commercial ranges and oven installations in galleys.
The current is interrupted ahead of the make-and-break
action of the switch contacts. That eliminates the usual
pitting and burning of contacts. This switch cannot be
repaired; you must replace it.
The basic function of an automatic control is
turning current on and off as required to maintain a
Bimetallic Blade Control
The bimetallic blade control switch, as shown in
figure 7-12, is operated by the expanding and
contracting effect caused by heating two pieces of
dissimilar metals that are welded together. Repair of
this control is limited to an adjustment in its temperature
Figure 7-12.Bimetallic blade control switch.
Figure 7-13.A. Helix control; B. Helix components.
A helix control (fig. 7-13, view A) is used in some
domestic, semi-commercial, and commercial
installations. It is operated by thermostatic metal that
coils and uncoils when heat is applied, regulating a
switch to make and break the electric circuit. Repairing
this unit consists of replacing miscellaneous parts, such
as the dials, switch assembly, helix, helix guard, and so
on (fig. 7-13, view B).
A hydraulic control is probably the most frequently
used control for automatically regulating the
temperature of cooking appliances. In this control, a
capillary tube filled with fluid is connected to hydraulic