McDonnell & Miller
Boiler Controls. McDonnell & Miller Low Water cut-offs are specially designed to protect steam and hot water boilers from the hazards of a low water condition. In operation they will interrupt the electrical current to the firing device, if the water in the system drops below the boiler manufacturer’s minimum safe water level. Our low water cut-offs also provide an additional circuit for a low water alarm, should you desire to install one, for additional protection.
If you have any questions please give us a call at 1-800-781-7405 or email us your request. Sales@NationalPumpSupply.com
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120601 McDonnell & Miller FS8-W - 1" Flow Switch
McDonnell & Miller
$248.95120601 McDonnell & Miller FS8-W - 1" Flow Switch General purpose flow switch w/NEMA 4X enclosure 120601. Mcdonnell & Miller 120601 Instruction Manual For general purpose applications with environmental exposure, or those requiring a...$248.95 -
114400 McDonnell & Miller FS4-3 1" Flow Switch
McDonnell & Miller
$204.95114400 McDonnell & Miller FS4-3 1" Flow Switch 1" NPT. Click here for more info on McDonnell & Miller Flow Switches Universal design serves the widest variety of applications. For starting or stopping electrically operated equipment such as...$204.95 -
120611 McDonnell & Miller FS251 Flow Switch With NEMA 1 Enclosure
McDonnell & Miller
$198.95McDonnell & Miller FS251 General Purpose Flow Switch With NEMA 1 Enclosure 120611, Replaces FS4-3. Information: McDonnell & Miller FS4 Brochure McDonnell & Miller FS4 Instruction Manual Features Universal design serves the widest...$198.95 -
120610 McDonnell & Miller FS254 Flow Switch With NEMA 4 Enclosure
McDonnell & Miller
$314.95120610 McDonnell & Miller FS254 Flow Switch With NEMA 4 Enclosure, Replaces FS8-W. McDonnell & Miller FS254 Brochure Features: Universal design serves the widest variety of applications For starting or stopping electrically operated...$314.95 -
113200 McDonnell & Miller FS-1 1/2" Liquid Flow Switch
McDonnell & Miller
$315.95113200 McDonnell & Miller FS-1 1/2" Liquid Flow Switch. McDonnell & Miller FS1 Instruction Manual Features: For general purpose applications where high sensitivity is required and moderate or low flow rates are encountered such as air...$315.95 -
123400 McDonnell & Miller AF3 Air Flow Switch
McDonnell & Miller
$228.95123400 McDonnell & Miller Air Flow Switch Model AF3. McDonnell & Miller AF1 Flow Switch Instruction Manual For general purpose low velocity applications where the most economical flow switch is desired. Paddle fits 8" (203mm)...$228.95 -
114639 McDonnell & Miller FS4-3RP-T 1" Flow Switch
McDonnell & Miller
$264.95114639 McDonnell & Miller FS4-3RP-T 1" Flow Switch FS4-3 With Test Button. McDonnell & Miller FS4 Brochure McDonnell & Miller FS4 Instruction Manual Universal design serves the widest variety of applications. For starting or stopping...$264.95 -
181725 McDonnell & Miller Relief Valve 250-3/4-100
McDonnell & Miller
$184.95181725 McDonnell & Miller Relief Valve 250-3/4-100. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21 kg/cm2) between...$184.95 -
181905 McDonnell & Miller Relief Valve 250-3/4-60
McDonnell & Miller
$184.95181905 McDonnell & Miller Relief Valve 250-3/4-60. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21 kg/cm2) between...$184.95 -
181525 McDonnell & Miller Relief Valve 250-3/4-50 - 3/4" NPT
McDonnell & Miller
$184.95181525 McDonnell & Miller Relief Valve 250-3/4-50 - 3/4" NPT. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21...$184.95 -
122800 McDonnell Miller Air Flow Switch Model AF1
McDonnell & Miller
$304.95122800 McDonnell Miller Air Flow Switch Model AF1. McDonnell & Miller AF1 Flow Switch Instruction Manual For general purpose applications with medium and high velocity requirements: Paddle fits 8" (203mm) minimum duct size, or 6" (152mm) if...$304.95 -
144690 McDonnell & Miller RB-24E-L Low Water Cut Off
McDonnell & Miller
$154.95144690 McDonnell & Miller RB-24E-L Low Water Cut Off. This Item Usually Ships The Same Day!$154.95 -
123450 McDonnell & Miller AF3D Air Flow Switch
McDonnell & Miller
$264.95123450 McDonnell & Miller Air Flow Switch Model AF3D. McDonnell & Miller AFE-1 Instruction Manual For general purpose low velocity applications where the most economical flow switch is desired. Paddle fits 8" (203mm) minimum duct...$264.95 -
153601 McDonnell & Miller PSE-801-M-120 Probe Control
McDonnell & Miller
$308.95153601 McDonnell & Miller PSE-801-M-120 Probe Control with manual reset (steam) uses patented technology to monitor changes in water conductivity. When defined parameters are exceeded the new PSE-800 makes a decision to shut the burner off based...$308.95 -
181625 McDonnell & Miller Relief Valve 250-3/4-75
McDonnell & Miller
$184.95181625 McDonnell & Miller Relief Valve 250-3/4-75. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21 kg/cm2)...$184.95 -
144692 McDonnell & Miller RB-24E Low Water Cut Off
McDonnell & Miller
$174.95144692 McDonnell & Miller RB-24E Low Water Cut Off. This Item Usually Ships The Same Day!$174.95 -
114410 McDonnell & Miller FS4-3Z Flow Switch 1 NPT
McDonnell & Miller
$224.95114410 McDonnell & Miller FS4-3Z Flow Switch 1 NPT. This Item Usually Ships The Same Day!$224.95 -
181225 McDonnell & Miller Relief Valve 250-3/4-30
McDonnell & Miller
$184.95181225 McDonnell & Miller Relief Valve 250-3/4-30 Relief Valve 3/4" NPT Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3...$184.95 -
144676 McDonnell & Miller RB-122E Low Water Cut Off
McDonnell & Miller
$174.95144676 - McDonnell & Miller RB-122E Low Water Cut Off. This Item Usually Ships The Same Day!$174.95 -
354081 McDonnell & Miller PA-800 Probe Assembly
McDonnell & Miller
$114.95354081 McDonnell & Miller PA-800 354081 -Probe Assembly for 750, 750-MT-120, PS800, PS801, PS850, PS851. This Item Usually Ships The Same Day!$114.95 -
176234 McDonnell & Miller 751P-MT-120 LWCO - 120V w/standard probe
McDonnell & Miller
$312.95176234 McDonnell & Miller 751P-MT-120 LWCO - 120V w/standard probe. Mcdonnell & Miller Series 751P/752P LWCO Brochure Mcdonnell & Miller Series 751P/752P LWCO Instruction Manual The Series 751P/752P probe type LWCOs...$312.95 -
144694 McDonnell & Miller RB-24E-A Low Water Cut Off
McDonnell & Miller
$224.95144694 McDonnell & Miller RB-24E-A Low Water Cut Off. This Item Usually Ships The Same Day!$224.95 -
176296 McDonnell & Miller 752-MT-24 Low Water Cut Off
McDonnell & Miller
$312.95176296 McDonnell & Miller 752-MT-24 Low Water Cut Off. Information: Product Brochure This Item Usually Ships The Same Day!$312.95 -
115200 McDonnell & Miller FS4-3T2-1 - 1" Flow Switch
McDonnell & Miller
$314.95115200 McDonnell & Miller FS4-3T2-1 - 1" Flow Switch With NPT Body Medium Flow Rate 115200. McDonnell & Miller FS4 Instruction Manual Features: For starting or stopping electrically operated equipment such as signal lights, alarms,...$314.95 -
120605 McDonnell & Miller FS8-WZ Flow Switch 1 NPT
McDonnell & Miller
$314.95120605 McDonnell & Miller FS8-WZ Flow Switch 1 NPT. *Please note image is generic. Information: Mcdonnell & Miller 120601 Instruction Manual Features: For general purpose applications with environmental exposure, or those requiring...$314.95 -
304200 McDonnell & Miller Head Gasket
McDonnell & Miller
$12.95304200 McDonnell & Miller Head Gasket. This Item Usually Ships The Same Day!$12.95 -
181405 McDonnell & Miller Relief Valve 250-3/4-40
McDonnell & Miller
$184.95181405 McDonnell & Miller Relief Valve 250-3/4-40. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21 kg/cm2) between...$184.95 -
114785 McDonnell & Miller FS5-J-1 Flow Switch 1 BSTB
McDonnell & Miller
$274.95114785 McDonnell & Miller FS5-J-1 Flow Switch 1 BSTB. McDonnell & Miller FS5 Instruction Manual Features: In-line configuration eliminates need for a pipe tee Sizes available: 3/4" NPT, 1" NPT Materials of construction: Brass, carbon...$274.95 -
122920 McDonnell Miller AF1-J Air Flow Switch
McDonnell & Miller
$214.95122920 McDonnell Miller AF1-J Air Flow Switch. *Please note image is generic. McDonnell & Miller AF1 Flow Switch Instruction Manual For general purpose applications with medium and high velocity requirements: Paddle fits 8" (203mm) minimum...$214.95 -
120602 McDonnell & Miller FS8-WJ Flow Switch 1 BSTP
McDonnell & Miller
$284.95120602 McDonnell & Miller FS8-WJ Flow Switch 1 BSTP. *Please note image is generic. Information: Mcdonnell & Miller 120601 Instruction Manual Features: For general purpose applications with environmental exposure, or those...$284.95 -
153605 McDonnell & Miller RBT-3000 LWCO & Fuel Economizer
McDonnell & Miller
$264.95153605 McDonnell & Miller RBT-3000 LWCO & Fuel Economizer. Technical Brochure The RBT-3000 is a combination Low-Water Safety Cut-Off and Fuel-Saving controller for residential heating systems. The Low Water Cut-Off is specifically designed...$264.95 -
144693 McDonnell & Miller RB-24E-S Low Water Cut Off
McDonnell & Miller
$184.95144693 McDonnell & Miller RB-24E-S Low Water Cut Off. This Item Usually Ships The Same Day!$184.95 -
181425 McDonnell & Miller Relief Valve 250-3/4-45
McDonnell & Miller
$184.95181425 McDonnell & Miller Relief Valve 250-3/4-45. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21 kg/cm2) between...$184.95 -
181325 McDonnell & Miller Relief Valve 250-3/4-36
McDonnell & Miller
$184.95181325 McDonnell & Miller Relief Valve 250-3/4-36. Features and Benefits: For tanks and hydronic heating systems Protects against over-pressure Minimizes hammering with flash steam Low differential pressure – 3 psi (.21 kg/cm2) between...$184.95