The furnace limit switch is an important safety component in any residential or commercial HVAC system. Given this, it’s in your best interest to be as informed as possible about this component to avoid any issues or problems down the line. To make things easier for you, here’s everything you need to know about furnace limit switches.
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The furnace limit switch is designed to shut off the furnace if the temperature inside the furnace gets too high. Without a limit switch, your furnace could overheat and cause a fire. In this blog post, we’ll explain what a furnace limit switch is, how it works, and why it’s important to keep it in good working order.
A furnace limit switch is a type of safety switch that is mounted inside the furnace. This switch is triggered when the temperature inside the furnace reaches a certain point. The limit switch is designed to shut off the furnace before it gets too hot, preventing the risk of overheating and fire. The temperature at which the limit switch is triggered is usually between 130 and 160 degrees Fahrenheit.
When the furnace limit switch is triggered, the furnace will shut off until the temperature inside the furnace drops below the limit switch’s set point. The furnace will then restart and continue to operate normally. However, if the furnace limit switch is not working properly, it may not shut off the furnace when the temperature reaches a dangerous level. This can be a major safety hazard and should be addressed immediately.
It’s important to keep your furnace limit switch in good working order. Regularly inspect the switch for signs of wear or damage. To keep your furnace limit switch in good condition, it’s also important to keep it clean. This can be done by using compressed air to blow out any dust or debris that may have accumulated inside the switch. It’s also important to check the wiring of your furnace limit switch periodically. If any of the wires have become loose or frayed, they should be replaced.
Aside from what we’ve already mentioned, it’s also vital to make sure that the furnace limit switch is the correct size for the furnace. If the switch is too small, it won’t be able to sense the temperature accurately, leading to the furnace shutting down prematurely. If the switch is too large, it could lead to the furnace shutting down too late, allowing the furnace to become dangerously hot.
Overall, the furnace limit switch is an important safety component in any HVAC system. It is designed to shut off the furnace before it gets too hot, preventing the risk of overheating and fire. Make sure to regularly inspect the switch for signs of wear or damage and contact a professional HVAC technician if needed. By keeping your furnace limit switch in good working order, you can ensure the safety of your home or office.
There are “limit switches” and “micro switches” as switches that are inexpensive and readily available.
But be careful if you are selecting them based on price alone.
In recent years, machines have become smaller and more precise, and the number of designers and device users who have this problem is increasing.
In the background, it is not uncommon for people to be unaware of the characteristics of micro switches when using them.
In this article, we will explain the basic knowledge of micro switches and their advantages and disadvantages for each application.
We will also explain METROL's "precision positioning touch switches" from the perspective of a "third switch" that is not a micro switch nor limit switch.
●What you can learn from this article
・Basic knowledge of micro switches and limit switches
・Three risks that tend to be overlooked when selecting switches
・Differences between micro switches and Metrol’s precision positioning switches
・A collection of use cases of precision positioning switches
We publish the [collection of touch switch introduction cases] that we would like to show those who are involved in design, production technology, purchasing, and maintenance who deal with switches!
As the name suggests, a switch is something that "switches".
There are three typical contact switches as below:
A switch opens and closes an electrical circuit (ON/OFF).
Therefore, switches are incorporated into electric products around us, robots, and production facilities, etc. to perform control.
First, we will explain the characteristics of micro switches and limit switches.
A micro switch is a small plastic-encased switch with a snap action mechanism and contacts. (See Fig. 1)
When a part called an actuator is moved up and down, the internal contact opens and closes, turning power on and off.
A limit switch is a switch covered with a plastic or metal cover to make a micro switch waterproof and dustproof.
Its role is to detect the presence or absence like a micro switch, but it is used in a harsh environment with water, oil, dust, etc.
When operating, a part called a dog* is attached to the facility and used by operating the actuator part of the limit switch. (See Fig. 2)
Both micro switches and limit switches play the role of "presence/absence detection or existence detection" because they notify the existence of the detected object when it comes into contact with the actuator.
What is “presence/absence detection”?
and so on. (See Fig. 3)
Micro switches are used in a variety of places for presence/absence detection, to home appliances to industrial production facilities.
For example
Home appliances:
Industrial products and facilities:
Microswitches are embedded in all of these presence/absence detection mechanisms.
Some common specifications include:
From the above, it can be said that the micro switch is a low-cost switch useful in a clean environment where precision is not required.
The price of a micro switch is attractive in terms of design, but the cost of the switch itself (initial cost) is just the tip of the total cost iceberg. Keep in mind that improper use and usage can lead to increased costs.
Risks that lead to cost increases in the long term can be broadly divided into three categories.
Repair costs due to switch failure (labor, travel, service costs)
Facility outages incur costs for maintenance staff urgently dispatched to the site to respond. This is the source of potential cost increases.
Appropriate cost management is required based on the purchase of spare parts for sensors and the track record of paid repairs.
This is the cost associated with installing the intermediate mechanism required for switch operation.
Installing a dog or actuator to operate a micro switch may result in costs such as increased space and parts, increased facility size, and increased assembly time.
Examples: Intermediary actuators, design/manufacturing costs and assembly time of dogs, potential lost costs due to space requirements
Even if the performance of the machine as a whole is excellent, frequent failures or malfunctions in individual sub-functions (e.g. door opening/closing, loading/unloading) and short stoppages can cause customer dissatisfaction and damage to the brand image.
This leads to
・Decrease in facility utilization/availability *1
・Opportunity loss due to idle machines
and so on, also a loss for the user.
You should avoid the situation in which an expensive facility stops due to a switch failure, as it costs more to repair a damaged brand image.
In conclusion, it is necessary to pay attention to future opportunity loss (switching to other companies, etc.) due to the deterioration of the brand image.
There are quite a few cases in which the lack of specifications is discovered later, triggered by troubles caused by defective or damaged micro switches.
The company is the world’s best What Triggers a Limit Switch? supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
Troubles caused by micro switches are triggered when the lack of specifications becomes apparent later. Below are three cases.
Many micro switches are IP40 (non-waterproof, non-dustproof), so moisture, water, oil, and chips can cause problems such as corrosion and deterioration.
Assume that the user's site is an environment that leads to problems, even if it is not assumed at the design stage.
If a micro switch for presence/absence detection is used for positioning or returning to origin that requires precision, there is a risk of instability.
If the electrical life limit is exceeded, or if the switch is used in an application where a strong impact is applied to the switch, failure will occur early.
Avoid using the switch itself as a stopper when using it to limit the range of motion of the machine.
If the load is large, the plastic case may crack or warp, or the mounting position may shift.
It is better to think that the concept of 'repeatability' does not exist in principle of micro switches for presence/absence detection.
The reason is because there is a mechanism called "snap action mechanism*."
The "snap action mechanism" is a mechanism that quickly contacts and releases the contact with a "snap" via a leaf spring when turning on and off, and a micro switch is defined as a switch with this mechanism. (See the video)
This snap action mechanism generates a hysteresis*, and the reproducibility of the switch operation timing is not stable, which means the repeatability is low. Therefore, the snap action itself is effective in extending the life of the contact, but it works in the direction of lowering the accuracy.
*The birth background of the "snap action mechanism"... In the past, AC 100V was the main power supply and a large voltage current flowed through the contacts, so a structure called "snap action" was born to prevent the contacts from welding or galvanic corrosion by quickly contacting and releasing the contacts. *What is hysteresis? The distance between the point where the actuator moves for the first time from the free position when the actuator is pushed in, and the point where it moves for the first time when returning.
From the design stage, it is important to rigorously estimate the usage conditions of the switch.
Avoiding troubles before they occur leads to future maintenance and after-sales service cost reductions and customer satisfaction.
Below are four things to consider when selecting:
So, what other options exist besides micro switches?
We will explain METROL's "precision positioning touch switches" that are different from micro switches.
METROL's "precision positioning touch switches" were developed based on the design concept of a contact-type switch with high durability that are versatile and can be used in a variety of facilities, and perform high-precision detection even in harsh environments.
Their uses are similar to those of micro switches and limit switches, but the development concept is significantly different from that of "presence/absence detection."
We will explain the five reasons why positioning touch switches are selected.
Precision positioning touch switches feature a high repeatability of ±0.5 μm to ±10 μm.
Since there is no hysteresis, positioning is possible with higher repeatability than presence/absence detection.
Unlike micro switches, one of the reasons for its high precision is that it does not have a snap action mechanism.
Combining it with the machine coordinates of facilities and devices enables highly accurate positioning and measurement on the order of microns.
Long-term endurance tests are conducted using endurance test equipment dedicated to touch switches to confirm accuracy. (See the video)
Depending on the series, we guarantee an accuracy life of 1,000,000 times for short ones and 10,000,000 times for long ones.
It is so waterproof and dustproof that it is used inside machine tools that use cutting oil.
Unlike plastic switches, most of them are covered with a metal case and have IP67 (resistance to water, oil, dust, etc.) specifications.
For switches with IP67 or higher, a waterproof test is performed before shipment.
It does not require a dog like a limit switch, making the machine smaller and reducing assembly man-hours.
All series are planned, designed, and manufactured at our factory in Tokyo, and many switches can be customized and made to order according to standards such as shape, material, contact force, and cable length.
Many precision positioning touch switches have been introduced in applications such as:
The development of the "precision positioning switch" was triggered by the increasing need for jigs for automatic equipment and high-precision sensors that determine the origin of stages.
When automatic equipment and NC machine tools began to spread rapidly, there were few sensors suitable for micron precision detection, and inexpensive micro switches and proximity sensors were used instead.
Because micro switches are primarily intended for “presence/absence detection”, micron-precision applications require careful judgment.
As a result, erroneous detection and durability problems occurred, and the "precision positioning switch" was born as a product to meet these needs.
We have a wide lineup of precision positioning touch switches, but we would like to introduce the best-selling representative six series.
[PT series] Evaluation by users who adopted ????“With a wide variety of sizes, we are satisfied with the delivery time and price. ” ????"For seating. Accurate and reliable detection is possible. Best for small and tight spaces. ” ????"Used to measure the thrust of our machinery. We adopted this ultra-compact product for use in narrow spaces. ” 口click here for buyer reviews
[MT series] Evaluation by users who adopted ????"There had been a phenomenon that the line had stopped due to malfunction, so we installed it to reduce judgment errors. ” ????“Previously, we measured the length of a workpiece with a side length sensor and distinguished different types. This product is a ON/OFF type, but it can be handled by combining multiple items, resulting in cost reduction. In addition, the environment is harsh, but it works stably. ” 口click here for buyer reviews
[BP series] Evaluation by users who adopted ????"It's convenient because you can hit it from any direction. ” ????"It is used for confirming the return of the slide core of the mold. The ball plunger and limit switch were installed separately, but this one is enough, and you don't have to think about the position of the limit switch in the narrow opening. ” ????“With limit switches, we have to be careful about the direction of entry, but this structure was helpful because conventional switches would break if they entered from multiple directions. ” ????"We use it as a backlash killer for product bearings. We think it's an ideal product that has both a ball plunger and a switch function in a compact body." 口click here for buyer reviews
[CS series] Evaluation by users who adopted ????"Resolution is high and reliable" ????"Used for moving end point detection of the device. The end point is in an environment in which it changes slightly due to the external environment, but the touch sensor can reliably detect the contact of the workpiece. In addition, it's inexpensive. ” ????"Even in areas where we are concerned about minute positional misalignment of the workpiece, the resolution and repeatability are high and excellent. It seems to be reliable for long-term use of 10 million times." 口click here for buyer reviews
The series introduced so far is only a part, and there are many other variations.
If the specifications and conditions of use are fixed, you can search by narrowing down with the button below.
The advantages of micro switches are, above all, their ease of use, availability, and low cost.
Not all products require micron-level precision and tough durability.
There is no need for over-engineered precision touch switches for presence/absence detection of mice and home appliances.
If the total cost goes up, it cannot be said that the product design meets the needs of the user.
It is necessary to select the optimum switch with the right item in the right place, whether price is the priority or accuracy and usability are the priority.
As you can see from the three risks that are often overlooked,
・When the switch on the door of the home appliance is broken
・When a door with a safety device of a production facility costing tens of millions of yen is broken
the scope of impact and the urgency are unmatched.
If the facility stops, production activities will stop.
It is important to determine whether this is an acceptable case for general consumer goods, or whether it is an industrial product that requires professional reliability.
At the design stage, after considering what are the long-term cost drivers of the switches to be adopted, it is important to select from among the appropriate options without being confused by the initial cost.
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Our engineers will respond to any questions regarding product usage methods or requests to customize products.
We can provide our best support if details about application, usage environment and what kind of workpieces will be detected can be provided.
Use our contact form below to contact us.
Our engineers will respond to any questions regarding product usage methods or requests to customize products.
We can provide our best support if details about application, usage environment and what kind of workpieces will be detected can be provided.
Use our contact form below to contact us.
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