In this short podcast, Bryan talks about filtration and IAQ, especially as they relate to virus control. He also answers the age-old question: “Can filters capture viruses?” While it may seem like particle size matters when it comes to filter efficacy, filters are not nets that strain air particles and prevent pollutants from passing through. When we talk about particles, we tend to focus on ones that are 0.3 microns in diameter, which tend to be medium-sized particles. Viruses tend to be among the smallest particles that we aim to control when it comes to IAQ. Filter media are crisscrossed fibers that catch particles in different ways. Inertial impaction is one means of stopping particles from passing through; the initial impact stops the particles from passing through. Interception happens when particles graze filter fibers and get stuck. Electrostatic attraction relies on energy to attract and catch particles. Diffusion happens when smaller particles move more erratically due to Brownian motion and get caught in the filter media.  Viruses are among those smaller particles. Smaller particles’ erratic motion makes them more likely to collide with the filter media, so they aren’t necessarily harder to catch. Higher MERV ratings are associated with higher capture efficiencies. HEPA filters surpass the MERV scale and have also been proven to filter viruses out of the air, but we rarely use true HEPA filtration in residential HVAC because they are too restrictive for total system airflow. We can use bypass HEPA filtration to filter the air without creating a massive restriction at the unit. Large filter-back returns with 2” filters can help catch more particles with a greater surface area without tanking the static pressure.   Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast  HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

Can Filters Capture Viruses? - Short #172

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In this short Q&A; podcast episode, Bryan answers Gunther's question about kitchen exhaust and makeup air. Gunther asked if there were any studies that showed that makeup air should come very close to the hood to avoid infiltration. He also asked how to educate others who push back against the idea, particularly in kitchen exhaust systems of around 600 CFM. Commercial facilities, especially restaurants, bring in makeup air to balance out the air being exhausted. There are costs associated with makeup air, but there are plenty of valid reasons to add it to residential structures. Being able to control the makeup air allows us to control where we bring air in from (especially when it comes to drawing in humid air or dirty attic air from gaps and cracks, particularly in vented attics). Open-combustion appliances in the building envelope are also prone to backdrafting if the structure is under negative pressure. The structure is also more likely to have its dryer vents experience leaks under negative pressure.  The International Residential Code (IRC) (section M1503.6.2) requires makeup air when you have an exhaust system >400 CFM. The Florida Residential Code (section M1503.4) requires kitchen exhaust systems exceeding 400 CFM to have makeup air at approximately the same rate as the exhaust rate. Furthermore, the Florida Mechanical Code (section 505.2) specifies that kitchen exhaust systems exceeding 400 CFM must have makeup air to balance the air pressure and ensure proper ventilation.   Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.    Purchase your virtual tickets for the 5th Annual HVACR Training Symposium at https://hvacrschool.com/Symposium24.    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.

Q&A - Kitchen Exhaust and Makeup Air - Short #197

This episode featured Bryan Orr interviewing Sam Myers, the building science consultant at Retrotec. Retrotec manufactures products like blower doors and duct testers for measuring air tightness and leakage in buildings. Sam discussed his role at Retrotec, which involves training contractors on using their tools properly, product design, software testing, presenting at conferences, and running trade show booths. He talked about the demanding travel schedule this requires but also the rewards of educating the industry. The main topic was duct leakage testing - why it's important, how it's done, interpreting the results, and investigating and fixing duct leaks when problems are found. Sam explained that while a duct leakage test provides a number, that number alone doesn't indicate if the leakage is acceptable or problematic. However, it points technicians in the right direction for further investigating issues like comfort problems, indoor air quality concerns, or high energy bills. He provided tips on using tools like smoke tests and thermal cameras to visually identify leaks, checking common leak areas like connections and return duct penetrations, and the value of testing before and after making repairs to verify the work. Sam also discussed using low-cost manometers for other tests, like checking room pressure imbalances caused by duct leaks. Topics covered included:  Sam's role and work at Retrotec The importance of duct leakage testing How duct leakage tests are performed Interpreting duct leakage test results Common duct leak sources like connections and return penetrations Methods for pinpointing and verifying duct leaks Using manometers for other diagnostic tests Tips for contractors getting started with duct testing    Learn more about Retrotec's resources at https://retrotec.com/.  Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.    Purchase your virtual tickets for the 5th Annual HVACR Training Symposium at https://hvacrschool.com/Symposium24.    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.

Duct Leaks - Measuring, Preventing & Repairing w/ Sam Myers

In this short Q&A; podcast episode, Bryan answers Jeremy's question about checking the charge on rooftop units, and he gives some RTU tips. Rooftop units often come in sets, so you can use a thermal camera to look at all of the RTUs and compare them. A thermal imaging camera may even show you where subcooling begins in the condenser, which can be a useful diagnostic hack. Try to avoid hooking up gauges each time you check the charge on a rooftop; RTUs have a fixed factory charge, and losses from your gauges can add up over time. Your senses will also come in handy; check for odd sights, sounds, and smells. Checking suction pressure and superheat is less risky and imperfect, but it'll give you some diagnostic data. You can also check discharge temperatures to check for signs of compressor overheating (remember: 225 stay alive).  Here are some tips for RTUs:  Get familiar with the service manual and wiring diagrams; these items will help you with the job and help you build on your knowledge of RTUs in general. Make sure you have all of your materials at the ready, including extra screws. Make sure you have access to the BAS system, if necessary. Safety is critical on rooftop units, especially when it comes to ladders, lockout/tagout, and ensuring that you have safe access to the unit (this burden is often on the client).  Pay attention to specialized equipment, including ERVs and economizers. Be mindful of curb installation, transformer taps, and phase monitoring, as those items may not be set up properly. Build up a basic working knowledge of variable frequency drives or VFDs (or know where to find information about them; THIS livestream is a good start), Keep systems clean to prevent overheating. Prevent oil logging whenever you have to replace a compressor.    Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.    Purchase your virtual tickets for the 5th Annual HVACR Training Symposium at https://hvacrschool.com/Symposium24.    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.

Q&A - RTU Tips - Short #196

This episode features an insightful conversation with Brynn Cooksey, an experienced HVAC contractor and trainer from Southeast Michigan. Brynn shares his expertise in conducting proper load calculations, sizing the equipment correctly, improving duct design, and addressing common issues contractors face. Brynn emphasizes the importance of performing accurate load calculations, especially in older housing stock where equipment is frequently oversized by 50% or more. He discusses how oversized equipment leads to short cycling, poor efficiency, and increased utility costs for homeowners. His approach involves educating customers by involving them in the measurement process and using metrics like "duct deficiency" to demonstrate the inefficiencies of their current systems. The discussion then shifts to heat pumps and the unique challenges of implementing them in cold climates like Michigan. Brynn advocates for a "dual fuel" approach, utilizing heat pumps for efficiency while supplementing with gas heat during extremely cold temperatures. He stresses the necessity of a tight, well-insulated thermal envelope and proper duct design to ensure optimal heat pump performance. Topics covered include:  Conducting blower door tests for accurate load calculations Downsizing equipment and solving duct issues in retrofit applications The "duct deficiency" metric for demonstrating system inefficiencies Aeroseal duct sealing: benefits, limitations, and proper application Identifying and addressing cracked heat exchangers due to airflow issues Training sales teams on a hands-on, educational sales process The importance of building science education for contractors Overcoming hesitancy in trusting load calculation results  Brynn encourages contractors to embrace building science principles, trust the load calculation process, and focus on system design rather than simply swapping out equipment. By proving these methods to themselves, contractors can transform their businesses and deliver true value to customers through improved comfort, efficiency, and cost savings.   Learn more about HVAC U and its course offerings at https://www.hvactrain.com/.  Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.    Purchase your virtual tickets for the 5th Annual HVACR Training Symposium at https://hvacrschool.com/Symposium24.    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.

Practical Loads, Ducts and Sales w/ Brynn Cooksey

In this short Q&A; episode, Bryan answers podcast listener Cooper's question about starting an internal training program. Eugene Silberstein has been on the podcast before to offer his perspective on this topic, which you can listen to  HERE.  Bryan recommends a combination approach: instructor-led, hands-on, and self-paced learning, all deployed together. Hands-on learning often gets missed, and we can give inexperienced techs experience with some basic troubleshooting tasks or breaking down and reassembling things. The Socratic method can also be employed here; the instructor can ask their trainees questions instead of the other way around. When the instructor is the one who asks the questions, they allow their trainees to be wrong, learn from their mistakes, and make their own connections to the fundamentals. Learning plans and curriculums are great for giving trainees a structure, but they need to be reinforced with the hands-on component in this trade. When determining what to teach, try to focus on what's most important in your market—the first area of effectiveness—and then understand how to reinforce it. The continuous growth mindset is also critical; the apprenticeship phase is never truly over, and the instructor needs to be able to improve their program over time without letting the idea of unattainable perfection discourage them from giving their training.   You may also read  our tech tip about setting up an internal training program and our recent  SkillCat guide if you want to deploy training in your business. The ESCO All Access Subscription Bundle for the HVACR Learning Network is another excellent resource. Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.    Purchase your virtual tickets for the 5th Annual HVACR Training Symposium at https://hvacrschool.com/Symposium24.    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.

Can Filters Capture Viruses? - Short #172

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