Photo Guide to Steam Heating Controls & Gauges
InspectAPedia^® -

What are the various gauges, switches, & controls found on residential steam heating systems?
How can I identify, inspect, and use controls and gauges on residential steam heating systems?
Steam heating system low water cutoff, water feeders
Pressure and Temperature Gauges on Steam Heating Boilers - Troubleshooting & Repair Guide
Hartford loop & other safety controls found on steam systems
Steam heat condensate return pump systems & controls
Questions & answers about residential steam heating system controls, valves, gauges

Steam heat controls: here we provide a photo guide to all types of controls found on residential & light commercial steam heating systems. We tell you what each control does, where it is located, what it looks like, and we link to in-depth information about setting controls or diagnosing & repairing problems with steam heat controls. This article series provides an illustrated inspection and repair guide to Steam Heating Systems.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Types of Controls Found on Residential Steam Heating Systems

Steam boiler schematic (C) Carson Dunlop Associates

All of the steam heating system controls described in our introduction are illustrated below and described in greater detail in individual articles found in this steam heat series.

If you don't know what kind of heat your building uses, we explain how to figure out the answer at HEATING SYSTEM TYPES.

If your heating system is not working properly, see NO HEAT - BOILER.

Sketch of a one-pipe typical steam heating system (left) is provided courtesy of Carson Dunlop Associates. In a one pipe system each radiator is served by a single pipe: steam rises into the radiator and condensate (water) returns from the radiator through the same pipe loop, as you can see at left.

A two-pipe steam heating system is similar but provides a separate loop of piping that collects condensate and returns it from the radiator to the boiler.

List & Photographs of All Controls found on Steam Heating Systems

If your heating system looks like a heating boiler but your heating radiators have valves which hiss and let air escape as heat is coming on your heat is probably being delivered in pipes which circulate steam from the steam boiler up through radiators in the occupied space.

Although both hot water - hydronic heating systems (discussed at BOILERS, HEATING) and steam boilers (discussed here at STEAM HEATING SYSTEMS) use a boiler that heats water, the heat distribution method and most of the heating boiler controls are different between these two systems.

Both steam boilers and hot water boilers may share certain controls that monitor and manage the heating source such as an oil burner or gas burner. Heater burner controls make sure that there is a safe proper combustion flame, control draft, and protect against flue gas spillage. Examples include the CAD CELL RELAY SWITCH (oil burners) or Spill Switches (gas burners).

Steam Boiler pressure controls:

Because the operating temperature, pressure, and form of heat distribution are different from hot water heat (typically 20-30 psi of hot water), steam boilers (typically less than 0.5 psi steam) use use controls that monitor steam pressure (Pressure Switch, Steam Boiler) shown at left as well as RADIATOR STEAM VENTS (shown later in this article) and other steam piping controls.

And because all steam heating systems consume some water during every heating cycle, steam boilers carefully monitor the water level in the boiler (Low Water Cutoff Valves, Boilers) and require that water be added either manually (now rare, but found on some older steam systems) or automatically (WATER FEEDER Valves, Steam).

These and other steam controls are illustrated below.

Five Common Safety Devices on a Steam Heating Boiler

The sight glass described just below is just one of the safety devices found on a steam boiler, which will also include
a pressure/temperature relief valve, almost always a
low water cutoff valve,
a Hartford Loop (to prevent loss of water out of the boiler by siphoning out of boiler water from a piping leak), and on many modern residential steam systems, an
automatic water feeder valve may also be installed.

Photo Guide to the Steam Boiler Sight Glass

The sight glass on a steam boiler is an important safety and operating device since it allows the homeowner or inspector to see at a glance when the steam boiler is low on water.

Steam systems use varying amounts of water.

Unlike a hydronic heating boiler, some of the water in the steam boiler is lost through the building's radiator steam vents at each heating cycle.

Just how much water the steam boiler will lose varies widely depending on a number of factors.

But if a heating boiler loses its water without also being shut down it will certainly be damaged by the heat of the oil or gas burner (or coal or wood), and it could lead to a dangerous explosion or fire.

If your steam boiler has an automatic water feeder, you should still check the water level (and clarity) in the sight glass frequently, but the risk of a ruined boiler from lost water is of course much less.

Photo Guide to the Steam Boiler Pressure Control Safety Switch

The pressure control switch on a steam heating boiler is designed to shut the heating system down should unsafe high pressures develop.

As we repeat at our description of pressure gauges on a steam boiler, residential steam heating systems are almost always designed to operate at very low pressures, perhaps around .5 psi - that' s 1/2 of one psi.

You should see similar settings on the pressure gauge (at left in our photograph) and on the steam pressure control switch (the gray box at right in our photo) on your boiler.

Photo Guide to Steam Boiler Low Water Cutoff Valves

Here's a photo of a low water cutoff safety valve LWCO on a steam boiler. This valve on a steam heating boiler needs to be flushed clean weekly (more or less) during the heating season. The yellow handle you see in the photo is used for that purpose.

More photos and details about low water cutoff valves on steam boilers can be read at LOW WATER CUTOFF CONTROLS

Photo Guide to Steam Boiler Automatic Water Feeders

Above are photographs of a couple of different but still modern automatic water feeder valves on a steam boiler.

Here we show the "manual feed" button which can be found on the automatic water feeder in the photo at above left.

Details about water feeder valves can be found at WATER FEEDER VALVES

Identification of Relief Valves on Steam Boilers

Low pressure steam boilers still require a pressure/temperature safety relief valve. A pressure relief valve is a spring-loaded device that will open to spill excess pressure (and temperature) in the form of water, steam, or a mix of the two, at a pre-determined pressure in order to protect the heating appliance from damage, or worse, a dangrouse BLEVE explosion. (BLEVE EXPLOSIONS)

However the valve operates at different temperatures and pressures than found on a hydronic (hot water heating) boiler. Residential steam boilers typically operate at below 1 psi, and on residential steam systems the pressure/relief valve is usually set to open at 15 psi.

Photo contributions needed. CONTACT us.

Photos of Steam Traps on Residential Steam Heating Systems

Steam traps such as the Hoffman-style steam trap shown at left are installed on residential steam heating systems (usually at the bottom of the radiator at the opposite end from the steam input side) in order to allow air and condensate out of the radiator while at the same time, stopping the escape of steam (or slowing it) until the steam can condense to water (thus transferring its heat to the radiator itself).

We explain the function, identification, & troubleshooting of steam traps at STEAM TRAPS.

Steam Vents on Residential Heating Systems

Details about the inspection, repair, replacement, function, and identification of steam vents on one pipe and two pipe steam heating systems can be read at Steam Vents

Also see RADIATORS for more extensive information about steam radiator troubleshooting.

Condensate Return Pumps & Condensate Systems on Residential Steam Heating Systems

Steam condensate return pump system (C) D Friedman

Our photo at above left illustrates a steam condensate return pump system in a home

Our second steam condensate return system (above right) shows the reservoir and condensate pump motor (grey pump and new piping on the right side of the condensate reservoir at the left in that picture). This system also includes chemical injection into the steam condensate.

Details about steam condensate piping, return pumps, and leaks are found at CONDENSATE RETURN PIPES, PUMPS, STEAM

Steam Boiler Pressure Gauge and Normal Pressure Ranges

Pressure and Temperature gauge on steam heating boilers: Residential steam heating systems are almost always designed to operate at very low pressures, perhaps around .5 psi - that' s 1/2 of one psi.

You should see similar settings on the pressure gauge (at left in our photograph) and on the steam pressure control switch (the gray box at right in our photo) on your boiler.

Details about gauges on heating equipment can be read at GAUGES ON HEATING EQUIPMENT and see Pressure Gauges, Boilers for more details about pressure gauges on hydronic (hot water) heating boilers (these are not steam systems).

Questions & Answers regarding this article

Questions & answers about residential steam heating system controls, valves, gauges

Ask a Question or Search InspectAPedia

HTML Comment Box is loading comments...

Recommend / Share this Article

...

Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

STEAM HEATING SYSTEMS
  AQUASTAT CONTROL Functions
  BACKDRAFTING HEATING EQUIPMENT
  BACKFLOW PREVENTER VALVE, HEATING SYS
  BANGING HEATING PIPES RADIATORS
  CAD CELL RELAY SWITCH
  CHECK VALVES, HEATING SYSTEM
  Chemical treatments, Boiler
  Circulator Pumps & Relays
  COMBUSTION GASES & PARTICLE HAZARDS
  CONDENSATE RETURN PIPES, PUMPS, STEAM
  DIAGNOSE & FIX BOILER
  DRAFT HOODS - gas fired
  DRAFT MEASUREMENT, CHIMNEYS & FLUES
  DRAFT REGULATORS, DAMPERS, BOOSTERS
  ELECTRIC MOTOR OVERLOAD RESET SWITCH
  ELECTRICAL POWER SWITCH FOR HEAT
  EXPANSION TANKS
  FIRE SAFETY CONTROLS
  GAUGES, HEATING EQUIP.
  LIMIT SWITCH, BOILER
  LOW WATER CUTOFF VALVE
  MIXING / ANTI-SCALD VALVES
  PRESSURE, TEMPERTURE SETTINGS, CONTROLS
  PRESSURE SWITCH, STEAM BOILER
  RELIEF VALVES - STEAM TP VALVES
  SIGHT GLASS, STEAM BOILER
  SPILL SWITCHES
  STACK RELAY SWITCH
  STEAM PRESSURE GAUGE
  STEAM TRAPS
  STEAM VENTS
  THERMOSTATS, HEATING / COOLING
  WATER FEEDER Valves, Steam

  RADIATOR STEAM VENTS
  RADIATOR STEAM VENTS, AUTOMATIC
    Install Steam Vents to Control Heat

For details about the controls, components and switches commonly found on hot water heating systems see the articles listed below in which we explain how to identify, set, re-set, repair, replace, or avoid problems with the components of a hot water heating system..

Hot Water Heating Boiler Operating Details - 39 Steps to Hot Water Heating Success
Air Bleeder Valves for Hot Water Heating Systems: Radiators, Baseboards, Convectors
Aquastats Heating Boiler Primary Controls: A guide to Aquastats for control of hot water heating boilers and tankless coils
BLUE vs YELLOW COMBUSTION FLAMES - the Blueray history and blue flame vs. yellow flame combustion, flame color & combustion efficiency, & how oil competes with gas as a heating fuel.
CAD CELL RELAY SWITCH on oil fired furnaces or boilers as flame sensors & safety devices
Check Valves Guide to check valves and backflow preventers on hydronic (hot water) heating systems (gas or oil fired)
Circulator Pumps Guide to circulator pumps and circulator relays on hydronic (hot water) heating systems (gas or oil fired)
Draft Hoods on gas fired heating equipment, function and safety
Draft Regulators & barometric dampers on oil fired heating equipment
Electrical Power Switches: Where to Turn On or Off Heaters for Furnaces & Boilers, Heat Pumps or Electric Furnaces or Air Conditioners
Expansion Tanks Guide to pressure control and expansion tanks on hydronic (hot water) heating systems (gas or oil fired)
Flue Gas Spill Switch on gas fired heating equipment sense combustion and protect from blocked flues
Gas Piping, Valves, Controls: Guide to LP and natural gas meters, valves, tanks, piping, gas leaks, gas regulator assembly & other gas controls
Gauges for Temperature & Pressure: Guide Temperature & Pressure Gauges on Hot Water or Steam Heating Boilers
LOW WATER CUTOFF CONTROLS: Guide to LWCOs on hot water heating systems
MIXING / ANTI-SCALD VALVES: Guide to mixing valves on hot water heating systems and radiant heat systems
Oil Burners: Guide to Oil Burners for heating systems, boilers & Furnaces: basic parts, operation, maintenance, performance & money-saving tips
Oil Tanks: Guide to Heating Oil Underground & Above ground Oil Storage Tank Leaks, Testing, Problems & Solutions, Home Buyer's / Home Owner's Guide
Oil Piping: A guide to heating oil piping, valves, controls, leaks, repairs for heating systems
Parts & Components Guide for Heating Boilers: How to Identify the Components of Hot Water Heating Boilers - A Guide to Hydronic Heating System Parts
RELIEF VALVES - TP VALVES: A guide to temperature and pressure relief valves & safety controls on hot water and steam heating systems
Stack Relay Switches: Guide to finding, resetting, maintaining stack relays on oil fired furnaces or boilers as flame sensors & safety devices
Steam Boiler Inspection, Diagnosis, Repair books at the InspectAPedia bookstore - Amazon.com
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update, (see next item in this list). ITT Fluid Technology, 1133 Westchester Avenue
White Plains, NY 10604, tel +1 914 304 1700 fax +1 914 696 2950 www.ittfluidbusiness.com
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
The Heat Efficiency of Steam Boilers, Bryan Donkin
Steam Boiler Operation, Principles & Practice, James J. Jackson
TANKLESS COILS: A Guide to tankless coils used to produce domestic hot water on heating boilers: hot water quantity, safety, temperature control, leaks, corrosion, repairs
Thermostats & Heat Controls for furnaces & boilers, oil & gas fired, heat pumps or electric furnaces or boilers
Water Feed Valves: A guide to water-feeding/pressure-reducing valves on hot water and steam heating systems
Zone Valves: A guide to zone valves for heating zone control on hot water heating systems

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
DUST CONTAMINATION FROM HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
Plastic Heating Vent Pipe & Other Heating Safety Recall Notices
Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Links to our list of additional information on heating system inspection, repair, maintenance
...

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

Photo Guide to Steam Heating Controls & Gauges InspectAPedia® -

Types of Controls Found on Residential Steam Heating Systems

List & Photographs of All Controls found on Steam Heating Systems

Steam Boiler pressure controls:

Five Common Safety Devices on a Steam Heating Boiler

Photo Guide to the Steam Boiler Sight Glass

Photo Guide to the Steam Boiler Pressure Control Safety Switch

Photo Guide to Steam Boiler Low Water Cutoff Valves

Photo Guide to Steam Boiler Automatic Water Feeders

Identification of Relief Valves on Steam Boilers

Photos of Steam Traps on Residential Steam Heating Systems

Steam Vents on Residential Heating Systems

Condensate Return Pumps & Condensate Systems on Residential Steam Heating Systems

Steam Boiler Pressure Gauge and Normal Pressure Ranges

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Photo Guide to Steam Heating Controls & Gauges
InspectAPedia^® -