Current protection is important in a number of electrical applications. For both safety and the protection of expensive, important pieces of equipment, current protection is often required within electrical systems. 

While there are a number of ways to accomplish this goal, PTC thermistors are often used for the job. Let’s take a closer look at what these resistors can accomplish so you can determine if they are right for your project.

What is a PTC Thermistor?

The concept behind a PTC thermistor is quite simple. These resistors are designed to have a positive temperature coefficient, which is where the “PTC” name comes from. As temperature rises, the resistance that is offered by the thermistor increases, allowing circuit designers to tie the flow of current to the temperature that is being experienced. 

This type of resistor is popular because it can be used in a variety of applications. It can be used for current protection – which we will talk more about in a moment – but it can also be used as a time delay function within a circuit, it can be used in the motor starting process, and it can also be used to self-regulate heating components. If you’d like help understanding some of the various ways our PTC thermistors can be put to use, feel free to get in touch with our expert team today. 

Implementing a PTC Thermistor for Overcurrent Protection

Often, fuses are used as a form of current protection, as the fuse will blow if the current exceeds a set limit and the circuit will be broken. The problem with this arrangement is obvious – if the fuse is blown, it will need to be replaced. As a better solution, a PTC thermistor can be used to accomplish the same goal without the downside of ongoing, potentially frequent replacements being required. 

For current protection, you’ll typically be looking at a switched PTC thermistor. This is a type of resistor that maintains a steady level of resistance at a given temperature range, but the resistance will suddenly jump up (or “switch”) once a certain temperature is reached. That design allows the switched PTC thermistor to act effectively as a fuse, only it won’t need to be replaced after the overcurrent event. Once the additional flow of current has abated and the temperature in the thermistor returns to normal levels, the resistance will drop and the performance of the circuit will be allowed to continue once again. 

Protecting circuits from the inevitable, occasional rush of additional current is essential for countless businesses. At the same time, utilizing standard fuses for the job adds a layer of maintenance and ongoing upkeep that is not desirable. The PTC thermistor is an elegant solution to this problem, as it essentially automates the fuse management task. There is no fuse to blow, and the current can go up and down without doing any damage to the equipment that is downstream of the thermistor. 

Order from Calco Electric Today

In addition to our extensive selection of quality products, it’s the expertise of the staff at Calco Electric that allows us to stand apart from the competition. If you would like to learn more about the PTC thermistors we offer, or if you are ready to place an order, please reach out today and we will be happy to serve you. 

We all can appreciate the need for an accurate thermostat to regulate temperatures within a home or building. But for some industries, the accuracy of a thermostat is an absolute necessity for safety and to protect the equipment inside. Narrow differential thermostats are used in heat-treating ovens. Those industries include:

• Heavy construction machinery
• Aerospace
• Mining
• Metalworking
• Tool and die sectors

Typical heat-treating applications include aging, annealing, baking, brazing, drying, hardening, normalizing, solution-treating, tempering, and more.

The temperature differential refers to the variance between the temperature outdoors and whatever it is indoors. If you’re trying to cool the building to 72°F and it is 100°F outside, the thermostat will work harder to catch up. And with heat-treating ovens and furnaces that reach temperatures as high as 1400°F, you need a thermostat with a narrow differential to ensure the building is kept cool enough inside without error.

This is where Calco Electric’s narrow differential thermostats excel.

Narrow Differential Thermostats Require Extreme Precision

Narrow differential thermostats need the ability to turn on and off at close tolerances. A narrow differential allows the heat to turn on and off rapidly. Calco Electric’s narrow differential thermostats provide the following benefits:

• 100% regulated temperature
• Snap action and creep action
• Personalized wire length and type
• 100% RoHS Compliant
• 100,000 life cycles for long-term capacity
• Personalized terminals located at the same or opposite ends
• Use of a snap action with bimetal discs to open and close the contact
• 17AME-H thermal switch
• The lowest temperature is from 0°C to 180°C
• High resistance to shock and vibration

Thermostats have adjustable temperature settings that determine how often the system cycles. A low differential setting is similar to a narrow differential setting. The tighter this setting, the more the system will cycle and the tighter the temperature will remain. A broad differential setting will result in longer cycle times. But where heat-treating ovens are used, that wide setting can be problematic.

Three Advantages of Narrow Differential Thermostats

Though a wide differential can increase efficiency and extend equipment life in most circumstances, it’s not ideal for personal comfort. It can be dangerous where heat-treating ovens are in use. For this reason, a narrow differential thermostat will provide the following advantages.

• Ability to control the temperature of an application under a minimal range
• More comfort for personnel working close to ovens that can reach temperatures as high as 1400°F
• Heat-treating ovens do not have the same compressor minimum run-time constraints - rapid cycling from a wide differential would cause excessive wear, and tear - narrow differential thermostats are far more efficient and effective
• Safer working conditions for employees in close proximity to heat treating ovens

Contact Calco Electric for More Information

For more details about narrow differential thermostats and the benefits they can provide for your application, contact the team at Calco Electric. Our experienced, trained staff will gladly answer any questions you have about these thermostats. 

Bimetal thermostats are used in a variety of products, even in your toaster or electric blanket. But what are they and how do they work?

Read on to learn more about these thermostats and how Calco Electric can help you find the best one for your project.

What Is a Bimetal Thermostat?

A bimetal thermostat is a device that uses two metals that react differently to heat. One of the metals will expand more rapidly than the other when exposed to heat, creating a round arc. The pairing is typically copper and steel or a copper alloy like brass and steel.

As the temperature gets hotter, the more pliable metal (for instance, the copper) will arc so much that it opens a contact and shuts off the electricity to the circuit. As it gets colder, the metal contracts, closing the contact and allowing the electricity to flow again.

The longer this strip is, the more sensitive it is to temperature changes. That’s why you can often find these strips in tightly wound coils.

A thermostat like this is extremely cost effective, which is why they’re in so many consumer appliances.

How Does a Bimetal Thermostat Switch On and Off?

These thermostats are designed to be self-regulating. As the temperature increases, the system switches off. As it cools, it switches back on again.

In your home, this means you simply have to set a temperature and it will regulate when the furnace (or air conditioner) turns on and off. In the case of a toaster, the strip will shut off the heat and trigger the spring that pops the toast up.

Not Just for Your Furnace

Have you ever had a piece of toast that came out black when you didn’t want it? That could be the result of a faulty bimetal thermostat. These devices are everywhere in your home, from your toaster to your dryer to your iron.

These little things are a key safety feature. If your iron or clothes dryer becomes overheated, it’ll simply shut off. That can prevent a fire and may be part of the reason there’s been a 55% drop in fires since 1980.

How to Troubleshoot Bimetal Thermostats

Troubleshooting this kind of thermostat is simple. Simply expose it to heat and see if it reacts.

You can use a heat gun if you have one. If you don’t, a hair dryer will work well too. Point it at the coil and see if the strip or coil changes shape.

If you don’t see much change, it may be that the strip or coil is worn out. It may have what is known as “thermal fatigue.” That’s the degradation of metal after a number of cycles of heating and cooling.

Drawbacks of Bimetal Thermostats

There are a few drawbacks you should be aware of. First, these thermostats are more sensitive to hot temperatures than cold ones. If you need to detect changes in lower temperatures, it might not be the way to go.

Second, a thermostat like this only has a lifespan of about 10 years. There may be more durable options, depending on the job.

Calco has a wide range of options for thermal regulation, no matter what your project is.

Shop Calco Electric’s Selection of Bimetal Thermostats

We have a wide range of bimetal thermostats for all your needs. There are cost-effective ones that can keep your project affordable and ones that can handle higher temperatures up to 400C.

Take a look at what we have to offer!

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