circuits.

• How do I wire the L8148E1299 for a zone valve system? The L8148E terminals are designed to allow integration with up to two V8043 zone valves; additional valves require an external transformer to prevent overloading the 50VA internal unit.
• Can I use this relay with PEX piping? Because the minimum high-limit setting is 180°F, verify your PEX tubing's maximum temperature rating. Many technicians recommend models with lower ranges for PEX to avoid thermal degradation.
• What causes the transformer to burn out on these units? Never apply a jumper across terminals B1, B2, or B3 during testing, as this creates a direct short that will damage the internal 50VA transformer.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.