In this episode of the HVAC School Podcast, Bryan interviews Rachel Kaiser, a chemist with a passion for making science more accessible and understandable, especially when it comes to the topic of combustion. Rachel shares her background of how her family's restaurant business sparked her early interest in chemistry and the science behind mixing ingredients to produce desired results.

Rachel dives deep into explaining the fundamental chemistry behind the combustion process. She breaks down the three key components required for combustion to occur - fuel, oxygen, and a heat source - and how the ideal chemical reaction is represented. However, she emphasizes that in the real world, factors like using natural gas (a mixture of gases) as fuel instead of pure methane and air (also a mixture) as the oxygen source lead to incomplete and imperfect combustion reactions.

The discussion highlights the importance of combustion analysis and monitoring for byproducts like carbon monoxide (CO) and nitrogen oxides (NOx). Rachel stresses that testing is crucial not just for technician safety but to ensure proper combustion for occupants as well. High CO levels, for instance, indicate incomplete combustion and the likely presence of other undesirable compounds.

Topics covered include:

• The chemistry definition of combustion/flame
• Ideal vs real-world combustion reactions
• The three requirements for combustion
• Natural gas as a fuel mixture
• Air as the oxygen source and mixing considerations
• Carbon monoxide and nitrogen oxides as byproducts
• The role of combustion analysis
• Using visuals/experiments to teach combustion chemistry
• Applying chemistry knowledge for troubleshooting

Connect with Rachel on LinkedIn and ask her more about chemistry in HVAC HERE. You can also view her presentation from the 5th Annual HVACR Training Symposium and/or purchase your virtual ticket to all sessions HERE.

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.

In this short episode of the HVAC School podcast, Bryan talks about hoses and their various types and applications, particularly focusing on NAVAC hoses.

Charging hoses (NAVAC: NH5 and NH5L) ideally shouldn't be longer than 5-6 feet, as the longer the hose, the more refrigerant it will hold. Manifold gauges also have leak points, so it's usually better to use probes instead of manifolds to help with charging. Charging hoses with ball valves (NH5S and NH5SC) can help you control the flow and are great for recovery. Whenever you use charging hoses, they will have a core depressor on one side only (usually the 45-degree side, if applicable); the right amount should be exposed, and the seal should be in good shape.

Larger-diameter hoses with higher burst pressure are advantageous for recovery (though it's better to have separate hoses for recovery and evacuation). Larger-diameter hoses of a shorter length will allow you to get a higher flow rate, including cases where you have 1/4" connectors (though the F1028 & F1029 Rapid Y connection fittings can help out with those cases where you have 1/4" connectors by giving you the ability to connect two 3/8" hoses); hoses with a diameter of 3/8" are usually the biggest recommended ones for recovery. NAVAC's recovery hoses are the NHR38AA and NHR38AB.

Evacuation hoses are even bigger. Some good evacuation hoses include the NH34AB and NH34AC; they are short 3/4" hoses that are vacuum-rated and quite flexible. NAVAC also has smaller hoses, which tend to look more like recovery hoses. You do not want to use 1/4" hoses and core depressors for evacuation, but they are good for charging.

Check out all of the hoses NAVAC has to offer at https://navacglobal.com/products-by-category/hoses-kits/.

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.

In this episode of the HVAC School podcast, Bryan interviews Pat Ward, an HVAC technician who specializes in servicing and maintaining computer room air conditioning (CRAC) units for data centers. They dive deep into the unique challenges and setups involved in cooling these critical facilities.

Pat provides an overview of data centers, explaining that they are essentially industrial-scale computer rooms that generate immense amounts of heat from the servers and need precise environmental controls. CRAC units are specialized air conditioning systems designed to maintain the temperature and humidity within tight parameters suitable for electronic equipment.

Unlike typical comfort cooling, CRAC units supply air around 70°F to avoid excessive dehumidification. Humidity control is crucial, often requiring supplemental humidifiers or dehumidifiers. Pat discusses common configurations like air-cooled direct expansion (DX) units as well as chilled water systems with computer room air handlers (CRAHs). Redundancy is a major consideration, with units networked together to stage capacity and provide backup.

The conversation covers many other topics related to data center cooling such as:

• Using economizers and free cooling with outdoor air when conditions allow
• Potential issues with mildly flammable refrigerants in these applications
• Typical maintenance tasks like coil cleaning, filter changes, and refrigerant checks
• Accessing and navigating the control systems which often require passwords
• Advice for technicians new to working on CRAC units, like studying the equipment layout
• The massive scale of large data center installations with arrays of 20+ CRAC units
• Causes of overheating and how to avoid them
• Growth opportunities in the CRAC niche of HVAC

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.