Range boilerGuide to Range Boiler Water Heaters for Making Domestic Hot Water

  • RANGE BOILERS - CONTENTS: Definition of range boiler & a guide to range boilers & side arm coil water heaters. Pressure relief valves needed on some range boiler tanks. Use of an overflow pipe instead of a relief valve on boilers or range boilers. Attic-located antique steel tank: identification procedure. How to obtain more hot water quantity, pressure, flow, at less cost. Sketches and photographs of range boiler water heaters in building basements and attics
  • POST a QUESTION or READ FAQs about installing, using, & repairing range boilers used for hot water supply in buildings
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Range Boilers for making domestic hot water:

In this article we define range boilers, and we explain the operation of range boilers used for making domestic hot water for washing and bathing. We provide photos and sketches as well as text to help identify the types of tanks found inside old buildings.

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How a Range Boiler Makes Domestic Hot Water from a Heating Boiler

gas range boilerA range boiler is an older type of domestic hot water heater which uses a separate hot water tank which is connected to a heating boiler as well as to domestic hot water piping in the home. Thanks to Carson Dunlop Associates, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.

Below we describe some alternative ways to make hot water, either to replace or to supplement an existing hot water supply system. After knowing what the hot water problem really is, there are steps we can take to get more hot water or to increase hot water pressure.

How does a Range Boiler Work?

Water circulates from inside the range boiler tank through a heat-exchanger coil that may be inside the heating boiler or it may be external, such as a Side Arm Coil. Heat inside of the physically separate heating boiler warms water that circulates, usually by gravity (or convection) between the range boiler and the heating boiler.

Modern indirect-fired water heaters use the same principle as the range boiler but add heat controls and a circulator pump, as we discuss in detail at Indirect-fired Water Heaters.

In our photo at page top you can see the old galvanized steel range boiler in the far corner of the basement. A newer (but still quite old) gas fired water heater has been installed in front of our old range boiler.

See WATER HEATERS for details about conventional direct-heated residential hot water systems.

Plumbing Connections for a Range Boiler

You'll find at least four pipes connected to a range boiler tank, possibly five if the tank uses an overflow line in an attic instead of a pressure relief valve.

Don't do what we did early in our HVAC career: some of those many connections on the range boiler seemed to have no purpose so we eliminated and capped off a pipe that seemed unnecessary. It was a mistake. All four pipes which we describe here are needed:

  1. Cold water into the water tank, coming from the building water supply. Cold water would typically enter at the bottom of the tank.

  2. Hot water leaving the water tank headed for plumbing fixtures. Hot water would leave from the top of the tank.

  3. A gravity line from near the bottom of the range boiler heater which by gravity permits cooler, heavier water in the tank to flow into a loop of heating pipe or into a side-arm coilwhich heats the water. Cold water would flow from tank bottom down to the heating location.

  4. Hotter water rises by convection or "gravity" and flows back to the range boiler water tank.
range boiler coal fired

In their earliest use range boilers were heated by a coal or wood stove as we show at far left.

In a later design range boilers may have included their own little gas or coal heater as we show in the sketch at left.

Later the same design was used in combination with a side arm coil to heat water in the range boiler tank using a coal or oil or gas fired heating boiler.

Range Boiler Operating Characteristics

Range boilers can provide a large volume of hot water, depending on the tank size. But they have a slow recovery rate once the hot water from the range boiler tank has been consumed.

It would be unusual to find a range boiler installed as new equipment in a modern building.

Range boilers are vertical or horizontal hot water systems whose water is heated by circulating the water from within a water storage tank (the range boiler) through a heat exchanger which is inside or connected to the exterior of a heating boiler. The water in the hot water tank range boiler is heated by circulating its water through the heat exchanger which itself is heated by the water inside or from the heating boiler.

The sketch illustrates how a very early type of coal-fired water heater range boiler worked. As homeowners shifted fuels from coal to oil or gas and installed central heating boilers, often the range boiler water heater was adapted to work with these systems as well, as you can see in the photograph.

As with the indirect-fired boiler described next, range boiler water heating tanks are usually located close to the heating boiler and will have both cold and hot water lines leaving the tank to supply the building with domestic hot water and a loop of piping that runs between the bottom of the hot water tank and a nearby heating boiler.

Follow the pipes to see which pipes are performing which function. Our photo shows a silver steel range boiler hiding back in the corner behind the newer (though pretty old) gas fired water heater. (Notice also the efflorescence on the masonry block foundation, where the downspout has been spilling by the house foundation?)

The difference between RANGE BOILER WATER HEATER
INDIRECT WATER HEATERS is in the details. The heat exchanger that heats water in the range boiler is in or at the heating boiler. The water in an indirect fired water heater such as the SuperStorTM unit is heated by a finned copper coil located inside the hot water tank. The internal coil is in turn heated by circulating water inside the coil to and from the heating boiler. The range boiler is an old concept in use for about 100 years. Indirect fired water heaters are a modern system and are in current sales and use.

Because you might also encounter other smaller steel tanks connected to hot water heating boilers and found in building basements or attics see EXPANSION TANKS for a guide to these tanks that absorb pressure increases on hot water heating systems.

CONTACT us with comments about this attic tank.

Range Boiler Safety

Unless the range boiler is vented to an overflow pipe like the attic tank in our discussion below, range boiler tank should be protected by a pressure/temperature relief valve just as any pressurized tank. If none is installed your range boiler does not meet modern safety standards - it is unsafe, and a relief valve should be installed promptly.


The characteristics of various water heaters such as life expectancy, cost, safety, and capacity are discussed

Ways to improve hot water quantity, pressure, and flow are discussed beginning

Attic Range Boiler & Other Attic Water Tanks: Photos, Pipes, Insulation, & Measurements Help Identify a Large, Antique, Insulated Steel Tank Found in an Attic: a Solar Water Heater

Attic tank range boiler (C) D Friedman C Jones

Question: Can You Identify This Old Tank in the Attic of our 1917 Home?

My wife and I purchased our 1917 home in downtown Riverside, California in 1984. In a few more years this house will be 100 years old.

To celebrate its coming birthday, I have started working on a small book about the history of the house.

When we bought the house we were told we were only the third owners, and the women we bought the house from (in her nineties) had her daughter (in her seventies) sell it to us.

The daughter told us her parents lived in the house for over fifty years and that they had not really done much to the house over all those years.

Attic tank range boiler (C) D Friedman C Jones

This is an attic storage tank probably used for a solar water heater system. Details are at SOLAR WATER HEATER ANTIQUE - separate article

These Clues Can Identify the Original Use of Attic Tanks or Other Water Tanks Found in Older Homes

Take a look at and record the following information about an unidentified attic storage tank

How to Identify Heating Boiler Expansion Tanks in Attics

It looks from the partial exposure as if the tank is in a location where people used to put expansion tanks on hot water heating boilers - instead of a relief valve, if pressure in the system got too high, water would push into the tank and if the tank got too full, water would flow out of a drain into an outdoor location, sometimes even a roof gutter or downspout.

But based on its piping connections shown at SOLAR WATER HEATER ANTIQUE - separate article this tank is something else. Usually an expansion tank has just one inlet pipe that feeds water from the hot water heating system, and for attic-located expansion tanks, an overflow drain line


Continue reading at INDIRECT FIRED WATER HEATERS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see ATTIC EXPANSION TANKS, HEATING used with some older hot water heating systems.



Or see WATER HEATERS - home

Suggested citation for this web page

RANGE BOILERS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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