Heating Boiler Diagnosis, Inspection, Repair Guide

How to inspect & repair central hot water heating boilers - hydronic heating
Questions & Answers about heating boilers: inspection, diagnosis, repair, efficiency, tuning & maintenance
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Residential heating boiler inspection, installation, diagnosis, &repairs: we describe how to inspect & troubleshoot all types of residential heating systems and we describe just about every common heating system defect or operating problem. The articles listed on the left side of this heating boiler home page describe the 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 include product safety recall and other heating system hazards. The limitations of visual inspection of heating systems are described.

Hot water or Steam Boiler Heating System Diagnosis & Repair - where to start?

If you have no heat, see HEATING LOSS DIAGNOSIS-BOILERS.. You can also continue your heating furnace diagnostic procedures with the articles at Related Topics headed under BOILER CONTROLS & SWITCHES. If your heating system is fired by an oil burner, you can go directly to those diagnostics at OIL BURNER INSPECTION & REPAIR. Gas burners are discussed at GAS BURNER Flame & Noise Defects.

The article below explains hot water heating boilers (hydronic systems). If your building is heated by steam, see STEAM HEATING SYSTEMS. If you don't know what kind of heat your building uses, we explain how to figure out the answer in more detail at HEATING SYSTEM TYPES.

First, determine what type of heating system is installed

Warm Air Heating Systems - Furnaces: If the heat in your building is provided by warm air that flows out of ceiling, wall, or floor air supply registers into the occupied space, or if your heating system uses a water-to-air heating system then the air which warms the living space is probably being delivered through large or small diameter ducts, registers, air filters, and a furnace blower, and the air is being heated by a gas, oil, or electric furnace, or perhaps by a heat pump or a geothermal system. See FURNACE CONTROLS & SWITCHES.

Hot Water or Steam Heating Systems - Boilers: If the heat in your building is provided by warm or hot metal radiators, heating baseboards containing finned copper tubing, or wall convectors that look like a radiator but contain finned copper tubing, or if heat is provided by flexible rubber, plastic, or metal tubing run in building floors or ceilings, then the warm or hot water circulating in those devices is probably being delivered by piping circulating water heated by a heating boiler, or possibly by a steam boiler or a heat pump or geo-thermal system. See BOILERS, HEATING and RADIANT HEAT Floor Mistakes to Avoid.

What's the difference between a heating boiler and a furnace?

In general, a "heating boiler" heats the building using hot water. A "furnace" heats a building using hot air or "warm air". Don't confuse the two since their means of making and distributing heat, their controls, and their equipment are mostly different. For a detailed guide to inspecting and maintaining warm air heating systems or furnaces, see FURNACES, HEATING.

What's the difference between a hydronic (hot water) boiler and a steam boiler?

A "steam boiler" delivers heat to the occupied space in the form of steam: the boiler literally "boils" water and sends steam rising up through steam riser pipes and through steam radiators in the occupied space. If your heating radiators have valves which hiss and let air escape as heat is coming on your heat is probably being delivered in pipes which circulate steam from the steam boiler up through radiators in the occupied space. For a detailed guide to inspecting and maintaining steam heat systems see STEAM HEATING SYSTEMS.

How is heating boiler efficiency or economy measured? What does boiler AFUE mean?

Each model of heating boiler is assigned an AFUE number. AFUE is an abbreviation for Annual Fuel Utilization Efficiency. In short, the AFUE tells you, for each dollar you spend on energy for heating by gas, oil, or another fuel, just how much of your dollar shows up inside the occupied space of your building as heat.

Details are at AFUE DEFINITION, RATINGS

What is a Hydronic or "hot water" Heating System?

What are we looking at when we're talking about oil-fired hot water heat? It's helpful to form a simple working definition that helps understand the system. An oil-fired forced hot water or "hydronic" heating system is a collection of components which heats a building by heating and then circulating hot water through heat-radiating devices located in the occupied space.

A "heating boiler" is 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 through the system. Safety controls of various types are installed at various points protect against a number of potential hazards.

How does a Heating Boiler Work?

We discuss how heating boilers work in step-by-step detail at BOILER OPERATION DETAILS

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.

Below we give the basics of heating system inspection using the physical location "map" of components to assure completeness. See full details of heating system inspection procedures provided at HEATING SYSTEM INSPECT DIAGNOSE REPAIR

Heating components: Identify the heating system components in each building area.
Heating fuel & fuel delivery: 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).
Heat distribution: 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.
Heating controls: 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.

Continue with Hydronic Heating Diagnosis & Repair

If you have no heat, see HEATING LOSS DIAGNOSIS-BOILERS

You can also continue your heating boiler diagnostic procedures with the articles at Related Topics headed under BOILER CONTROLS & SWITCHES.

If your heating system is fired by an oil burner, you can go directly to those diagnostics at OIL BURNER INSPECTION & REPAIR.

Gas burners are discussed at GAS BURNER Flame & Noise Defects.

Frequently Asked Questions (FAQs) about hot water heating system inspection, installation, troubleshooting, repairs

Question: does my Burnham residential boiler require annual service?

Does my Burnham residential boiler need annual service. It worked fine last season. - Dick 9/19/11

Reply: yes

Yes, Dick, there is no Santa Claus; your heating boiler needs annual service not only to assure safe, reliable operation, but because without an annual cleaning, particularly for oil fired heating boilers, my experience is that the cost of operating the equipment will be significantly greater - the improvement in operating efficiency of an oil fired heating boiler following annual cleaning and adjustment can be significant - I've seen a 33% reduction in operating cost following cleaning and adjusting a dirty oil fired boiler or furnace.

Question: Boiler trips circuit breaker - intermittent failure of boiler to turn on

I have a 3 year old Peerless WV-DV boiler, 1 zone (thermostat), 2 circulator pumps, no valves, serviced annually. This year when turning thermostat up the boiler refused to come on. The 20 amp circuit breaker had tripped. It wouldn't reset, kept tripping immediately. I turned the power switch off at the boiler, reset the breaker, turned the power back on at boiler, turned thermostat up and boiler came on normally. I then, over the course of an hour, turned thermostat up and down, each time boiler shut off and came back on normally. Then is got warm here for a few days, didn't use. When it got cold again, same problem, I had to turn off power at boiler, reset breaker, turn power back on at boiler, then boiler works. I also replaced the breaker in case that was a problem. So what is the issue here? Any help would be appreciated. - Scott Moberg 10/14/11

Reply:

Scott:

It sounds as if there is either a wiring short circuit or an electric motor (perhaps on the burner) that was seized. A seized motor can draw high amps and trip the breaker. You can sometimes get the motor running again by repeated attempts or by adding an electric motor hard start capacitor, but on an oil burner I'd expect it's time to replace the motor.

Question: hot water recirculating loop is not maintaining temperature

having a problem with a hot water recirculating loop from boiler to storage tank with tempering valve to building. not able to maintain proper temp. any ideas? - Vivek 10.26/11

Reply:

Vivek,

If the hot water recirculating loop (I am guessing you mean domestic hot water for washing and bathing, not a building heating system) is not maintaining the required temperature I'd check in this order:

- is this a change in behavior or has it always been this way. If it's a new condition I'd look for a change in hot water use or a failure of a tempering valve (or someone messed with the valve) or a change in the water heater temperature settings

- if the problem has always been there, to the above I'd add a check for missing insulation on the water piping

Question: how do I figure out the age of my heating boiler or furnace?

Would like to know the age of a National U.S. Radiator boiler, Boiler # 109-5. It is a five section boiler, with Crane forged into the sections. Only can see the two end section numbers, F10900201 and F10900301. Just curious, thanks for any help. - Gary Forbes 11/5/11

Reply:

Gary, see AGE of HEATERS, BOILERS, FURNACES (article links listed at Related Topics ) for tables, charts, and links to books that give means to decode the age of heating and cooling equipment using the model and serial number.

Question: no heat on upper floor, no air bleeder valves

its just the upper floor and i don't have bleeder valves at the base board the expansion tank at the boiler is hard to tell how full it is - Luke 11/10/11

Reply:

Luke, at AIRBOUND HEAT SYSTEM REPAIRS we describe a variety of ways to get air out of an air-bound hot water heating system.

Question: books on troubleshooting residential heating boilers

are there any books on troubleshooting residential boilers & how to wire them - Kevin 1/12/12

Reply:

Kevin, at References, related articles we list a variety of books on heating system installation & troubleshooting; when I was servicing heating systems, in addition to attending trade school for absolutely-required practical knowledge and theory, I found too that quite a few manufacturers gave away free booklets and pamphlets with excellent detail about their equipment. And don't forget to check the installation and service manual for the specific equipment you are examining.

Question: How do you add antifreeze to a boiler? What kind of antifreeze do we use in a boiler? How much do you add?

How do you add anti freeze to you boiler and what kind do you use? - Don Rose 9/26/2012

Reply:

Don, some help on winterizing a boiler as well as a whole building is at Winterize- Heat Off Procedure.

The basic procedure is to use a pony pump (a transfer pump - see PUMPS, PONY PUMPS) to add antifreeze (buy at your local heating supplier) to the water mix in the boiler until our test gauge shows that we've got enough antifreeze in the system to protect down to at least a bit below the lowest expected temperature.

The service tech uses a pony pump connected to a boiler drain or zone drain valve, typically using a pair of washing machine hoses to form a loop between a boiler drain, a bucked of antifreeze & water mix, and a zone drain.

The pump pushes antifreeze into the system from the bucket; keeping the drain end of the second hose below the level of antifreeze in the bucket avoids introducing air into the system and thus avoids having to bleed that air out.

Complete details about how to add anti-freeze to a hot water heating boiler and system are found at ANTIFREEZE for BOILERS where we explain what kind of anti-freeze to use, how much to add, how to get it into the system, and what are the effects of antifreeze on heat transfer and heating system operation and costs.

Question: How to diagnose gurgling sound coming from boiler and radiant heat tubing

I have radiated heat at night tub gurgles and boiler makes noise - Jeff 10/8/12

Reply:

Jeff, gurgling in hot water heating lines is often due to air in the piping. Check for a leak and for an air purging device that is not working.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
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  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
  Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
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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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.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

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Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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Hot water or Steam Boiler Heating System Diagnosis & Repair - where to start?

First, determine what type of heating system is installed

What's the difference between a heating boiler and a furnace?

What's the difference between a hydronic (hot water) boiler and a steam boiler?

How is heating boiler efficiency or economy measured? What does boiler AFUE mean?

What is a Hydronic or "hot water" Heating System?

How does a Heating Boiler Work?

How to Inspect a Heating System using Physical Location of Components

Continue with Hydronic Heating Diagnosis & Repair

Frequently Asked Questions (FAQs) about hot water heating system inspection, installation, troubleshooting, repairs

Question: does my Burnham residential boiler require annual service?

Reply: yes

Question: Boiler trips circuit breaker - intermittent failure of boiler to turn on

Reply:

Question: hot water recirculating loop is not maintaining temperature

Reply:

Question: how do I figure out the age of my heating boiler or furnace?

Reply:

Question: no heat on upper floor, no air bleeder valves

Reply:

Question: books on troubleshooting residential heating boilers

Reply:

Question: How do you add antifreeze to a boiler? What kind of antifreeze do we use in a boiler? How much do you add?

Reply:

Question: How to diagnose gurgling sound coming from boiler and radiant heat tubing

Reply:

Ask a Question or Search InspectApedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Heating Boiler Diagnosis, Inspection, Repair Guide