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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153900 McDonnell & Miller Low Water Cut Off 69
McDonnell & Miller
$462.95153900 McDonnell & Miller Mechanical Low Water Cut Off 69. Float Type Low Water Cut Off For Millivolt Service. Information: McDonnell & Miller LWCO Model 69 General Catalog McDonnell & Miller LWCO Model 69 Installation...$462.95 -
114780 McDonnell & Miller FS5-1 - 1" Flow Switch
McDonnell & Miller
$339.95114780 McDonnell & Miller FS5-1 - 1" Flow Switch 114780. 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,...$339.95 -
123000 McDonnell & Miller Air Flow Switch AF1-S
McDonnell & Miller
$444.95123000 McDonnell & Miller Air Flow Switch AF1-S. *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)...$444.95 -
169550 McDonnell & Miller WFE-24V Universal Water Feeder Uni-Match
McDonnell & Miller
$424.95169550 McDonnell & Miller Universal Water Feeder Uni-Match WFE-24V. McDonnell & Miller WFE-24V Instruction Manual McDonnell & Miller Universal Water Feeders are ideal for use in residential or small commercial applications. Versatile...$424.95 -
114760 McDonnell & Miller FS5-3/4 - 3/4" Flow Switch
McDonnell & Miller
$354.95114760 McDonnell & Miller FS5-3/4 - 3/4" Flow Switch 114760. Information: McDonnell & Miller FS5 Instruction Manual Features: For general purpose applications requiring low flow rate sensitivity In-line configuration eliminates need...$354.95 -
119700 McDonnell & Miller FS7-4 - 1-1/4" Flow Switch
McDonnell & Miller
$574.95119700 McDonnell & Miller FS7-4 - 1-1/4" Flow Switch Paddle Style. Information: McDonnell & Miller FS7 Overview McDonnell & Miller FS7 Instruction Manual Features: Universal design serves the widest variety of large pipe...$574.95 -
114641 McDonnell & Miller FS4-3S 1" Flow Switch
McDonnell & Miller
$514.95McDonnell & Miller FS4-3S 1" Flow Switch w/Stainless Steel Body Monel Bellows 114641. McDonnell & Miller FS4 Brochure McDonnell & Miller FS4 Instruction Manual Universal design serves the widest variety of applications. For starting or...$514.95 -
115400 McDonnell & Miller FS6-3/4 - 3/4" Flow Switch
McDonnell & Miller
$569.95115400 McDonnell & Miller FS6-3/4 - 3/4" Flow Switch-High Sensitivity. McDonnell & Miller FS6 Instruction Manual This McDonnell & Miller flow switch is for heavy duty applications where high sensitivity is required, such as water...$569.95 -
114900 McDonnell & Miller FS4-3T2-3/4 - 3/4" Flow Switch
McDonnell & Miller
$324.95114900 McDonnell & Miller FS4-3T2-3/4 - 3/4" Flow Switch With NPT Body Medium Flow Rate 114900. McDonnell & Miller FS4 Instruction Manual Features: For starting or stopping electrically operated equipment such as signal lights, alarms,...$324.95 -
149500 McDonnell & Miller LWCO 67-LQHU
McDonnell & Miller
$498.95149500 McDonnell & Miller Mechanical Low Water Cut Off 67-LQHU. Float Type Low Water Cut Off For Millivolt Service. Mcdonnell & Miller LWCO Series 67 Instruction Manual Mcdonnell & Miller LWCO Series 67 Submittal...$498.95 -
115300 McDonnell & Miller FS4-3T3-1 - 1" Flow Switch
McDonnell & Miller
$351.95115300 McDonnell & Miller FS4-3T3-1 - 1" Flow Switch With NPT Body Low Flow Rate 115300. McDonnell & Miller FS4 Instruction Manual Features: For starting or stopping electrically operated equipment such as signal lights, alarms, motors,...$351.95 -
140100 McDonnell & Miller Mechanical Low Water Cut Off 61
McDonnell & Miller
$574.95140100 McDonnell & Miller Mechanical Low Water Cut Off 61. Mechanical For Steam Boilers. Mcdonnell & Miller LWCO Series 61 Instruction Manual Features: For residential and commercial low pressure steam boiler applications For boilers...$574.95 -
115000 McDonnell & Miller FS4-3T3-3/4 - 3/4" Flow Switch
McDonnell & Miller
$324.95McDonnell & Miller FS4-3T3-3/4 - 3/4" Flow Switch With NPT Body Low Flow Rate 115000. McDonnell & Miller FS4 Instruction Manual Features: For starting or stopping electrically operated equipment such as signal lights, alarms, motors,...$324.95 -
149400 McDonnell & Miller 67 Mechanical Low Water Cut Off
McDonnell & Miller
$586.95149400 McDonnell & Miller 67 Mechanical Low Water Cut Off. Mcdonnell & Miller LWCO Series 67 Instruction Manual Mcdonnell & Miller LWCO Series 67 Submittal Sheet Features: For boilers of any steaming capacity Residential and...$586.95 -
115600 McDonnell & Miller FS6-1 - 1" Flow Switch
McDonnell & Miller
$507.95115600 McDonnell & Miller FS6-1 - 1" Flow Switch-High Sensitivity. This McDonnell & Miller flow switch is for heavy duty applications where high sensitivity is required, such as water treatment systems, cooling systems for electronic circuits,...$507.95 -
153928 McDonnell & Miller PSE-802-U-24 Low Water Cut Off
McDonnell & Miller
$364.95153928 McDonnell & Miller PSE-802-U-24 Low Water Cut Off. The Series PSE-800 probe type LWCO uses patented technology to monitor changes in water conductivity. When defined parameters are exceeded the new PSE-800 makes a decision to shut the...$364.95 -
123200 McDonnell & Miller AF2 Air Flow Switch Model AF2
McDonnell & Miller
$348.95123200 McDonnell & Miller Air Flow Switch Model AF2. McDonnell & Miller AF1 Flow Switch Instruction Manual For low velocity applications: Paddle fits 8" (203mm) minimum duct size Two electrical knock-outs allow connection from either...$348.95 -
115652 McDonnell & Miller FS6-W-1 - 1" Flow Switch
McDonnell & Miller
$584.95115652 McDonnell & Miller FS6-W-1 - 1" Flow Switch With NEMA 4X Enclosure. McDonnell & Miller FS6 Instruction Manual This McDonnell & Miller flow switch is for heavy duty applications where high sensitivity is required, such as water...$584.95 -
120060 McDonnell & Miller FS7-4J Flow Switch 1-1 4 BSTP
McDonnell & Miller
$574.95120060 McDonnell & Miller FS7-4J Flow Switch 1-1 4 BSTP. *Please note image is generic. McDonnell & Miller FS7 Overview McDonnell & Miller FS7 Instruction Manual Features: Universal design serves the widest variety of large...$574.95 -
153916 McDonnell & Miller PS-802-U-24 Low Water Cut-Off
McDonnell & Miller
$354.95153916 McDonnell & Miller PS-802-U-24 Low Water Cut-Off. This model has been replaced and the new model is 153928 PSE-802-U-24. This Item Usually Ships The Same Day!$354.95 -
169400 McDonnell & Miller Water Feeder 101A-120v
McDonnell & Miller
$504.95169400 McDonnell & Miller Water Feeder 101A-120v McDonnell & Miller 101-A Electric Water Feeder Instruction Manual Electric Water Feeder Features: For low pressure steam boilers with cold water feed Eliminates necessity to manually add...$504.95 -
153929-LWCO McDonnell & Miller PSE-802-RX2-24 Low Water Cut Off
McDonnell & Miller
$328.95153929-LWCO McDonnell & Miller PSE-802-RX2-24 Low Water Cut Off. The Series PSE-800 probe type LWCO uses patented technology to monitor changes in water conductivity. When defined parameters are exceeded the new PSE-800 makes a decision to shut...$328.95 -
114550 McDonnell & Miller FS4-3D 1" Flow Switch
McDonnell & Miller
$358.95McDonnell & Miller FS4-3D 1" Flow Switch 4-3 W/2 SPDT Switches 114550. McDonnell & Miller FS4 Brochure McDonnell & Miller FS4 Instruction Manual Universal design serves the widest variety of applications. For starting or stopping...$358.95 -
113550 McDonnell & Miller FS1-J Flow Switch
McDonnell & Miller
$332.95113550 McDonnell & Miller FS1-J Flow Switch. *Please note image is generic. McDonnell & Miller FS1 Instruction Manual For general purpose applications where high sensitivity is required and moderate or low flow rates are encountered such as...$332.95 -
153602 McDonnell & Miller PSE-802-M-24 Low Water Cut Off
McDonnell & Miller
$378.95The series 153602 - McDonnell & Miller PSE-802-M-24 Low Water Cut Off. The Series PSE-800-M Manual Reset LWCO is a new addition to the McDonnell & Miller probe type low water cut-off group of products. These controls are used as the...$378.95 -
176295 McDonnell & Miller 751P-MT-SP-120 LWCO
McDonnell & Miller
$328.95176295 McDonnell & Miller 751P-MT-SP-120 LWCO. The Series 751P/752P probe type LWCOs provide protection against low water conditions for commercial and industrial applications. These controls are fully CSD-1 compliant and are primarily used as...$328.95 -
114800 McDonnell & Miller FS4-3T1-3/4 - 3/4" Flow Switch
McDonnell & Miller
$318.95114800 McDonnell & Miller FS4-3T1-3/4 - 3/4" Flow Switch. McDonnell & Miller FS4 Instruction Manual Features: For starting or stopping electrically operated equipment such as signal lights, alarms, motors, automatic burners, metering...$318.95 -
176214 McDonnell & Miller 751P-MT-U-120 LWCO
McDonnell & Miller
$348.95176214 McDonnell & Miller 751P-MT-U-120 LWCO. Mcdonnell & Miller Series 751P/752P LWCO Brochure Mcdonnell & Miller Series 751P/752P LWCO Instruction Manual The Series 751P/752P probe type LWCOs provide protection...$348.95 -
153927 McDonnell & Miller PSE-802-RX2-24 LWCO
McDonnell & Miller
$408.95The series 153927 McDonnell & Miller PSE-802-RX2-24 Low Water Cut Off. This Item Usually Ships The Same Day!$408.95 -
313600 McDonnell & Miller 37A-130 Replacement Float for 847 and 851
McDonnell & Miller
$412.95313600 McDonnell & Miller 37A-130 Replacement Float for 847 and 851. This Item Usually Ships The Same Day!$412.95 -
119900 McDonnell & Miller FS7-4L - 1-1/4" Flow Switch
McDonnell & Miller
$568.95119900 McDonnell & Miller FS7-4L - 1-1/4" Flow Switch With Extended Paddle & Paddle Arm 119900. Information: McDonnell & Miller FS7 Overview McDonnell & Miller FS7 Instruction Manual Features: Universal design serves the widest...$568.95 -
153827 LWCO McDonnell & Miller PSE-801-120 Probe Control
McDonnell & Miller
$324.95The Series 153827-LWCO McDonnell & Miller PSE-801-120 Probe Control type LWCO 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...$324.95 -
153828-LWCO - McDonnell & Miller PSE-801-U-120 Probe Control
McDonnell & Miller
$358.95The Series 153876 - McDonnell & Miller PS-801-U-120 Probe Control type LWCO 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 on...$358.95 -
115100 McDonnell & Miller FS4-3T1-1 - 1" Flow Switch
McDonnell & Miller
$328.95115100 McDonnell & Miller FS4-3T1-1 - 1" Flow Switch With NPT Body High Flow Switch. McDonnell & Miller FS4 Instruction Manual Features: For starting or stopping electrically operated equipment such as signal lights, alarms, motors,...$328.95 -
311200 McDonnell & Miller 21-30 Replacement Float for 21
McDonnell & Miller
$404.95311200 - McDonnell & Miller 21-30 Replacement Float for 21. Click here for more info on Mcdonnell Miller Mechanical Level & Boiler Controls For boiler receiver tanks Float operated Proportional feed action Soft seat provides positive...$404.95 -
114763 McDonnell & Miller FS5-D-3/4 - 3/4" Flow Switch
McDonnell & Miller
$359.95McDonnell & Miller FS5-D-3/4 - 3/4 Flow Switch With/2 SPDT Switches 114763. McDonnell & Miller FS5 Instruction Manual Features: In-line configuration eliminates need for a pipe tee Sizes available: 3/4" NPT, 1" NPT Materials of...$359.95 -
354001 McDonnell & Miller E-11M-24V Manual Reset Switch 24V
McDonnell & Miller
$357.95354001 McDonnell & Miller E-11M-24V Manual Reset Switch 24V. Information: McDonnell & Miller LWCO Series 67 Instruction Manual McDonnell & Miller LWCO Series 67 Submittal Sheet Features: For boilers of any steaming...$357.95 -
153603 LWCO McDonnell & Miller PSE-801-M-U-120 Probe Control
McDonnell & Miller
$394.95The Series 153603-LWCO - McDonnell & Miller PSE-801-M-U-120 Probe Control type LWCO 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...$394.95 -
115654 McDonnell & Miller FS6-WJ-1 Flow Switch 1 BSTP
McDonnell & Miller
$484.95115654 McDonnell & Miller FS6-WJ-1 Flow Switch 1 BSTP. *Please note image is generic. McDonnell & Miller FS6 Instruction Manual This McDonnell & Miller flow switch is for heavy duty applications where high sensitivity is required,...$484.95 -
115653 McDonnell & Miller FS6-WJ-3 4 Flow Switch 3 4 BSTP
McDonnell & Miller
$584.95115653 McDonnell & Miller FS6-WJ-3 4 Flow Switch 3 4 BSTP *Please note image is generic. McDonnell & Miller FS6 Instruction Manual This McDonnell & Miller flow switch is for heavy duty applications where high sensitivity is required,...$584.95