Manufacturers furnish information regarding the area
effectively heated by units to enable proper planning
and location of the units. Generally, units under
50,000 Btu per hour are designated to operate on
low-pressure steam or high-temperature hot water.
Space heaters are used for heating rooms and
similarly enclosed spaces, either in addition to, or in
place of, a central heating system. They are desirable as
a means of providing heat to a small space because of
their simplicity of construction, low initial cost, and
reasonable fuel consumption. They may be placed
directly in the space or at such a location where heat can
be delivered through a single register into the space.
Space heaters are sometimes classified by the
manner in which they transfer heat to the space to be
heated; for example, by radiation and/or convection.
The terms direct-fired and indirect-fired are also used
to identify such heaters. In this manual, space heaters
are identified as direct-fired units and by their heat
source or fuel. This discussion will include electric,
gas-fired, coal-fired, and oil-fired units.
Electric Heaters and Installation
Space heaters with electrically powered heating
elements are used in spaces where it is desired to
eliminate cold spots and maintain uniform
temperatures, where other fuels are useful as portable
units on the floor to overcome floor drafts, and as fixed
units mounted in, or to walls or ceilings. They are
generally rated in kilowatts (kW). One kW (1,000
watts) is equal to 3,415 Btu per hour.
Electric space heaters are available in two general
typesthe radiant and natural convection type and the
forced warm-air (fan) type. In the radiant and natural
convection type, heat from electric elements rises and
strikes parabolic (bowl-shaped) reflectors. The
reflectors are highly polished curved metal surfaces,
which deflect the heat outward into the place where
heat is desired (fig. 4-3). Some radiant heat units have
no deflectors but provide a combination of radiant and
natural convection heat, which rises from the coils into
a chamber open on the side where heat is required. The
electric baseboard convection heater is an example of
this type. The forced warm-air type uses a motorized
fan to circulate heat from the heating element outward
into the space (fig. 4-4). The electric units are operated
manually with an ON-OFF switch or automatically
with a thermostat.
Figure 4-3.Radiant electric space heater.
Figure 4-4.Forced warm-air electric space heater.
In the selection and installation of electrical space
heaters, safety must be assured. Units that are to be
installed should bear the label of the Underwriters
Laboratories (UL). They should also conform to the
safety standards outlined in space heating equipment
UL-573. All electrical work required for an
installation should be done according to the
manufacturers instructions and by a qualified
Gas Heaters and Installation
Gas-fired space heaters are clean in operation; they
are easily operated and require no fuel handling. They
are adaptable for use with natural gas, manufactured
gas, or liquefied petroleum gas. Their construction
features are similar regardless of the type of gas used.
Basically, there are two typesthe vented and the
VENTED UNITS are enclosed metal cabinets
with either top and bottom or front and rear grilles for