procedures. Check the simplest and more obvious
items before progressing to the other checks.
With warm-air systems, the amount of heat
reaching each room is determined by what two
What are the four airflow designs of gas-fired
What safety device on gas-fired heating
equipment reacts to the operation of the pilot
What device shuts off the gas supply when the
temperature inside the heating unit becomes
What are the three internal areas of an oil-fired
What device is the nerve center of the heating
What are the two most commonly used types of
A steam-atomizing burner requires a steam
pressure of what range for atomizing?
Electrode adjustments should always be set on
burners according to what publication?
What instrument is used to determine the percent
of CO2 produced by combustion?
DOMESTIC HOT-WATER HEATING
AND HOT-WATER BOILERS
Learning Objective: Identify types of hot-water
boilers, their fittings and accessories, and their
The Navy uses both cast-iron and steel hot-water
boilers as sources of heat for domestic hot-water
systems in residences and other buildings. Small
hot-water heaters heat the hot water for domestic and
for limited industrial uses.
Hot-water boilers come in many shapes and sizes.
They are constructed with a firebox for burning fuel
and have provisions for passing the hot gases over the
heat-absorbing surfaces of the boiler. In most cases,
baffles guide the gases over the most effective route.
These baffles also retard the flow of the gases from the
furnace, so water can absorb as much of the heat as
possible. Both ends of the boiler have openings for
cleaning the boiler tubes and for washing the interior of
the boiler. Since most boilers are stationary units
permanently installed at the site, they have specified
fittings and accessories for a specific heating job.
Some boilers, however, called package boilers, are
complete units, including fittings and accessories.
These boilers are normally mounted on skids so they
can be moved to different sites.
This accounts for the term package boiler.
Package boilers usually have the same accessories and
controls as the comparable stationary type of hot-water
or steam boiler. Cast-iron boilers are seldom used as
package boilers because of the danger of cracking the
boiler sections during transportation.
Cast-iron hot-water boilers vary in size from small
domestic units to moderately sized units capable of
developing 31 through 98 horsepower. These boilers are
usually constructed of several sections joined together
by push nipples (round pieces of metal pipe tapered at
both ends). Pipes, known as header connections (fig.
4-58) ordinarily connect the boiler sections.
Cast-iron boilers normally do not have brick
settings. Usually, the only bricks used with these
boilers are those that are sometimes used as a base for
the boilers. In most cases, the bases are made of cast
iron. Square sectional cast-iron boilers are similar to
the typical unit shown in figure 4-59. This boiler
consists of a front and rear section and a number of
intermediate sections, depending on the size of the
boiler. The sections are connected on each side at the
top and bottom either by push nipples or by an outside
header. When nipples are used, these sections are held
firmly together by rods and nuts.
The boiler has a separate base that does not contain
water and, therefore, requires a floor of fireproof
construction. Boilers that have water in their bases are
referred to as wet-bottom boilers. These boilers are
relatively small water units that may be installed on
floors constructed of combustible materials. This
method of installation, however, is not desirable.
The construction of square sectional boilers is
ordinarily such that the sections can be taken through
regular-sized doors for assembly inside the boiler
room. This is a distinct advantage from the standpoint
of both installing new equipment and replacing broken
sections. Cast-iron boilers resist the chemical action of
corrosive agents much better than steel boilers.
The disadvantage of cast-iron hot-water heating
boilers is the danger of the sections cracking or
breaking when improperly handled or fired.