HVAC School - For Techs, By Techs

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.

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.

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.

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.

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:

• Design and preparation before installation
• Squeegee, tape, insulation, and mastic
• Brands that Neil likes
• Splicing flex duct
• Finding friction rate and balancing
• Downsizing equipment
• Building codes and inspections
• Balancing supply and return
• Return grille placement on homes with few large returns
• Getting feedback
• Equivalent lengths of straight vs. 90 boots
• Duct vs. register velocity
• Takeoffs
• Dos and Don'ts of duct installation
• Filters

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.

In this short podcast episode, Bryan explains what happens to a compressor when it's overheating. He also covers possible causes and troubleshooting strategies.

One of the Kalos techs came across an overheating compressor case that looked like a textbook TXV problem: the superheat was high at the condensing unit on the compressor side. However, the air handler superheat was appropriate, and the suction pressure was low. TXVs, however, respond to the superheat dropping and reduce the pressure even more. Overall, the mass flow rate and velocity drop, meaning that the refrigerant temperature can increase as it spends more time in the suction line.

We were missing a few key measurements to diagnosing compressor overheating. In those cases, we want to know the return gas temperature, discharge line temperature 6 inches out from the compressor, and the compression ratio (absolute discharge pressure / absolute suction pressure). You'll generally want to see a compression ratio between 2.6 and 3 on residential HVAC equipment; the lower the compression ratio, the better the efficiency. A compression ratio higher than 3 can lead to compressor overheating. A return gas temperature consistently above 65 degrees can also make a compressor run hot. The discharge line temperature should not exceed 225 degrees.

Then, you must determine if the charge is correct. (Are you starving the evaporator?) Check if you have restrictions and if your suction line is improperly insulated. Restrictions and heat transfer in the suction line can lead to compressor overheating.

It's bad for a compressor to run hot, but they can go their entire lives without tripping on the thermal limit. Compressors that run hot can have lubrication issues and will have shorter lifespans. The best thing you can do is try to reduce the compression ratio. (Clean the condenser, keep head pressure low, keep good indoor airflow, etc.)

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.

In this podcast episode, Kaleb, Joe, Eric, and Bryan answer some troubleshooting and commissioning questions from Facebook.

Whether we're talking about troubleshooting, commissioning, or any other HVAC/R task, the best training is on-the-job training. Meetings, educational videos, and quizzes also help to a lesser extent, but bypassing training altogether is a mistake. Senior techs can also become better diagnosticians when they teach others. "The Diagnostic Game" is an especially useful tool to help teach newbies how to troubleshoot a system.

However, training is something that is ultimately what you make of it. When you consider external training, you must consider the value of that training. (For example, NOVAR training would be useless for a residential tech but critical for a grocery refrigeration tech.) You also want to make sure your training makes you a valuable job candidate and that you stay motivated throughout training.

When it comes to diagnosis, you can't truly diagnose the equipment until you know how it operates under normal conditions. Until you become familiar with normal equipment operation, you're essentially relying on trial-and-error. Getting the answer correct is only part of the equation; you also need to know why the answer is what it is when troubleshooting.

Kaleb, Joe, Eric, and Bryan also discuss:

• Leaving subcooling just shy of the target value
• Balancing the charge during a hot pull down
• How much can we expect techs to do training on their own time?
• Just-in-time education
• The relationship between training and pay raises
• "Understand before you do"
• Replacing parts on a unit with a failed compressor
• Megohmmeters and multimeters
• The Kalos residential commissioning process
• Troubleshooting no-cool calls
• Inspecting customers' homes
• Communicating with customers
• Money-losers for residential companies
• Classroom training vs. field experience
• Fluid dynamics in ductwork

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.

In this podcast episode, Ty Newell from Build Equinox comes on to discuss the CERV2 and how it embodies "advanced fresh air." The CERV2 is the second-generation version of the CERV.

A basic ERV allows for discharge air leaving the home to pass the intake air. When the airstreams cross through a core, there is an exchange of sensible and latent energy. The ERV may promote dehumidification and cooling of the incoming air. The CERV is a form of ERV technology, but it addresses the issues that may arise from crossing the airstreams. For example, we don't always want to exchange energy, so sensors can examine the air content and determine when and when not to exchange energy.

The CERV, an advanced fresh air solution, went into development in 2008, and the first unit was built in 2010. The CERV has sensors for carbon dioxide and VOCs; either one of those may dominate the air quality in the home. The CERV also uses a heat pump to exchange energy and help heat or dehumidify fresh air coming in. The CERV also has higher CFM than most ventilation solutions, meaning that it can flush out pollutants effectively. So, the CERV acts as a supplementary heating/cooling source for maximum comfort and indoor air quality.

Build Equinox is a small company, and it has about 400 CERV/CERV2 units spread throughout North America. However, because the market is small, they can examine feedback very closely.

Ty and Bryan also discuss:

• Potential downsides of bringing in outside air
• Dehumidification for CERV
• Recirculation mode
• CERV unit controls
• Using hydrocarbon refrigerants
• Concerns with microchannel coils
• Oil carry, miscibility, and foaming
• Superheat control
• Assessing indoor air quality
• Sensitivity to IAQ threats
• Latent-dominated, sealed residential constructions
• Testing and choosing sensor technology

Check out more at buildequinox.com.

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.

Our main man, Bill Spohn, joins us again to talk specifically about combustion. He also explains how to select and properly utilize a combustion analyzer.

It's critical to do combustion analysis when you service equipment for the first time or just after installation. We need benchmarks, so that's when our combustion analyzers can come in handy. (Of course, you also want to use your senses to inspect the equipment.) Commissioning is another good time to bust out your combustion analyzer.

Combustion analyzers should properly measure oxygen, temperature, and CO. Oxygen and temperature sensors tell you the combustion efficiency, and the CO sensor tells you about the carbon monoxide content. However, the CO sensor should also have a NOx filter to prevent nitric oxides from showing up as CO. The goal is to have no CO present in the living space, and sensors that pick up NOx can raise a false alarm.

Some combustion analyzers also have pressure sensors, which can detect static pressure drops across heat exchangers or filters. You can use these for some building-performance tests, including zonal pressure diagnostics. You can also potentially measure ambient CO with your combustion analyzer.

Once you have your combustion analyzer, you need to calibrate it and maintain it. Temperature sensors rarely need recalibration, but your CO sensor needs occasional recalibration after repeated exposure to gas. NOx filters can also expire and may need replacement.

Overall, combustion analysis is a critical part of gas furnace inspection. However, it's best to use other inspection methods too, such as looking for heat exchanger leaks.

Bill and Bryan also discuss:

• Flame displacement
• Condensation buildup
• Nitric oxides on CO sensors
• Dilution of CO and base signals
• CO alarms
• How CO sensors work
• How air enters the home
• Induced-draft systems under negative pressure in the flue

Learn more about Refrigeration Technologies HERE.

In this short podcast, Bryan shares some of his advice for people looking to get into the trades by starting an HVAC/R career.

When you step into the HVAC/R trade, you must remember that you'll acquire a mix of skills and talents that all work together. You must reflect on yourself and see if you'll be a good fit for the trade. Do you enjoy working with your mind and your hands? Do you enjoy working to some degree? If you don't like pressure or dislike working with your mind or hands, then the HVAC/R trade isn't for you.

When starting an HVAC/R career, you don't want to rely on a system or process to provide you with everything you need. Trade schools won't provide the full scope of field education, so you can't rely on them for everything. Instead, join social media groups where professionals discuss equipment and answer questions. Watching reliable YouTube channels helps a lot, too.

Self-motivation is the key to success in this career. Don't go into an HVAC/R career if you aren't motivated to jump into new tasks or subjects. The best way you'll learn in the trade is by practicing with your own hands. Brazing and soldering are more advanced skills that your senior techs probably won't let you do on customers' equipment. However, you can read plenty of guides and practice on your own once you feel confident. You can also study for and take EPA tests on your own.

There are several points of entry to the trade: apprenticeships, trade schools, and entry-level positions with companies. The one you choose will largely depend on the availability and quality of each in your area. You want to spend a lot of time working with your hands, no matter which path you choose.

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.