C D S       PRODUCTS  
TEMPERATURE                 SWITCHES
HOW THEY WORK
AVAILABLE TEMPERATURE SETTINGS
450°F =232C°
390°F =199C°
365°F =185C°
350°F =177C°
295°F =146C°
285°F =141C°
280°F =138C°
270°F =132C°
260°F =127C°
250°F =121C°
230°F =110C°
220°F =104C°
212°F =100C°
205°F =96C°
200°F =93C°
195°F =91C°
185°F =85C°
175°F =79C°
165°F =74C°
160°F =71C°
155°F =68C°


C.D.S.Temperature Switches have a unique principle of operation. Various combinations of bismuth, tin, cadmium, lead, and antimony metals are mixed in our plant under closely controlled laboratory conditions to become eutectic alloys.

C.D.S.Temperature Switches are all available in the factory settings listed at the right.

Eutectic temperatures exist in nature and can only be discovered. It is not possible to "design" an alloy to have a particular eutectic melting point.

This is the reason for the somewhat scattered spacing between available temperature settings.

When temperature setting is not specified, 212°F. will be supplied. This choice is based solely on popularity and is not to be considered as a recommendation.







A eutectic alloy is a metal that has a very specific melting point with little or no "semi—soft" state. It is 100% solid at temperatures below its melting point and 100% liquid at temperatures above its melting point.

A small amount of the proper eutectic alloy is introduced into the switch during assembly. While "SET", this alloy makes a solid mechanical lock between the crimp in the housing and the flange on the center stem.

Consult the equipment manufacturer's recommendation when selecting a. temperature setting. The temperature at which a piece of equipment is in danger of damage should be considered rather than a temperature a few degrees above normal. This will eliminate unnecessary tripping of the switch in warm weather, during heavy loads, etc. when the equipment is in no real danger.

When the switch reaches its temperature setting, the eutectic alloy instantly changes to liquid and can no longer hold the center stem down against a spring force which urges it upward. It therefore moves to the "TRIPPED" position. The opposite end of the center stem carries the moveable contact which, depending on the model, opens, closes, or grounds the switch terminals.

TO RESET A TRIPPED SWITCH


C.D.S. Temperature Switches can be easily reset without special tools in the shop or in the field. After removing the tripped switch from its installation, remove the cap (acorn nut) and follow these four steps.

     

  1. Using any available heat source (blow torch, cigarette lighter, hot exhaust manifold, etc., but not an oxy-acetylene torch), hold the switch in an upright position and heat the lower portion of the housing to a temperature slightly above the setting. This will liquefy the eutectic alloy.

  2. Depress the center stem completely down (flush to 1/16" protrusion above the threaded boss

  3. Remove the switch from the heat source, maintaining the depressed position of the center stem, and gently tap the bottom of the switch to make sure all of the alloy flows back into position.

  4. Continue holding the center stem depressed and quench the lower portion of the switch in water or wait for it to cool well below the setting temperature. Replace the cap and reinstall the switch.

Because of this principle of operation, C.D.S. Temperature Switches are insensitive to vibration and rough handling. Nothing can change the factory setting of the switch. They are non-adjustable which 'prevents their being inadvertently adjusted to a setting too high to protect the equipment on which they are installed.

The use of  bushings is not recommended. A C.D.S. Temperature Switch having the proper thread size should be installed directly on the equipment it is to protect.

CAUSE OF SHUTDOWN

C.D.S. Temperature Switches provide cause of shutdown indication regardless of the time interval between shutdown and discovery. Without removing the switch, remove the cap and observe the position of the center stem. If the switch is tripped, the center stem will protrude 1/8" to 3/16" above the threaded boss and it is certain that the equipment reached the setting of the switch because nothing else can trip it. If the switch is still set, something other than overheating caused the shutdown.

A Standard switch is inspected for a tripped condition by loosening the terminal nuts and checking the free play of the terminal screw. Axial play of about 1/8" indicates the switch is still set. A tripped switch has no play.

The series 8000 Temperature Switch is reset In much the same way as other C. D. S. Temperature Switches.  Loosen the terminal nuts about 3/16 inch. Heat the lower portion of the switch slightly above its setting to melt the alloy. Push the terminal screw completely down, tap gendy on the bottom, and cool the switch well setting, continuing to hold the screw down. Hand tightenthe nuts and re-install the switch.

C. D. S. Temperature Switches can be reset as often as necessary without loss of accuracy of performance. Printed resetting instructions are furnished with each switch.

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C D S PRODUCTS   P.O.   Box 96   Newport Beach,   CA    92662
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