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 -
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 -
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 -
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 -
126400 McDonnell & Miller 21 Make-Up Water Feeder Model 21
McDonnell & Miller
$957.95126400 McDonnell & Miller Make-Up Water Feeder Model 21. Mcdonnell & Miller Model 21 Instruction Manual For boiler receiver tanks Direct mounting eliminates need for equalizing connections Proportional feed action Mounting Flange –...$957.95 -
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 -
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 -
173003 McDonnell & Miller 150S-HD Head Mechanism Only
McDonnell & Miller
$974.95173003 McDonnell & Miller 150S-HD Head Mechanism Only, Automatic Reset, for 150S, 157S, 158S. Please Contact Us For Lead Time!$974.95 -
143600 McDonnell & Miller Mechanical Low Water Cut Off 64
McDonnell & Miller
$694.95143600 McDonnell & Miller Mechanical Low Water Cut Off 64. Mechanical LWCO For Steam Boilers. Mcdonnell & Miller LWCO Series 64 Instruction Manual Features: For residential and commercial low pressure steam boiler applications For...$694.95 -
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 -
126800 McDonnell & Miller 25-A Make-Up Water Feeder
McDonnell & Miller
$1,308.95126800 McDonnell & Miller Make-Up Water Feeder Model 25-A. McDonnell & Miller Model 21 Water Feeder Instruction Manual Features: For boiler receiver tanks Float operated Proportional feed action Soft seat provides positive seal Seal...$1,308.95 -
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 -
142400 McDonnell & Miller Mechanical LWCO 63
McDonnell & Miller
$684.95142400 McDonnell & Miller Mechanical Low Water Cut Off 63. Mechanical For Steam Boilers. Mcdonnell & Miller LWCO Series 63 Instruction Manual Features: For residential and commercial low pressure steam boiler applications For boilers...$684.95 -
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 -
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 -
127100 McDonnell & Miller 25-A-HD Head Assembly
McDonnell & Miller
$1,157.95127100 McDonnell & Miller 25-A-HD Head Assembly. Features: For boiler receiver tanks Float operated Proportional feed action Soft seat provides positive seal Seal between float chamber and valve chamber is not a positive seal Maximum water...$1,157.95 -
123010 McDonnell & Miller AFE-1 Air Flow Switch
McDonnell & Miller
$1,097.95123010 McDonnell & Miller Air Flow Switch Model AFE-1 Hazardous Environment Applications. Information: McDonnell & Miller AFE-1 Instruction Manual For industrial hazardous environment applications requiring a NEMA 7 (Class I, Division I,...$1,097.95 -
171702 McDonnell & Miller Hi Pressure Level Control 150S
McDonnell & Miller
$997.95171702 McDonnell & Miller Hi Pressure Level Control 150S. McDonnell & Miller 150S Instruction Manual Features and Benefits For commercial and industrial low or high pressure Boiler applications For boilers of any steaming...$997.95 -
120201 McDonnell & Miller FS7-4W - 1-1/4" Flow Switch
McDonnell & Miller
$649.95120201 McDonnell & Miller FS7-4W - 1-1/4" Flow Switch w/NEMA 4X Enclosure 120201. Information: Mcdonnell & Miller 120201 Instruction Manual Features: For applications requiring a water-tight, dust-tight or a NEMA 4X rated flow switch...$649.95 -
132800 McDonnell & Miller Water Feeder LWCO 47-2
McDonnell & Miller
$1,298.95132800 McDonnell & Miller Water Feeder LWCO 47-2. Features: For steam and hot water boilers with cold water feed Continuous maintenance of minimum safe water level, independent of electrical service Proportional feed action Quick hook-up...$1,298.95 -
120160 McDonnell & Miller FS7-4S - 1-1/4" Flow Switch
McDonnell & Miller
$894.95120160 McDonnell & Miller FS7-4S - 1-1/4" Flow Switch With Stainless Steel Body 120160. Mcdonnell & Miller 120160 Instruction Manual Features: Universal design serves the widest variety of large pipe applications, including heating and...$894.95 -
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 -
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 -
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 -
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 -
172806 McDonnell & Miller 150S-M Combo LWCO & Pump Controller
McDonnell & Miller
$1,074.95172806 McDonnell & Miller 150S-M Combo LWCO & Pump Controller. McDonnell & Miller 150S Instruction Manual Features and Benefits For commercial and industrial low or high pressure Boiler applications For boilers of any steaming...$1,074.95 -
173502 McDonnell & Miller Hi Pressure Level Control 157S
McDonnell & Miller
$1,317.95173502 McDonnell & Miller Hi Pressure Level Control 157S. Information: McDonnell & Miller 150S/157S Instruction Manual Specifications For boilers of any steaming capacity Model 157S - 173502 Monel bellows provides corrosion...$1,317.95 -
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 -
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 -
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