LARGER VIEW of an octopus furnaceHeating System Inspection, Troubleshooting, Repair Guide
Step by Step Heating System Inspection & Service Procedure Guide

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

How to inspect, service, & repair heating systems:

This heating system diagnosis and repair website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning 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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

How to Inspect Heating Systems - Example of An Approach to the Forensic Inspection of Any Complex System

Photograph of a badly rusted furnace

We include product safety recall and other heating system hazards. The limitations of visual inspection of heating systems are described. We continue to add to and update this text as new details are provided. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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.

The photograph shows a severely rusted tankless coil mounted on a steel heating boiler. If the coil-mounting surface on the boiler itself is severely rusted it may be necessary to replace the entire heating boiler. While a welder could weld on a new mounting surface for a new coil, none of the repairmen are likely to warrant such a "fix" and further, the welder, knowing that the owner is facing the cost of a whole new boiler, is likely to set a high fee for even attempting the repair.

It is important to recognize and report the significance of rust like this on a heating boiler. At this website we describe organized procedures for inspecting complex systems for defects, using the organized step by step method to assure inspection heating system inspection completeness and accuracy but without losing the ability to discover unexpected problems as well.

© 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 CONCEPTS - How to Select an Inspection Methodology for Heating System Inspection & Diagnosis

Step 1: Select a Heating System Inspection Road Map to Guide the Inspection Sequence

In order to be as thorough, accurate, and safe as possible, a heating system inspector should use a well-defined order of discovery which assures that s/he examines all important heating system components. Several possible heating system inspection "road maps" can be used for this purpose. Two approaches inspect the heating equipment by physical layout of components, or by inspecting the heating system in the detailed order that it will operate during the heating system operating cycle.

Of these "heating system inspection road maps", the first of these inspection methods is physically convenient, that is: inspect each heating system component where each is located in each building area, and this is the most common approach in use in the field. But but it is the second option, heating boiler or furnace operating sequence, that best assures that the inspector considers proper system operation and that s/he identifies all of the system components.

Thinking thorough the sequence of steps in operation of a home heating system requires that the inspector understand how heating systems work. An inspector who cannot follow this sequence does not understand heating system operation and is rather likely to miss important system defects.

So how should a heating system be inspected? For efficiency the inspector may decide to examine each system component as s/he enters the area of the building where that component resides. So all heater components in the basement or crawl space are examined in one pass while the inspector is in that area, and so on.

But in thinking about the completeness and accuracy of the heating system check the inspector should also think through the system's operating sequence, using the components identified in that sequence to assure that s/he has not omitted something important.

Why is this second thought pattern needed? Because it is always easier to inspect and think about a building component that we see than to think about a component that is simply absent. In other words, if there is no temperature or pressure relief valve to see On a boiler, the inspector may fail to think about whether or not this is a serious safety hazard for the particular installation.

How to Inspect a Heating System using Physical Location of Components

This approach broadens the scope of the heating system inspection and it may aid in heating system defect recognition or problem diagnosis, for example by observing that a heating boiler is located in a small, air-tight room (possible combustion air problems), or that the furnace is quite close to the oil storage tank.

How to Inspect a Heating System Using the Sequence of Heating System Operation

This approach to heating system inspection Identifies most components of heating systems or of other mechanical systems and is most likely to give the most complete list system parts. It helps assure that all critical components are considered. Actual observation of heating system operation is important in enabling the inspector to identify malfunctions. The heating boiler or furnace inspector's field procedure should include this aid.

A detailed example of the steps in the sequence of operation of a heating system along with a detailed list of heating system components is provided below at Sample Inspection Procedure for Heating Equipment.

The Importance of Reporting to the Client the Significance of Heating System Defects

A superficial heating system inspection may simply identify the type of system present and perhaps the presence of obvious visual anomalies such as leaks. But an astute inspector understands more thoroughly the implications for safety or function of the defects that s/he observes and thus is more likely to inspect the heating system more thoroughly and is more likely to report the inspection findings in a meaningful way to the client.

It is essential that a heating system inspector clearly communicate to the client the significance of the inspection results. In other words, the client should be given to understand the need for action, or urgent action, the presence of unsafe conditions, or the indications that costly repairs or replacement are likely to be needed immediately or in the coming year or before next heating season.

The Importance of Thinking about the Possible Significance of Home Inspection Observations

Here are two examples of the difference between simply reporting a home inspection observation neutrally and thinking about the significance of a home inspection observation in a way that might lead to discovery of something important about a heating system.

Example Outdoor Inspection Observation: drip lines below roof eaves

Observation: The heating system inspector, before entering the home, observes outside that there are deep drip lines in the soil below the home's roof eaves. Drip lines indicate that there has been long term poor control of roof runoff.

Interpretation: there may have been a history of wet basement conditions.

Implications: especially if the home is heated by a furnace located in the basement or crawl space, watch out for signs of rusting of the furnace heat exchanger, particularly in steel hot-air furnaces. A rusted and thus leaky furnace heat exchanger is a possibly dangerous condition, risking high Carbon Monoxide CO levels in the building - a condition that can lead to a fatality - someone could die.

Action: look inside for corroborating clues first of water entry and second of rust on the furnace or its components. Test or recommend testing of heat exchanger for leaks and safety.

An Example of Neutral (irresponsible) home inspection reporting of heating system condition

Photograph of a badly rusted furnace

Outside we observed roof overflow or drip lines below the house eaves.

Photograph of a badly rusted furnace

Inside, A BrandX natural-gas fired 90,000 BTUH steel hot air furnace heating system is installed.

The system appears to be 20 years old. In response to turning up the heat we observed that the system operated normally: heat came out of the air supply registers. (Our inspection excludes heating system disassembly and therefore cannot examine the condition of the furnace interior components. You should have the system inspected by a qualified technician.)

What's wrong with this heating system inspection report is that it does not explain that drip lines under gutters mean that there has been a history of gutter overflow, poor maintenance, and a risk of water entry in the building. Worse, the report make clear that there are special reasons to be concerned about the reliability and safety of this heating system and there is no clue that costly replacement could be needed.

An Example of More-responsible home inspection reporting of heating system condition

Outside we observed roof overflow or drip lines below the house eaves. This means that water has been spilling by the house foundation for a long time, that roof gutters and downspouts are needed, and that the home may have been exposed to a history of water entry or leaks which in turn could cause problems indoors.

Inside, A BrandX natural-gas fired 90,000 BTUH steel hot air furnace heating system is installed. In response to turning up the heat we observed that the system operated normally: heat came out of the air supply registers. (Our inspection excludes heating system disassembly and therefore cannot examine the condition of the furnace interior components. The system appears to be 20 years old and based on age alone is likely to be at or near the end of its useful life - significant expense will be involved when furnace replacement is needed.

In response to turning up the heat we observed that the system operated normally: heat came out of the air supply registers. Our inspection excludes heating system disassembly and therefore cannot fully examine the condition of the furnace interior components.

However, we observed heavy rust on the bottom of the furnace and other evidence of a history of water entry in the basement. A furnace exposed to these conditions is at extra risk of hidden rust damage such which could include a leaky heat exchanger. If the heat exchanger is leaking this heating system would be unsafe, should not be used, and would almost certainly require immediate replacement - a significant expense.

We recommend that before completing purchase of the home, and certainly before using the system in the coming heating system, you should have the furnace inspected and tested by a qualified technician, and you should specifically ask the technician to make a thorough inspection and test of the furnace heat exchanger for leaks and safety.

For effective examination of any complex structure, the professional uses all of these tools

Addressing the question of completeness of coverage of components, for a thought-guide to inspecting heating equipment we selected Sequence of Operation as a model. (See BOILER OPERATION DETAILS for step by step boiler operation sequence details.

It is the possible significance of a home inspection observation that leads a good inspector to examine the property further for confirmation or refutation of the presence of a possibly serious building defect.

We discuss this concept of thinking carefully about and pursuing possible implications of home inspection observations as a way to assure that an inspection is thorough and as a means to minimize the chances of missing an important condition at a property, in these articles:

Heating System Inspection Procedure Articles

also see


Continue reading at HEATING INSPECTION CONCEPTS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.




Suggested citation for this web page

HEATING SYSTEM INSPECTION at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher - Daniel Friedman