Top 10 HVAC Tech Tips

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

To celebrate HVAC School’s 100,000 YouTube subscribers milestone, we've 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, resulting 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 like Florida but not so much in the dry Southwestern USA.

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 pressure (TESP) is a great way to understand the big picture of static pressure. However, TESP 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 TESP 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, “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 are great for helping you understand the widely used symbols. This video on schematics and wiring basics is a good place to get started. 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 their 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.” Unfortunately, he's kind of right.

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, you can watch this Kalos training video on 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 “Condensate Drain Codes & Best Practices” and “Drain Cleaning Protocol.”


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 ensure 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?



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