HVAC School - For Techs, By Techs

In this short podcast episode, Bryan covers why and how to test heat pump defrost during maintenance. Heat pumps need defrost because the outdoor coil absorbs heat in heating mode. Moisture collects and freezes on the coil during this process, and the rate at which it happens depends on the temperature and the amount of moisture in the outdoor air. Frost interferes with heat transfer and airflow and must be defrosted; the reversing valve shifts and auxiliary heat turns on.
Before testing, identify the equipment brand and model, defrost control, and the defrost type (time & temperature or demand defrost); you may have a thermostat (open/close switch) or thermistor, and those have different operating and testing considerations. Some controls also allow you to accelerate timing.
Forcing defrost according to the manufacturer's literature will let you discover whether the command sequence works, but it may not tell you whether the sensors are working. Common visual checks can also help you resolve defrost issues dealing with sensors, base pan heaters, and poor airflow.
The key takeaway is to pay close attention to the defrost sequence, conditions, defrost logic, sensor type, and your own spidey senses when testing or diagnosing defrost.
This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, NAVAC, Filtrete, and the 2027 AHR Expo.
Resources
Learn Everything About Heat Pump Defrost (video)
HVAC Defrost Troubleshooting | Timers, Sensors, and Boards (video)
Heat Pump Defrost Cycle & Heat Strip Wiring Safety | HVAC Heating Season Preparation (video)
How to Test Heat Pump Defrost and How Defrost Works (video)
Upgrading Time & Temperature Defrost with Demand Defrost for Heat Pumps (tech tip)
Heat Pump Defrost Troubleshooting Tips (tech tip)
Coil Temp Sensors: Thermostats vs. Thermistors (tech tip)
HVAC School calculators
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Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

In this live stream episode, Bryan sits down with Tony Gonzalez, who has spent more than 25 years at Fieldpiece and now leads the company's training department. Tony started out packing boxes in the warehouse straight out of high school, and the two longtime industry veterans use his experience to dig into why culture matters so much when you are building a business that lasts. As Bryan puts it, culture may be talked about in HVACR, but it is true everywhere.
Tony walks through TURTL, the five core values that anchor Fieldpiece's culture: Tribe, Upfront homework, Right stuff, Trust, and Lean. The missing "E" is intentional, since it reminds everyone to leave their ego at the door. He explains why values can't be purely aspirational, and how Fieldpiece keeps them alive through recognition, one-on-ones, and development reviews. Bryan shares how the same ideas show up at Kalos, including the phrase "professional pride, personal humility."
The conversation then turns to leadership, which both guests agree is where culture is won or lost. They discuss why your culture is defined by the worst behavior you tolerate, why people stay at a company, and why curiosity should come before judgment. Tony describes the "bank account" of care that makes hard conversations productive, along with the Radical Candor idea of avoiding ruinous empathy. Bryan adds that clarity is kindness and that small problems should be dealt with before they become mountains.
They close by looking at team building, using Bryan's flight crew analogy and the "right people on the bus" idea from Good to Great. Every role matters, leaders shouldn't only hire people like themselves, and snap judgments can make you overlook great talent. Bryan wraps up with a few of his leadership commitments, and Tony's final advice is to start documenting what matters to your organization, live it consistently, and give yourself grace on the leadership journey.
Topics Covered:
Tony's 25-year career at Fieldpiece, from warehouse to head of training
The TURTL core values and why "Turtle" has no E
Keeping core values visible through quarterly recognition, one-on-ones, and development reviews
Leaders as culture carriers, and how culture shows up when things go wrong
Defining culture as a social operating system and the worst behavior you tolerate
Professional pride and personal humility, and leaders who celebrate their team's success
Why people stay: growth, recognition, fair compensation, and connection to the mission
Curiosity before judgment, root cause thinking, and celebrating failure
Making "deposits" of care so difficult conversations go well
Radical Candor, ruinous empathy, and clarity is kindness
Handling bad news and building a safe environment for people to speak up
Building a flight crew: hiring for attitude, valuing different strengths, and avoiding the horns effect
The weakest link in the chain and treating every role as equally important
Book recommendations: Good to Great, The Power of Company Culture by Chris Dyer, and Delivering Happiness by Tony Hsieh
Bryan's leadership commitments: truth over comfort, open doors with no gatekeeping, and people over plans
Key takeaway: leaders must live the culture, give yourself grace, and define your North Star.
This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, Copeland, Santa Fe Dehumidifiers, and TruTech Tools.
Resources
Good to Great by Jim Collins (book)
The Power of Company Culture by Chris Dyer (book)
Delivering Happiness by Tony Hsieh (book)
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Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

In this short podcast episode, Bryan discusses electrical connections and whether tighter is better (or if a connection is tight enough to fail). 
Torque is a turning effect; force is applied at a distance from the screw's center, and that force creates pressure at the connection. A quarter-turn doesn't tell us how much force we have applied. You may notice a tight screw with other signs of a poor connection, like discoloration; tightening the connection may not help.
At a connection, we want very little resistance to current flow, and we get increased resistance and heat where we don't want it when connections are poor; according to Watt's law, when the resistance stays the same, doubling the current creates four times the heating power. However, temperature alone doesn't tell you the cause; thermal imaging is useful evidence, but we need operating conditions and current measurements, too. 
The key takeaway is that tightening the connection as much as possible may do more harm than good; having a torque screwdriver and using it can help. When making new connections, use the torque screwdriver to torque to the proper specs right out of the gate. We must also consider wire sizing, wire placement, exposed conductors, and unacceptable double lugging. We must also be mindful of ferrules, including proper selection and crimping. Make all adjustments safely (without voltage), and if you do not have the manufacturer's data immediately available, look it up. Eventually, you will get an idea of what "good" looks like.
Remember: tighter doesn't necessarily mean better.
This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, NAVAC, Filtrete, and the 2027 AHR Expo.
Resources
Tightening Electrical Threaded Terminal Connections (tech tip)
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Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Glycol secondary loop systems are showing up in more and more grocery stores, and in this episode of the HVAC School Podcast, Bryan Orr sits down with Max, one of the company's lead startup techs and its in-house subject matter expert on glycol skids. Max explains what these systems are, why clients are choosing them for retrofits, and what it takes to commission one without taking a live store down. The big picture: a traditional DX rack chills a water and propylene glycol mix in a heat exchanger, and that glycol is pumped around the store to cool the medium-temperature cases.
The conversation starts with the "why." Reduced refrigerant charge inside the building, keeping flammable or higher-GWP refrigerants out of the sales floor, regulatory pressure, and zero-emissions initiatives all push clients this way. Max is upfront that efficiency isn't one of the reasons at this scale, since the extra heat exchange step, lower suction temperatures, and pump energy all cost something. He also covers the trade-off in reliability: case-level controls are simple, but a fault in one of the skid's main valves can take out every case at once, so techs have to move fast.
From there, Max walks through the skid itself, from the brazed plate heat exchanger, VFD-controlled pumps, and air separator to the expansion tank, strainers, suction guide, controller, and EEV drivers. He then covers flow control with balance valves, defrost strategy, and the importance of proper vents and drains in the piping. The two get into the details of startup and commissioning, and some key takeaways include pressure testing instead of pulling a vacuum, filling and purging air, and verifying that the refrigerant-side valves are wired and driven correctly so a swapped valve doesn't flood the rack.
The back half of the episode is practical field advice. Max shares how to recognize air in the loop, why store humidity and dew point matter so much for case performance, which specialty tools and fittings he carries, and how to handle glycol mixing and top-offs.
Topics Covered
What a glycol secondary loop system is, and how it differs from direct expansion
Why retrofits are happening: refrigerant charge reduction, safety, EPA regulation, and zero-emissions goals
Efficiency penalties at small scale, and why efficiency isn't the driver
How glycol behaves in the coil: no latent exchange, a temperature gradient, and frost patterns
Reliability trade-offs: simple case controls versus centralized, mission-critical valves
Staging a retrofit so the store stays open, including pre-piping, pre-testing, and pipe cleaning
Brazing versus soft solder, and whether nitrogen flow matters with glycol
Skid components: heat exchanger, VFD pumps, air separator, feeder tank, expansion tank, strainers, and suction guide
Controller inputs, EEV drivers, and emergency mobile chiller connections
Balance valves (automatic versus manual) and defrost methods, including off-time and electric
Fluid distribution: pitching pipe for air and drainage, plus vents and drains
Propylene versus ethylene glycol, the 35% mix, freeze point, and why more glycol hurts heat transfer
CO2 as a secondary fluid for low-temperature applications
Commissioning steps: electrical checks, pressure testing, filling, purging, and testing valve operation
Proving performance: flow, glycol concentration, temperature, and superheat on the rack side
Troubleshooting air in the system and pressure changes as glycol chills
Store humidity, dew point targets, and case performance
Heat reclaim using glycol loops
Tools: PT ports, manometers, female-to-female hoses, refractometer, and transfer pumps
Service tips: distilled water, matching glycol brands, and glycol safety
This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, NAVAC, and Filtrete.
Resources
HVAC School calculators
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Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

In this short podcast episode, Bryan talks about why your thermostat is reading the wall, not the actual air temperature.
A thermostat is an instrument designed to read temperature (and sometimes humidity); it displays those readings based on sensors and makes decisions. Most of these sensors are thermistors, which are resistors that change resistance with changes in temperature. Thermistors have low mass and respond to radiant, convective, and conductive heat.
Air coming through the wall (convective heat), the temperature of the things around the thermostat (radiant heat), AND the wall temperature (conductive heat) can influence your thermostat's reading. We may see a service call where the thermostat reads above the air temperature and runs the air conditioning unit even when the air temperature is already below the set point. Our first move as technicians should be to ask customers when they noticed the problem; the timing can give us some clues about what is going on. Looking behind the thermostat is one of the first things we should do, as air can move through the hole where wires come through, especially if there is air leakage elsewhere. If there is a temperature difference and an airflow path, that could be the source of the issue.  
Use a reliable temperature probe near the thermostat, off the wall and away from the thermostat casing and electronics, to get a reliable temperature measurement to compare to the thermostat. If the probe and thermostat disagree after several minutes, we should investigate deeper for a warm wall. Infrared thermometers and thermal imagers can help you identify warm surfaces. Keep in mind that thermostats may have sensors in different locations, offsets, and programmed corrections as well. 
If you find an open wire penetration, use non-flammable insulation and/or an appropriate putty to close it. Be careful not to block the sensing vents, too. Let everything settle and repeat the comparison. Some other solutions include changing the location of the thermostat or remote sensor.
This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, Copeland, and Santa Fe Dehumidifiers.
Resources
HVAC School calculators
Submit a podcast question
Learn about the GRIT Foundation
Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.