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.

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

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.

• Identify the heating system components in each building area.
• At the heating boiler or furnace, identify the fuel source and follow fuel supply piping to its source (an oil tank, LP gas tank, or gas meter, for example).
• At the boiler or furnace, identify the heat distribution method and follow the delivery of heat (warm air or hot water) leaving the furnace or boiler, and returning to it. Failure to consider this whole path logically risks failing to notice potential problems such as return air taken at a furnace itself or the absence of adequate return air.
• At the boiler or furnace identify each of the controls and safety devices and observe their condition. Those devices that are intended for normal operation by the home owner are usually also operated and tested by the inspector. Other devices such as temperature/pressure relief valves are not normally operated but are visually inspected for evidence of a problem.

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

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

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:

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-04-06 - by (mod) - converted gas furnace not working properly

Ken

I agree that your converted-gas furnace does not sound as if it is working proprerly, but I can't say if the issue is a clogged orifice or wrong jets or wrong air shutters or wrong regulator conversion or a gas leak. Any of those is

unsafe.

Safest is to turn off the system and call for help from a trained service tech or at the very least, check with the manufacturer of your gas furnace brand and model to review the gas conversion kit you used to be dead sure that you have all of the right parts installed properly.

Watch out: making a mistake risks fire, explosion, injury, or death. Sorry but it's true. That's at least part of why the manufacturers' instructions typically state "must be installed by a licensed / trained service technician"

On 2020-04-06 by ken

my resent converted gas to lp furnace ,burner flame is inside burner tube at startup for from 10 to 30 seconds

On 2017-11-02 - by (mod) - open heating system expansion tanks

John I don't know what your tank is doing, for sure. But from our conversation I think you probably have an open heating system

That means that the system is never under high pressure. Instead an expansion tank, open to atmospheric pressure, is located in the building attic, above the highest heating radiator.

Here is a photo of one such tank that I photographed in a home in the U.S. in New England. https://inspectapedia.com/water/JSM-465-20Sep06dfs.jpg

In most heating discussions and sources a header tank is in essence an expansion tank (to accomodate expansion when the boiler and heating system are operating and hot). Unlike a simple closed-system "expansion tank", a header tank is also used to fill the heating boiler - that's what that ball valve is for.

Opening the ball valve, in a conventional header tank plumbing set-up, will feed water through the header/expansion tank and into the boiler. You should not normally have to add water to a hot water heating boiler but might need to do so after servicing.

You will see these pipes connected to a header tank:

a cold water inlet supply through a ball valve

tank overflow pipe discharging to a suitable drain or possibly to outdoors - this feature means the tank is never under compression nor high pressure, it remains at atmospheric pressure, unlike a more-common closed expansion tank design

We might find a header tank in the loft of an older building where there will also be a cold water storage tank. Header tanks are more-common in the U.K. than in the U.S. or Canada, leading me to ask if your system is located in the U.K.

Header tanks are discussed at ATTIC EXPANSION TANKS, HEATING

I would like to see photos of the header tank, its location relative to the boiler, piping, valves, and also of the boiler and its tags showing the boiler brand and model - then I could offer more. Use the page top or bottom CONTACT link to send images if you can.

Harwood Associates in the UK has a brief web article on header tanks

https://www.harwoodandassociates.co.uk/faqs/terminology/header-tank/

where that company notes two warnings:

1. Watch out for modifications to the original piping layout - someone who doesn't understand the operation may have changed pipes incorrectly

2. Harwood adds that on some hot water heating boiler systems using a header tank the cold feed and vent pipes may be combined as one or even just have a cold feed pipe. This only acceptable if the boiler manufacturer says so in their literature.

On 2017-11-02 by JOHN VARE

I may have made a mess of my responses so, just to make sure, I have assumed it's not just an expansion tank because it has a ball valve. My plumber had said a while back that the ball valve may not be working properly and that I should ensure there was water in the header before I bled the rads. That seems to have triggered the problem and I don't know what to do next.

Sorry - put the wrong name in the box before.I

On 2017-11-02 by John

Thank you for your response. I'm not sure that the header tank is solely for expansion, because there is a ball valve fitted.

My plumber in the past advised me as follows: to bleed the radiators, ensure the system is down (ie not heating) and then bleed all the radiators starting from the furthest one from the boiler. But first ensure that there is water in the header tank or air will get in.

That's why I put the water in and this seems to have triggered the problem. By the way, this morning I don't have hot water either! Not going to have a good day!

On 2017-11-01 - by (mod) -

John

I'm not clear on exactly what kind of heating system we are discussing. Tell me more about header tank. If you are describing what I consider an expansion tank, You would not be adding water to it. In fact if the tank or waterlogged you might indeed find the system Spilling at the relief valve or failing to operate correctly.

One hot water heating radiator was cold While others were hot suggest an air blockage or possibly a rusted debris blockage at that radiator. If that's the case I'm not sure that trying to bleed air at that radiator would fix the problem. Particularly if the radiator is blocked with debris.

On 2017-11-01 by JOHN VARE

One radiator out of 4 remained cold but warm at the bottom. Assuming airlock I bled all the radiators. I first checked that the header tank had water in it as I suspected the ball valve was faulty.

I dipped with an absorbent stick and it seemed dry so I poured some water into the tank. After bleeding I turned the system on and demanded heat at the thermostat and the clock as usual.

After a few minutes, all radiators were now cold. Suddenly there was pronounced turbulence in the header tank with steam rising.

After looking at a schematic of a typical installation I concluded that all the boiler heat was affecting the water in the header tank and not feeding the circulation system.

Could this be right and ,if so, would that be because the pump was not driving the hot water through the system. Is this likely and could it be producing the behaviour I saw? (I immediately turned the system off at the programmer to be on the safe side)

On 2015-12-21 - by (mod) -

Rerun

Search InspectAPedia for MEASURE DRAFT and you'll find details at https://inspectapedia.com/heat/Chimney_Draft_Measurement.php

On 2015-12-20 by rerun

Can't seem to find out info how to setuo & read BACHARACH MZF draft meter . I'm looking for neg. draft, should the needle swing to the left or right of zero?

(Apr 4, 2015) vicky m. said: thank you - this was a GREAT help

Question: how can I learn to service and repair my own heating system? What is included in annual heating system service?

I think I have finally reached the last straw with my home heating oil/service company—I intend to purchase oil without any contract with them and in fact will call shortly to ask them to refund the $200 we paid for a service but have not yet received.

With regard to servicing the furnace, can you tell me what should be included in a proper annual service and the best way to identify people in my area who can do this? My background is marine engineering and I started my career working on tankers with boilers 100 times the size of a home heating furnace.

I am not against paying someone for a good service at a fair price, but would not rule out doing it myself if I could learn the subtleties of the home heating furnace.

We installed a propane fireplace as part of a kitchen renovation that provides significant supplemental heat and I am leaning towards putting in a wood burning insert into our fireplace since I have adequate wood supply access

Your thoughts on any and all of this are more than welcome Thanks - S.N.

Reply: List of typical steps in oil fired heating system service or maintenance, recommendations for DIY home heating service

Stephen,

I appreciate the frustration that can arise when you have trouble obtaining good service from your oil heating service company.

Even a qualified and well-intended heating service technician is faced with over-work and over-scheduling during the heating season.

Being given a large number of service calls to perform during a single 8-hour shift can lead the tech to skip some service steps that s/he thinks can be passed over even though system performance and economy may have been better if they were performed. I've even seen techs who skipped system cleaning entirely, just changing out the nozzle and oil filter and "calling it it a day".

Watch out: cleaning and servicing oil fired heating equipment is a dirty messy business, and it takes some time. If your "annual heating service call" takes just fifteen minutes, or if the service tech looks as clean at the end of the job as s/he did when they knocked on your door, I would suspect that the heating system was not adequately cleaned.

If my service tech was not planning to take down the flue, open and clean the boiler or furnace, then if necessary I would offer to pay extra to have those steps performed.

You'll more than earn back the service call cost in heating system reliability and economy over the heating season.

Also see HEATING COST SAVINGS METHODS

And I've run into the "bad heating service" problem myself when an oil company sent out a heating service tech whose inexperience and bad attitude were matched only by his sloppy rushed job and the heating system operating problems he left behind.

But a polite call to the oil company's service manager was able to solve our problem - an experienced, well qualified, and polite service technician was dispatched to our building and we were happy with the result.

How to Learn to Service & Repair Your Own Heating System

Nevertheless, especially with your technical background, if you want to service your own heating system you can certainly learn to do so. But considering that there are both cost and life-safety issues involved, you'll want to

1. Take a heating service course 
   
   from your local continuing education facility or trade school in your area. Figure three to six months of one or two evening classes a week to obtain a rudimentary understanding of heating system operating and basic annual maintenance.
   
   The course should include an understanding of how the heating systems work, their safety and operating controls, basic wiring, annual service procedures, and common problems and solutions
   
   (BOILER OPERATING PROBLEMS).
2. Purchase the necessary heating system test equipment.
   
    Old timers who serviced oil fired heating equipment would eyeball the smoke level in the combustion chamber, blow a puff of cigar smoke at the oil burner to assess the draft, and they would then spit on the flue vent connector (stackpipe) to test system operating temperature. If the spit immediately puffs away the stack temperature is too high (over 450 degrees F);
   
   if the spit drools down the flue pipe the stack temperature is too low (under 300 degrees F), and if it sits in place and sizzles the stack temperature was about right - say 400 to 450 degrees F.
   
   But as cigar smoking and spitting during service calls became an issue with some homeowners, and as oil fired heating equipment has become more energy efficient it also has become more sophisticated and it requires more precise adjustment than smoking and spitting.
   
   We can no longer adequately tune oil burners or gas burners "by eye" alone. You'll need a test kit such as the combustion test kit made by Bachrach [1] that can measure draft, stack temperature, smoke level and CO2 or CO levels. You will probably also want a nozzle wrench, some cleaning brushes, a HEPA vacuum cleaner you can dedicate to sucking up oil burner or gas burner soot and debris, and you probably already have the other basic tools (screwdrivers, wrenches, VOM) you'll need.

Watch out: what is missing from even the dedicated smart DIY approach to heating service is experience, as well as having the back-up of a still more experienced expert back at the heating service company who remains on call to the on-site service techs. A service tech with experience has come across a variety of heating system operating defects. S/he can often recognize and fix a problem quickly while a beginner, fresh out of oil burner service school, will have a more difficult time figuring out what to do when something has gone wrong.

Typical annual service of oil fired heating equipment includes

1. a visual inspection of the system and its safety controls for leaks, burn marks, soot, corrosion, other signs of trouble
2. disassembly and removal of the flue vent connector
3. removal of part of the boiler cover
4. cleaning by brush and vacuum to remove soot from the flue vent connector and if needed, the chimney
5. cleaning by brush and vacuum to remove soot and debris from the boiler heat exchanger and if needed the combustion chamber
6. cleaning of the oil burner nozzle assembly
7. replacement of the oil burner nozzle
8. replacement of the oil filter screen inside the fuel unit (this step is too often skipped by some service techs)
9. replacement of the oil filter cartridge in the oil filter canister
10. reassembly of the burner assembly, check/set electrode gap
11. check/set combustion air
12. check/set draft at the air inlet shutter and barometric damper, confirm adequate combustion air supply for the system
13. confirm operation of the safety controls and cad cell switch
14. return system to operation and run to observe proper operation, flame, noise, soot, etc.
15. measure CO2 and smoke and stack temperatures (before and after service) and adjust the system draft if needed
16. inspect for oil or air leaks
17. clean up the mess you've made

In sum, even though I am trained and experienced in heating and air conditioning system installation, service, and repair, and although I research and write about a wide variety of HVAC system inspection, diagnosis, and repair procedures, I prefer to have our home oil fired heating boiler serviced and repaired by an experienced heating service technician whose experience is more extensive than mine, and who has the backup of senior service experts in his home office. In fact I gave away my Bachrach Fyrite® combustion test kit a few years ago.

Followup comment

You make an excellent case for having an experienced technician perform the service—now that I have severed, at least temporarily, my relationship with the heating oil/service company I need to find the right person to do the job—the fee I actually paid was $317 for the service that I had not yet received—does this sound like the going rate?—your list of tasks certainly will help me discuss the scope of the service with them—do you have a recommendation on how to locate an experienced  tech not with the heating oil company? - S.N.

Reply:

Good point - when I was in the HVAC service business, we were an independent heating and A/C service company - we didn't sell heating oil - and as a result our clients believed (reasonably IMHO) that we were selling and delivering a genuine effort to clean tune and adjust the system to peak operating efficiency and reliability.

Now many if not most HVAC service people take pride in their work and they are going to do their best to properly clean, tune, and adjust your heating system even though their home company is in the business of selling heating oil.

But if you prefer, you might be able to find an independent heating service company in your area. If not, you may want to develop a better relationship with a large company that has a big enough service staff that they actually conduct training for their people and employ one or more senior experts in the home office as service manager or consultant for the men and women in the field.

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Continue reading at HEATING INSPECTION CONCEPTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• HEATING SYSTEM INSPECTION - home
• HEATING INSPECTION CONCEPTS - home
• HEATING INSPECTION PROCEDURE-GENERAL
• HEATING SYSTEM INSPECTION DETAILS
• INDOOR INSPECTION of HEATING SYSTEM
• HEATING BOILER INSPECTION GUIDE
• HEATING FURNACE INSPECTION GUIDE
• FINAL BOILER/FURNACE ROOM INSPECTION CHECKS
• GAS BURNER FLAME & NOISE DEFECTS
• GAS BURNER SOOT CAUSE & CURE
• GAS BURNER PILOT LIGHT PROCEDURE
• OIL BURNER INSPECTION & REPAIR
• HEATING SYSTEM SAFETY INSPECTION
• SAFETY RECALLS CHIMNEYS VENTS HEATERS

also see

• Can X-Ray Vision Warn of Sink Holes? in Florida or elsewhere
• Developing your X-Ray Vision - 6th Ed. The Science of Building Inspections - advanced home inspection techniques including "The Limits of Vision," "Inattentional Blindness," "Invasive Inspection Methods," "Missed Defects," & "Contextual Inspection," "Termite Inspections," "Moisture & Building Water Entry," © Daniel Friedman 2006-1987
• Developing your X-Ray Vision - 5th Ed.- ppt slides Presentation slides © 2005 Daniel Friedman
• The Nature of Vision, Inspecting Complex Systems,why inspectors don't see certain defects and miss important omissions

Suggested citation for this web page

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

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING SYSTEMS

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