|
Thermostat:
The thermostat is usually a switch right behind the knob
you use to set the oven baking temperature. There's a long,
thin copper tube attached to it that leads into the oven
compartment. The tube senses the temperature inside the
oven and signals the thermostat to provide heat.
Another
type of thermostat, called an electronic/mechanical hybrid
unit, has a small electronic circuit board behind the knob.
It has a 4- to 6-inch sensor attached to it that protrudes
into the oven. The sensor changes resistance in the electrical
circuit with the change in oven temperature. The electronic
clock monitors the resistance of the sensor and turns on
or off the heat in the oven. When the oven reaches the temperature
you set, the sensor signals the circuit board to turn off
the electric or gas burner(s) in the oven.
Clock:
The clock is either electronic or mechanical. Electronic
clocks have lighted, digital readouts. When either clock
fails, you usually need to replace the whole clock. Mechanical
clocks usually have three dials: the clock dial, a start
time dial, and a stop time dial. You set the main clock
to the time of day. Then, when you choose a timed-bake or
self-clean cycle, the clock turns on the oven at the start
time and turns it off at the stop time. The start and stop
dials are for both timed baking and self cleaning.
Electronic keypad:
Some stove/ovens have a keypad for setting all oven, broiler,
timed-bake, and self-cleaning times and temperatures. Touching
the pad with your finger actuates a small switch in the
pad, which then sends the proper command to the circuit
board or clock. These keypads can't be serviced, so you
usually need to replace them when a problem arises.
Selector
switch for bake/broil/timed bake, etc.:
Electric and gas stove/ovens
have at least one control switch for the oven/broiler. On
some units, this is the same switch as the thermostat. On
others it is a separate switch. If it's a separate switch,
it works in conjunction with the thermostat. You set the
thermostat to the cooking temperature and set the selector
switch to allow bake, broil, timed bake and preheat.
Surface burner switches (electric
units only):
Surface burner switches are also referred to as "infinite
switches." They work in much the same way as a dimmer
switch for a light in your home. When you turn the switch
from low to high, you increase the electrical current flowing
through the electric burner, which adjusts the temperature
of the element.
Self-cleaning
buttons or switches:
In addition to clock controls for the self-cleaning feature,
there may also be other related devices, such as a door
lock button or switch or a switch to toggle between self
clean and normal bake. Most switches in self-clean cycles
are used to keep the oven door locked so it can't be opened
until the oven has cooled down.
Gas delivery (gas units only):
All gas stovetop burners use a similar system of gas delivery.
There's one control knob for each burner. Each knob is attached
to a small gas valve mounted to a main gas line or manifold.
As you turn the valve on, gas flows through the valve into
a "venturi" tube, which mixes the gas with air
to create the proper mix for combustion. The mixture then
flows into the burner itself, where the standing pilot or
spark ingnitor ignites the flame. You regulate flame size
by adjusting the burner control knob, which restricts the
amount of gas that flows through the valve.
The oven and broiler work in a similar way. The thermostat
knob may be attached to a small gas valve mounted right
to a main gas line. As you turn the valve on, gas flows
through the valve into a tube attached to a safety control
valve. The safety control valve doesn't allow gas to flow
through to the burner unless there is an ignition source
available. The ignition may be provided by a standing pilot
light or by an electric igniter. When gas flows and ignites,
the flame stays lit until the thermostat senses the proper
temperature and shuts off gas flow, usually at the safety
valve.
With a digitally controlled system the clock sends the signal
straight to the safety valve. Then, if the electric igniter
is working properly, the safety valve opens and sends the
gas to the burner, and the hot igniter ignites it. A digital
system uses a small electronic sensor inside the oven to
sense temperature. When the set temperature is reached,
the circuitry sends a signal to turn the safety valve off,
which stops the flow of gas. When the oven temperature cools
slightly, the resistance of the sensor changes. This causes
the circuit board to restart the heating process and re-light
the burner.
The
cooktop (electric units only):
Electric stove/ovens have open, coil-type burners on their
cooktops. Or, the whole cooktop may be what's called a "smoothtop,"
where burners are mounted under glass that conducts heat
to your cookware.
Coil type burners:
Cooktops usually have four to six metal burners (or heating
elements). Each is a coiled sheath with a wire in the center
and no moving parts. The wire becomes red hot, which heats
the metal sheath by conduction, and the sheath glows red.
You see this glowing when you turn on the element. The drip
pans beneath coil burners catch spills and reflect heat
back to your cookware.
Euro type burners:
Euro burners are solid, smooth, and 6 to 8 inches in diameter.
Each has an internal coil of wire in the center and no moving
parts. When the wire receives electricity, it becomes hot,
which heats the solid metal surface. Although the surface
of the burner doesn't glow bright red, it becomes very hot.
Smoothtop ranges:
Smoothtop ranges work similarly to coil-type burners. There
is a coiled wire beneath each burner area. When electricity
is applied to the wire, it glows red hot. Heat created is
conducted through the glass and either radiated to the pan
on the cooktop or conducted from the glass to the metal
of the pan. Some smoothtop ranges also have red halogen
lights to supplement the coil-type elements. These get hot
immediately, to speed the burner's warm-up time.
The area beneath the cooktop:
Many cooktops with coil or gas burners can be raised for
cleaning and service. Manufacturers often place the model
and serial number tag for the appliance beneath the cooktop.
The interior of the oven (electric
units only):
In most non-convection ovens, you can see a heating element
at the bottom of the oven and the broil element at the top.
Each element is a coiled metal sheath with a wire in the
center and no moving parts. When electricity flows to the
wire, the wire becomes red hot and heats the metal sheath
by conduction. The sheath then glows red.
The area behind the broiler drawer
(gas units only):
This is where the safety valve, igniter, pilot assembly,
oven burner, and other components are often located. On
some units, these items are under the oven floor.
|
