McDonnell & Miller 751P-MT-SP-120 Control

The McDonnell & Miller 751P-MT-SP-120 (Part Number 176295) is a heavy-duty 120Vac manual reset low water cut off engineered for precise level monitoring in commercial and industrial hot water and steam boilers. As a CSD-1 compliant safety control, this unit is designed to interrupt the burner circuit the moment a low-water condition is detected, requiring a manual intervention to resume operation once safe levels are restored. This specific 751P series model features a short probe (\'SP\') and a 20,000-ohm sensitivity, making it ideal for compact installations or applications with specific clearance requirements where a standard probe may be impractical.

Built for the rigors of the mechanical room, the 751P-MT-SP-120 includes a built-in test switch for streamlined diagnostic verification without needing to drain the system. The integrated LED status indicators provide immediate visual feedback: a green LED confirms the unit has 120V power, while a red LED signals an active low water condition. Its electronic sensing technology eliminates moving parts, reducing the potential for mechanical failure due to sediment or scale buildup. This control is frequently utilized as a primary or secondary LWCO on hydronic boilers and satisfies ASME safety codes for secondary protection on steam systems up to 15 psi.

• CSD-1 Compliance: Meets strict safety standards requiring a manual reset after a low-water event, preventing automatic burner restarts.
• Short Probe Design: Engineered for tight manifold or boiler tapping configurations where space is limited.
• Diagnostic Test Switch: Allows technicians to verify internal relay functionality and safety circuit interruption instantly.
• Electronic Reliability: Features 20,000-ohm sensitivity to ensure accurate detection in various water qualities, including glycol mixtures.
• Visual Monitoring: Dedicated green and red LEDs simplify troubleshooting by clearly displaying power and alert status.

Is the 751P-MT-SP-120 compatible with 24V control circuits?
No, this specific model is rated for 120Vac operation. For 24V systems, the 752P series equivalent should be utilized to match system voltage.

Will the control reset itself after a power outage?
If the water level is sufficient, the McDonnell & Miller 751P will resume operation after power is restored. However, if a low-water condition occurred specifically, the manual reset button must be depressed.

Can I use this as the only low-water protection on a steam boiler?
Per most codes, a manual reset LWCO like the 176295 serves as the secondary protection on steam boilers, usually paired with an automatic reset primary control.

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.