HVAC School - For Techs, By Techs

Latest Episodes:

Triple Evacuation - Short 121 Jun 29, 2021

Show notes

In today's short podcast, Bryan explores triple evacuation. Many people believe that we don't like triple evac, but that's simply NOT true. We're here to set the record straight.

If the manufacturer tells you to follow triple evacuation processes, then it's a good idea to do what they say. We won't argue with that. However, our argument is that the procedure can be more time-consuming than it's worth when it's NOT necessary.

Deep vacuum technically counts as a vacuum pulled below 500 microns (in residential, that target is usually 200-300 microns). Most modern micron gauges and tools make it easy to achieve a deep vacuum. In a triple evacuation, you pull the vacuum three times (instead of once). Between pulling vacuums, you break with nitrogen before pulling the vacuum back down.

Triple evacuation originated in a time when micron gauges and vacuum pumps were less reliable. We did not take deep vacuum very seriously, especially since mineral oil (MO) typically did not break down inside the system. (Modern oils like polyolester/POE break down rather easily, so pulling a deep vacuum is much more vital nowadays.)

Instead of merely breaking with nitrogen, Bryan recommends flowing it. It's best to flow the nitrogen with force to move the oil around more effectively. In turn, your vacuum will pull down more quickly and efficiently.

So, triple evacuation isn't bad, but it can be time-consuming. Just be sure to follow all best practices if you perform a triple evacuation.

Join us as we cover:

Deep vacuum targets
Micron targets
Breaking with nitrogen
Flowing nitrogen
POE vs. mineral oil
Old manufacturer literature about deep vacuum
Microns

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.

How to Teach the Physics of Everyday Life Jun 24, 2021

Show notes

In today's podcast, Bryan explains how he teaches physics. He believes that teaching physics is about continuously building a mental model, and he covers the methods and mindsets that facilitate that learning style.

The basic Wikipedia definition of physics states that it is a science that deals with matter, energy, and their interactions. Even then, we can simplify "matter" to "stuff." Simplifications like these help students feel more familiar with the subject and NOT feel intimidated by the material. Students learn best when they feel like they can grasp the topics out of the gate. That is why the math-based approaches of traditional education might turn students away from physics. Some students who don't like math might feel out of their depth when teachers approach topics with a mathematical approach.

Instead, effective teaching is about attaching experiences to a concept. Teachers can take stock of what students already know and build on that. They can also attach experiences to a concept, such as by allowing students to have hands-on experiences with physics examples in the real world. Once students have relevant experiences, they have the tools to learn through similes and analogies.

Bryan covers:

Socratic learning
Comparing levers to seesaws for educational purposes
Experimentation and experience
Similes, metaphors, and analogies
Shortcomings of math-based learning methods
Creating "cartoons" in your head to learn topics
Teaching superheat and subcool with mental "cartoons"
States of matter
Humidity and the weight of water vapor
Electron movement
Steam and why it's complicated
Teaching electricity with comparisons (water, drawbridges, jump ropes)
How children (and babies) learn about physics as they navigate the world
Mythbusting

Remember, when it comes to education, the goal is to learn, NOT to impress people.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Be Careful With Cold Tanks - Short 120 Jun 22, 2021

Show notes

In today's short podcast, Bryan explores the dangers of cold tanks during refrigerant recovery.

Whenever you have a recovery tank, you only want to fill it to 80% capacity in the liquid state. The same goes for all sorts of vessels (coils, etc.).

However, capacity isn't the only factor to consider for safety. We need to know what our maximum temperature will be. You will be in greater danger of overfilling a tank when it is cold because higher temperatures increase the pressure. High pressure in a closed space may lead to explosions. When you fill a tank to 80% under cold conditions, normal temperature conditions could put you in the danger zone (let alone temperatures above 100°F).

So, it's better to determine your tank fill based on densities at the MAXIMUM temperatures you will encounter, NOT for the measurements at artificial cooling conditions (such as when you put the tank in ice water during recovery).

In the end, just be careful when you're recovering into a cold tank or using tanks when it's cold outside. That will help you avoid hydrostatic pressure buildup and explosions.

Bryan covers:

The 80% capacity rule for filling vessels with liquid
Why the 80% capacity rule varies by temperature
Temperature, pressure, and density
Hydrostatic pressure
AHRI's 77°F guideline
Ice buckets for recovery
What to do if a tank vents its refrigerant on you while driving

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Dehumidification Facts w/ Nikki Jun 17, 2021

Show notes

In today's podcast, Nikki and Bryan discuss dehumidification. They cover the relationship between cooling and dehumidification, humidity control, and dehumidifier installation practices.

If the A/C unit is the king, the dehumidifier is the queen. The A/C unit controls cooling and humidity, but it can only do so much. A dehumidifier helps the A/C manage comfort under more demanding conditions. Many factors contribute to comfort, including sensible heat ratio (SHR), relative humidity (RH), and ventilation. Dehumidification reaches all of those factors.

Humidity control requires a holistic approach. Band-aid fixes DO NOT work. Dehumidifiers should work with the A/C system and building design to keep RH in the 50-55% range. Proper installation is vital. For example, tying into the HVAC supply is a recommended practice. Returns are the opposite; dedicated returns are preferred. Other factors to consider are proper sizing, Manual J, and customer expectations.

Join Nikki and Bryan as they cover:

Relative humidity targets
Sensible heat ratio (SHR)
Latent removal capacity
Ventilation
Building design and tightness
Manual J
Challenges with ductless systems
Ducting into the supply with dedicated returns
Installation practices
Dehumidifier sales and customer service

And much more…

To learn more about Santa Fe Ultra series, go to www.santa-fe-products.com. You can scroll through the products to find the Ultra series free-standing ventilating dehumidifiers.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

TXV Troubleshooting w/ Trevor Jun 10, 2021

Show notes

In today's podcast, Trevor and Bryan discuss how to troubleshoot thermostatic expansion valves (TXVs/TEVs). They also dive into the various types, applications, and components of TXVs.

TXVs are metering devices that control evaporator superheat to protect compressors from harm. Controlling heat also regulates pressure, which improves efficiency and prevents issues like floodback and overheating. TXVs contain several components that manage the forces that open and close the valve. These components include powerheads, diaphragms, springs, and more. The components all contribute to a delicate balance that can be broken when they fail or are installed improperly. TXV failures lead to high or low superheat and eventually compressor failure.

When you diagnose a TXV, you may encounter hunting, broken powerheads, filthy screens, and improperly sized valves. Once you verify the cause of the issue, you'll likely have to adjust the TXV, replace a component, or replace the whole TXV. That can be a tricky decision that will largely depend on the type of failure, the type of TXV (conventional vs. balanced port), and the TXV's application (residential HVAC, refrigeration, etc.).

Join Bryan and Trevor as they cover:

Opening and closing forces
Internal and external equalization
Non-bleed/hard shutoff TXVs and design limitations
Conventional valves vs. balanced port valves
Brazing in TXVs
Strapping the TXV bulb to the suction line
TXVs in refrigeration vs. HVAC
Liquid quality, sight glasses, and subcooling
TXV sizing
Suction pressure/superheat hunting
High and low superheat causes
Adjusting vs. replacing valves

And much more...

Check out Emerson's HVACR training HERE. Then, navigate to "Contractor Tool Box Talks with Emerson."

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Push Pull Recovery - Short 119 Jun 08, 2021

Show notes

In this short podcast episode, Bryan discusses push-pull recovery, how it works, and what we need to know about it.

Push-pull recovery is a somewhat counterintuitive method of recovering liquid rapidly. We simply do that by pulling refrigerant out of the system and pushing it into the tank. However, when we pack refrigerant into a tank, the tank pressure and temperature increase. So, it can be more difficult to get refrigerant into the tank as the job goes on.

When we recover liquid refrigerant on large systems (20+ pounds of charge), you connect a line from the liquid line or receiver and attach it to one side of the tank. Then, you pull from the system the other side of the tank should lead into the recovery machine. Attaching to the recovery machine helps depressurize the tank.

When pulling out of the tank, you'll want to make sure the refrigerant is a vapor. The recovery machine should be pulling only vapor refrigerant out of the tank. While you're depressurizing your tank, you will be pressurizing your system to push the liquid refrigerant out of the system and into the recovery tank. (Short hoses with a large diameter are usually best for quick recovery.)

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.

Small System Vacuum Tip - Short 118 Jun 01, 2021

Show notes

In this short podcast episode, Bryan goes over one of his most valuable tips for pulling a vacuum on a small system.

It can be very difficult to pull a vacuum on a small system, especially when you're dealing with a low-temperature application like a freezer. When you pull a vacuum, you're creating a low-pressure area that affects molecule behavior. So, you're creating a situation where the molecules push their way out of the system and into your vacuum pump. The low temperature and small tubing, especially capillary tubes, make this process exceptionally difficult. A very good vacuum pump can still have a hard time achieving a deep vacuum.

To make this process a little easier, Bryan likes to add heat. When you add a heat blanket around components with oil, you negate the low-temperature obstacle and make it easier to separate refrigerant from oil. You may also use a heat gun on areas where using a heat blanket is impractical. If the area is cold or has refrigerant and oil together, then you'll benefit from applying heat. Don't go crazy and use open flames, but a heat blanket or heat gun will usually be safe.

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.

How to END Callbacks May 20, 2021

Show notes

In this podcast episode, Bryan and Eric Mele explain how HVACR technicians can END callbacks with a few best practices.

Rushing through calls will often lead to callbacks. One of the most common mistakes techs make is failing to check the condensate drain before walking away from a job. To end callbacks, technicians would be wise to check the entire system and note any possible problem areas; in commercial HVAC and refrigeration, pay attention to variation across evaporators, condensers, and drainage systems.

Customer service is a huge component of residential HVAC; you can prevent callbacks by listening to the customer's concerns, addressing their comfort issues (even if it lies beyond the obvious problem), checking your "five pillars," and thoroughly explaining what you've done. Even if a problem seems to drag out, take all the steps necessary to alleviate your customers' fears.

Electrical problems also cause callbacks, especially dual-run capacitors. So, it's a good idea to check for wiring rubouts and make sure the wires look clean and organized. If you can offer an electrical solution to the customer at a cost, do it, even if they might decline it; that way, the callback is on them, not you.

Overall, being thorough, communicating with the customer, and offering solutions is the key. If possible, it's best to explain everything at once and have one money conversation. If you can't get a full diagnosis until the customer approves a repair, be transparent about that.

Eric and Bryan also discuss:

Multi-equipment setups in commercial settings
Dealing with difficult customers
Managing customers' expectations
HVAC in new homes
Determining if a unit has been set up correctly
Smart thermostats
Cleaning drains and equipment
Preventing flooded starts
OEM vs. aftermarket parts
Commonly replaced parts (reversing valves, TXVs, etc.)
Establishing a process that works

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Compressor Overheating Diagnosis & Prevention May 13, 2021

Show notes

In this podcast episode, Bryan and Eric Mele discuss the diagnosis and prevention of compressor overheating in HVAC and refrigeration.

The main causes of compressor overheating are inadequate cooling back to the compressor, low charge, restrictions, and sometimes even poor suction line insulation. We want to keep the suction temperature low while maintaining appropriate superheat. If the suction line temperature is too high, the compressor can't cool down well enough. Dirty condenser coils, low voltage, weak capacitors, or an inadequate condenser fan can also lead to compressor overheating.

Electrical problems, including too little capacitance, will make a compressor go out on thermal overload. When you have refrigerant problems, the thermal mass will just keep growing; it takes a long time to heat the compressor up, and it will take a long time to cool it down.

In a thermal overload, a bimetallic disk in the compressor will open and break all three legs of power. When a compressor goes out on thermal overload, it will make an open circuit, and you will read infinite ohms. Knowing that the compressor has gone out on thermal overload is just the beginning of compressor overheating diagnosis.

So, to begin diagnosis, you'll want to make sure there's refrigerant in the system. Inspect the unit visually and note anything that seems odd. Then, you'd check your capacitor for electrical problems. You can also feel the compressor to get an idea of the extent of the overheating (try not to burn yourself). You'll also want to monitor the amp draw, condensing temperature, suction pressure, and superheat.

Eric and Bryan also discuss:

Axial fans
Condenser fan intermittent failures
Resetting the compressor
Cooling down the compressor
Setting up your meter
Being out on high pressure
Wrapping wire to increase ammeter resolution
High return gas temperature

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Re-tapping Transformers - Short 117 May 11, 2021

Show notes

In this short podcast episode, Bryan and Eric Mele talk about re-tapping transformers for single-phase equipment in 208v applications.

Most single-phase equipment can work for 230v or 208v, meaning that they can operate with low voltage. However, we typically see 208v in commercial buildings. The sine waves of 208v equipment are 120 degrees out of phase, not 180 degrees (as in split-phase applications). We get lower voltage from leg to leg (208v, though the voltage can be a little higher or lower). Power companies generally put out slightly higher voltage to reduce line losses.

Most systems can work on multiple voltages, but they come with a transformer that's set to the 230v or 240v setting. However, under those settings, you can experience issues in 208v applications. If you put equipment tapped to 230v or 240v in a commercial setting, you may have issues, especially if you're farther away from the air handler. You may not get full 208v and may see contactors that don't pull in intermittently, and you may get intermittent cooling calls. Intermittent problems become worse when you have long thermostat wiring.

In those cases, re-tapping the transformer is your only option. When the original voltage is incorrect, you'll need to re-tap the primary (high-voltage power going in). If you fail to tap the primary correctly, the voltage going out of the secondary won't be correct. When it's time to test the equipment, you'll always want to be sure to test the equipment under load.

Make sure you cap extra wires and cap them independently of each other; those wires do have voltage, and we need to be cognizant of that.

Learn more about Refrigeration Technologies HERE.

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.