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Here we provide an inspection and repair guide to Steam Heating Systems. You will also see that this website answers most questions about central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

If you don't know what kind of heat your building uses, see our introduction at BOILERS, HEATING. If your heating system is not working properly, see NO HEAT - BOILER / FURNACE DIAGNOSIS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links 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.

How to determine what type of heating system is installed: steam heat, hot water heat, or warm air heat

Steam Heating Systems - Steam Boilers:

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.

Steam boilers use controls and heat distribution that differ from those found on hot water or "hydronic" heating systems. See STEAM HEATING SYSTEMS .

Hot Water Heating Systems - Boilers: If the heat in your building is provided by warm or hot metal radiators, heating baseboards containing finned copper tubing, or wall convectors that look like a radiator but contain finned copper tubing, or if heat is provided by flexible rubber, plastic, or metal tubing run in building floors or ceilings, then the warm or hot water circulating in those devices is probably being delivered by piping circulating water heated by a heating boiler, or possibly by a steam boiler or a heat pump or geo-thermal system.

See BOILERS, HEATING and RADIANT HEAT Floor Mistakes to Avoid.

Warm Air Heating Systems - Furnaces: If the heat in your building is provided by warm air that flows out of ceiling, wall, or floor air supply registers into the occupied space, or if your heating system uses a water-to-air heating system then the air which warms the living space is probably being delivered through large or small diameter ducts, registers, air filters, and a furnace blower, and the air is being heated by a gas, oil, or electric furnace, or perhaps by a heat pump or a geo-thermal system.

See FURNACES.

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

Safety Devices on a Steam Heating Boiler Include These Items:

The sight glass 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

Guide to Relief Valves on Steam Boilers

Low pressure steam boilers still require a pressure/temperature safety relief valve. However the valve operates at different temperatures and pressures than found on a hydronic (hot water heating) boiler.

- details in process .

Guide to 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

Guide to Condensate Return Pumps & Condensate Systems on Residential Steam Heating Systems

- details in process .

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.

More 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).

How to Identify, Reset, or Adjust Hot Water Heating Boiler or Steam Boiler Controls and Switches

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STEAM HEATING SYSTEMS
  Cad Cell Relay Switch Flame Sensors
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
DRAFT HOODS - gas fired
DRAFT REGULATORS - barometric dampers
  Cad Cell Relay Switch Flame Sensors
  Circulator Pumps & Relays
  Draft Regulators, Dampers
  Expansion Tanks
  Gauges on Heating Equipment
  Limit Switches, Boilers
  Low Water Cutoff Valves, Boilers
  Mixing Valves
  Relief Valves - TP Valves
  Sight Glass, Steam Boiler
  Pressure Switch, Steam Boiler
  Spill Switches
  Stack Relay Switch
  Steam Pressure Gauge
  Steam Vents
  LOW WATER CUTOFF CONTROLS
  WATER FEEDER VALVES

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
• Cad Cell Relays 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 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
• 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

More Information on Building Diagnostic Inspections and Repairs

• Carbon Dioxide Gas Toxicity
• Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
• Dust from HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
• 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.)

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