Dictionary of Heating Boiler Components - Boiler Parts Guide
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How to Identify the Components of Hot Water Heating Boilers - A Guide to Hydronic Heating System Parts
What are the basic components of heating boilers and hot water heat?
List of heating system parts with definitions and links to detailed articles
How to inspect & repair central hot water heating boilers - hydronic heating
Questions & answers about components & controls on hydronic (water) heating boiler systems

Dictionary of heating boiler terms: here we explain how to identify & name all of the parts & components of Hot Water Heating Boilers and hot water heating systems including oil burners and their parts, boiler parts, hot water baseboard and its parts, hot water radiators, and hot water convector units and their parts and controls.

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A List & Dictionary of Oil Fired Heating Boiler Parts & Components

Each simple definition includes links to detailed articles discussing how to identify, inspect, diagnose, and repair each component of the heating system.

This website answers most questions about central hot water heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects.

Below we list and describe the parts and controls on heating boilers. Also see BOILER CONTROLS & SWITCHES for a description of the key heating boiler operating controls and switches. If your building uses steam heat see STEAM HEATING SYSTEMS. If your building uses warm air heat see FURNACE CONTROLS & SWITCHES.

The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Heating Boiler - an enclosed steel or cast iron container that uses an energy source to heat water (or make steam) that is sent through heat radiating devices in the occupied space to heat a building. Hydronic heating boilers use hot water to distribute heat through piping and baseboards or radiators. Steam heating boilers produce steam to distribute heat through one pipe or two pipe steam heat systems and steam heat radiators. Some heating systems use a hydronic boiler to heat water that is circulated thorough a heating coil inserted in the plenum of a warm air furnace heating system, using a water-to-air heating method.
Air bleeders and air purge devices to vent out un-wanted air from hydronic (hot water) heating systems. Air in heating distribution piping, boilers, radiators, can prevent hot water circulation and thus stop heat from being delivered to the occupied space.
Air Scoops Purgers Separators - automatic air purging devices referred to as air scoops, air purgers, or air separators vary in internal design, but all are intended to capture air in hot water piping, sending it either to an expansion tank or to an air bleeder/air vent.
Automatic water feeder to provide makeup water in the system; note that different water feeder valves are used on a hydronic heating boiler (hot water circulates) than on a steam boiler (steam circulates)
Baseboards - electric or hot water heat radiating devices transmit heat from hot water or steam into the occupied space; Leak stains, repairs indicating history of freeze-ups? Also see BASEBOARD, CONVECTOR, RADIATOR TYPES
COLD HOT WATER BASEBOARD / RADIATOR and UNEVEN HEAT DIAGNOSIS as well as LEAKS at BASEBOARD, CONVECTOR, RADIATOR
Boiler flue vent connector "stack pipe" or "flue" see Flue Vent Connectors - Boilers, Furnaces and barometric damper - also see Chimneys
Chimney and chimney flue - the flue vent connector sends gases into the chimney whose job is to vent these combustion products safely outdoors, above the building.
Circulator pumps which force hot water through heating baseboards, radiators, or convector units
Combination control - combining High Limit and "Low Limit" (which may or may not be in use depending on presence of a tankless coil)
Draft hoods assure proper exhaust gas venting on gas-fired heating boilers
Electric switch turning the heating system electrical power on and off
Expansion Tank to absorb initial system pressure increase
Flame sensing device: Cad Cell or Stack Relay(watch for sensitive relays and learn about the re-stepping lever)
High Limit and Low Limit (if tankless coil) separate controls on older equipment
Low water cutoff control, a safety device used on steam boilers and some hydronic heating systems to shut down the heating boiler if its water is lost.
Mixing valve to temper outgoing domestic hot water from a tankless coil or to control radiant floor heat temperature
Oil Burner & oil burner parts: oil pump (fuel unit), blower, nozzle, electrodes, transformer, electric motor, air shutter, oil delay valve
Oil Burner reset switch & oil burner motor reset switch (these are two separate controls); a reset switch may be on the cad cell relay or on the stack relay of the oil burner as well as a reset switch on the oil burner electric motor
Oil tank, oil piping, oil valves, oil gauges
Oil Burner Controls, aquastat: high limit, low limit, circulator controls, cad cell relay, other flame sensors
Piping on heating systems: Hot water (or steam) distribution piping and on steam systems, condensate return piping
Piping valves on heating systems: Hot water distribution piping drain and balancing valves
Pressure Relief Valve safety device prevents boiler explosions by releasing temperature and pressure if other safety controls fail
Pressure and Temperature gauge -12 psi cold, less than 30 psi hot. Over 30 psi dumps relief valve.(Typical operating temperature settings LO-120-160 HI-180-200 degF. Typical operating temperature observed at the gauge will be below the high, and can be as low as nighttime room temperature in non-heating season if no tankless coil is in use. The temperature/pressure gauge may help in checking for normal conditions before and during boiler operation. However the gauge can be wrong!)
Radiators - hot water or steam. Steam: observe steam valves on each radiator and identify one pipe vs two-pipe distribution system. radiating devices transmit heat from hot water or steam into the occupied space; Leak stains, repairs indicating history of freeze-ups? Hot water radiators and baseboards may have a manually-operated air bleeder valve. Each steam radiator has a steam vent to permit steam to rise into the radiator.
Sight glass: a glass tube used on steam boilers to give a visible indication of the boiler's water level
Spill switches are used to sense flue gas spillage at gas-fired equipment at the combustion gas exhaust venting systems and will turn off the heating appliance if gas spillage is detected.
Tankless coil or a side-arm coil or other alternative ways of making domestic hot water using the heating boiler; tips about leaks, missing mixing/tempering valve, relief valve (some jurisdictions). Risk of scalding water at the house sinks/tubs if there is no mixing valve.
Zone Valves which control hot water circulation through multiple heating zones

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BOILERS, HEATING - see detailed links at page left
BOILER COMPONENTS & PARTS
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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.
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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Dictionary of Heating Boiler Components - Boiler Parts Guide InspectAPedia® -

A List & Dictionary of Oil Fired Heating Boiler Parts & Components

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Dictionary of Heating Boiler Components - Boiler Parts Guide
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