In this short Q&A podcast episode, Bryan answers a listener-submitted question about superheat, including what it is and how we measure it.

Superheat is the number of degrees a refrigerant is above its saturation point. The saturation point is where you will have a liquid-vapor mix, so superheat only exists when a substance is a vapor. Saturated refrigerant should only exist in the evaporator and condenser, during which it is being boiled or condensed.

We usually measure superheat at the evaporator coil outlet and compressor inlet. The superheat at the evaporator outlet is usually around 5-14 degrees Fahrenheit, and it's often between 10 and 20 degrees at the compressor inlet (compressor superheat). However, many systems try to get lower superheat values, and some manufacturers may require higher superheat values at the compressor inlet to prevent liquid refrigerant from getting into the compressor. Accumulators can help keep liquid refrigerant out of the system as well. We may also measure superheat coming out of the compressor on the discharge line (discharge superheat); this superheat may exceed 100 degrees Fahrenheit. Discharge superheat can let you know if the compressor is overheating the oil and causing breakdown or carbonization.

We use superheat to set the charge for fixed-orifice metering devices (as opposed to subcooling for TXVs), as superheat is a measure of how well we're feeding our evaporator coil. When the system is off, the superheat will be 0. A system will equalize, and the refrigerant will be at saturation when that happens.

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

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In this episode of the HVAC School podcast, Bryan interviews Zach from Southeast Clean Air Solutions about the intricacies of professional duct cleaning. Zach specializes in addressing duct cleaning challenges specific to the Southeastern climate, with a particular focus on fiberglass-lined ducts. The conversation delves into the complexities of cleaning different types of duct systems, highlighting the significant variations in time, technique, and approach depending on the duct materials and home configuration.

The discussion reveals that duct cleaning is far more nuanced than many homeowners realize. A typical residential duct cleaning can take between six to eight hours, with metal ductwork being significantly faster to clean than flexible ducts or fiberglass-lined systems. Zach emphasizes the importance of careful cleaning techniques, especially with delicate flex ducts that can easily be punctured or damaged during the cleaning process. He recommends a two-person approach, with one team member working inside the home and another in the attic or crawl space to ensure thorough and safe cleaning.

Beyond the cleaning process, the podcast explores critical maintenance strategies for maintaining clean and efficient HVAC systems. Zach and Bryan discuss the importance of proper filtration, home maintenance, and understanding when duct cleaning is truly necessary. They challenge the common misconception of a fixed cleaning schedule, instead advocating for system assessment based on specific conditions like household dust, humidity, and the health needs of home occupants.

Key Topics Covered:

• Duct cleaning techniques for different duct materials (metal, flexible, fiberglass-lined)
• Time requirements for professional duct cleaning
• Challenges of cleaning ducts in various home configurations
• Importance of proper filtration and maintenance
• Factors determining duct cleaning frequency
• Risks associated with poorly maintained duct systems
• Two-person approach to thorough and safe duct cleaning
• Specialized considerations for homes in humid climates
• Post-cleaning sealant application for fiberglass-lined ducts

Learn more about NADCA and find certified duct cleaning contractors at https://nadca.com/.

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 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

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

In this short podcast, Bryan talks about electric vehicles and whether EVs present an opportunity for HVAC technicians. The residential sales lead at Kalos recently mentioned that keeping an EV in a conditioned garage is advantageous, and it's an upgrade we can offer our customers.

In hot weather, EV battery performance and health can be degraded. On top of that, the vehicle consumes power when the vehicle gets hot so that the A/C can control the climate inside the car and preserve the interior. Most people also charge their electric vehicles in the garage at night, so it would stand to reason that conditioning the garage can yield energy savings and improve vehicle longevity. Attic encapsulation above the garage is also an option to limit warm, moist attic air from leaking into the garage; HVAC upgrades can include using closed-cell foam to encapsulate the attic and install a dehumidifier in there.

Conditioning a garage requires you to think about insulation. In our market (Florida), block walls don't insulate very well. Even when we can't do very much with the walls, we can usually use some polyiso boards inside the garage. However, we could get some moisture challenges, and carbon monoxide could be an issue if combustion appliances are in the garage (like furnaces, water heaters, or gas-powered cars). We can recommend using heat pump water heaters, and we should quote a low-level CO monitor in cases when garages have a CO risk.

It's important to make sure the garage remains separate from the rest of the house even when we do these upgrades. Keeping the garage separate helps prevent chemicals from getting into the airstream, especially yard chemicals or cleaners.

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 6th 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.