bellows (fig. 7-14). A bulb located on one end of the
capillary tube is filled with fluid and then is put in the
heat zone. It transfers heat-created pressure through the
capillary to the diaphragm. The expanding diaphragm
presses a system of levers that snap the electrical
contacts open, thus cutting off electrical current to the
controls. Automatic recycling takes place with slight
temperature drops, maintaining a constant set
temperature.
the two small, slotted lock screws (fig. 7-14) that are
behind the dial. Now, with one hand, hold the main
center hub of the control and move the slotted adjusting
plate to the right to raise the temperature or to the left to
lower the temperature. That is a delicate adjustment, so
move the dial a little at a time.
Certain types of hydraulic controls have a safety
device, normally set at 450°F, that trips upon reaching
the set temperature and requires manual resetting. It
may take several hours before the appliance has cooled
down enough to allow the operator to reset the unit.
If you find that the circular slots in the adjusting
plate prevent you from turning the plate for the desired
temperature change, remove the two lock screws
carefully so you can move the adjusting plate a full 180
degrees. Replace the two adjusting screws and continue
the calibration process as before.
Repairing a hydraulic control is usually limited to
adjusting the temperature setting to correspond with the
temperature recorded in the appliance. You can adjust
the temperature control by loosening, but not removing,
A timer is used to control a circuit to an appliance
automatically or give a warning to the operator that a
predetermined time has lapsed. Figure 7-15 shows a
typical wiring diagram of an electric range single-pole
oven timer.
Figure 7-14.—Hydraulic control.
7-12
