What Is a Bimetallic Thermostat?
A bimetallic thermostat is a temperature control device that uses a piece of metal known as a bimetallic strip, which changes its shape in response to temperature fluctuations.
Thermostats that employ contacts made of two dissimilar metals, laminated together and referred to as bimetallic strips, are generally categorized as bimetallic thermostats. This time-tested method offers exceptional weather resistance and reliability.
Uses of Bimetallic Thermostats
Bimetallic thermostats find application in a diverse range of scenarios due to their dependable performance and straightforward design. They are commonly employed in devices and systems requiring temperature regulation. Examples include temperature control in household appliances like refrigerators, air conditioners, and water heaters.
They are also used in electronic and electrical equipment to safeguard against overheating damage. When the bimetal detects a specific temperature threshold, it can interrupt the electrical circuit, providing equipment protection. Instances include computer power supplies and electric heaters.
Moreover, they can be used for triggering alarms when temperatures fall outside a designated range. They are frequently used in greenhouses and laboratories to signal temperature deviations beyond desired limits.
Owing to their reliability and ruggedness, bimetallic thermostats have widespread utility in applications related to temperature control and control circuit operations.
Principle of Bimetallic Thermostats
Bimetallic thermostats function through the utilization of a bilayer metal strip known as a bimetallic strip. Bimetals consist of two metal layers with distinct coefficients of thermal expansion. As each metal layer has a different coefficient of thermal expansion, one layer expands or contracts more than the other in response to temperature fluctuations.
This differential expansion or contraction leads to an alteration in the overall shape of the bimetal. Common metals used include chromium and manganese alloyed with iron and nickel alloys for the high-expansion coefficient side, and iron and nickel alloys with lower expansion coefficients for the low-expansion coefficient side.
Iron and nickel are chosen due to their affordability, ease of processing, and durability. Bimetallic thermostats are devices that harness the shape change of bimetals to control temperature. Typically, the bimetal is anchored at one end with a connected contact or switch located at the other end.
As temperature rises, the difference in expansion rates between the metal layers causes one layer to expand significantly, bending the entire device and actuating the contacts or switches.
How to Choose a Bimetallic Thermostat
When selecting a bimetallic thermostat, several crucial factors should be taken into account:
1. Rated Voltage
Verify the voltage rating of the bimetallic thermostat based on the specifications of the electrical equipment and circuit it will be used with. Ensure that the chosen voltage does not exceed the maximum allowed by the product; common products support voltages ranging from around 100 V AC to 250 V AC.
2. Current Rating
Consider the current rating per the electrical equipment and current requirements. It is important to avoid exceeding the rated current, which can result in issues such as contact welding. Selecting a thermostat with an appropriate current rating ensures proper operation and reliability.
These thermostats are frequently used in control circuits, with products commonly rated at 20 A or lower. Smaller units may have ratings as low as 3 A.
3. Temperature Setting Range
Determine the required temperature range for the specific application and choose suitable products accordingly. Many products only operate within certain temperature ranges. Temperature setting options encompass a wide range, spanning from a few degrees Celsius to several hundred degrees Celsius.
4. Reset Type
The reset type of the contact is also a crucial consideration. There are two types: automatic reset and manual reset. Automatic reset thermostats revert to their original state automatically when the temperature returns to the specified range.
Manual reset types require manual intervention to reset them once they have been triggered. Selection should align with the intended application.