This page lists free PDF downloads of manuals for controls used on steam heating systems, some of which, such as a LWCO may also be found on some hot water or hydronic heating systems.

Steam Boiler Control Manuals

This page lists PDF downloads of manuals for low water cutoff valves & controls found on steam heating systems and on some hydronic heating boilers as well.

Boiler Water Feeder Manuals & Instructions

Water feeder controls for steam boilers are listed separately

at WATER FEEDER MANUALS

Water feeder controls manage the actual replenishment of water in a steam or hydronic heating boiler.

Boiler Low Water Cutoff Valve LWCO Manuals & Instructions

Low water cutoff controls or LWCOs are safety devices that will turn off a heating boiler if the boiler water level drops below a safe level.

In addition to the LWCO manuals and guides listed below, see

• LOW WATER CUTOFF VALVE, BOILER
• LOW WATER CUTOFF VALVE NOT WORKING
• LWCO LOW WATER CUTOFF on STEAM BOILERS - how to flush the LWCO

Illustration: A McDonnell & Miller LWCO PS-801-802 851 series probe type low water cutoff control.

B&G LWCO Control Reference

• Bell & Gossett HOW HYDRONIC [HEATING] SYSTEM COMPONENTS REALLY WORK [PDF] (2012) CounterPoint from B&G, Bell & Gossett (a Xylem brand), Xylem Inc. 8200 N. Austin Avenue Morton Grove, Illinois 60053 Phone: (847) 966-3700 Fax: (847) 965-8379 www.xyleminc.com/brands/bellgossett retrieved 2019/11/06

Crown Boiler LWCO & Panel Kit Controls

• Crown OC PANEL KIT MANUAL for Aruba IV (Gas Hot Water) or Freeport II (Oil Hot Water) boilers [PDF] (2013) (at Velocity Boiler Works) - Crown Boiler Company Manufacturer of Hydronic Heating Products P.O. Box 14818, 3633 I Street Philadelphia, PA 19134 www.crownboiler.com - this control is manufactured by Potter Electric Signal Company, St. Louis, MO - local copy saved as Crown-OC-Panel-Kits.pdf
• Crown OC PANEL LOW WATER CUTOFF (LWCO) KIT MANUAL For Hot Water Boilers [PDF] (2013) (at Velocity Boiler Works) - Auto Reset p/n 450602, Manual Reset p/n 450604, cal copy saved as Crown-OC-LWCO-Kit.pdf
  
  This is an add-on low water control that is a direct plug-in part for the control panel on Crown Aruba 4 and Freeport 2 boilers. The control panel accepts various plug-in's like the one described here, providing energy savings such as an outdoor air reset monitor and a high limit reset function.
  
  Watch out: if you OC Panel LWCO card is the manual reset model, you'll havec to manually reset the unit if it detects the absence of water in your boiler.
  
  Excerpt: The OC (Option Control) Panel Low Water Cutoff (LWCO) Cards are advanced, microprocessor based low water cutoffs for detecting the absence of water in a heating system.
  
  OC Panel LWCO Cards use patented signal processing to identify when the probe signal levels have decreased due to possible fouling.

Hydrolevel Control Manuals - Safgard & VXT LWCOs & Water Feeders

• HYDROLEVEL Safgard 170 SERIES LOW WATER CUT-OFF MANUAL [PDF] (at Hydrolevel) - local backup copy saved as Hydrolevel-Saftard-170-Manual.pdf
• Hydrolevel Safgard™ 400 Series Steam LWCO [PDF], Hydrolevel Company, 126 Bailey Road, North Haven, CT 06473 USA, Tel: (203) 776-0473 Website: www.hydrolevel.com Retrieved 2017/04/06, original source: http://hydrolevel.com/safgard-400-series-steam/
• Hydrolevel Safgard™ 450 Series Steam LWCO [PDF], retrieved 2017/04/06, original source: http://hydrolevel.com/safgard-400-series-steam/
• Hydrolevel Safgard 550/650/750 SERIES 120VAC LOW WATER CUTOFF MANUAL (LWCO) [PDF] (at Hydrolevel website) 2025/12/06 - local backup copy saved as Safgard-550-650-750-LWCO-Manual.pdf
• HYDROLEVEL SafGard™ Model 1150 Low Water Cutoff for Residential Hot Water Boilers [PDF] retrieved 2017/08/17, original source: http://hydrolevel.com/wp-content/uploads/2015/12/Safgard-1150-LWCO-Installation-Sheet.pdf
• Hydrolevel VXT RESIDENTIAL Model VXT-24 Programmable WATER FEEDER for Steam Boilers - 24VAC Operating Voltage [PDF] (2015) Installation, Maintenance, Troubleshooting Instructions" [PDF] Hydrolevel Company, 126 Bailey Road, North Haven, CT 06473 USA Tel: (203) 776-0473 Website: www.hydrolevel.com, retrieved 2016/09/27, original source: http://hydrolevel.com/wp-content/uploads/2015/12/VXT-24-Instructions-rev-04-22-15.pdf
• VXT-24 WATER FEEDER, STEAM MANUAL [PDF] (pre-2015)
• Hydrolevel VXT-120 WATER FEEDER MANUAL [PDF] (2020) (at Hydrolevel) Programmable water feeder for steam boilers, 120VAC, includes programmable water feed delay settings and programmable feed amount settings (using DIP switches) - local copy saved as VXT-120-Instruction-Manual.pdf
  
  Instructions include wiring diagrams and settings for use with Hydrolevel Safgard controls, McDonnell & Miller controls, OLder float style controls, and the Honeywell Model-RW-700 Guard Ring control.
  
  Excerpt: Water Damage Potential: Failure to maintain the VXT Series feeder can result in excess mineral deposits collecting in the valve.
  
  If left unchecked, these deposits can impede valve operation with the potential for overfilling the heating system and allowing water to escape radiators into the living space.

 

Xylem - McDonnell & Miller LWCO Control Manuals

• McDonnell & Miller Controls - XYLEM Global Headquarters, 1133 Westchester Avenue, White Plains, NY 10604, Tel: +1-914-323-5700, Fax: +1-914-323-5800
• ITT McDonnell & Miller GUARDDOG® Model RB-24E Conductance Type Low Water Cutoff for Residential 24VAC Hot Water Boilers [PDF], (2009)ITT 8200 N. Austin Ave., Morton Grove IL 60053 USA, Tel: 847-966-3700 retrieved 2017/08/17, original source: https://www.torrco.com/ASSETS/DOCUMENTS/CMS/EN/83260_PROD_FILE.pdf
• McDONNELL & MILLER SERIES 47 & 247 MECHANICAL WATER FEEDERS / SERIES 47-2 & 247-2 Combination MECHANICAL WATER FEEDER & LWCO INSTRUCTION MANUAL [PDF] (2015) Xylem, Inc. 8200 N. Austin Avenue Morton Grove, Illinois 60053 Phone: (847) 966-3700 Fax: (847) 965-8379 Website: www.mcdonnellmiller.com
• McDonnell & Miller ITT Series 47 & 247 Mechanical Water Feeders, Series 47-2 & 247-2 Combination Mechanical Water Feeder & Low Water Cut-Off Installation & Maintenance Instructions [PDF], (2007) retrieved 4/23/2017, original source: http://s3.supplyhouse.com/manuals/1350993347279/84563_PROD_FILE.pdf
• McDonnell & Miller ITT Models 51, 51-2 & 53 Water Feeders & Models 51-2, 51-S-2 & 53-2 Feeder Cut-OffCombination Instruction Manual, [PDF] retrieved 4/23/2017, original source: https://www.nationalpumpsupply.com/content/pdf/mcdonnell-&-miller-series-51-51s-53-instruction-manual.pdf
  
  
• McDONNELL & MILLER No. 2 SWITCH LWCO INSTRUCTIONS [PDF] (2012) For series 47,247,63,51,and 53 water feeders to add the low water cut-off function.
  Product description excerpt:
  
  The No.2 Switch will help to maintain a minimumwater level in the boiler during normal operation.The switch will shut off the burner in the event theboiler water level falls.Once the water level isrestored to its normal level, the switch will allowthe burner to operate.
• McDonnell & Miller Series FS6 High Sensitivity Liquid Flow Switches
• McDonnell & Miller RBT-3000 LWCO & Fuel Economizer (The RBT-3000 is a combination Low-Water Safety Cut-Off and Fuel-Saving controller for residential heating systems.)
• McDonnell & Miller Series 67 & 767 LOW WATER CUT-OFFS for STEAM BOILERS, INSTALLATION & MAINTENANCE MANUAL [PDF] (MM-201(E) ) (2015) ITT Corporation, 8200 N. Austin Ave. Morton Grove, IL 60053 tel: 847-966-3700 fax: 847-966-9052 www.mcdonnellmiller.com
  
  Includes troubleshooting, wiring diagrams, regular maintenance requirements and installation details for LWCOs.
• McDonnell & Miller Series 67 & 767 Low Water Cut-Offs for Steam Boilers, INSTALLATION & MAINTENANCE MANUAL [PDF] (MM-201(E) ) (2007) ITT Corporation, 8200 N. Austin Ave. Morton Grove, IL 60053 tel: 847-966-3700 fax: 847-966-9052 www.mcdonnellmiller.com
• McDonnell & Miller SERIES 69 LOW WATER CUTOFF INSTRUCTION MANUAL [PDF] Xylem Inc. 8200 N. Austin Avenue Morton Grove, Illinois 60053 USA Tel: (847) 966-3700 Website: www.mcdonnellmiller.com Retrieved 2019/02/15
  
  Example LWCO MAINTENANCE SCHEDULE:
  
  Blow down weekly (at least once) when the boiler is in operation.
  
  Disassemble and inspect annually. Replace the low water cut-off if it is worn, corroded, or if components no longer operate properly.
  
  Inspect the shield, float and bellows annually. Remove all sediment and debris.
  
  We recommend replacement when the switch no longer operates properly.
  
  If you choose to replace the switch, order the McDonnell & Miller replacement switch and follow the Repair Procedure provided.
  
  Replace the low water cut-off every 10 years.
  
  More frequent replacement may be required when severe conditions exist such as rapid switch cycling, surging water levels, and use of water treatment chemicals.
• McDonnell & Miller Series 194 – Low Water Cut-Off/Pump Controllers
• Xylem McDonnell & Miller Series 750 Low Water Cut-Off For Use with Remote Sensors MANUAL [PDF] (2015) (MM-213-M) (at national pumps supply co) Models MM 750-MT-24 / 750-T-24 (24VAC models) and 750-MT-120 / T-120 (120VAC models) - local copy saved as McDonnell-Miller-750-LWCO-Manuall.pdf
  
  This LWCO is used as a primary conductance type control on commercial or industrial hot water boilers where remote level sensing is required, and it is also used as a secondary control on commercial or industrial steam boilers. It can be used in boilers in which an antifreeze mixture is used as a water/glycol mixture up to 50% concentration.
• Xylem McDonnell & Miller PSE-800-M Low Water Cut-off INSTRUCTION MANUAL [PDF] (2019) at Xylem, local backup copy saved as Xylem-McDonnell-Miller-PSE-800-Manual.pdf
  
  Excerpts:
  
  The probe is a manual reset low water cut-off control.
  
  The control unit has a red LED light to alert personnel to a low water condition and a green LED to indicate normal operation.
  
  When a low water condition occurs, the burner turns off and the red LED begins to blink.
  
  When the water level is not restored to a level above the probe within 60 seconds, the control locks out.
  
  Press the reset button when the water level is restored to a level above the probe.
  
• McDonnell & Miller PS-801 & PS-802 Low Water Cut-Offs PRODUCT SPECIFICATIONS [PDF], electronic operating probe-type LWCO control
• McDonnell & Miller PS-801 Low Water Cut-Off INSTALLATION & MAINTENANCE INSTRUCTIONS [PDF], electronic operating probe-type LWCO control
• McDonnell & Miller Low Water Cutoff LWCO Probe Type Series PS-801 Steam Boiler LWCO & Series PS-851 GuardDog Hot Water Boiler LWCOInstallation & Maintenance Manual [PDF], (2007) ITT, 8200 N. Austin Ave., Morton Grove IL 60053, Tel: 847-966-3700, Website: www.mcdonnellmiller.com
• McDonnell Miller Series 1575 Low Water Cutoff for Steam Boiler INSTRUCTIONS, mechanical unit, [PDF] (2015) Xylem Inc. 8200 N. Austin Avenue Morton Grove, Illinois 60053 Phone: (847) 966-3700 Fax: (847) 965-8379 www.mcdonnellmiller.com, retrieved 2017/04/06, original source: http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2013/10/MM-286C.pdf
• McDonnell & Miller ITT Series 150S & 157S Low Water Cut-Off Pump Controllers for Steam Boilers [PDF], retrieved 2017/04/06, original source: http://dominion.com.mx/fichas/control-de-nivel-mcdonnell-miller-259.pdf
• McDonnell & MIller, HEATING BOILER BASIC OPERATION [PDF] McDonnell & Miller, retrieved 2019/11/06 original source: www.controlcomponents.com.au/Open-File/557/Boiler%20control%20basics.pdf
• McDonnell & Miller WFE Uni-Match 323H ELECTRIC WATER FEEDER INSTRUCTION MANUAL [PDF] (2019) (at Xylem.com) - local copy saved as MM-Uni-Match-Water-Feeder-Manual.pdf
  

• STEAM VENTS, VARI_VALVE SELECTION & INSTALLATION MANUAL [PDF]

 

Taco LWCO Control Manuals

• Taco LF-Series Foam Compensating LOW WATER CUTOFF with Test Button & Dual Vision [PDF] (2009) retrieved 2017/04/06, original source: http://www.taco-hvac.com/uploads/FileLibrary/102-207.pdf
  The probe of this device is installed "above" the manufacturer's minimum safe water level.
• Taco LN-Series LWCO Instruction Sheet [PDF] (2008) op. cit.
• Taco LT-Series LWCO Instruction Sheet [PDF] (2005) op. cit.
• TACO® Comfort Solutions™ LTA-2 LOW WATER CUTOFF for HOT WATER BOILERS [PDF] (2009), retrieved 2017/08/17, original source: http://www.taco-hvac.com/uploads/FileLibrary/102-350.pdf
• Taco LTR Series LWCO for Hot Water Boilers [PDF] (2015) op. cit.

Watts LWCO Control Manuals

• WATTS SAN89 LWCO INSTALLATION INSTRUCTIONS [PDF] (2008) Watts USA: 815 Chestnut St., No. Andover, MA 01845-6098; www.watts.com
  or Watts Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscanada.ca
  
  
  Excerpt:

  Series SAN89 Float and Switch Assemblies for Servicing Low Water Cut-Offs feature a one piece unit that facilitates installation and ensures the most up-to-date construction.

  Model SAN89D is a complete float and dual switch assembly.

  Model SAN89S is a complete float and single switch assembly. Maximum Working Pressure: 15psi (103 kPa).
  

  
  
• See additional research CITATIONS & REFERENCES found at the end of the this page
• Also see MANUALS & PARTS GUIDES - HVAC - home - Master Index to All Brand Names & HVAC manuals, wiring diagrams, installation and repair guides
• Also see MANUALS for HEATING & A/C SYSTEM CONTROLS

...

...

Continue reading at STEAM HEATING SYSTEMS & CONTROLS - home , or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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