McDonnell & Miller Liquid Flow Switch, Series FS250

McDonnell & Miller General-Purpose, Liquid Flow Switches. The McDonnell & Miller Series FS250 – FS251 (NEMA1 version), and FS254 (NEMA4 version). These flow switches incorporate key changes to address customer expressed needs of greater reliability and lower flow sensing capabilities in a general purpose flow switch.

If you need a different model other than those listed, please contact us at

SKU: a62c01eaba48 Category: Tag:



McDonnell & Miller Liquid Flow Switch, Series FS250

Features and Benefits
Common switching mechanism for both the FS251 and FS254
Measured flow-rate sensing of 5.8 gpm in 1” pipe (2.2 fps) in horizontal pipe installations, which is 18% lower than measured flow of comparable general purpose flow switches from major competitors. (Refer to submittal MM-627 for flow rates.)
1-inch NPTM brass pipe connection
1”, 2”, 3” and 6” Stainless steel paddles standard
Section IV boiler ratings of 250º F and 160 psig
No lead construction
Housing materials:
– FS251 – stamped sheet steel base with glass reinforced
polycarbonate cover
– FS254 – Cast aluminum base and cover



    • Over 50 years of industry knowledge
    • Fast customer service; response within 15 minutes
    • Best price quality ratio
    • We facilitate the total procurement, purchase and engineering process of our customers