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  • RB-24E, GuardDog Electronic <br>24V LWCO (Water) Product Image
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    RB-24E, GuardDog Electronic 24V LWCO (Water) 144692 RB-24E, GuardDog Electronic 24V LWCO (Water)
    SKU: 144692
    Brand: Mcdonnell & Miller
    (7)
    $85.99 each
    243
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  • RB-122E, GuardDog Electronic<br> 120V LWCO (Water) Product Image
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    RB-122E, GuardDog Electronic 120V LWCO (Water) 144676 RB-122E, GuardDog Electronic 120V LWCO (Water)
    SKU: 144676
    Brand: Mcdonnell & Miller
    (6)
    $85.99 each
    72
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  • 150S-HD, Head Assembly for 150 series<br>(Snap Switch) Product Image
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    150S-HD, Head Assembly for 150 series (Snap Switch) 173003 150S-HD, Head Assembly for 150 series (Snap Switch)
    SKU: 173003
    Brand: Mcdonnell & Miller
    (10)
    $483.99 each
    85
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  • 67, Float Type<br>Low Water Cutoff (Steam) Product Image
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    67, Float Type Low Water Cutoff (Steam) 149400 67, Float Type Low Water Cutoff (Steam)
    SKU: 149400
    Brand: Mcdonnell & Miller
    (23)
    $268.99 each
    188
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  • 120V Electronic Auto Reset LWCO, (Water)<br>Electrical Knock-outs: 4 Product Image
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    120V Electronic Auto Reset LWCO, (Water) Electrical Knock-outs: 4 LTA1203S-2 120V Electronic Auto Reset LWCO, (Water) Electrical Knock-outs: 4
    SKU: LTA1203S-2
    Brand: Taco
    (11)
    $77.19 each
    79
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    79 Wed, Nov 4
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  • Model 3250-Plus Fuel Smart Hydrostat for Oil Boilers (Temperature Limit, LWCO, & Boiler Reset Control) Product Image
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    Model 3250-Plus Fuel Smart Hydrostat for Oil Boilers (Temperature Limit, LWCO, & Boiler Reset Control) 48-3250 Model 3250-Plus Fuel Smart Hydrostat for Oil Boilers (Temperature Limit, LWCO, & Boiler Reset Control)
    SKU: 48-3250
    Brand: Hydrolevel
    (11)
    $156.61 each
    117
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  • 751P-MT-120, GuardDog Electronic manual reset LWCO<br>w/ Probe (Water) Product Image
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    751P-MT-120, GuardDog Electronic manual reset LWCO w/ Probe (Water) 176234 751P-MT-120, GuardDog Electronic manual reset LWCO w/ Probe (Water)
    SKU: 176234
    Brand: Mcdonnell & Miller
    (4)
    $161.99 each
    111
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  • 150-14H, Gasket for 150 Product Image
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    150-14H, Gasket for 150 325600 150-14H, Gasket for 150
    SKU: 325600
    Brand: Mcdonnell & Miller
    $6.89 each
    450
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    450 Wed, Nov 4
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  • Safgard 5500 LWCO w/ Manual Reset & Test Button/Light - 120V Product Image
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    Safgard 5500 LWCO w/ Manual Reset & Test Button/Light - 120V 45-550 Safgard 5500 LWCO w/ Manual Reset & Test Button/Light - 120V
    SKU: 45-550
    Brand: Hydrolevel
    (10)
    $195.12 each
    45
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    176
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  • Safgard 1100 LWCO w/ Auto Reset & Burner Circuit Test Button - 24V Product Image
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    Safgard 1100 LWCO w/ Auto Reset & Burner Circuit Test Button - 24V 45-1100 Safgard 1100 LWCO w/ Auto Reset & Burner Circuit Test Button - 24V
    SKU: 45-1100
    Brand: Hydrolevel
    (12)
    $96.65 each
    125
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  • 24V Electronic LWCO (Water) 1" Probe Product Image
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    24V Electronic LWCO (Water) 1" Probe LTR0243T-1 24V Electronic LWCO (Water) 1" Probe
    SKU: LTR0243T-1
    Brand: Taco
    (2)
    $84.99 each
    83
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  • PSE802-24, Electronic 24V Low Water Cutoff with Auto Reset (Steam) Product Image
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    PSE802-24, Electronic 24V Low Water Cutoff with Auto Reset (Steam) 153927-LWCO PSE802-24, Electronic 24V Low Water Cutoff with Auto Reset (Steam)
    SKU: 153927-LWCO
    Brand: Mcdonnell & Miller
    (4)
    $158.99 each
    96
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  • EL1214, 3/4" NPT Standard Ceramic Probe (2-7/8" ID) Product Image
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    EL1214, 3/4" NPT Standard Ceramic Probe (2-7/8" ID) 45-214 EL1214, 3/4" NPT Standard Ceramic Probe (2-7/8" ID)
    SKU: 45-214
    Brand: Hydrolevel
    (6)
    $47.92 each
    66
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  • Model 3200-Plus Fuel Smart Hydrostat for Gas Boilers (Temperature Limit, LWCO, & Boiler Reset Control) Product Image
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    Model 3200-Plus Fuel Smart Hydrostat for Gas Boilers (Temperature Limit, LWCO, & Boiler Reset Control) 48-3200 Model 3200-Plus Fuel Smart Hydrostat for Gas Boilers (Temperature Limit, LWCO, & Boiler Reset Control)
    SKU: 48-3200
    Brand: Hydrolevel
    (8)
    $133.87 each
    91
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  • Safgard 1150 LWCO w/ Auto Reset & Burner Circuit Test Button -120V  Product Image
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    Safgard 1150 LWCO w/ Auto Reset & Burner Circuit Test Button -120V 45-1150 Safgard 1150 LWCO w/ Auto Reset & Burner Circuit Test Button -120V
    SKU: 45-1150
    Brand: Hydrolevel
    (12)
    $90.88 each
    99
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  • 750-MT-120, GuardDog Electronic <br>Manual Reset LWCO <br>(Water) Product Image
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    750-MT-120, GuardDog Electronic Manual Reset LWCO (Water) 176207 750-MT-120, GuardDog Electronic Manual Reset LWCO (Water)
    SKU: 176207
    Brand: Mcdonnell & Miller
    (1)
    $135.99 each
    76
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  • OS-100 Outdoor Sensor Kit for HydroStat 3200-PLUS and 3250-PLUS Product Image
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    OS-100 Outdoor Sensor Kit for HydroStat 3200-PLUS and 3250-PLUS 48-140 OS-100 Outdoor Sensor Kit for HydroStat 3200-PLUS and 3250-PLUS
    SKU: 48-140
    Brand: Hydrolevel
    (4)
    $36.44 each
    33
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  • 150S-M-HD, Head for Float Combo LWCO Pump Ctrl <br>w/ Man. Reset (Steam) Product Image
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    150S-M-HD, Head for Float Combo LWCO Pump Ctrl w/ Man. Reset (Steam) 172809 150S-M-HD, Head for Float Combo LWCO Pump Ctrl w/ Man. Reset (Steam)
    SKU: 172809
    Brand: Mcdonnell & Miller
    (1)
    $519.99 each
    30
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  • Safgard 400 Non-Cycling Steam Primary LWCO  - 24V Product Image
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    Safgard 400 Non-Cycling Steam Primary LWCO - 24V 45-400-HYDROLEVEL Safgard 400 Non-Cycling Steam Primary LWCO - 24V
    SKU: 45-400-HYDROLEVEL
    Brand: Hydrolevel
    (12)
    $176.78 each
    91
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  • PA-800, Probe Assembly for 750, 750-MT-120 & PS800 Series Product Image
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    PA-800, Probe Assembly for 750, 750-MT-120 & PS800 Series 354081 PA-800, Probe Assembly for 750, 750-MT-120 & PS800 Series
    SKU: 354081
    Brand: Mcdonnell & Miller
    (1)
    $57.90 each
    59
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  • CTRD-101, Cartridge & Strainer Kit, Model<br>CTRD-101 Product Image
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    CTRD-101, Cartridge & Strainer Kit, Model CTRD-101 310453 CTRD-101, Cartridge & Strainer Kit, Model CTRD-101
    SKU: 310453
    Brand: Mcdonnell & Miller
    (10)
    $123.99 each
    51
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  • Safgard 170SV LWCO w/ Auto Reset, Shorter Probe - 120V Product Image
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    Safgard 170SV LWCO w/ Auto Reset, Shorter Probe - 120V 45-175 Safgard 170SV LWCO w/ Auto Reset, Shorter Probe - 120V
    SKU: 45-175
    Brand: Hydrolevel
    (4)
    $96.99 each
    35
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  • 67-12, Sylphon Gasket <br>for 67 & 80 Product Image
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    67-12, Sylphon Gasket for 67 & 80 318900 67-12, Sylphon Gasket for 67 & 80
    SKU: 318900
    Brand: Mcdonnell & Miller
    (1)
    $5.19 each
    87
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  • Model 3150 HydroStat for Oil Boilers (Temperature Limit & LWCO) Product Image
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    Model 3150 HydroStat for Oil Boilers (Temperature Limit & LWCO) 48-3150 Model 3150 HydroStat for Oil Boilers (Temperature Limit & LWCO)
    SKU: 48-3150
    Brand: Hydrolevel
    (4)
    $140.59 each
    53
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    106
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FAQs, Manuals & Videos

Resources

Articles

  • A low water cutoff is a device that detects when the fluid level in hot water and steam boilers drops below the minimum safe operating level specified by the boiler manufacturer. If this should occur, the low water cutoff will cut-off the burner and shut down the boiler. If a boiler is "dry-fired" (burned without water in it), it can result in boiler failure, or a possible fire/explosion. The low water cutoff can therefore be one of the most important safety devices in your hydronic heating system. Low water cutoffs are available in line voltage or low voltage models, for either water or steam systems.

    We carry a wide selection of Taco, McDonnell and Miller, and Hydrolevel low water cutoffs for residential, commercial, and industrial boiler applications.

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