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Heating System Inspection Step by Step Guide
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This website gives detailed step by step procedures to be used during the inspection of a heating system in order to be thorough, organized, and accurate. We describe how to inspect residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects. 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. © Copyright 2008 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 Inspect Heating Systems - Example of An Approach to the Forensic Inspection of Any Complex System

This document presents a detailed methodology for inspecting, diagnosing, & repairing defects on residential heating systems with attention to inspection methods selected to assure completeness, accuracy, and the maximum level of defect detection. The heating system inspection methodology described here serves as a guide to the forensic diagnostic inspection of any complex system where the highest probability of detecting important safety or operating defects is important.

© Copyright Daniel Friedman 2008-1993 all rights reserved -- Tri-State ASHI Home Inspection Education Seminar - Initial Presentation November 6-7, 1993 -- Last update 11/10/2007

How to Relate Heating System Inspection Procedures to Home Inspection Standards of Practice

This presentation follows a procedure for inspecting, using heating system operating sequence as a method to assure that all important system components are considered. A version of the ASHI Standards of Home Inspection Practice (readers should check most recent Standards version for changes) is mapped into this heating system inspection procedure but does not guide the actual inspection sequence. The organization of home inspection standards is not intended as a guide to an inspection sequence nor as a guide to heating system inspection reports. Home Inspection Standards requirements during the inspection of a home heating system are identified in italics in the text below.

HEATING INSPECTION PROCEDURE - A Detailed Step by Step Inspection Procedure for Heating Systems & Heating Equipment

Heating System Inspection: Outdoor Observations

Outdoor heating system inspection from a distance

Viewpoint #1:--Distant (from the heating equipment): walking around the house, from the ground, just looking, notice and record:

Type of Heating Equipment Installed

Age of the neighborhood, other inspections done in the area, age of the house, may suggest type and even the brand of equipment which may be in place. Builders of developments often purchased many of the same brand and model for all the houses there.

What Heating Fuel Is or Has Been in Use

ASHI 9.2.A.1 The inspector shall describe the energy source Identify probable fuel source: oil, gas, electric, coal, wood, solar Notice the oil filler and vent, spills, and whether or not there is easy access to the oil tank filler pipe.

Also notice any evidence of old, possibly abandoned oil tanks (abandoned oil lines, protruding pipes, age of property, depressions in the soil), or of changes from one type of fuel to another (coal bins). These have potentially major cost implications (improperly abandoned oil tanks) or safety concerns (changes of fuel, unsafe chimneys).

Venting and possible hazards noted from outside:

[Examples of "distant" implications] ASHI 9.1.A.4 chimneys, flues, and vents Look for, then at the chimney. Is there a chimney? If not is there electric heat, direct-vent equipment, or no heat? Thinking about what chimneys do lets you understand the implications of your observations. These items are examples, not a comprehensive list.

Heating System Chimney & Venting Observations Made From Outdoors

• Sooty chimney top or soot stains on roof: system has not been operating properly
• Soot washed off: system may have been repaired/replaced
• Soot heavy and fresh or smoky exhaust seen, system currently needs service or repair
• Watch out for Repco boilers which run sooty as they crash.
• Heat seen rising from heating flue in July - the house may have a tankless coil for domestic hot water. If not, is the primary control set up properly?
• Is there a separate oil-fired water heater using same flue? What's running making that exhaust? Reserve questions for later.

If there is no chimney cap

• is flue blocked by debris?
• has wind-blown rain damaged the masonry interior?
• has wind-blown rain run down chimney into flue vent piping and on into the equipment?
• Did it cause rust damage? Fire chamber damage?

Masonry chimneys

• damaged flue liner? Damage by condensation, frost, acid rain, sulphation (especially with gas-burning equipment)
• Loose bricks?
• Unlined single-wythe brick flues (still common in large cities)--if damaged, risk of fire, leaking flue gases, blocked flues. Look further in the attic and assure there's a cleanout or suggest vent connector be pulled to check for blockage.

Old stone chimneys

• often stop at foundation, heaters were added, connected in to very base of chimney - easily blocked by fallen debris.
• Signs of history of water entry (risk unsafe flue: blocked, fire risks - falling debris
• possible damaged heating equipment (more likely for furnaces than boilers)

Heating System Chimney & Oil or Gas Supply Observations Made From Outdoors

Heating System Inspection: Indoor Observations

Viewpoint #2--Distant view of the heating equipment from the living area.

Heating System Inspection In the living area

These observations and conclusions can be made quickly without needing to ask anyone anything, as soon as you enter the building:

Type of Heat Distribution
ASHI 9.1.A.7 the presence of an installed heat source in each room. ASHI 9.3.D.4 The inspector is not required to observe the uniformity of heat supply to various rooms.

• Air registers: hot-air furnace. Begin looking for supply and return grilles. Identification tip: return grilles often have no controlling louvers and may be centrally located. Distribution problems are not discussed in this presentation.
• Baseboards - electric or hot water. Leak stains, repairs indicating history of freeze-ups?
• Radiators - hot water or steam. Steam: observe steam valves on each radiator and identify one pipe vs two-pipe distribution system.
• Nothing visible: is there electric or hot water radiant heat. Watch for multiple types of heat supply: e.g.: baseboards, with electric heaters in bathrooms.

Heating System Observations In the Utility Room

Viewpoint #3--Distant broad view of the heating equipment from the utility room. The equipment is directly in view but not yet closely examined.
ASHI 9.1.A. The Inspector shall observe permanently installed heating systems including: [items are listed later]
ASHI 9.2.A.2 The inspector shall describe heating equipment and distribution type

1. Identify/confirm type of equipment
2. Housekeeping, location of combustibles
3. Air supply
4. Sooty operation, odors, noises
5. Evidence of recent maintenance
6. Service tags vs filth atop the equipment or in the chimney was it really serviced?

Heating Boilers Detailed Inspection Guide

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

Heating Boiler Inspection Before Operation

What are we looking at? Form a working definition that helps clients understand the system too: 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.

• Do you see some reason not to turn this system on? (See Safety Concerns for the Home Inspector below.) 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.

Heating Boiler Inspection by Sequence of Operation

Training in proper operation sequence of heating system equipment and in the function of its controls is a step towards technical correctness.If you do not understand how a mechanical system works you cannot reliably expect to observe missing or defective components. This discussion is an exercise using sequence of operation to work for completeness. It is not technically exhaustive, it focuses on a specific example: oil-fired hot water, zoned, heating system.

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.

How a Heating System Works - 39 Steps in the Operation of a Heating System

For a complete and accurate inspection of a heating system, the inspector may think through the step by step description of how a heating boiler works. In the reference cited just below we name each heating system component and what it does, in the order that heating system components operate during the heating cycle. Items shown in [brackets] are ones which may not be present on some heating systems. The detailed step by step description of how a heating boiler operates can be read at BOILER OPERATION DETAILS

How to Inspect the Heating System Controls and Switches

While going through the detailed sequence in the operation of the heating boiler, the heating system inspector should watch for and inspect the condition of the heating boiler controls and safety devices (as required by ASHI 9.1.A.3 automatic safety controls). Our detailed description of heating system controls, what they do, how to set them, how to inspect them, is at BOILER CONTROLS & SWITCHES

How to Inspect Heating Systems for Leaks, Rust, Corrosion Damage

The inspector must be particularly alert for evidence of leaks, corrosion, or other signs of damage to the heating system. Our deatailed description of where to look for leaks on heating boilers and what those leaks or leak signs may mean can be found at BOILER LEAKS CORROSION STAINS

How to Recognize Heating System Defects by the Implication of Clues

The heating system inspector must be alert for many signs of heating system malfunction or safety defects. To inspect a heating system effectively, the inspector must understand the implications of what s/he is observing since otherwise an important clue may go unrecognized and a major heating system defect may go unreported. We discuss the interpretation of heating system observations and clues further at Heating Equipment Malfunction & Implications

Heating Boiler Inspection Final Checkpoints

How to Operate Heating Equipment During an Inspection

Heating System Operating Defects

• Noises, smoke, soot, back pressure at inspection port (watch out for burns and fires if this port is opened), sloppy startup, rumbling, sloppy or delayed shutdown-flame lingers (very dangerous).
• Feeling piping (hot!) can indicate if circulator is running--quick change in temperature vs convection.
• Some leaks occur only at peak operating temperature--eg at relief valve.
• Startup problems: noises, puff back, flapping barometric damper, vibrations
• Particularly in cold weather, if the system was on and running, observe and note that it was running normally when you last touched it. Witnessed. (Frost damage issues lurk here.)

Heating Equipment Malfunction & Implications

• Leaks are never acceptable, anywhere. Leaking relief valves need immediate attention and repair (Leaking relief valve could be due to water-logged expansion tank, improper control settings (temperature 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
• Relief Valves: Do not touch the heating boiler or water heater temperature or pressure relief valve - it may open and fail to shut down.
• Corrosion on heating system parts: Do not pick at corrosion as you may start a catastrophic, un-stoppable leak requiring total system shut-down.
• Tankless coils for making hot water: If there is different water pressure/flow observed in the kitchen in which the hot water pressure is significantly less than cold, even before examining the building's mechanical systems you may speculate that a tankless coil installed may be installed. What other clues suggest that the local water supply may be hard in minerals and that there may be a risk of clogged piping? When the water supply is high in minerals, the hot water pipes or tankless coils clog up before cold water piping. Is a water softener installed? Is there known "hard" water--have mineral deposits clogged the coil? Are there "cleanout" plumbing fittings on the tankless 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 tankless coil mounting plate?

Heating System Operating Sequence Inspection Tips

If the furnace or boiler turns on immediately when the thermostat is turned-on or up from the living area what does this mean?

Alternative Heating System Controls

• Air vents at radiators - may indicate that there has been a history of air blockage in the hot water heating system.
• Pressure switch at a steam boiler is typically set to .2 to .5 psi. Higher settings may indicate a history of difficulties with heat distribution in the building.
• Lower-pressure relief valve
• Water feeder, manual or automatic. (Don't mess with either, they may open and be hard to shut off.)
• Low Water Cutoff on some systems. (Also found on some hydronic boilers.)
• Different piping on some systems - one-pipe vs two-pipe, easy to identify and very different implications for retrofit/conversion to other heating methods such as hot water.
• Immediately recognized from the living area by presence of steam valves on radiators. Don't confuse steam valve with air bleeder valves found on hot water radiators.
• Steam rises--hence no circulator pump may be installed - if you see a pump is it a separate hydronic zone? (Some steam systems also circulate hot water through a lower building area. Or is the pump you see a condensate return pump?

Heating System Component Malfunction Example

A pressure control set to 10 PSI indicates some operating problem with system, addressed by a service person who's trying to "force" steam into the house rather than debugging a problem, probably with piping or steam valves. Service has been by someone unfamiliar with steam systems.

Absence of any sign that the occupants ever drain and clean the automatic water feeder suggests risk of inoperative key safety device. Needs attention even if you see absolutely no problems. Modified piping? improperly sloped radiators?

A Guide to Hot Air Heating Furnace Inspections

• Furnaces follow a simpler operating sequence than hot water boilers and steam boilers which we discussed above.
• Hot air heating furnaces use different controls than hot water boilers since the furnace distributes heat by warm air. For example, a fan/limit switch is normally used to turn the blower on and off.
• A Working Definition of a hot air furnace can aid explaining the system to clients and owners: A furnace is a steel or cast iron "box" connected to a series of duct work which runs through the house bringing hot air to grilles (registers). A fan, usually at the furnace, circulates air from cold-air return grilles through duct work to the furnace where the air is heated and then returned through "supply ducts" to the living area.
• Operating sequence of a hot air heating furnace: The building or building room cools, as temperature drops the thermostat switch closes (calls for heat), oil burner is turned on, oil is pumped from tank to burner, ignited, burned,
• Hot gases pass through a fire chamber (steel can) and out an exhaust flue, past a barometric damper to a chimney to outdoors.
• ASHI 9.2.C. The inspector shall open readily open-able access panels provided by the manufacturer or installer for routine homeowner maintenance
• Understanding functions=understanding implications: eg: wet basement, steel furnace, high CO risks from rusted heat exchanger.

Heating System Inspection Final Check Thought Process

• Hot heating water movement from house supply into boiler, through circulating equipment.
• Fuel movement from tank through burner up flue and chimney.
• Air movement into house and to burner and up flue and chimney.
• Air movement inside duct work (for furnaces)
• Complete operation sequence reviewed?
• Other building conditions observed which raise questions?
  wet basement, poor housekeeping, poor maintenance, extensive building additions may stretch boiler capacity, ...
• What's missing ?
• Did we leave the system operating normally?

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Technical Reviewers

Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.

• Daniel Friedman - InspectAPedia.com ^TM Website Author/Editor
• Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

More expert information on this topic

More Information on Inspecting and Repairing Heating Systems

• 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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