HVAC School - For Techs, By Techs

Latest Episodes:

Intro to ACCA Manual T Aug 18, 2022

Show notes

Ed Janowiak joins the podcast to introduce us to ACCA Manual T.

Compared to other manuals, Manual T is one of the least-considered ACCA manuals. However, it's the manual that advises us on how not to blow high-velocity air on people and has maintained the same standards since the mid-1900s. Unlike Manuals J, S, and D, Manual T is not recognized in code compliance.

Manual T deals with air distribution; it helps us find out the throw and spread, which informs our ductwork design in Manual D. We need to know the customer's expectations and the air velocity we'll need to manage at the registers before designing the ductwork. Register placement is also a critical element of Manual T.

Throw and spreqd can vary wildly, and register selection and placement are going to have a significant effect on comfort as a result. Register placement on the ceiling may achieve the Coanda effect to assist with air distribution, and that can be especially useful in low-load or passive homes. Low-load homes are an interesting case, as they use less hardware than other homes, meaning that we need to make the most of calculations and equipment selection.

Manual T ultimately focuses on using the diffusers and registers, rather than the equipment, to spread air throughout a space. Knowledge of the principles in Manual T also allows us to communicate, establish, and manage expectations with the customer.

Ed and Bryan also discuss:

Registers, diffusers, grilles, and vents
Filter restrictions
ACCA Manual LLH
Air movement in the occupied vs. unoccupied zone
Manual T as an extension of Manual D
What it means to lend credibility in this industry
Floor vs. ceiling registers based on climate

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.

Net Refrigeration Effect - Short #150 Aug 16, 2022

Show notes

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.

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.

Systems Thinking - Gas and Combustion Aug 11, 2022

Show notes

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

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.

HVAC School Admin Discussion - Moderating a Successful Community Aug 04, 2022

Show notes

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

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.

Systems Thinking - HV / LV / Condensate Jul 28, 2022

Show notes

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"

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.

Systems Thinking - Copper & Line sets Jul 21, 2022

Show notes

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.

Systems Thinking In HVAC w/ Eric K Jul 14, 2022

Show notes

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.

Logical Fallacies - False Cause & Strawman Jul 07, 2022

Show notes

Nathan Orr joins Bryan to talk about some logical fallacies, namely the false cause and strawman. They explain how those fallacies show up in the trade.

It's difficult to present arguments without using fallacies, but people tend to rely on fallacies to uphold extreme religious or ideological viewpoints or conspiracy theories. Fallacies are also often easier to communicate than nuanced science and data.

"False cause" relates to the phrase "correlation does not equal causation." It can be tempting to link coincidences and say that one thing causes the other, but that could very well not be true. For example, more compressors fail during lightning storms. It's reasonable to assume that lightning causes the failures, but lightning is not simply striking all of the compressors; other power outages and other conditions that happen during storms are more likely plausible causes.

Confirmation bias also makes it easy to cling to a false cause. People are likely to disregard data that doesn't align with what they already believe.

A strawman misrepresents (or deliberately misstates) another argument to make it easier to attack. People often apply the strawman fallacy to conversations about forming ice in a system during vacuum and duct sizing. Strawman arguments happen more often in business matters, especially if people impugn the intentions of the other party.

In many cases, being open to new information will prevent you from falling prey to logical fallacies.

Nathan and Bryan also discuss:

Flat-earthers
Inverter board failures at night
Evaporator coil corrosion
Simultaneous capacitor and fan motor failures
Logical fallacies in chance and gambling
The pitfalls of anecdotal evidence and small samples
Appeal to emotion
Defining "better"
Mounting TXV bulbs
Heuristics and mental shortcuts

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.

Tips for Learning in HVAC/R w/ Trevor Matthews Jun 30, 2022

Show notes

Refrigeration Mentor founder Trevor Matthews returns to the HVAC School podcast to talk about personal development and training, including tips for learning in HVAC/R.

When you're looking at a problem in the field or in training, it pays to take a step back, cool down, and reevaluate your mindset. Trevor recommends thinking about the worst-case scenario and seeing how you can either prevent it or grow from it. It's good to walk away for a little bit anytime you feel like you're overanalyzing anything so that you don't make blunders.

Trevor has found that reading books is one of the best ways to learn about HVAC/R. HVAC/R professionals can greatly benefit from investing in themselves and setting up their own self-directed training programs. Trainers and mentors can't be the only ones motivating HVAC/R professionals, holding them accountable, and stimulating their growth.

Many times, our own limiting beliefs of ourselves hold us back, and we need to convince ourselves that we can learn difficult things, even if it isn't easy. We can also limit our ratio of entertainment to education; focusing more on the latter can greatly benefit your personal development.

Setting educational goals is also difficult when we work long hours and simply don't have the time or energy to invest in ourselves. The industry needs reform, and reform that raises base rates and prevents an over-reliance on overtime might also attract some new professionals to the field.

Trevor and Bryan also discuss:

Trevor's new podcast
Clearing your head
Books about doing the hard things first
Autodidactism and "learning how to learn"
Subconscious cost-benefit analysis
The industry's addiction to overtime
Helpful books and podcasts for personal development
Getting rid of "tunnel vision"

Recommended book/podcast list:

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.

Threaded Connection Tips - Short #149 Jun 28, 2022

Show notes

In this short podcast episode, Bryan shares some of his top threaded connection tips. He also clears up some confusion about connection types.

Threaded connections include flare and compression-type fittings (like chatleff or Aeroquip fittings). The threads don't actually make the seal; the pressure pushing the surfaces together is what makes a seal.

Bryan doesn't recommend putting traditional thread locks on flares, but refrigerant oil or mild assembly lubricants can help the flare come together more smoothly without imperfections. However, you need to be careful when using a torque wrench and use the lowest acceptable specification to avoid over-torquing.

Leaks are common problems with flare fittings, but those often happen in cases where flares are poorly made. Scored faces, loose flares, and over-torqued flares are common causes of leaks. However, many modern flaring tools can make perfect flares quite easily. You must also remember to deburr the copper for the best results.

Compression-type fittings often have O-rings, which are the parts that actually do the sealing. (Leaks WILL happen without the O-ring in place.) You can use an assembly lubricant with these fittings, but you still have to be mindful of torque spec adjustments.

Pipe-thread connections actually rely on the threads, not pressure or an O-ring, to create a seal. Pipe dopes (or thread sealants) tend to be best on these connections, but you want to leave the last couple of threads bare so that pipe dope doesn't get into the system.

As with brazed and soldered joints, the copper used for threaded connections needs to be cleaned, cut squarely, and deburred for best results.

Bryan also covers: