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Latest Episodes:

What is Correct Airflow? Sep 28, 2020

Show notes

The great Ed Janowiak (Jon-Oh-Wok) joins us to talk about what correct airflow really looks like. He also explains how to design for it appropriately.

The ACCA design series (Manuals J, S, and D) all go hand in hand to design HVAC systems properly for a given space. Correct airflow will depend on how a technician or designer uses the ACCA design series. When we say "correct airflow," we mean that the CFM per ton matches the sensible and latent load for a space while maximizing comfort for building occupants. In many cases, 400 CFM per ton is the rule-of-thumb baseline for many systems, but it's not a one-size-fits-all solution. The point of the ACCA manuals is to use math to determine solutions tailored to a specific space and avoid rules of thumb.

Many technicians prefer higher airflow in the field because it leads to fewer technical problems. However, the occupied space can suffer from reduced latent removal when you have higher airflow. Variable-speed technology helps a bit to allow longer runtimes to help with dehumidification, but consumers may not be in the market to purchase those solutions.

We can use airflow grids to determine the CFM on a running system. When those grids determine that the CFM per ton is below 300, that means the equipment is likely failing to match the required sensible BTUs. Airflow also affects pressurization, which you can measure with a manometer. Overall, you will want to track airflow trends and work to optimize the airflow.

Ed and Bryan also discuss:

Using software for calculations
Friction rate
Sensible heat ratio (SHR)
Equipment selection and code compliance
Relative humidity targets
Intermittent ventilation
Ancillary dehumidification
Duct sweating
Residential vs. commercial equipment design gap
Blower door testing
Testing delivered capacity and balancing
Zonal pressure testing
Extended performance data

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.

Digital Compressor Facts Sep 24, 2020

Show notes

Have you ever heard a compressor that keeps changing in sound as it runs? Trevor with Emerson tells us more about what that is all about and how the digital compressor operates.

Small Refrigeration Talk Sep 21, 2020

Show notes

Joe and Eric join us, and we have a general conversation about small self-contained refrigeration units, including residential and commercial. Small refrigeration includes self-contained reach-ins and small walk-ins. These units typically use capillary tube metering devices.

Some of the biggest failures that occur in small refrigeration systems happen because of dirty condensers and user error (leaving doors open, etc.). You'll also want to check that the fans are working, the compressor is running, the coil is free of ice, and that the airflow isn't blocked. Inspection is the key, and gauging up is typically a last resort.

Refrigeration temperature measuring strategies can vary wildly by application. For example, open cases measure discharge air temperature. Systems with enclosed boxes (like walk-ins) typically sense return or box temperature. Small reach-in systems also typically have dial cold controls in a challenging location: buried at the end of the evaporator. There are straight and curly cold controls, but new equipment has made a shift towards electronic controls.

On small refrigeration units, we don't usually see start capacitors or hard start kits; however, we do see PTC relays and thermal overloads.

Domestic refrigerators also count as small refrigeration. They have independent controls that move air from the freezer to the refrigerator section of a normal household fridge; there is usually no cooling apparatus in the refrigerator. In systems with defrost timers, a bimetal defrost thermostat would open when the element detects no more ice on the coil, and defrost would terminate.

Joe, Eric, and Bryan also discuss:

Capillary tubes vs. other fixed-orifice metering devices
Capillary tube restrictions and R-134A
Leaky systems
Vacuum
Box temperature vs. coil temperature controllers
Set point and customer expectations
Safety controls
Resistance in circuits
Defrost fan delay and failsafe
Hoarfrost

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.

Single Pole Contactors & Crankcase Heaters Sep 17, 2020

Show notes

Kaleb, Joe, and Eric join us again to discuss some myths about single-pole contactors. We also cover some weird crankcase heater wiring configurations.

When you have a single-pole contactor on a unit with no other resistance crankcase heater attached, the contactor energizes the compressor but is NOT a source of crankcase heat. That myth about single-pole contactors likely stems from a misunderstanding of Ohm's law and resistance heat.

We care about crankcase heat because we want to prevent refrigerant from migrating into the compressor during the off cycle. A crankcase heater keeps the compressor shell warm and prevents vapor refrigerant from condensing in the compressor. Overall, crankcase heat helps prevent flooded starts and oil loss. Some crankcase heaters can be wrapped around the outside of the crankcase, and others can be inserted into the compressor.

The crankcase heater and compressor winding can connect across an open contact to form a series circuit. (If you hook across L1 and T1 so that the other side has constant potential when the contact is open, a path can go to the crankcase heater.) The resistance in the compressor winding can contribute to the crankcase heat strategy, but Joe and Eric argue that the resistance is insignificant.

Overall, we need to remember that resistive heat is resistive heat; in a resistive circuit, your wattage is your wattage, and you can convert that directly to BTUs.

Kaleb, Joe, Eric, and Bryan also discuss:

Two-pole and three-pole contactors
Resistive heat
Operating A/C and heat pumps in low-ambient conditions
Ohming compressors
Jumpering in place of a single-pole contactor
Wire sizing
Loud thumping when the unit shuts off
Trickle current during the compressor off cycle
Power factor, reactive power, and actual power
Low-resistance circuits
Capacitor purposes, wiring, and sizing
Small charge and flood back prevention
3/8" lines

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.

Electronic Expansion Valves Sep 14, 2020

Show notes

Trevor Matthews with Emerson Canada comes on the podcast once again to talk about electronic expansion valves (also known as EEVs). He explains how they work, what they do, and how to diagnose them.

Trevor compares electronic expansion valves to TXVs on steroids; they accomplish similar tasks, but EEVs have faster response times, better accuracy, and can improve system efficiency. The valve operates on a controller, which is the "brain" of the EEV that tells it to open or close. EEVs can come in the on-off variety (pulse-width modulation) and stepper valves, which rely on a motor to control the mass flow through the metering device. Pulse-width modulators are less accurate than stepper valves because they only have two operation settings.

When installing EEVs or systems with EEVs, in many cases, the valve will point down. When brazing in stainless steel valves, you'll usually use a 30% (or higher) silver solder. It's also a good idea to wrap the valve and flow nitrogen while brazing. The bulbs of these valves MUST be insulated and strapped properly. The bulb and transducer need to be outside the refrigerated box in low-temperature conditions.

When troubleshooting EEVs, the best thing to do is start off by reading the manual; you want to understand the valve and controller. Then, check the parameters and determine where the pressure transducer and temperature probe are located.

Trevor and Bryan also discuss:

Balance of forces and superheat control
Solenoid valves
How stepper motors control the mass flow
Various refrigerants and EEVs
Setting parameters on EEV controls
Flux and flux-coated rods
Evaporator feeding
EXD-SH and EXD-U02 controllers
Connections, cabling, and wire splices
Expansion valve hunting
Objectional current and electrical issues with controllers
Battery backup vs. solenoids

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.

Introduction to CoreSense Sep 10, 2020

Show notes

Trevor Matthews from Emerson Canada joins us on the HVAC School podcast again to talk about CoreSense by Emerson.

Each CoreSense module has the potential to protect compressors. The technology can detect issues like overheating, short cycling, locked rotor, missing phase, low oil, and more. In short, the goal is to notify the technician or mechanic that something happened; sometimes, the control can also shut the compressor off and lock it out. Overall, it wants to communicate with the technician; different flashing codes indicate different sets of issues.

If you have CoreSense software on a laptop, you can access compressor data while the system is running. The software is available for A/C and refrigeration applications, so you can use the technology in residential HVAC as well.

Modern compressors can take a lot of abuse but last a long time. However, they can be expensive and are a total nightmare to install. Technologies like Emerson's can help technicians diagnose and fix compressors before we need to go through the financial and physical hassle of installing a new compressor. When you think about it, buying several CoreSense modules for a rack will probably cost less than a single compressor replacement. While the up-front costs may seem a bit high, Emerson packs the value into their new technology and allows customers and technicians to invest in guided troubleshooting and failure prevention.

Trevor and Bryan also discuss:

LED light flashing codes
Tying CoreSense into Emerson controllers
Scrolls vs. semi-hermetic compressors
Compressor expenses
Residential product line accessories
Zero point
Performance Alert vs. phase monitors
Application Engineering bulletins (AE8-1367 [semi-hermetic] and AE8-1424 [scroll])
Outlier diagnostics

Refrigeration Software (CoreSense Protection, Diagnostics & Performance Alert) – https://climate.emerson.com/OPI/documents/clc/CoreSense_PC_Communication_Software.exe

Air Conditioning Software (CoreSense Communications) - https://climate.emerson.com/OPI/documents/clc/CoreSense_PC_Communication_Software_AC.exe

HVACR Fault Finder App:

(Android) - https://play.google.com/store/apps/details?id=Emerson.FaultFinder&hl=en_US

(Apple) - https://apps.apple.com/ph/app/hvacr-fault-finder/id465325739

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.

How to Get The Most From Online Education Sep 03, 2020

Show notes

Alex Meaney from MiTek/Wrightsoft joins us again because he's an awesome trainer and knows a thing or two about how to more out of online education for the trades.

During the COVID-19 pandemic, we've seen a dramatic shift from in-person to online education. The transition has been hard on students and educators alike, but there are still ways to make it work.

Preparation is the key. Before you enter a class, make sure you look at the agenda and required or suggested reading. It's also a good idea to make sure you have the correct devices to access and participate in your online class; don't wait until right before the class to see if you have the right software or technology. We also recommend familiarizing yourself with the vocabulary before attending a class.

One way to boost the effectiveness of online training is to make yourself responsible for another person's learning. When you tutor or teach others, you raise the stakes of your own education. It's also good to take a class with a buddy, as you can fill the gaps in each other's learning.

The learning environment is also important; put away all your distractions, have a clean work area, and close the door to get the most out of your online class. On that same note, make sure you're comfortable; have a snack and a drink during your online training. If you need to keep your hands busy, find a quiet way to get your hands moving; we suggest writing notes down with a pencil.

Alex and Bryan also discuss:

Wrightsoft education changes
Preparation tips for instructors
Education as an investment
Ineffectiveness of PowerPoint slides
Accountability in education
Forcing yourself to have the space to learn
Time management
Asking questions
Watching recorded material
Microphone and camera awareness

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.

Preventing and Troubleshooting Compressor Issues Aug 27, 2020

Show notes

Our good friend Trevor Matthews from Emerson Canada joins us to talk about compressors, mostly preventing compressor failure and troubleshooting issues.

Whenever we're installing or servicing a compressor, we need to think about possible systemic issues right off the bat. The compressor is the heart of the system, but everything else in the system affects how the compressor runs. You'll want to know which type of compressor you're working with as well as the manufacturer. As always, you'll want to check the superheat, subcooling, amps, TD across the condenser, and (especially) discharge line temperature.

The compression ratio is also a telling sign of the system and compressor's health. You take the compression ratio by dividing the absolute suction pressure into the absolute discharge pressure. However, we must also consider the compressor's application; by design, refrigeration compressors can deal with higher head pressures than A/C compressors.

Anytime a compressor fails, you'll want to investigate why it failed. You can only see what happened inside a compressor if you cut it open and inspect it. During the inspection, look for signs of overheating and damaged components. Whether a burnout, flooded start, or thermal overload caused the failure, you will be able to see clues about the failure and can piece together the compressor's story. Once we finish troubleshooting and diagnosing a compressor, we can focus on preventing future compressor failure. We'll have a better idea of the operating conditions we need to avoid.

Trevor and Bryan also discuss:

Head pressure (discharge pressure vs. liquid line pressure)
Compressor types
Compressor overheating
Return gas temperature
Burnout
Line driers
The 80/20 rule
Flooded starts
Short cycling
Non-bleed TXVs
Recovery and evacuation
Thermal limit
Advanced temperature scroll protector (ATSP)

Emerson Flow Chart - https://www.hvacrschool.com/wp-content/uploads/2020/08/2004ECT-126_NOTRUNNING.pdf

Compressor Installation Guide -

https://hvacrschool.com/wp-content/uploads/2018/01/Compressor-Installation.pdf

Emerson System Cleanup Bulletin -

https://climate.emerson.com/CPID/GRAPHICS/Types/AEB/ae1105.pdf

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.

Suction Line Temperature - Short #100 Aug 25, 2020

Show notes

In this short podcast episode, Bryan discusses the importance of suction line temperature and what it can tell you about an HVAC system.

There are two main places to take your suction temperature: at the evaporator outlet and right where the suction line goes into the condensing unit. When the former number is high, you could have a starved/underfed evaporator. When the latter number is high, you may have poor suction line insulation. If the refrigerant is too hot when it goes into the compressor, you can overheat the compressor over time.

Under normal operating conditions, you will see about a 10-degree swing. At a 75-degree indoor temperature, the evaporator temperature will probably have around a 35-degree TD. So, you run around a 40-degree evaporator coil under 75-degree indoor conditions. (That is true of all refrigerants.) If the refrigerant picks up 10 degrees of superheat in the evaporator, you'll have about a 50-degree suction line at the evaporator coil outlet (+/- 5 degrees or so). Then, when you measure the suction line before the compressor, the temperature can increase about 3-5 degrees more. Overall, you'll want your temperature to be below 65 degrees at the compressor inlet.

If you see a lower temperature, then you'll want to start looking at airflow. If you see a warmer suction line temperature, you'll want to make sure the suction line is insulated, that there are no restrictions, and that the system is not undercharged with refrigerant. We are fans of non-invasive testing; that way, you can measure the temperatures without hooking up gauges and getting the pressures. Measuring pressures is not always necessary, but we highly recommend checking the suction line temperature whenever possible to benchmark the system.

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.

Duct Installation Best Practices Aug 20, 2020

Show notes

In this podcast episode, Neil Comparetto from Comparetto Comfort Solutions joins Bryan and Kaleb to discuss some duct installation best practices he has learned. You might be able to take away some of his duct installation tips and apply them in the field.

Neil used to focus a lot on making the ducts look good, but nowadays, he focuses a lot more on performance; the work of art is in the data, not the beauty of the building materials. The quality of the seal on the duct is more important than the duct's appearance. Neil focuses a lot on leakage, and he says it all starts by committing to low-leakage connections in your mindset. He does as much sealing as he can before hanging the ducts.

Flex duct is one of Neil's favorite materials even despite its poor durability. Flex duct is quiet, well-insulated, pretty cheap, normally leak-free, and quick to install. Of course, you must install it in straight lines and pull it tight for best results, but its performance is pretty close to that of normal sheet metal.

It can be difficult to separate the install from the design, so some design features are beyond the installer's control. However, if possible, it's best to keep the duct system as small as possible. Shorter ducts reduce the likelihood of leakage and the area available for thermal transfer, especially in unconditioned spaces.

Neil, Kaleb, and Bryan also discuss: