Xylem-McDonnell & Miller 157S-RLS-MD Pump & LWCO Control Max Differential 177251

The Xylem-McDonnell & Miller 157S-RLS-MD (Part No. 177251) is a combination pump controller and low water cut-off (LWCO) control engineered for reliable, safe operation of steam boiler systems. Featuring a Remote Level Sensor (RLS) design and Maximum Differential (MD) configuration, this control provides both automatic pump management and critical boiler protection in a single, robust unit.

Product Overview

The 157S-RLS-MD is part of McDonnell & Miller’s trusted 157S series — a go-to solution for hydronic and steam boiler professionals who demand dependable low water cut-off protection. The remote level sensor design allows flexible installation, while the maximum differential setting maximizes the operating range between pump-on and pump-off water levels, reducing short-cycling and extending equipment life.

Key Features

• Combination pump controller and low water cut-off in one unit
• Remote Level Sensor (RLS) design for flexible installation options
• Maximum Differential (MD) configuration minimizes pump short-cycling
• Automatic pump control based on boiler water level
• Low water cut-off shuts down burner to prevent boiler damage from low water conditions
• Engineered for steam boiler applications
• Part of the reliable McDonnell & Miller 157S series
• Part Number: 177251

Application

Designed for use on steam boilers where both pump control and low water protection are required. The 157S-RLS-MD is ideal for commercial and light industrial steam heating systems, providing dual-function control that simplifies installation and reduces the number of components needed on the boiler.

Why Choose McDonnell & Miller

McDonnell & Miller, an Xylem brand, has been a trusted name in boiler controls and low water cut-offs for decades. Their products are known for rugged construction, dependable performance, and compliance with industry safety standards — making them a preferred choice among HVAC and plumbing professionals.