McDonnell & Miller

264 products

Friendly National Boiler Supply customer support expert smiling in a clean mechanical room office setting.

Need help finding a replacement part?

Fill out the part request form and someone will get back to you shortly.

PART REQUEST FORM

Safeguard your commercial steam and hydronic boiler systems with industry-standard McDonnell & Miller boiler controls and safety devices. We stock a comprehensive selection of authentic M&M Low Water Cut-Offs (LWCO), liquid flow switches, and pump controllers engineered for critical commercial and industrial applications.

Trusted Boiler Safety & Liquid Level Controls

A dry-firing boiler can lead to catastrophic equipment failure or severe safety hazards. McDonnell & Miller controls act as the first line of defense, reliably monitoring water levels and system flow to shut down burners or activate feed pumps before damage occurs.

Essential M&M Safety Controls

  • Low Water Cut-Offs (LWCO): Float-operated and probe-type cut-offs for commercial steam and hot water boilers to prevent dry-fire conditions.
  • Liquid Flow Switches: High-sensitivity switches for HVAC chillers, hydronic heating loops, and industrial process cooling to verify active fluid flow.
  • Pump Controllers & Water Feeders: Mechanical and electronic boiler water feeders to automatically maintain safe operational water levels.