McDonnell & Miller

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
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    120601 McDonnell & Miller FS8-W - 1" Flow Switch

    McDonnell & Miller

    $184.95
    120601 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...
    $184.95
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    $184.95
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  • 120611 McDonnell & Miller FS251
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    120611 McDonnell & Miller FS251 Flow Switch With NEMA 1 Enclosure

    McDonnell & Miller

    $128.95
    McDonnell & 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...
    $128.95
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    $128.95
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  • 114400 McDonnell & Miller FS4-3 1" Flow Switch 1" NPT
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    114400 McDonnell & Miller FS4-3 1" Flow Switch

    McDonnell & Miller

    $134.95
    114400 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 signal...
    $134.95
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    $134.95
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  • 120610 McDonnell & Miller FS254 Flow Switch
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    120610 McDonnell & Miller FS254 Flow Switch With NEMA 4 Enclosure

    McDonnell & Miller

    $178.95
    120610 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 equipment...
    $178.95
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    $178.95
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  • 113200 McDonnell & Miller FS-1 1/2" Liquid Flow Switch
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    113200 McDonnell & Miller FS-1 1/2" Liquid Flow Switch

    McDonnell & Miller

    $214.95
    113200 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...
    $214.95
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    $214.95
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  • 114639 McDonnell & Miller FS4-3RP-T 1" Flow Switch FS4-3 With Test Button
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    114639 McDonnell & Miller FS4-3RP-T 1" Flow Switch

    McDonnell & Miller

    $178.95
    114639 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...
    $178.95
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    $178.95
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  • 123400 McDonnell & Miller Air Flow Switch Model AF3
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    123400 McDonnell & Miller AF3 Air Flow Switch

    McDonnell & Miller

    $149.95
    123400 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) minimum...
    $149.95
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    $149.95
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  • 123000 McDonnell & Miller Air Flow Switch Model AF1-S
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    123000 McDonnell & Miller Air Flow Switch AF1-S

    McDonnell & Miller

    $292.95
    123000 McDonnell & Miller Air Flow Switch AF1-S. 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...
    $292.95
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    Qty in Cart: 0
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    $292.95
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  • 114780 McDonnell & Miller FS5-1 - 1" Flow Switch
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    114780 McDonnell & Miller FS5-1 - 1" Flow Switch

    McDonnell & Miller

    $224.95
    114780 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, carbon &...
    $224.95
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    $224.95
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  • 126400 McDonnell & Miller Make-Up Water Feeder Model 21
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    126400 McDonnell & Miller 21 Make-Up Water Feeder Model 21

    McDonnell & Miller

    $598.95
    126400 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 –...
    $598.95
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    $598.95
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  • 169550 McDonnell & Miller Universal Water Feeder Uni-Match WFE-24V
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    169550 McDonnell & Miller WFE-24V Universal Water Feeder Uni-Match

    McDonnell & Miller

    $278.95
    169550 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...
    $278.95
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    $278.95
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  • 114760 McDonnell & Miller FS5-3/4 - 3/4" Flow Switch
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    114760 McDonnell & Miller FS5-3/4 - 3/4" Flow Switch

    McDonnell & Miller

    $224.95
    114760 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 for a pipe...
    $224.95
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    $224.95
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  • 153900 McDonnell & Miller Low Water Cut Off 69
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    153900 McDonnell & Miller Low Water Cut Off 69

    McDonnell & Miller

    $262.95
     153900 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 Manual ...
    $262.95
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    $262.95
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  • 119700 McDonnell & Miller FS7-4 - 1-1/4" Flow Switch
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    119700 McDonnell & Miller FS7-4 - 1-1/4" Flow Switch

    McDonnell & Miller

    $359.95
    119700 McDonnell & Miller FS7-4 - 1-1/4" Flow Switch Paddle Style. McDonnell & Miller FS7 Overview McDonnell & Miller FS7 Instruction Manual Features: Universal design serves the widest variety of large pipe applications, including heating...
    $359.95
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    $359.95
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  • 126800 McDonnell & Miller 25-A Make-Up Water Feeder
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    126800 McDonnell & Miller 25-A Make-Up Water Feeder

    McDonnell & Miller

    $864.95
    126800 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 between...
    $864.95
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    Qty in Cart: 0
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    $864.95
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  • 114900 McDonnell & Miller FS4-3T2-3/4 - 3/4" Flow Switch
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    114900 McDonnell & Miller FS4-3T2-3/4 - 3/4" Flow Switch

    McDonnell & Miller

    $214.95
    114900 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, motors,...
    $214.95
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    Qty in Cart: 0
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    $214.95
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  • McDonnell & Miller FS4-3S 1" Flow Switch w/Stainless Steel Body Monel Bellows 114641
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    114641 McDonnell & Miller FS4-3S 1" Flow Switch

    McDonnell & Miller

    $414.95
    McDonnell & 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...
    $414.95
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    $414.95
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  • 181525 McDonnell & Miller Relief Valve 250-3/4-50 - 3/4" NPT
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    181525 McDonnell & Miller Relief Valve 250-3/4-50 - 3/4" NPT

    McDonnell & Miller

    $124.95
    181525 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 kg/cm2)...
    $124.95
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    Qty in Cart: 0
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    $124.95
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  • 115400 McDonnell & Miller FS6-3/4 - 3/4" Flow Switch
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    115400 McDonnell & Miller FS6-3/4 - 3/4" Flow Switch

    McDonnell & Miller

    $334.95
    115400 McDonnell & Miller FS6-3/4 - 3/4" Flow Switch-High Sensitivity. McDonnell & Miller FS6 Instruction Manual This Mcdonnell & Miller flow swicth is for heavy duty applications where high sensitivity is required, such as water treatment...
    $334.95
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    $334.95
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  • 120160 McDonnell & Miller FS7-4S - 1-1/4" Flow Switch
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    120160 McDonnell & Miller FS7-4S - 1-1/4" Flow Switch

    McDonnell & Miller

    $598.95
    120160 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 hydronic...
    $598.95
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    Qty in Cart: 0
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    $598.95
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  • 171702 McDonnell & Miller Hi Pressure Level Control 150S
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    171702 McDonnell & Miller Hi Pressure Level Control 150S

    McDonnell & Miller

    $768.95
    171702 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...
    $768.95
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    Qty in Cart: 0
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    $768.95
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  • 132800 McDonnell & Miller Water Feeder LWCO 47-2
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    132800 McDonnell & Miller Water Feeder LWCO 47-2

    McDonnell & Miller

    $868.95
    132800 McDonnell & Miller Water Feeder LWCO 47-2. Mcdonnell & Miller LWCO Instruction Manual Features: For steam and hot water boilers with cold water feed Continuous maintenance of minimum safe water level, independent of electrical...
    $868.95
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    Qty in Cart: 0
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    $868.95
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  • 115300 McDonnell & Miller FS4-3T3-1 - 1" Flow Switch
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    115300 McDonnell & Miller FS4-3T3-1 - 1" Flow Switch

    McDonnell & Miller

    $214.95
    115300 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,...
    $214.95
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    Qty in Cart: 0
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    $214.95
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  • 123200 McDonnell & Miller Air Flow Switch Model AF2
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    123200 McDonnell & Miller AF2 Air Flow Switch Model AF2

    McDonnell & Miller

    $226.95
    123200 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 end...
    $226.95
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    $226.95
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  • 140100 McDonnell & Miller Mechanical Low Water Cut Off 61
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    140100 McDonnell & Miller Mechanical Low Water Cut Off 61

    McDonnell & Miller

    $374.95
    140100 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 of any...
    $374.95
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    Qty in Cart: 0
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    $374.95
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  • 120201 McDonnell & Miller FS7-4W - 1-1/4" Flow Switch
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    120201 McDonnell & Miller FS7-4W - 1-1/4" Flow Switch

    McDonnell & Miller

    $444.95
    120201 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. 1-1/4"...
    $444.95
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    Qty in Cart: 0
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    $444.95
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  • 115000 McDonnell & Miller FS4-3T3-3/4 - 3/4" Flow Switch
    Add to Cart

    115000 McDonnell & Miller FS4-3T3-3/4 - 3/4" Flow Switch

    McDonnell & Miller

    $214.95
    McDonnell & 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, automatic...
    $214.95
    Add to Cart
    Qty in Cart: 0
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    $214.95
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  • 149400 McDonnell & Miller 67 Mechanical Low Water Cut Off
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    149400 McDonnell & Miller 67 Mechanical Low Water Cut Off

    McDonnell & Miller

    $338.95
    149400 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...
    $338.95
    Add to Cart
    Qty in Cart: 0
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    $338.95
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  • 122800 McDonnell Miller Air Flow Switch Model AF1
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    122800 McDonnell Miller Air Flow Switch Model AF1

    McDonnell & Miller

    $214.95
    122800 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...
    $214.95
    Add to Cart
    Qty in Cart: 0
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    Price:
    $214.95
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  • 127100 McDonnell & Miller 25-A-HD Head Assembly
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    127100 McDonnell & Miller 25-A-HD Head Assembly

    McDonnell & Miller

    $764.95
    127100 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 supply...
    $764.95
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    Qty in Cart: 0
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    Price:
    $764.95
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  • 115652 McDonnell & Miller FS6-W-1 - 1" Flow Switch
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    115652 McDonnell & Miller FS6-W-1 - 1" Flow Switch

    McDonnell & Miller

    $384.95
    115652 McDonnell & Miller FS6-W-1 - 1" Flow Switch With NEMA 4X Enclosure. McDonnell & Miller FS6 Instruction Manual This Mcdonnell & Miller flow swicth is for heavy duty applications where high sensitivity is required, such as water...
    $384.95
    Add to Cart
    Qty in Cart: 0
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    Price:
    $384.95
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  • 123010 McDonnell & Miller Air Flow Switch Model AFE-1
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    123010 McDonnell & Miller AFE-1 Air Flow Switch

    McDonnell & Miller

    $734.95
    123010 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, Group...
    $734.95
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    Qty in Cart: 0
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    $734.95
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  • 143600 McDonnell & Miller Mechanical Low Water Cut Off 64
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    143600 McDonnell & Miller Mechanical Low Water Cut Off 64

    McDonnell & Miller

    $394.95
    143600 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 boilers...
    $394.95
    Add to Cart
    Qty in Cart: 0
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    Price:
    $394.95
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  • 142400 McDonnell & Miller Mechanical LWCO 63
    Add to Cart

    142400 McDonnell & Miller Mechanical LWCO 63

    McDonnell & Miller

    $458.95
    142400 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 of any...
    $458.95
    Add to Cart
    Qty in Cart: 0
    Quantity:
    Price:
    $458.95
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  • 173502 McDonnell & Miller Hi Pressure Level Control 157S
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    173502 McDonnell & Miller Hi Pressure Level Control 157S

    McDonnell & Miller

    $878.95
    173502 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 resistance Float...
    $878.95
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    Qty in Cart: 0
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    Price:
    $878.95
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  • 169400 McDonnell & Miller Water Feeder 101A-120v
    Add to Cart

    169400 McDonnell & Miller Water Feeder 101A-120v

    McDonnell & Miller

    $378.95
    169400 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...
    $378.95
    Add to Cart
    Qty in Cart: 0
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    Price:
    $378.95
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  • 149500 McDonnell & Miller Mechanical Low Water Cut Off 67-LQHU
    Add to Cart

    149500 McDonnell & Miller LWCO 67-LQHU

    McDonnell & Miller

    $268.95
     149500 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...
    $268.95
    Add to Cart
    Qty in Cart: 0
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    Price:
    $268.95
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  • 181625 McDonnell & Miller Relief Valve  250-3/4-75
    Add to Cart

    181625 McDonnell & Miller Relief Valve 250-3/4-75

    McDonnell & Miller

    $124.95
    181625 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) between...
    $124.95
    Add to Cart
    Qty in Cart: 0
    Quantity:
    Price:
    $124.95
    Subtotal:
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