Photograph of  a modern oil-fired heating boiler Heating Boiler Guide
Inspect, Install, Troubleshoot & Fix problems hot water boilers

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Residential heating boiler inspection, installation, diagnosis, &repairs:

This article series explains how to inspect & troubleshoot all types of residential heating systems and we describe just about every common heating system defect or operating problem.

On this page we provide an ARTICLE INDEX to RELATED ARTICLES that includes a live link to - articles describing all of 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.

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.

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

Oil fired hot water heating boiler (C) Daniel FriedmanArticle Series Contents

First, determine what type of heating system is installed

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 geothermal system.

See BOILERS, HEATING - this article (continue below)


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.


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,


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


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.


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


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


Is Heating by Hot Water Boiler a Good Approach?

The choice of heating system type involves choices of heat distribution (such as by hot water or steam (boilers), or by air (furnaces), or by using electric heat), or by more hybrid methods such as hot water or electric radiant heat in floors or ceilings, or other approaches. There is no single "right answer" or "best" approach since we need to match the type of heat distribution, heat production, heat fuel to climate, construction, site conditions, fuel availability and other factors.

Reader question: 4/16/14 Diane Logsdon (no email) - are we crazy to consider buying a house that uses hot water boiler heat?

COMMENT: I just looked at a home to buy that has hot water boiler heat. Don't know age but owners say they have always had it maintained since he is a plumber. Are we crazy to consider a house with this type of heating system. How energy efficient are they?


Diane I must be totally confused. Why would using a hot water heating system be less efficient than forced warm air? The heat loss rate of the house in which you are interested is the first determinant of heating cost. Look at the home's insulation, age, quality of construction, and for signs of air leakage such as thermal tracking.

Perhaps you meant to ask something else and I just don't get it.

Efficiency of Different Heating Methods

The efficiency of hot water heating systems (boilers, or hydronic heat) varies depending on the age and type of equipment, the fuel source (oil or gas for example), and very importantly, the state of tune of the system. An old clunky slow-speed oil fired hot water boiler that has not been cleaned or tuned-up might chug along reliably at 65 % efficiency.

I could clean and tune the system and get it up to perhaps 75% efficiency - meaning that if we ignore the very important heating efficiency factors of house insulation, heat loss, drafts, how heat is distributed, and if we just look at the boiler itself, 25 cents on the dollar is going up the chimney.

A new high-efficiency oil fired heater might run at the high 80's of efficiency or close to 90%, sending ten cents up the chimney for every dollar spent on fuel.

Those exact same efficiency ranges can be found in forced warm air heating systems (furnaces) and depending on how heat is made, on radiant heat systems.

Electricity is one of the most efficient heat producers once it's at the home, but once we factor in differences in fuel costs, in many areas of the world electricity is one of the more expensive ways to heat a home.

Efficiency and costs of different heating fuel sources are compared


Reader follow-up: people around here say "stay away from a house with a heating boiler"

It is just the idea that it is a boiler. When I tell people this they say stay away from it! I don't think there are many left in our Bloomington-Normal area. I have a friend who had one at her house and she said it was wonderful even heat but everyone who came to the house said that would have to be replaced right away.

She finally sold her house but it was tough. I'm thinking that if we wanted to resale the house later on it could be a problem. It is the age of the house which has been very well maintained over 60 years by one couple and he was a plumber. Thanks for your answer and I think the house is well insulated and of quality construction. I am not sure what air leakage such as thermal tracking means. Diane

Reply: millions of homes heated by hot water (hydronic) heating systems

Gee Diane, there are literally millions of homes heated by hot water.

Sometimes when a type of heating system falls into disuse in an area it is because the contractors who knew how to install and service it have retired or died. Indeed for a given community or area of use it can make sense to prefer buying a product (house or car) that many people in that area know how to fix

. In the U.S. in the 1970's it was very easy to find someone who knew how to fix a VW Beetle and very tough to find a mechanic who knew how to repair the triple-throat-Solex carburetors on a Porsche. But for the area you are discussing, I fear you may be hearing from people with strong opinions that, at least in your comments, they have not backed up with information.

Thermal tracking means stains that can tell us something about building heat loss. You can help me out in managing InspectAPedia by telling me why you didn't try our page top or page bottom search function to search for that term to read about it.

Take a look


Should I buy this house?

Finally, having inspected thousands of homes, I've found very few that were in such bad shape that one would think buying the home is a mistake. Once you choose a house because you like the neighborhood and like the house and the price seems reasonable, most repairs, even a new heating system, make up a rather small percentage of the value of the property so in my OPINION are not reasons to refuse to go ahead with the purchase.

The purpose of a home inspection is not to kill the deal nor to tell you to buy or not buy the house, but rather to tell you what to expect to need to repair and in what priority order - to protect against expensive surprises or dangerous conditions.

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

Antifreeze installationinto a heating boilerHow do you add anti freeze to you boiler and what kind do you use? - Don Rose 9/26/2012


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.


Continue reading at BOILER CONTROLS & SWITCHES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BOILER REPAIR DIAGNOSTIC FAQs - questions and answers posted originally on this page.

See HEATING SYSTEM TYPES if you don't know whether your heat is provided by a furnace (hot air) or boiler (hot water), or steam boiler (steam heat) or whether your fuel is oil, gas, or electric, and whether your heat is hot water, steam, or warm air

Or see this

Article Series Contents

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