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This document presents the detailed sequence of steps to use when inspecting residential heating systems with focus on heating boilers and furnaces, on assuring completeness, accuracy, and on maximum heating system defect detection. The heating system inspection methodology involved is intended to be generalized to the forensic diagnostic inspection of any complex system in order to have the highest probability of detecting important safety or operating defects.

This sounds fancier than intended. Our object is to use an organized procedure for inspecting for defects, without losing the ability to discover unexpected problems as well.

The methodology discussed includes both details specific to heating boilers (the full outline at "Contents") and more general complex-system inspection methods (listed immediately below).

© 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.

© Copyright Daniel Friedman 2008-1993 all rights reserved -- Tri-State ASHI Seminar -- Last update 08/03/2010 - first presentation November 6-7, 1993

Detailed Steps in the Sequence of Examination of Oil-Fired Hot Water Boilers

Viewpoint #4--Detailed close scrutiny of the equipment, after a few "sanity checks"
ASHI 9.1.A.1 The inspector shall observe ... heating equipment

Inspect before operating the boiler

What are we looking at? Form a working Definition: A system which heats the house. A steel, copper, or cast iron "box" of hot water, connected to a loop of pipe (and radiators or baseboards) which runs around through the living area. The same physical water stays in the boiler and is circulated by a pump so that heat is delivered to the living area. Burning oil makes hot gases which are used to heat the water before being exhausted outside. Pumps move fluids. Safety controls at various points protect against a number of potential hazards.

We include links to detailed heating system articles that explain how boiler or furnace parts and components work, how to inspect or repair them, and description of common problems that occur with each heating system component.

• Do you see some reason not to turn this system on? (See SAFETY, HEATING INSPECTION.) What about other problems?
• Is the system safely connected to a chimney?
• Look at the temperature/pressure gauge: normal operating values?
• Look for leaks in the boiler itself (Cast iron is more resistant to death by leaks than steel. Older cast iron systems without tankless coils, if shut off in summer, may be at risk of leakage and hidden damage. Steel rusts through. Cast iron cracks or leaks at joints.)
• Look for leaks at controls now and again in the sequence below
• Leaks at valves or fittings which drip into the jacket of a steel boiler or onto controls or zone valves risk failure and loss of heat.
• Is there a tankless coil? If so, address both topics, looking at heating first, DHW second.

Examine components in the sequence of operation

Examine the accessible parts of the system. Let your eye travel from component to component in the sequence of operation. Apply the inspection logic discussed earlier, at each step. Consider the implications should each component be missing, damaged, inoperative, leaky, noisy, sooty, repaired by an amateur, etc. Think through the operating sequence as you examine each component in that order. The following are the steps in one common set-up. This list is lengthy and detailed. The actual visual examination may take only a few minutes.

The following 39 steps in a heating boiler operating sequence are discussed in more detail at BOILER OPERATION DETAILS. Similar information is provided for warm air heating systems at FURNACE OPERATION DETAILS.

1. Room temperature drops,
2. room thermostat switches "on" ASHI 9.1.A.2 normal operating controls - see THERMOSTATS
3. [zone valve opens and] circulator [starts] [except in Canada where circulators may be set up to run continuously and where the thermostat directly turns on the oil burner] [Circulator usually located on cooler return-side of the distribution piping loop-longer life.] - Zone Valves
4. boiler temperature and pressure are indicated on the TP gauge and should show increase not to exceed normal operating limits (200 deg F or less and less than 30 psi) - Gauges on Heating Equipment
5. hot heating water leaves boiler passing by the ...
6. air scoop (not always present; avoids air-bound baseboards)
7. [air purge] (not always present; often leaky or sealed off)
8. [automatic] water feeder (normally the manual valve for water supply to boiler is "on", the automatic valve is closed unless the boiler pressure drops below 12-15 psi. This valve is often also a backflow-preventer.) - Water Feeder Valves, Hydronic Boiler
9. expansion tank (waterlogged, dumping relief valve)(attic? no r v?=some old equipment) - Expansion Tanks
10. [zone valve] (not always used, shorter life on the "hot" supply side of <->piping) - Zone Valves
11. distribution piping (watch for mineral salts indicating small clogged leaks)
12. baseboards - which warm the room and thus the ... ASHI 9.1.A.6 heat distribution systems including fans, pumps, ducts and piping with supports, dampers, insulation, air filters, registers, radiators, fan-coil units, convectors - RADIATORS and Air Bleeder Valves
13. room thermostat senses the heat increase. Water passes - THERMOSTATS
14. more distribution piping returning to boiler past
15. zone service drain and [flow balancing valves] (are they leaky?) - Zone Valves
16. [circulator pump] (if it's not a convection system used on older houses) - Circulator Pumps & Relays
17. back into the boiler.
18. temperature in the boiler drops as cooler water returns.
19. temperature sensor feels the temp drop and tells the ...
20. primary control or high-limit control, but nothing happens (in the U.S.) until ...
21. temperature drops 15 deg F below the HI setting on the primary control. Then the
22. primary control turns on the oil burner (any drip/leak damage onto the control?) (Canadian systems: thermostat may activate burner directly.) - AQUASTAT CONTROL Functions
23. burner pumps oil from the tank through ... (did we see the tank? is there an oil filter?)
24. [copper] fuel line (and possibly sends excess back through a return line) See OIL TANK PIPING & PIPING DEFECTS or GAS PIPING, VALVES, CONTROLS depending on type of heating system fuel used.
25. [past one or more Fire-o-Matic safety valves] (fusible link used in some jurisdictions) through the pump unit, sending ...
26. high pressure oil to burner nozzle for spray into fire chamber (chamber ok?)
27. transformer makes high voltage sent as spark to ignite oil (tar ooze at transformer?) and ...
28. blower unit sends combustion air into the fire chamber... (is there adequate combustion air? how about when the boiler room door is closed?)
29. Oil begins to burn (rough start or poor shut-down? smoke, soot, odor, noise ?) A flame sensor makes sure that combustion is occurring. CAD CELL RELAY SWITCH or Stack Relay Switch
30. hot gases pass through tubes in steel or between sections in cast iron boiler, sending heat back into the heating water through the heat exchanger. (soot acts as insulation--boiler cleaned recently?)
31. hot gases are collected at top of boiler and sent out through exhaust flue ...
32. where the barometric damper assures proper and even draft; hot gases continue ..., up
33. up the chimney to outdoors.
    ASHI 9.1.A.4 chimneys, flues, and vents (is the chimney improperly shared or vented to multiple floors?) ASHI 9.1.A.5 solid fuel heating devices [e.g. wood and coal stoves]
34. boiler temperature rises up to the "HI" limit. (Thinking of High take a look for a pressure relief valve and look for defects there: leaking, corroded, not piped to floor, reduced diameter piping.) - RELIEF VALVES - TP Valves on Boilers
35. sensor informs Primary Control which turns off the burner-(sloppy shut down?) (Circulator is continuing to run)
36. the room is warm enough according to the thermostat so the ...
37. thermostat senses the temperature rise and opens its switch. (Special thermostat sophistication and functions excluded here)
38. circulator stops (except in Toronto) - Circulator Pumps & Relays
39. Oil or gas burner will either stop then or continue until HI limit (AQUASTAT CONTROL Functions) is reached. - OIL BURNERS and OIL BURNER NOISE SMOKE ODORS

Look closely at controls, peripherals, key components,

• Combination control - combining High Limit and "Low Limit" (which may or may not be in use depending on presence of a tankless coil). See BOILER CONTROLS & SWITCHES for details.
• High Limit and Low Limit (if tankless coil) separate controls on older equipment - Limit Switches, Boilers
• Flame sensing device: Cad Cell or Stack Relay (watch for sensitive relays and learn about the re-stepping lever) - CAD CELL RELAY SWITCH
• Automatic water feeder and Expansion Tank - Expansion Tanks
• Pressure Relief Valve - RELIEF VALVES - TP VALVES
• 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!) - Gauges on Heating Equipment
• Tankless coil--leaks, missing mixing/tempering valve, relief valve (some jurisdictions). Risk of scalding water at the house sinks/tubs if there is no mixing valve. - TANKLESS COILS

Leaks and Corrosion - some implications

• Surface rust--repairable. Clean when serviced and monitor
• Exfoliation--very serious, possibly not repairable, risks loss of boiler.

Common Heating System Leak Locations

• Coil mounting plate - see rust stains below and around plate
• Pipe fittings at face of coil plate - mineral salts
• Leaks around bolt openings - suspect hidden damage

Examples of understanding function and implications:

• Leaks are never acceptable, anywhere on a heating system. Leaking relief valves need immediate attention and repair (Leaking relief valve could be due to water-logged expansion tank, improper control settings (temp too high), improper automatic water feeder operation (pressure too high), or defective valve (leaky). True, you only have to report the valve. Did you miss problems at the other components?) Corroded relief valves also need test and repair/replacement
  
  Do not touch the relief valve- it may open and fail to shut down.
  
  Do not pick at corrosion as you may start a catastrophic, un-stoppable leak requiring total system shut-down.
• Different water pressure/flow observed in the kitchen: hot water pressure significantly less than cold--is a tankless coil installed? is a water softener installed? is there "hard" water--have mineral deposits clogged the coil? Are there "cleanout" plumbing fittings on the coil piping? Does this suggest a history of clogging and acid-flush treatments? Can a clogged coil be repaired or replaced? How severe was that rust you observed at the coil mounting plate?

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HEATING SYSTEM INSPECT DIAGNOSE REPAIR
  HEATING INSPECTION CONCEPTS
  HEATING INSPECTION PROCEDURE-GENERAL
HEATING SYSTEM INSPECTION DETAILS
  PREPARATION for Heating System Inspection
  ATTENTION CONTROL During Heating Inspection
  OUTDOOR INSPECTION of HEATING SYSTEM
  INDOOR INSPECTION of HEATING SYSTEM
  HEATING BOILER INSPECTION GUIDE
    HEATING SYSTEM INSPECTION SEQUENCE
    INSPECT HEATING CONTROLS
    INSPECT FOR HEATING BOILER LEAKS
    HEATING SYSTEM DEFECT SIGNIFICANCE
  ALTERNATE HEATING INSPECTION SEQUENCE
  FUNCTIONAL UNDERSTANDING of HEATERS
  HEATING FURNACE INSPECTION GUIDE
  FINAL BOILER ROOM INSPECTION CHECKS
  OIL BURNER INSPECTION GUIDE
  OPERATE THE HEATING SYSTEM
  HEATER OPERATING DEFECTS REPORT
  IMPLICATIONS OF HEATING CLUES
  FINAL HEATER INSPECTION REVIEW
  SET HEATING REPAIR PRIORITIES

• Information on Hydronic (hot water) Heating Boilers:
  • 
    BOILERS, HEATING
    BOILER CONTROLS & SWITCHES
    BOILER LEAKS CORROSION STAINS
    BOILER OPERATING PROBLEMS
• Information on Steam Heating Boilers & Steam Radiators
  • 
    STEAM HEATING SYSTEMS
      Low Water Cutoff Valves, Boilers
      Sight Glass, Steam Boiler
      Pressure & Temperature Settings, Controls
      Pressure Switch, Steam Boiler
      Steam Pressure Gauge
      Steam Vents
      LOW WATER CUTOFF CONTROLS
      Water Feeder Valves, Steam
• Information on warm air furnace heaters
  • 
    FURNACES, HEATING
    FURNACE CONTROLS & SWITCHES
    
    DUCT SYSTEM & DUCT DEFECTS
    DUCT SYSTEM DEFECTS
• Information on Radiant Heating: RADIANT HEAT Floor Mistakes to Avoid
• Information on Electric Heat: ELECTRIC HEAT
• Information on chimneys flues, vents, combustion air
  • CHIMNEY INSPECTION DIAGNOSIS REPAIR
    CHIMNEYS & Flues - Asbestos Transite Pipe
    DRAFT HOODS - gas fired
    DRAFT REGULATORS, DAMPERS, BOOSTERS
    FLUE VENT CONNECTORS
• Information on Heat Pumps - HEAT PUMPS

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.

• 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
• ...