¡¡¡¡Last year, WellCircuits hosted the First PCB Design Contest. Kevin Ceresa was one of the participants, and his entry, the Audio Amplifier 60W, won second prize for Best Design. We are honored to have the opportunity to interview this passionate advocate of Open Source Hardware and electronics.To get brand praise, PCB manufacturing in China It is necessary to have the spirit of constantly improving the quality of products, but also to have a bunch of eternal heart fire. https://www.wellcircuits.com/

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¡¡¡¡Kevin Ceresa Interview Image

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¡¡¡¡WellCircuits Team: ¡°Hello Kevin, congratulations once again and thank you for agreeing to this interview.¡±

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¡¡¡¡Kevin: ¡°Thank you, it¡¯s truly an honor.¡±

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¡¡¡¡WellCircuits Team: ¡°Could you please introduce yourself briefly? Many other engineers in the WellCircuits community are eager to learn more about you.¡±

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¡¡¡¡Kevin: ¡°Sure! I am an electronic engineering student and began my career at 16 years old. I have worked on various electronic projects that gave me valuable experience, and I am still involved in a few startup projects.¡±

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¡¡¡¡WellCircuits Team: ¡°I visited your website, Swiss TI Lab, which was co-founded by you and Daniele Chiappa. Can you tell us more about your lab and the story behind its establishment?¡±

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¡¡¡¡Kevin: ¡°We decided to start the company after our first project launched on Kickstarter. After the initial phase, we continued to design electronic products for both companies and private clients.¡±

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¡¡¡¡WellCircuits Team: ¡°Regarding the 2017 WellCircuits PCB Design Contest, how did you learn about the competition, and what motivated you to participate?¡±

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¡¡¡¡Kevin: ¡°As a WellCircuits customer, I found a post about the contest on their Facebook page. I joined to challenge myself and thought one of my designs could be a good fit for the competition.¡±

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¡¡¡¡WellCircuits Team: ¡°Why did you choose your Audio Amplifier 60W project as your contest entry? And how did it feel when you learned that you were one of the winners?¡±

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¡¡¡¡Kevin: ¡°I initially built the amplifier to enhance my skills with the PCB design software I was using, after completing an advanced course. I chose it as my contest entry because it was one of my best designs on a 2-layer PCB and the most practical project for the community. When I found out I won, I was thrilled ¡ª I didn¡¯t expect to win at all.¡±

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¡¡¡¡WellCircuits Team: ¡°What do you think is the most important quality for a good designer?¡±

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¡¡¡¡Kevin: ¡°Experience is crucial when designing electronic projects. It helps you avoid mistakes during schematic design and layout, significantly reducing the time needed to complete the project.¡±

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¡¡¡¡WellCircuits Team: ¡°How do you see the future of open-source hardware?¡±

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¡¡¡¡Kevin: ¡°With the advancement of technology and decreasing costs of electronics, more people can leverage community knowledge to build anything. I believe WellCircuits plays a significant role in this evolution.¡±

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¡¡¡¡WellCircuits Team: ¡°Thanks! What are your thoughts on our website and community? Do you have any suggestions for improvement?¡±

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¡¡¡¡Kevin: ¡°I think the website is well-designed, though it lacks translations into other languages. I¡¯ve ordered many PCBs from you, and I¡¯ve never had any issues. However, I don¡¯t use the community forum much.¡±

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¡¡¡¡WellCircuits Team: ¡°Thank you for your feedback. Our Spanish website is now available, and we are also working on Russian and Japanese versions. One last question: If we hold another PCB Design Contest, would you participate again, and would you encourage your friends to join as well?¡±

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¡¡¡¡Kevin: ¡°I will definitely participate again. I¡¯ve already suggested the contest to my friends, and I¡¯ll remind them to join if the competition is held again.¡±

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¡¡¡¡WellCircuits Team: ¡°That¡¯s all. Thank you once again, Kevin. We wish you all the best!¡±

　　What is High Frequency (HF) PCB?contemporaneity PCB meaning Our competitors have not made large-scale improvements, so we should get ahead of everyone in the project. https://www.wellcircuits.com/

　　

　　High Frequency PCB

　　

　　In today¨s technological landscape, high-frequency electronic devices are becoming increasingly essential, particularly in wireless networks. The rapid growth of satellite communications and the shift toward high-speed, high-frequency information products demand the use of high-frequency substrates. Devices like satellite systems, mobile phone base stations, and other communication products require high-frequency PCBs for optimal performance.

　　

　　Key Features of High Frequency PCBs

　　

　　High Frequency PCB Features

　　

　　The dielectric constant (DK) should be small and stable, with lower values minimizing signal delay.

　　

　　The dissipation factor (DF) should also be low to ensure high-quality signal transmission, reducing signal loss.

　　

　　Thermal expansion properties should be matched with the copper foil to prevent separation due to temperature variations.

　　

　　Water absorption must be low, as higher absorption can negatively impact the dielectric constant (DK) and dissipation factor (DF) in humid environments.

　　

　　The material must exhibit excellent heat resistance, chemical resistance, impact endurance, and peel strength.

　　

　　Materials Used in High-Frequency Circuit Boards

　　

　　Materials for High Frequency PCBs

　　

　　High-frequency PCBs for wireless applications and high-speed data transmission, especially those in the GHz range, require specific material properties:

　　

　　Adapted permittivity (dielectric constant).

　　

　　Low attenuation to ensure efficient signal transmission.

　　

　　Homogeneous construction with low tolerances in insulation thickness and dielectric constant.

　　

　　Typically, high-frequency is defined as frequencies above 1 GHz. Currently, PTFE (polytetrafluoroethylene), commonly known as Teflon, is widely used for high-frequency PCBs, especially those operating above 5 GHz. FR4 and PPO substrates are commonly used for frequencies between 1 GHz and 10 GHz. The differences between these materials are as follows:

　　

　　Regarding laminate cost, FR4 is the least expensive, while Teflon is the most costly. In terms of dielectric constant (DK), dissipation factor (DF), water absorption, and frequency characteristics, Teflon outperforms the other substrates. For applications requiring frequencies above 10 GHz, Teflon is the optimal choice, despite its higher cost and poorer heat resistance properties. To enhance the thermal and mechanical properties of PTFE, fillers like SiO2 or fiberglass are added. Additionally, because PTFE has molecular inertia and doesn¨t easily bond with copper foil, special surface treatments (such as chemical or plasma etching) are used to improve adhesion, though these may affect the dielectric performance.

모모What is FR-4?In order to grow rapidly, FLEX PCB Do not hesitate to change the strategy and rearrange the products, so as to obtain unexpected results. https://www.wellcircuits.com/

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모모FR-4 is a grade for flame-retardant fiberglass reinforced epoxy material. Therefore, FR-4 PCBs offer a higher level of heat resistance compared to standard PCBs. The FR-4 board is classified into three categories based on the number of copper trace layers:

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모모Single-layer PCB

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모모Two-layer PCB

모모

모모Multilayer PCB

모모

모모High TG PCB Specifications

모모

모모The 몷Tg몸 refers to the glass transition temperature of the PCB. It indicates the temperature at which the material begins to transition from a solid state to a liquid state (learn more about Tg). If the operating temperature exceeds the specified Tg value, the circuit board can lose its structural integrity, which may negatively affect its functionality.

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모모Standard PCBs typically have a Tg value of 130뫢C C 140뫢C, while high-Tg PCBs range from 170뫢C to 180뫢C.

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모모Typical Application Areas

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모모Multilayer boards

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모모Industrial electronics

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모모Automobile electronics

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모모High-temperature electronic components

　　The typical depth of the V-cut is 3/4 of the board¨s thickness. If you plan to use V-cuts, we recommend maintaining a safe distance from the V-cut line to any traces. Please consider this when designing your panels.So, RF PCB On the contrary, there is still a lot of room to play. https://www.wellcircuits.com/

　　

　　V-cut example 1

　　

　　V-cut Example 1

　　

　　V-cut example 2

　　

　　V-cut Example 2

　　

　　V-cut example 3

　　

　　V-cut Example 3

　　

　　V-Cut Machine

　　Among all metal core PCBs, aluminum PCBs are the most common type. The base material consists of an aluminum core with standard FR4. It features a thermal clad layer that dissipates heat efficiently, cooling components and enhancing the overall performance of the products. Currently, aluminum-backed PCBs are considered the solution for high-power and tight tolerance applications.Therefore, this is the choice RF PCB The reason, there is no denying its positive impact. https://www.wellcircuits.com/

　　

　　aluminum PCB

　　

　　Advantages of Aluminum PCB

　　

　　Environmentally Friendly: Aluminum is non-toxic and recyclable. Manufacturing with aluminum also conserves energy due to its ease of assembly. For PCB suppliers, using this metal helps maintain the health of our planet.

　　

　　Heat Dissipation: High temperatures can severely damage electronics, so using a material that can dissipate heat is essential. Aluminum transfers heat away from vital components, minimizing potential damage to the circuit board.

　　

　　Higher Durability: Aluminum provides greater strength and durability than ceramic or fiberglass bases. It reduces the risk of breakage during manufacturing, handling, and everyday use.

　　

　　Lightweight: Despite its strength, aluminum is a surprisingly lightweight metal. It adds durability and resilience without increasing the weight of the product.

　　

　　Applications of Aluminum PCB

　　

　　Audio Devices: Input/output amplifiers, balanced amplifiers, audio amplifiers, pre-amplifiers, and power amplifiers.

　　

　　Power Supply: Switching regulators, DC/AC converters, and SW regulators.

　　

　　Communication Electronics: High-frequency amplifiers, filtering appliances, and transmitter circuits.

　　

　　Office Automation Equipment: Motor drives, etc.

　　

　　Automobile: Electronic regulators, ignition systems, power supply controllers, etc.

　　

　　Computers: CPU boards, floppy disk drives, power supply devices, etc.

　　

　　Power Modules: Inverters, solid-state relays, rectifier bridges.

　　

　　Lamps and Lighting: With the growing promotion of energy-saving lamps, various energy-efficient LED lights are well-received in the market, and aluminum PCBs are increasingly used in LED lighting applications.

　　

　　aluminum PCB application

　　

　　If you have any questions regarding PCB and PCBA, please feel free to contact me at

　　The image above is from the crowdfunding project ＾Neosegment Digit￣ by Maks Surguy on Crowd Supply. The project has gained significant attention, raising a total of $6,500. We are proud to support Maks in assembling this project.Down-to-earth right PCB manufacturing in China In-depth research is the only way to pursue development. https://www.wellcircuits.com/

　　

　　Wellcircuits has also assisted creators with the assembly of the following projects on Crowd Supply:

　　

　　ALio Proto Board: The All-in-One Prototyping Board

　　

　　Neosegment Digit

　　

　　Paperino

　　

　　Crowd Supply is a popular crowdfunding platform based in Portland, Oregon, known for supporting creators in bringing innovative and useful hardware to life. Their mission is to provide the necessary funding and resources to help creators deliver high-quality products to their backers.

　　

　　We first met at the 2017 Open Source Hardware Summit, where we discussed the potential for future collaboration. Both of our goals are aligned in helping enthusiasts bring their projects to life. Today, we are excited to announce our partnership:

　　

　　Any successful crowdfunding project on Crowd Supply is eligible for a 10% discount (up to $300) on PCB assembly services at Wellcircuits. You can also apply for a coupon code for your backers. Simply send your project link to anson@wellcircuits.com to receive your discount.

　　

　　As a professional PCB production and assembly company, Wellcircuits has earned a strong reputation among engineers worldwide. This partnership will leverage our strengths to ensure smooth execution for crowdfunding projects. All of our components are original, and we guarantee on-time delivery, ensuring your supporters receive their products as quickly as possible. Additionally, you can count on excellent after-sales service at Wellcircuits.

　　

　　Let¨s create something amazing together!

　　Among all metal core PCBs, aluminum PCBs are the most common type. The base material consists of an aluminum core with standard FR4. It features a thermal clad layer that dissipates heat efficiently, cooling components and enhancing the overall performance of the products. Currently, aluminum-backed PCBs are considered the solution for high-power and tight tolerance applications.Actually, it’s not just this reason, FLEX PCB Its own advantages are also obvious, and it is normal for the market to perform well. https://www.wellcircuits.com/

　　

　　aluminum PCB

　　

　　Advantages of Aluminum PCB

　　

　　Environmentally Friendly: Aluminum is non-toxic and recyclable. Manufacturing with aluminum also conserves energy due to its ease of assembly. For PCB suppliers, using this metal helps maintain the health of our planet.

　　

　　Heat Dissipation: High temperatures can severely damage electronics, so using a material that can dissipate heat is essential. Aluminum transfers heat away from vital components, minimizing potential damage to the circuit board.

　　

　　Higher Durability: Aluminum provides greater strength and durability than ceramic or fiberglass bases. It reduces the risk of breakage during manufacturing, handling, and everyday use.

　　

　　Lightweight: Despite its strength, aluminum is a surprisingly lightweight metal. It adds durability and resilience without increasing the weight of the product.

　　

　　Applications of Aluminum PCB

　　

　　Audio Devices: Input/output amplifiers, balanced amplifiers, audio amplifiers, pre-amplifiers, and power amplifiers.

　　

　　Power Supply: Switching regulators, DC/AC converters, and SW regulators.

　　

　　Communication Electronics: High-frequency amplifiers, filtering appliances, and transmitter circuits.

　　

　　Office Automation Equipment: Motor drives, etc.

　　

　　Automobile: Electronic regulators, ignition systems, power supply controllers, etc.

　　

　　Computers: CPU boards, floppy disk drives, power supply devices, etc.

　　

　　Power Modules: Inverters, solid-state relays, rectifier bridges.

　　

　　Lamps and Lighting: With the growing promotion of energy-saving lamps, various energy-efficient LED lights are well-received in the market, and aluminum PCBs are increasingly used in LED lighting applications.

　　

　　aluminum PCB application

　　

　　If you have any questions regarding PCB and PCBA, please feel free to contact me at

　　Among all metal core PCBs, aluminum PCBs are the most common type. The base material consists of an aluminum core with standard FR4. It features a thermal clad layer that dissipates heat efficiently, cooling components and enhancing the overall performance of the products. Currently, aluminum-backed PCBs are considered the solution for high-power and tight tolerance applications.In addition to these aspects, PCB manufacturing in China The performance in other aspects is also relatively good, which has attracted everyone’s attention and research. https://www.wellcircuits.com/

　　

　　aluminum PCB

　　

　　Advantages of Aluminum PCB

　　

　　Environmentally Friendly: Aluminum is non-toxic and recyclable. Manufacturing with aluminum also conserves energy due to its ease of assembly. For PCB suppliers, using this metal helps maintain the health of our planet.

　　

　　Heat Dissipation: High temperatures can severely damage electronics, so using a material that can dissipate heat is essential. Aluminum transfers heat away from vital components, minimizing potential damage to the circuit board.

　　

　　Higher Durability: Aluminum provides greater strength and durability than ceramic or fiberglass bases. It reduces the risk of breakage during manufacturing, handling, and everyday use.

　　

　　Lightweight: Despite its strength, aluminum is a surprisingly lightweight metal. It adds durability and resilience without increasing the weight of the product.

　　

　　Applications of Aluminum PCB

　　

　　Audio Devices: Input/output amplifiers, balanced amplifiers, audio amplifiers, pre-amplifiers, and power amplifiers.

　　

　　Power Supply: Switching regulators, DC/AC converters, and SW regulators.

　　

　　Communication Electronics: High-frequency amplifiers, filtering appliances, and transmitter circuits.

　　

　　Office Automation Equipment: Motor drives, etc.

　　

　　Automobile: Electronic regulators, ignition systems, power supply controllers, etc.

　　

　　Computers: CPU boards, floppy disk drives, power supply devices, etc.

　　

　　Power Modules: Inverters, solid-state relays, rectifier bridges.

　　

　　Lamps and Lighting: With the growing promotion of energy-saving lamps, various energy-efficient LED lights are well-received in the market, and aluminum PCBs are increasingly used in LED lighting applications.

　　

　　aluminum PCB application

　　

　　If you have any questions regarding PCB and PCBA, please feel free to contact me at

　　The weather was sultry and humid after entering the night.among industrial water chiller It has given great spiritual support to entrepreneurs, and more entrepreneurs will contribute to this industry in the future. https://puremind.com/product-category/puremind-air-conditioner/industrial-chiller/

　　

　　The frequency of air conditioning is increasing.

　　

　　Hot summer day

　　

　　Is it advisable to stay in an air-conditioned room for a long time?

　　

　　Do I need to open the window to ventilate the air conditioner?

　　

　　The answer is coming ◎

　　

　　Turning on the air conditioner should not close the doors and windows.

　　

　　A set of experiments will show you.

　　

　　Many people have been in air-conditioned rooms for a long time.

　　

　　I will feel dizzy and sleepy.

　　

　　This may be that the indoor carbon dioxide concentration exceeds the standard.

　　

　　Experts said

　　

　　National standard of indoor carbon dioxide concentration

　　

　　The general requirement is below 1000ppm.

　　

　　For shopping malls, schools and other densely populated places

　　

　　Generally, the concentration of carbon dioxide is required to be below 1500ppm.

　　

　　When the indoor carbon dioxide concentration reaches 2000ppm

　　

　　The human body often feels dizzy and uncomfortable.

　　

　　There are only two or three people in the family.

　　

　　Why does the concentration of carbon dioxide exceed the standard?

　　

　　Two experimenters are in a 13-square-meter bedroom

　　

　　Close the doors and windows and turn on the air conditioner.

　　

　　By placing a good observer

　　

　　Real-time observation of indoor carbon dioxide concentration changes

　　

　　Over time

　　

　　The concentration of carbon dioxide keeps rising.

　　

　　Just half an hour.

　　

　　It has already exceeded 1500ppm.

　　

　　Experts said

　　

　　For the home environment

　　

　　This concentration has exceeded the standard

　　

　　after an hour

　　

　　The concentration of carbon dioxide in the air

　　

　　More than 2000ppm

　　

　　And it’s rising

　　

　　The experimenter opened the window for ventilation.

　　

　　After 15 minutes.

　　

　　Indoor carbon dioxide concentration

　　

　　Slowly dropped below 1000ppm.

　　

　　It can be seen that the doors and windows are closed and the air conditioner is turned on for 1 hour.

　　

　　It may cause the indoor carbon dioxide concentration to exceed the standard.

　　

　　If you sleep in this environment for one night,

　　

　　It is very likely that lack of oxygen will bring health risks.

　　

　　It is recommended to turn on the air conditioner.

　　

　　Open the window properly to get some air.

　　

　　For families that are inconvenient to open windows

　　

　　Consider purchasing a new fan.

　　

　　Instead of window ventilation

　　

　　Air-conditioned rooms should not stay long.

　　

　　Beware of “air conditioning disease”

　　

　　It is hot and hot in summer.

　　

　　Stay in an air-conditioned room for a long time

　　

　　Not only dizziness, headache

　　

　　It may also induce “air conditioning disease”

　　

　　Knowledge of small science popularization

　　

　　”Air-conditioning disease” is a series of diseases induced by long-term use of air conditioning. When using air conditioning, the space is relatively closed, the air is not circulating, pathogenic microorganisms are easy to breed, and the temperature difference between indoor and outdoor is large, so the body is not well adapted, so a series of symptoms will appear.

　　

　　Abdominal pain and diarrhea

　　

　　The stomach and intestines are very sensitive to the stimulation of temperature.

　　

　　Excessive indoor and outdoor temperature difference

　　

　　Accelerated gastrointestinal peristalsis

　　

　　Cause digestive dysfunction

　　

　　Cause abdominal pain and diarrhea

　　

　　catch a cold and have a fever

　　

　　Enter the room with low temperature from the hot outdoor.

　　

　　Easy to catch a cold and cough.

　　

　　Even induce asthma and pneumonia.

　　

　　Serious illness

　　

　　neck shoulder lumbocrural pain

　　

　　Thin clothes in summer

　　

　　Shoulder, knee, waist, etc.

　　

　　Exposed to the cool breeze for a long time

　　

　　It is easy to cause symptoms such as joint and muscle pain.

　　

　　It is easy to cause cervical spondylosis and scapulohumeral periarthritis.

　　

　　cardiac infarction

　　

　　From low temperature indoor to high temperature outdoor.

　　

　　Switch like this

　　

　　Will make blood vessels suddenly contract and expand.

　　

　　Repeated fluctuation of blood pressure may induce myocardial infarction.

　　

　　For the elderly with fragile blood vessels,

　　

　　be highly dangerous

　　

　　How to blow air conditioning healthily?

　　

　　Pay attention to these points!

　　

　　Air conditioning should be cleaned regularly.

　　

　　Whether it’s central air conditioning

　　

　　Or a stand-alone air conditioner at home

　　

　　It should be cleaned before use.

　　

　　It is recommended to clean it once every 1~2 months after use.

　　

　　Window ventilation is essential.

　　

　　Turn on the air conditioner

　　

　　Attention should be paid to frequent ventilation.

　　

　　It is recommended that every 2~3 hours.

　　

　　Just ventilate the room once.

　　

　　Ventilation for 10 to 15 minutes each time.

　　

　　Air conditioning wind blows upward.

　　

　　The temperature should not be too low.

　　

　　Cold air will stimulate sweat pores to contract suddenly.

　　

　　It is easy to cause dizziness, headache, runny nose,

　　

　　Symptoms such as joint pain.

　　

　　It is suggested that the temperature of air conditioner should be adjusted to 26≧

　　

　　The temperature difference between indoor and outdoor should not exceed 7≧

　　

　　When the air conditioner is turned on, the cold air sinks.

　　

　　So the wind had better blow upward.

　　

　　Avoid cold air blowing directly on your body.

　　

　　Drink more warm water.

　　

　　To prevent water loss from the body

　　

　　Causes dry skin and itchy throat.

　　

　　Drink plenty of warm water.

　　

　　Drink chrysanthemum tea, etc

　　

　　Eat more fresh fruits rich in vitamins.

　　Winter is coming, and many friends in the south are estimated to be inseparable from the company of air conditioning. Recently, some netizens who are familiar with the home appliance industry have summed up 10 cold knowledge about air-conditioning electric auxiliary heating. If you are afraid of cold, you may be able to learn it.For the current market situation, Puremind Commercial Air Conditioners It has a very advantageous development prospect and an extremely superior ecological environment. https://puremind.com/

　　

　　1. 38≧: According to the standard, the air outlet temperature should reach above 38≧ when air conditioning is heating, which is higher than human body temperature, otherwise it will feel like cold air when blowing on people.

　　

　　2, wind speed: air conditioning heating, high wind speed when the outlet temperature is low, low wind speed when the outlet temperature is high.

　　

　　3. Temperature: After the air conditioner is turned on for heating, the air outlet temperature of 40≧ is faster than that of 60≧. Because the hot air floats up, the high temperature of the outlet air will float up to the roof faster, and the lower temperature will help the middle and lower air to heat up.

　　

　　Comprehensive 2 and 3, if the air conditioner wants to heat well, it needs to turn on the large air volume, and after turning it on, the air will be discharged at 40≧ first, and then the air will be heated to about 50≧ after the room temperature rises.

　　

　　4. The purpose of electric auxiliary heat: it is to heat the air outlet temperature. When the outdoor temperature decreases, the heating performance of the air conditioner will be attenuated. Turning on electric auxiliary heat can increase the air outlet temperature and avoid people feeling cold wind blowing.

　　

　　5. When do you need to turn on the auxiliary heating? According to the national standard, when the outdoor temperature is above 0≧, the auxiliary heating of air conditioner is turned off by default, and users can turn it on manually. When the temperature is lower than 0≧, it is turned on by default, and the user can turn it off manually.

　　

　　6. Principle of electric auxiliary heating: The electric auxiliary heating is at the lower end of the internal heat exchanger, in front of the air outlet of the air conditioner, with PTC ceramic heating rods inside and aluminum fins outside. After electric auxiliary heating, the temperature will reach 200~300≧, so electric auxiliary heating can’t be dry-burned, and the air conditioner must be blown after it is turned on.

　　

　　7. Will electric auxiliary heating blow white powder? The consultant learned that in 2024, the air-conditioning models were sold, and the sleeve pieces had been passivated, or Teflon coating was sprayed on the surface to prevent white powder blowing. At present, the models on sale will not have the problem of blowing white powder.

　　

　　8. When defrosting the air conditioner, can you turn on the electric auxiliary heat to avoid excessive cooling of the room?

　　

　　No way. When the air conditioner is defrosting, the internal fan stops running, and the air conditioner does not give out air. If the electric auxiliary heat is turned on, it will dry up and may burn out the internal machine parts. When the air conditioner is defrosting, it is not good for the internal machine to keep blowing air.

　　

　　9. Air conditioners that do not stop defrosting. When some models defrost, the internal heat exchanger will heat up. Is the electric auxiliary heating turned on?

　　

　　No, electric auxiliary heating can only heat the outlet air temperature, but not the heat exchanger.

　　

　　10. Japanese air conditioners are good at heating without electricity, but domestic air conditioners are not good at heating with electricity.