545 episodes

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

HVAC School - For Techs, By Techs Bryan Orr

    • Business
    • 4.9 • 824 Ratings

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

    Net Refrigeration Effect - Short #150

    Net Refrigeration Effect - Short #150

    In this short podcast, Bryan explains what the net refrigeration effect (NRE) is and how it affects HVAC systems.
    The net refrigeration effect (NRE) is what happens in the evaporator coil. The evaporator is the heat absorber; as air passes over the coil, the cooler refrigerant within the evaporator absorbs that heat and boils. The NRE is the net energy change that occurs during that process. You can plot the NRE on a pressure-enthalpy chart.
    When air moves over the evaporator coil, there is a change in enthalpy or BTUs per pound in the refrigerant (usually called delta h). There should be more BTUs per pound in refrigerant exiting the coil than when it went in. We have to know how many pounds of refrigerant we’re circulating (mass flow rate) and how many BTUs are in those pounds.
    Many of those BTUs come from latent heat transfer, which happens when the refrigerant boils. When refrigerant undergoes a phase change, it remains at a constant temperature (sensible heat), but it continues absorbing heat. The heat absorbed contributes to the phase change, and that’s latent heat. Most of the NRE deals with those latent BTUs. (Note: this does NOT refer to latent heat loads.)
    In addition to the boiling or saturation phase, we also have to consider BTU changes when refrigerant flashes off at the beginning of the evaporator coil and heat obtained during the superheating phase at the top of the coil. We can maximize our NRE by running a cold evaporator coil (without freezing) and ensuring the evaporator is full of boiling refrigerant. BTUs absorbed in the suction line do NOT count towards the NRE, as they don’t contribute to cooling spaces or refrigerated boxes.
     
    Check out Eugene Silberstein’s book, Pressure Enthalpy Without Tears, at https://escogroup.org/shop/itemdetail.aspx?ID=1445. 
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    • 12 min
    Systems Thinking - Gas and Combustion

    Systems Thinking - Gas and Combustion

    Eric Kaiser returns to the podcast to talk about how we can use systems thinking to approach gas appliances and combustion in HVAC installation and service.
    Gas lines can be made of a few different materials, including black iron, copper, and CSST. These all have benefits, setbacks, and appropriate applications. For example, copper is common in propane (LP) systems but not natural gas. In coastal environments, galvanized pipe tends to be most common due to the increased likelihood of corrosion. Gas lines may also need sleeves to prevent them from interacting with moisture.
    The piping also needs to be routed in accordance with code; in many cases, joints need to be exposed so that a technician can check for leaks. Keeping joints inside walls is risky, especially when light switches cause sparks and could potentially ignite leaking natural gas. In any case, leak detection can be tricky unless you have a combustible gas leak detector and bubbles that work well for gas lines.
    Safety has to be the top priority when it comes to venting, especially on water heaters. A personal low-level CO monitor can also keep you and your customers safe by detecting small yet harmful amounts of carbon monoxide. Makeup air and combustion air are also important in gas appliances; unbalanced pressures may result in undesigned return paths. Traps and improper pitch may also lead to improper venting, as condensate may get trapped in the pipe and may lead to freezing or other complications.
    Eric and Bryan also discuss:
    Pipe material and flow rate Pipe sizing and connectors Regulator issues on gas water heaters and pool heaters Thread sealant products and best practices Bubble solution recommendations Signs and risks of backdrafting Exhaust pipe insulation Drain installation  
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    • 54 min
    HVAC School Admin Discussion - Moderating a Successful Community

    HVAC School Admin Discussion - Moderating a Successful Community

    Some admins from the HVAC School Facebook group join the podcast to discuss the art of moderating a successful community. Bryan is joined by Eric Kaiser, Ty Branaman, Michael Housh, and Neil Comparetto.
    A community based on a skilled trade gives people an inviting space to share information and ask questions. It’s also a space that allows people to practice how they present information. Groups also connect people across geographical locations, and we can get regional perspectives that change the way we think about things.
    However, community standards are necessary to keep groups professional and on-topic. Swearing is a slippery slope that may lead to personal attacks, which make the community hostile and unhelpful. The main goal is to keep a respectful atmosphere, and moderators have to draw the line somewhere, but there’s a difference between cultivating a productive atmosphere and being dogmatic.
    People who interact in those communities need to do it for altruistic reasons, not to satisfy their egos. Giving detailed, accurate answers (ideally with a source to back up the information) is the best way to contribute meaningfully. Engaging in rigorous debates with an open mind is also a great way to see many different viewpoints. 
    Debates in HVAC communities are great, but they require boundaries and mutual respect between debaters. Namecalling, blaming others, or dragging politics into the discussion is unproductive. Overall, it’s best to stay positive and try to keep things helpful, and admins try to maintain an atmosphere that can be both serious and lighthearted but is always helpful and respectful.
    HVAC communities and groups are not places to share other groups, content, or job postings. These groups are not marketing centers; they are forums for learning and discussing the work we do every day.
    Ty, Neil, Michael, Eric, and Bryan also talk about:
    How they got started in online HVAC communities Unproductive arguments about codes Banning and muting members Receiving feedback Avoiding logical fallacies in debates How egos hold people back Trite and unproductive catchphrases, slogans, and jokes Responding to disagreements productively Communicating with people appropriately Admitting fault and refraining from judging others who are incorrect Moderating posts for quality and shareability  
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    • 59 min
    Systems Thinking - HV / LV / Condensate

    Systems Thinking - HV / LV / Condensate

    Eric Kaiser returns to the podcast to discuss high-voltage wiring, low-voltage wiring, and condensate assemblies as they relate to systems thinking.
    On the high-voltage side, the disconnect should be in a secure location, and it should be able to keep water out. The wires should be appropriately sized, have an appropriate level of tension, and should not be vulnerable to chafing or abrasion. Overall, best practices include using proper grommets and ensuring that you have a solid connection. Do not run high voltage wiring in parallel with low-voltage or control wiring. It’s also worth noting that double-lugging is a poor practice that is against code.
    On the low-voltage side, you also need to be careful of where you route your wires to avoid induction, contact with hot surfaces, or abrasion. The insulation ratings also need to be appropriate.
    We can think of the condensate assembly as its own system. Condensate drains have uphills and downhills, and they may have traps, vents, and cleanouts throughout. Cleanouts and vents may be confused for each other, but cleanouts allow the technician to access and clean the drain. Cleanouts are also capped when in use, but vents are not. The location of a vent can help equalize the siphoning effects of pressurization.
    Condensate systems also consist of pans and switches. In those cases, redundancy is desirable to prevent overflowing. Secondary drain pans should be large enough to overlap with the primary pan, especially in horizontal air handlers.
    Eric and Bryan also discuss:
    Conductor length best practices Connecting stranded to solid wire Lug torquing Variation in wire sizing Testing low-voltage wires Cleanout tees Single vs. multiple drains with other appliances Drain pitch and if there could be “too much fall”  
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    • 46 min
    Systems Thinking - Copper & Line sets

    Systems Thinking - Copper & Line sets

    Eric Kaiser returns to the podcast to talk about how copper, piping, and line sets play into systems thinking.
    Nowadays, we have to think about POE and PVE oil, and we need to design line sets in a way that assists with oil carry while preventing liquid refrigerant migration. The height of the evaporator relative to the condenser is a major factor to consider during the design phase.
    Especially when chases are run underground, we need to watch for possible threats to the copper. Water softener discharge and excess pool water may damage the copper over time, and systems should be designed to keep line sets away from those. In many cases, Florida chases are sealed with mastic, which doesn’t prevent water from getting in (but does prevent rodents and insects from entering the home.
    Flowing nitrogen is one of the best practices you can do while brazing. Nitrogen displaces oxygen, which contributes to oxidation and produces scale. When cutting copper, you will also want to make sure that you don’t get copper shavings inside the tube. The pressure test is also an important step for leak detection. Following the manufacturer’s instructions, pressurize the system and apply a liquid leak reactant (bubbles) to joints and other common leak points.
    It’s a good idea to have at least one line drier in the system, and it should be able to work both ways in a heat pump system. Ideally, the line drier should be in a serviceable location, as it will be easier to detect restrictions when it’s on the line set.
    Eric and Bryan also discuss:
    Air and vapor barriers Long line guidelines Underground chase depth Derate values Controversial reaming/deburring practices Line drier best practices  
    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.

    • 33 min
    Systems Thinking In HVAC w/ Eric K

    Systems Thinking In HVAC w/ Eric K

    Eric Kaiser joins the podcast to talk about systems thinking in HVAC. Systems thinking allows us to solve problems and address customers’ comfort holistically instead of focusing on just the equipment. The key to systems thinking is to think outside the appliance.
    System design plays a major role in performance. Duct design, drain placement, and equipment placement all matter, and we can only do so much to mitigate factors of poor design. We need to assess the building envelope and consider how the HVAC system interacts with it. Building envelope and duct leakage will significantly affect HVAC performance and occupant comfort. 
    Ventilation also matters, especially since many homes rely on exhaust-only ventilation. However, the air that leaves the building must be replaced, and we often don’t control where that air comes from. When you control the source of your fresh air ventilation to meet ASHRAE 62.2, filtration may further help control the quality of the air that comes in.
    Installation and commissioning are other things we need to consider when thinking of the HVAC equipment systemically. The wiring needs to be correct, and we need to verify that the system is achieving the proper airflow in the first place. Static pressure is another factor that we must consider during commissioning, as an abnormal static pressure could indicate a filter that doesn’t fit or is too restrictive.
    It’s best to start by looking at the appliance and widening your scope from there until you know about the system as a whole.
    Eric and Bryan also discuss:
    Is the house a duct system? Oversizing equipment Stack effect Loose vs. tight houses Filtration best practices Radiant heat transfer Ductwork best practices Data trends of cause and effect  
    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.

    • 53 min

Customer Reviews

4.9 out of 5
824 Ratings

824 Ratings

jtel123 ,

Great podcast.

Love the podcast. Would like to see more technical discussions and less of the basics. Also would love to hear more on Market refrigeration and commercial refrigeration.

Tiggibrar ,

HVACR School

Thank you Bryan, re visiting all episodes, great resource for technicians. Delighted that you have quoted Douglas Adams. I thought I was the only one.

Big daddy popcorn Mike ,

Let me in on the conversation if you please get some questions

I’ve been doing eating eating heat ventilation and air-conditioning for 18 years plus recently a electrical company came in and did a pressure test for the duck work and the pressures are way off now they didn’t tape up none of the registers the supply they didn’t seal up the return was like a piece of cardboard in the hole cutting it with the flex running through it they weren’t 15 feet off the measurements were wrong the other the readings were off the charts so I will leave that all they did it incorrectly and there’s anyway I can join podcast and get down on it with you let me in I got some questions fellas

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