Weil McLain 510-312-209 Temperature Control

The Weil McLain 510-312-209 is a field-proven High Limit Temperature Control engineered for critical hydronic safety in residential and commercial boiler systems. Designed specifically for the Weil McLain EG, EGH, LGB, MGB, and SGO boiler series, this SPST aquastat provides reliable over-temperature protection. It operates on an automatic recycle logic, ensuring that the system restarts without manual intervention once water temperatures return to safe operating levels. The unit features a precise 140-240°F temperature range with a 10°F fixed subtractive differential, making it a staple for technicians maintaining tankless heater kits and domestic hot water loops.

This boiler high limit switch Includes a 3/4" NPT control well for secure immersion installation, facilitating accurate thermal sensing directly within the water column. As a veteran-grade replacement part, the 510-312-209 is manufactured to strict tolerances to prevent nuisance tripping while maintaining a strict safety ceiling. When used in LGB-21 through LGB-23 configurations, this device typically serves the dedicated high-limit safety function alongside separate operating controls to ensure redundant system protection and NEC compliance.

• Precise Thermal Regulation: Features a fixed 10°F subtractive differential for stable high limit protection across the 140-240°F range.
• Application Versatility: Direct OEM replacement for Weil McLain 510-312-209 in EG boilers, LGB series, and steam-to-hot-water conversions.
• Hardened Construction: Built for high-cycle automatic recycle applications, reducing service calls in demanding hydronic environments.
• Simplified Installation: Standard 3/4 inch NPT well ensures compatibility with existing boiler tappings and thermal paste applications.

What boiler models are compatible with the Weil McLain 510-312-209?
This control is optimized for Weil McLain EG, EGH, LGB, MGB, and SGO series boilers. It is commonly utilized in both steam and water trim sets where a high-limit safety boundary is required.

Does this unit require a manual reset?
No, this is an automatic recycle control. It will automatically close the SPST circuit once the water temperature drops by the 10°F differential below the setpoint.

Is the 3/4" NPT well included with the control?
Yes, the 510-312-209 is supplied with a 3/4 inch NPT brass well for immediate immersion mounting into the boiler section or supply manifold.

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.