Month: November 2020

Let’s get through all of the jargon and try to get to the point as quickly as possible. All of these ratings are a calculation of how much energy you have to put into a system in order to get a BTU of heating or cooling out.


But the problem is that cooling and heat pump equipment has a bunch of variables that impact the numbers so they are all a little different.

Here is a quick summary

EER (energy efficiency ratio) = BTUh of output ÷ Watts of Energy Input 

The nice thing with EER is you can measure it real-time if you know the watts being used and the BTU’s being produced. No conversions needed, no fancy math. Measured EER is an easy snapshot but rated EER is another matter as it is only based on RATED conditions. It doesn’t take into account seasonal temperature or runtime variations.

COP (coefficient of performance) = BTUh output ÷ BTUh of Energy Input 

In other words COP is the same as EER but you convert the input to BTUh from watts by multiplying watts by 3.413. Also easy with one more bit of math added in. The same issue in that it is snapshot of performance or based on only one set of operating conditions.

SEER (Seasonal Energy Efficiency Ratio) = BTUh output ÷ Watts of Energy Input / Averaged over an entire cooling season 

So SEER is just like EER but theoretically would be the average EER if you measured it all through the cooling season and then averaged it. The PROBLEM is that isn’t the same everywhere… so it is still based on a set of conditions that are meant to replicate an average.

HSPF (Heating seasonal performance factor) = BTUh output ÷ Watts of Energy Input / Averaged over an entire heating season 

This makes HSPF exactly like the SEER but the winter (heating season) version where the EER is calculated and then averaged out. The same challenge exists in that not all places have the same set of operating conditions.

The solution lies in understanding each efficiency measure as well as the requirements of the particular market you work in to provide your customers with the best possible products to serve their needs. If you live in a market with very high outdoor temps like Phoenix you want to look at the extended performance data on the equipment you see and find systems that continue t perform well at high temperatures.

If you are installing a heat pump in Maine the same is true but reverse it.

Ratings are great… being situationally aware is greater.

— Bryan



Based on HVAC School’s special episode for 100k subscribers. The episode features Eric Mele, Andrew Greaves, and Sam Behncke as special guests.


To celebrate HVAC School’s 100,000 subscribers milestone, Bryan Orr has released a video on a topic that applies to all sorts of HVAC techs. Customers don’t like making callbacks, and we know you don’t enjoy receiving them. Here are 10 tips that will make you a better tech and make your customers happier.


10. Pay attention to the way equipment is wired

Even if the equipment has come fresh from the factory, you will want to check your settings. Common issues arise with wiring settings and pin settings. DIP switches may also be inappropriate for the tonnage. Transformers may be tapped to 240 volts instead of 208 or vice versa, and that can result in chattering relays or contractors.

You’ll want to make sure the equipment settings are appropriate for its design and the climate you’re working in. For example, proper dehumidification is crucial in tropical climates. 

Don’t assume that your equipment starts off in perfect shape, even if no one has touched it since it left the factory. Andrew Greaves recommends treating each piece of equipment like it is custom-made.


9. Check static pressure more often (and don’t just check total external static!)


Checking total external static is a great way to understand the big picture of static pressure. However, total external static does not give specific insight into static pressure conditions in isolated areas.

Estimate airflow by measuring static pressure drops across the coil and the filter. Rapid drops indicate weak airflow through the filter and poor air distribution.

Frequently checking static pressure beyond the total external static is an excellent way to detect a unit’s airflow issues. If the manometer’s measurement is off, then you have the green light to diagnose the problem and take action. For more information on measuring static pressure, read Neil Comparetto’s article called Static Pressure — Why Measure It?


8. Start to read schematics

Reading schematics is not rocket science, but it sure seems like it is. Unfortunately, textbooks and other resources can only help up to a point. Educational resources can help you understand the symbols. A good resource is our  How to Read AC Schematics and Diagrams Basics. Still, you will only get comfortable interpreting schematics if you regularly expose yourself to them.

Sam Behncke stresses the importance of reading schematics regularly in commercial HVAC. Many commercial HVAC units have multiple motors and safeties and can be more complicated than residential units. You will have an easier time navigating a unit if you familiarize yourself with schematics.

The next time you think you want to get better at schematics, pull off the quarter panel and take a look. Do this with each unit you see, and you’ll be a schematics guru in no time!


7. Use isolation diagnosis

Isolation diagnosis is a method of problem-solving. It focuses on a single issue and allows you to focus on a problem with a specific part.

For example, you may suspect that something is wrong with the compressor. Unhook the compressor but leave everything else. Reset the power and see if anything else trips or malfunctions. If nothing else messes up, then isolation diagnosis narrows your problems down to a manageable number of possibilities. 

Rely on your senses to find an issue. Behncke says that your vision is your best tool. A technician’s watchful eye can completely disprove the phrase: “A technician is only as good as his tools.”

For an in-depth review of isolation diagnosis, we recommend reading HVAC School’s feature on the topic.


6. Pull better vacuums or evacuate better

Jim Bergmann calls evacuation “a lost art,” and that’s unfortunate. The good news is that you can help revive it! The key to pulling better vacuums is learning the best evacuation practices, understanding how pressure works within the vacuum, and using the finest equipment at your disposal.

You will want to use larger hoses, test vacuum pumps, and use a micron gauge at the system. Change oil regularly and pull the cores. Eric Mele says that today’s equipment makes evacuation a relatively easy process. Thirty years ago, the hoses may not have been large enough to make much of a difference but nowadays we have many great options.

If you’re interested in learning the nitty-gritty details of vacuum-pulling, we recommend listening to Pulling a Vacuum 2.0 w/ Jim Bergmann (Podcast).


5. Look for wire abrasions and rub-outs

Wire abrasions can cause all sorts of problems. Problems lead to callbacks, and nobody enjoys those. You can avoid some of these problems by making sure wires are securely fastened and don’t rub against the tubing, casing, or cabinet. 

Performing a solid visual inspection is the key here, as with most other tips on this list. Pay attention to how lines run around the compressor: make sure the compressor leads don’t rub against the lines or feeder tubes. Be aware of how your wires fit into your terminals. Everything should be secure to prevent unnecessary movement.

There are a few things you can do to fix or prevent rub-outs. Make sure to use a grommet to secure wiring that runs through the casing. Use proper crimper and connection type when you make crimps and connections. Ratcheting crimpers are designed for insulated terminals. Heat shrink connectors are also a great way to add extra support to your connections. To learn more about heat shrink connectors, check out this video.


4. Check for common airflow problems

The key to this one is to check for obvious issues. Check your ductwork for signs of crushing or improper sags. Those are some of the key culprits of poor airflow. If you want to learn more about preventing your flex ducts from looking like the sad example on the right, here are some Better Duct Installation Practices

Commercial HVAC techs will want to look out for pulley wear, messed-up sheaves, and belts in poor condition. Residential HVAC techs will want to focus on pin settings, improper setups that impede airflow, dirty evaporator coils, blower wheel problems, and returns with jammed filters. 

Again, don’t downplay the importance of visual inspection! It’s easy to get caught up in measurements, but simple visual inspections can catch obvious problems. Even someone who isn’t an HVAC tech can notice crushed ductwork and suspect an issue.


3. Clean drain lines and drain pans properly

We get it. Drain lines are nasty tunnels of slime and bacteria. Still, they need extra love and care. Do not just clean them from the tee or blow them out and leave. 

One of the best ways to perform a thorough cleaning is to get underneath the evaporator coil. Use small, thin bottle brushes to make sure you clean the hard-to-reach areas. Clean into the side pans and make sure the drain is pitched properly.

Some technicians don’t monitor the cleanliness of drain pipes, so some drain issues go misdiagnosed. Some techs have reported cracked drain pans, but the real problem may have been a dirty drain line. Be transparent with the customer. Let them know the state of their drains and perform services accordingly.

For more information on proper drain pipe maintenance, check out HVAC School’s Condensate Drain Codes & Best Practices.


2. Test all modes of operation

I think most of us can agree that you won’t need to turn on the heat when it’s 99 degrees outside. I’m sweating just thinking about it. So, why would you consider running the heat when you won’t be using it for several months? 

Well, when you change a control board or thermostat, it could affect other modes of operation. That could cause unnecessary problems later, and the customer would almost certainly prefer not to call a technician when they need heat. 

Even if it’s summer and difficult to test the heating mode, you could make sure that your unit runs the heating mode. All you have to do is see if it turns on. Nobody has to suffer from the heat, but you’ll spare yourself and your customer further discomfort. The same goes for running cooling mode in the winter.

This is also important for multi-stage equipment and humidifiers. Make sure multi-stage equipment works in stage up AND stage down modes. Ensure that humidifiers can also dehumidify if they perform both functions.


1. Leave the equipment running (& don’t rush to the finish!)

Resist the urge to rush out of a job without being 100% sure that the system operates correctly. Dakota Brown wrote a great article about finishing up a job thoroughly.

When you finish a job, take extra care to make sure nothing else is wrong with the unit or equipment. In summer, this means checking to see if a system is running and draining. When temperatures are colder, ensure that there is no CO spillage from gas furnaces.

If the unit shuts off before you leave, it would be wise to check with the customer and ask if the thermostat caused the shutdown. If not, that could indicate that there was a breaker or float switch trip.

Take quantitative measures to check the unit’s functioning. Use measurements to see if everything is running as it should. Use appropriate forms of non-invasive testing. An excellent diagnostic method is to check the five pillars.


These tips can change with each market (gas, refrigeration, etc.). However, technicians who apply these tips to their everyday jobs will see more satisfied customers and receive fewer callbacks. 

What are some other tips that have helped you in your trade? Please share your tips with us in the comments below! (or by replying to the email if you are seeing this via email)

I received an email from a podcast listener with some furnace related questions. Based on the nature of the questions I figured it would be better to ask an experienced furnace tech. Benoît Mongeau agreed to help by answering the questions. 

My name is Matt and I am a newer tech (fully licensed this September, have been doing the work for 2ish years) who lives in Northern Ontario, Canada. I really enjoy the HVACR school podcast. I don’t do any A/C stuff but I still enjoy listening and wrapping my brain around it. I have always struggled with the theory behind getting cold from hot. The bulk of my work is residential gas heating, mainly high-efficiency furnaces, and gas fireplaces. My questions for you are, (these are just ideas for your podcast though help is never turned down)

On a millivolt system (runs off of a thermopile)
– How to easily test for gas valve failure, what are the expected resistances across the solenoid in the gas valve?
– What expected readings should we consistently get from a properly working system (voltage of thermopile alone, with gas valve open, with thermostat closed etc)

On high efficiency
– What is the relationship between the pressures in the collector box of the secondary exchanger and the pressure switch?
– How does a clogged condensate trap lead to the pressure switch not closing?

Another Question
– Is it possible to check readings from the circuit board when the wires are in a harness? For example, I troubleshot a gas valve failure. It was either the board or the valve. The wires coming to the gas valve from the board are in a harness. How do I know which to check and what am I checking for. (Given that everything else was working I leaned toward a faulty gas valve and was right, just so you know!)

Thanks for your time and for doing the podcast.

All the best,

For the collector box/pressure switch:
During normal operation, the collector box is under a vacuum (negative pressure) when the inducer is running. That vacuum is what the pressure switch checks for. If the vacuum is sufficient the contacts will close and signal the board everything is good. If your condensate trap is blocked, the collector box will still be under a vacuum. That doesn’t change.

However, the pressure switch port (where the tube is attached on the collector box) should be at the bottom of the box, usually near the drain port. The backed up condensate will simply end up blocking that port and the switch will no longer be able to ”feel” the vacuum, the contacts won’t make and you will get an error (pressure switch not closing or stuck open).

What may also happen, but not always, is that the port will block during a cycle and the vacuum will remain stuck in the pressure tube. As your inducer comes off and normal pressure returns, the air can’t go in the pressure tubing because it’s blocked with condensate, and you’re basically trapping that vacuum inside. So the contacts will stay closed, until the next call for heat. When that call starts, the contacts will already be closed before the inducer starts, and that will also give you an error (pressure switch stuck closed).

Now if your exhaust is blocked, this will create back pressure and your collector box won’t be under the appropriate vacuum, and once again won’t close.

For millivolt systems:
Unfortunately, I can’t say what typical resistance values would be for a mV gas valve because I don’t know. I would say however that in three and a half years I haven’t had to replace a fireplace gas valve. They rarely go bad. In most cases the pilot tube/orifice is dirty, the thermopile is too weak, or, if it works with a wall switch, very very common: the switch is bad. Standard wall switches are meant for AC voltage.

Running millivolt DC thru them will work, but as soon as you have a bit of resistance in the switch contacts, that voltage will not get through. If it runs on a thermostat, usually it works better but you can still get the same problem.

For typical readings, I’d say between 450-650mV from the thermopile alone, open circuit. With the valve open (so, closed circuit) around 200-300mV. But this is very general, it may vary a lot between systems.

If your thermopile alone doesn’t produce enough mV’s, check your pilot flame. Make sure it hits the thermopile well. You might be able to adjust it (on some valves) to make it bigger. As I mentioned, the orifice or tubing may be blocked. That is relatively common especially if the pilot was kept off for a long time.
If your thermopile gives enough voltage but the valve won’t open, check your switch/tstat and even the wire itself for any significant resistance or short.

Isolate section by section and ohm it out. If everything is good and sufficient mV’s come back to the valve and it still won’t open, then yes, that valve might be bad. But I’d probably even replace a switch/tstat before I condemn the valve regardless, just to be sure, just because changing those valves in most cases is a total pain in the butt.

For the gas valve/board dilemma:
If your wires are all in a harness with a big fat connector on the board, there’s a good chance you won’t be able to pull it off and diagnose on the board pins, because by removing the connector you remove most or all of the safety circuits.

If you want to look at the gas valve, you need to hook your meter on the wires at the valve itself. If it’s just a standard 24v valve with 2 or 3 terminals (Common + hot or common + low and high solenoids) just pull the wires off (or connector) at the valve and you have to check for 24V on the wire across common and hot. Even with the valve disconnected if your board is OK it will still send 24V in that wire at the proper time in the sequence of operation (i.e. wait until the ignition sequence completes!!). If you don’t have 24 volts, the board is bad. If you have 24V, the gas valve is bad.

If it’s one of those Honeywell SmartValves, then that’s another story entirely. A good portion of the controls are actually inside that gas valve and it will have multiple wires going to it. They are a bit more difficult to diagnose. My best advice is to follow your electrical diagram. If there’s no way for you to disconnect wires at either end (which should never happen as far as I know…) you could always cut the wire and check your voltage in the wire itself. But try to avoid doing that.

— Ben

Most of the content in this article is based on Alex Meaney’s contribution to the HVAC School podcast in the October 2nd, 2020 episode: “How to Get The Most From Online Education.”


Attending a class from your bedroom or home office sounds very convenient, right? That was probably what many Americans would have thought several months ago. Now, many of us shudder at the thought of learning remotely. With distractions and technical difficulties galore, many students and trainees have struggled with online education. Maybe you are one of those people, but fear not! Rock Star HVAC design educator Alex Meaney addresses the challenges of online education and offers advice for struggling students and educators alike. He has provided some crucial tips for overcoming the obstacles of distance learning and getting the most from your online education.


Take advantage of early reading


It’s a good idea for educators to provide educational materials before an online training session or class. If students or trainees have access to readings and videos ahead of time, they may enter the class or training session with a basic understanding of the concepts. Educators, it’s on you to set your students up for success.


Students, I’m afraid you aren’t out of the woods yet. It helps to go into a class feeling prepared. You may want to familiarize yourself with heat gain/loss equations before entering a psychrometrics class. That way, you will be ahead of the curve and won’t have to waste valuable time memorizing formulas.


Meaney also stresses the importance of learning vocabulary before attending a class. It helps to feel like you “speak the language” of the topic before attempting to grasp challenging new material. For example, you don’t want to look like you’ve seen a ghost when the educator says a word like enthalpy in a psychrometrics course. 


Look for opportunities to tutor difficult subjects


Meaney also gives a seemingly counterintuitive piece of advice for students: seek opportunities to tutor confusing subjects. Tutoring increases a student’s investment in the subject by making them accountable for your classmates’ successes. 


Some of you may enjoy the added pressure, and some may not. Regardless, you will obtain a more in-depth understanding of the material if you teach it to others. It also feels great to help a friend grasp a tricky topic. Who doesn’t want to be a good person and benefit from the experience?


Take a class with a friend


Taking a class with a friend is also a good strategy for getting the most from remote education. Studying with a buddy is useful for filling the gaps in learning. One person may better understand a topic than the other and vice versa. 


Manhattan Institute lists a few other benefits of friendship in education. Even in the virtual classroom, friends provide comfort and security. You may feel more comfortable asking questions or requesting clarification if you aren’t afraid of being judged by your classmates.


Friendship is also a source of support in the learning environment, even in nontraditional, remote settings. Students reinforce their learning when they tell their friends what they found exciting or challenging about a class.


Educators: show your faces


Educators can create a more engaging environment for their students by adding a video of themselves explaining the content in videos or PowerPoint slides. Although these learning formats do not compare to lectures in real-time, it’s nice to see a human face among diagrams and charts.


Work in a clean, distraction-free zone


This is a big one. Maintaining an organized workspace is a must for students and educators. For most people, this means limiting distractions and maintaining the cleanliness of the workspace. 


Putting away cell phones is a good start. Putting the cell phone away minimizes the temptation to look at text messages or social media during class. The last several times I checked, #HVAC wasn’t trending on Twitter anyway.


It also helps to remove irrelevant documents and materials from the workspace. Paying bills is essential, but nobody wants to think about that while they’re trying to learn a new skill. Even if you just need to shove them on the floor for a bit, it’s better than keeping them in front of you.


Closing background programs and internet tabs on the computer eliminates clutter on the screen. We know you enjoy listening to HVAC podcasts and checking out family photos on Facebook, but class time is not the time for that. The webpages will still exist when the lesson is over. 


Meaney also recommends taking notes with a writing utensil, not on a phone or tablet. Involving the hands in the learning process is an excellent way to engage the body while taking in new information, especially for those fidgety hands-on learners. (If writing is not required, try squeezing a stress ball while you learn!)


Ensure a stable internet connection


Anyone who shares an internet connection with other people may consider minding their bandwidth usage. This means ensuring that other people in the home or office don’t stream videos or play video games online.


Many people love watching The Mandalorian and playing Grand Theft Auto V online, but heavy bandwidth usage strains internet connection. A spotty internet connection can result in long download times, buffering, and disconnection from online lectures. 


It would be best to let roommates and family members know when it’s class time. That way, they can do their part to respect and support your remote learning process. Netflix, Disney+, and the PlayStation Network can wait.


Set aside additional time to ask questions


Even with scheduled classes, students can benefit from managing their time. Students could consider reserving some time after a lesson to ask questions or do some independent learning. (For example, a student could set aside 2 ½ hours of their day for a 2-hour class.) If you don’t end up using the additional time, then it becomes free time. You can study some more, walk the dog, or take a nap. It’s your time. It is better to set aside more time than necessary than to plan poorly and need more time. 


Consider using the extra time to take advantage of the instructor’s availability. Ask questions! They love helping students understand their lectures. After all, they would not have chosen to teach if they did not enjoy helping others. There are plenty of jobs that pay better.


Don’t be tempted to skip material


It may be tempting to skip through sections of pre-recorded videos or speed up the playback, but it’s best to refrain from zipping through the first playthrough. Yes, the educator may talk slowly. Yes, you may already know what they’re talking about. That could change within seconds, and you don’t want to miss out on new information you’ll need later.


It’s okay to jump around and bypass some sections on subsequent playthroughs. You may choose to skip around the learning materials to focus on specific topics. Still, it would help to understand the terms and general subject before turning your attention to individual parts.


Take care of yourself


Not many people think about comfort in the learning environment, but it can significantly help the learning process. Exercising self-care is vital for getting the most from remote education. Hunger and thirst can ruin your mood and make it more difficult to concentrate. 


Bring a glass of water to class and have some snacks within reach. After all, eating or drinking during an online lecture is not as disruptive as eating in a classroom or auditorium.


Be aware of your microphone and webcam status


Students and educators can benefit everyone in the class by being mindful of their video and audio settings. 


Webcams are great because they can add a social component to distance learning. However, they can also disturb other students. Please wear appropriate clothing and monitor the activities of pets or other background distractions. Yes, everybody would love to see fido and tell him he’s a good boy. No, he is not helping anybody learn about the nuances of Manual J. . 


Students should ensure that they remain muted unless they have permission to speak. Even though we are strong proponents of staying comfortable in class, nobody wants to hear you crunch Doritos. Everyone’s online learning experience will improve if everyone makes an effort to be considerate and use technology appropriately.


Have faith that you will learn


The best thing students and educators can do to get the most from remote education is to remind themselves that we are all capable of learning. Distance learning is difficult for many people, and anyone who struggles with it is not alone. 


Getting the most from remote education primarily entails limiting distractions and temptations. Students can succeed with a healthy amount of educator guidance, discipline, and self-compassion.


The industry leaders are seeing positive trends and have faith in you, too. Dominick Guarino, chairman and CEO at National Comfort Institute, acknowledges that the HVAC industry is a little behind when it comes to online education. However, he and other industry leaders are optimistic about the progress contractors have made in distance learning over the past year. 


Educators can do the following things to maximize the effectiveness of their online classes:


  • Provide preliminary readings or vocabulary lists
  • Attach their face to the content to boost engagement
  • Make themselves available to answer questions
  • Be honest with what they do and do not know; follow up with students who ask difficult questions


Students can do the following things to get the most from their remote education:


  • Study materials and learn vocabulary ahead of time
  • Take a class with a friend
  • Seek opportunities to tutor difficult subjects
  • Set aside more time than the class itself
  • Ask questions!
  • Stay disciplined and committed to learning


Educators and students can benefit from:


  • Keeping a clean work environment
  • Minding bandwidth usage within their homes
  • Being aware of their microphone and camera usage


Remote education is efficient and cost-effective, but it presents a unique set of challenges for educators and students. 


To succeed in an online curriculum, students must hold themselves responsible for their learning. Taking responsibility includes limiting distractions within the workspace: putting away cell phones, closing unnecessary applications and tabs, and removing workspace clutter. 


Students should also challenge themselves and take advantage of opportunities to maximize their learning potential. These opportunities include tutoring other students, learning with a friend, asking questions, and setting aside additional time to learn the material. 


Students will learn to prepare themselves for class, manage their time, and take care of themselves in a challenging, unfamiliar educational environment. 


Educators can improve their students’ learning process by providing videos of themselves explaining the content, providing preliminary reading materials, and following up with students who ask complicated questions.

The biggest thing is to prepare and be intentional and learn how to learn in this brave new world we find ourselves in.

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