Basic Refrigerant Circuit Course June 4, 2025, 4:07 am - HVAC School

Sign In

Search In:

Event Videos Tech Tips Apps Books Podcasts Users

HVAC Feed
Resources
Content
- Start
- Podcasts
- Videos
- Social Media
- Tech tips
- Quizzes
Courses
Events
Jobs
- Create a Job Post
- Job Posts
Shop
Partners

Search In:

Event Videos Tech Tips Apps Books Podcasts Users

English▼

+

Chinese (Simplified)

Sign In

Get Tech Tips

Subscribe to free tech tips.

BACK

Basic Refrigerant Circuit Course June 4, 2025, 4:07 am

June 4, 2025

Print Friendly, PDF & Email

Share this Tech Tip:

Check out our most recent video

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

Audio Player

Bi-metal & Magnetic Switches – Short #252

HVAC School – For Techs, By Techs

Bi-metal & Magnetic Switches – Short #252

In this short podcast episode, Bryan covers some basics on bi-metal and magnetic switches.Bi-metal switches are made of two dissimilar metals that are bonded together[...]

0.8
1
1.2
1.5
2

Facebook
Twitter
Linkedin
Copy episode link Copied
Download

00:00

12:00

Bi-metal & Magnetic Switches – Short #252

byBryan Orr

In this short podcast episode, Bryan covers some basics on bi-metal and magnetic switches.

Bi-metal switches are made of two dissimilar metals that are bonded together and are often integrated into motors. When the temperature changes, the metals bend. In an overload circuit, they’re designed to bend and open the circuit in an overheat condition. Mercury thermostats also use these; they have a bulb attached to a bi-metallic coil, which causes it to wind or unwind when heated or cooled. Fan limit switches also use bi-metallic coils. Bi-metallic discs also exist, and they snap open to make or break a circuit.

Bi-metallic switches have a time delay and often auto-reset (with exceptions like rollout switches on furnaces), which is advantageous in some applications. However, they’re also affected by the ambient temperature and are more likely to trip in warm weather and less likely to trip in cold weather. Nuisance trips are more common than in magnetic switches, and they may weld themselves shut and fail closed (though failing open is relatively common as well).

Magnetic switches are usually more external to the equipment or parts they’re protecting (such as in the contactor or starter assembly instead of inside a motor itself). These switches are also more instantaneous and are better for mission-critical applications. These also respond to amperage and aren’t affected by ambient temperature. They’re more likely to fail open than closed.

Compared to bi-metallic technology, magnetic switches trip faster and are better for sudden issues rather than long-term operational overheating. In many cases, we use both of them to get the benefits of each.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

Subscribe to our YouTube channel.

Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android

Search Episodes

Bi-metal & Magnetic Switches – Short #252

08/12/2025

Bryan Orr

Fan Law 2 for Techs w/ Adam Mufich

08/07/2025

Bryan Orr

Understanding Voltage Drop – Short #251

08/05/2025

Bryan Orr

Understanding Airflow: David Bowie, a Used Car Lot, and a 40¢ Tool

07/31/2025

Bryan Orr

Returns – Passive? Active? Sizing? w/ Adam & Matt

07/24/2025

Bryan Orr

Fan of Fans – Short #250

07/22/2025

Bryan Orr

Keys to VRF Maintenance w/ Roman

07/17/2025

Bryan Orr

Maintenance Mindset – Short #249

07/15/2025

Bryan Orr

IAQ, Ethical Selling & Building Better Techs w/ Brynn Cooksey

07/10/2025

Bryan Orr

Crankcase Heaters – Short #248

07/08/2025

Bryan Orr

Search Results placeholder

Check our latest Tech Tips

A2L Dissipation Boards and Leak Sensors Oscilloscope Systems and Settings I’ve Done It This Way for 20 Years – And That’s the Problem

Nylog Blue Gasket -Thread Sealant for AC/R Systems

Nylog Blue Gasket -Thread Sealant for AC/R Systems One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER Venom Pack Condenser Cleaner is a high foaming pure concentrate liquid designed to tackle the toughest soils. The proprietary blend of specialty detergents will liquify heavily embedded grease and grime to restore heat transfer and increase the efficiency of the coil.

Viper Condensate Pan and Drain Treatment

Viper Condensate Pan and Drain Treatment Viper Condensate Pan and Drain Treatment is a sprayable gel. It coats the pan, p-trap and drain piping with a lubricative film to improve flow and prevent future soil adhesion. The slow dissolving enzyme gel will outperform and outlast conventional tablets and strips.

Nylog Blue Gasket -Thread Sealant for AC/R Systems

Nylog Blue Gasket -Thread Sealant for AC/R Systems One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER Venom Pack Condenser Cleaner is a high foaming pure concentrate liquid designed to tackle the toughest soils. The proprietary blend of specialty detergents will liquify heavily embedded grease and grime to restore heat transfer and increase the efficiency of the coil.

Viper Condensate Pan and Drain Treatment

Viper Condensate Pan and Drain Treatment Viper Condensate Pan and Drain Treatment is a sprayable gel. It coats the pan, p-trap and drain piping with a lubricative film to improve flow and prevent future soil adhesion. The slow dissolving enzyme gel will outperform and outlast conventional tablets and strips.

Nylog Blue Gasket -Thread Sealant for AC/R Systems

Nylog Blue Gasket -Thread Sealant for AC/R Systems One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

NAVAC

Find out more about the Innovative NAVAC line of Vacuum Pumps

Fast-Stat

Copeland

Santa Fe

UEI

Comments

To leave a comment, you need to log in.

Related Tech Tips

It Has a Flat For a Reason Read more

Testing Run Capacitors the Smart (and Easy) Way Read more

3 Things to Check When the Unit Won’t Keep Up Read more

More tech tips

loading

To continue you need to agree to our terms.

Terms and Conditions

Yes No

The HVAC School site, podcast and tech tips
made possible by generous support from

Interested in a HVAC Career?

Find A local trade school

Resources

Calculators
Tool list
Apps
Great Books
Software and Business
Other Resources we like
Unconformed

Content

Start
Podcasts
Videos
Social Media
Tech Tips
Quizzes
Courses

Events

6th Annual HVAC/R Training Symposium
Upcoming Events
Create an Event
Event Partnership

Jobs

Job Posts
Create a Job Post

Partners

Partners
Carrier
Copeland (Emerson)
Fieldpiece
NAVAC
Refrigeration Technologies
Santa Fe

Get Tech Tips

Subscribe to free tech tips

Email Address

First Name

Terms and conditions & Privacy Policy
EULA
Reuse License

©2025 - HVAC School | All rights reserved