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Let’s Talk Airflow: The Often-Overlooked Step in HVACR Diagnostics

HVAC Airflow System

Go with the flow.

How did your last HVACR service call go? After arriving at a client location and listening to the symptoms they’re experiencing, what were the first troubleshooting steps you performed? Did you immediately gauge-up and start measuring the system’s refrigerant pressures and temperatures? If so, depending on the symptoms they were noticing, you could have overlooked one of the easiest, fastest and least intrusive tests in your arsenal.

We’re talking about airflow checks. The tests for checking performance and airflow across the evaporator coil are easy, they’re non-intrusive, and they help pinpoint what and where problems exist. Correct airflow is critical to the health and performance of an HVACR system and diagnosing these issues help you better understand the results of other tests.

Three critical performance factors.

When you’re troubleshooting a faulty system, there are three main areas you should check:

1. Electrical

2. Airflow

3. Refrigerant charge

Each of these requires its own unique tests and each one affects the other. However, they all work together to help HVACR techs understand what’s happening within a system.

Depending on the system issues you’re noticing, for many service calls starting with a simple electrical test makes sense. Does the system have power? Does the compressor kick on? Are fans spinning? Is the system kicking out any error codes?

After checking the electrical components of the system, a quick visual inspection is easy and helps you understand the system’s components as well as what may be malfunctioning. These completely non-invasive tests include checking the air filter and looking for debris on or around the condenser.

The next test is to check for performance and correct airflow across the evaporator coil. Some technicians who know about the tools to perform these tests swear by them, while others may have the misperception that checking for proper airflow is difficult and complicated. It all depends on how they were trained. The reality is: Today’s modern innovations make airflow testing a piece of cake.

Checking evaporator coil performance helps you determine how efficiently the system is transferring heat and moving air across the coil. Plus, using the right tools will help indicate what side of the system potential airflow restrictions are located on. It is sort of a no-brainer to start with simple and non-invasive tests – and work your way up to more difficult tests.

By consistently checking airflow every time you troubleshoot a system, you’ll be able to diagnose issues faster and in a less invasive way. Then, if necessary, move on to perform more invasive tests like measuring refrigerant pressures. It just makes sense.

How to keep the air flowing.

HVACR systems depend on air. Air needs to be heated or cooled and then circulated throughout a home or commercial property. That air then returns to the air handling unit. During this cycle, there should be few restrictions to its flow. Inside the unit itself, the air needs to move across the heating or cooling elements at the right speed in order to work at peak efficiency.

Here are three tests to check for performance and correct airflow across the coil:

 

1. Delta T. There are two easy ways to check for evaporator performance. The first is to calculate the delta T across the evaporator coil by measuring the air temperature entering and exiting the evaporator coil. For cooling, Delta T is calculated by subtracting the supply dry bulb temperature from the return dry bulb temperature. A common rule of thumb for a good delta T is between 18 and 20. This means that the air coming out of a system should be 18 to 20 degrees cooler than it was going in. Check with the system manufacturer to find your system’s ideal delta T. When hooked up correctly, the Fieldpiece Job Link Flex Psychrometers, JL3RH connect to the Job Link® app to perform these calculations automatically.

 

2. Target Evaporator Exit Temperature (TEET). A second way to check airflow performance is to use the Fieldpiece Job Link® Flex Psychrometers, JL3RH and Job Link® app to calculate the system’s Target Evaporator Exit Temperature or TEET. The difference between Delta T and TEET is that TEET takes into consideration the latent heat used to condense water from the air, while a simple 20° temperature split ignores latent heat. Job Link uses the return air properties to calculate what the supply exiting dry bulb temperature should be based on indoor conditions. Then, compares this value to the actual supply dry bulb temp exiting the evaporator.

 

3. Total external static pressure test. Both of the previous tests use temperature measurements to verify optimum heat transfer across the evaporator coil. If, after performing these tests, you find that the delta T is not within range it may be caused by improper airflow or refrigerant charge. To check for airflow restrictions, you should perform a total external static pressure test, or TESP, using the Fieldpiece Job Link Dual Port Manometer Kit. The placement of your manometers varies for different equipment types, so be sure to check for correct placement to measure the static pressures. In general, you need to take a static pressure measurement on the return and supply side of the air handler. This kit is designed to easily and quickly perform this test. Compare this measurement to the manufacturer’s max static pressure value. If the TESP is too high, it indicates there’s an airflow issue. If the test comes back ok, then you can move on to checking for improper refrigerant charge. That’s just one example of the things we learn from measuring airflow.

What causes bad HVACR airflow?

Problems with airflow could be caused by a host of factors. Here are a few of the most common that you might come across and how to fix them.

1. Dirty, clogged filters. Every HVACR system should filter air before it’s recirculated into the home. If the filter is old or very dirty, it could create airflow problems by not allowing the system to draw in enough air to the evaporator. Checking and replacing filters makes a vast improvement in system performance.

2. Leaky ducts. Ductwork that has been damaged could be causing air to flow out of or into the system into attics or crawlspaces. This could make the system waste energy while heating or cooling spaces that it isn’t designed for. These may be quickly repaired with duct tape, or by replacing the defective portion of the ductwork if possible.

3. Improper ductwork installation. Air flows best and most efficiently in straight lines. Each time a system’s ductwork makes a turn, the airflow is disturbed. Not every duct is straight, but excessive twists and turns diminish the performance of the entire system.

4. Malfunctioning dampeners. Make sure to check the position and functionality of dampeners in the ducts throughout the system. Sometimes they get stuck open or closed and don’t move automatically when the system requests. This can cause airflow problems to entire portions of a home or business.

5. Improper fan speed. Fans on most systems are adjustable. If, after repairing ducts and replacing filters, you’re still getting poor airflow numbers, adjust the fan speed to help the system perform more efficiently.

HVACR airflow tools of the trade.

Today’s field technicians have a host of tools to check for evaporator performance and correct airflow. Here are some of the most handy and popular.

1. Job Link® System Dual Port Manometer Probe Kit, JL3KM2. This versatile tool gives HVACR pros the freedom to work the way they want to and get readings from optimal locations on every system, every time. Short hoses and independent sensors allow for precise placement with untethered freedom. It even allows techs to measure and record up to eight readings at once via the Job Link® app.

2. Fieldpiece Dual Port Manometer, SDMN5. This rugged tool measures gas pressure, static pressure and pressure differentials. Since it has dual ports, it is able to measure both P1 and P2 and quickly show you the difference. This easily informs you whether an air flow restriction is on the supply side or the return side before you embark on deeper explorations of duct work and the like.

3. Job Link® System Flex Psychrometer Probe, JL3RH. This probe has a flexible wand that fits easily into ducts, plenums, registers or grilles to give you accurate diagnostic information that ranges from the dry bulb and %RH to the wet bulb and enthalpy.

4. Job Link® App. The app wirelessly displays the measurements from all of the Fieldpiece Job Link products you’re already using, and it instantly calculates evaporator delta T, Target Evaporator Exit Temp (TEET) and total external static pressure (TESP). The industry leading 1000’ (LoS) wireless range has you covered even on large job sites. This powerful tool helps techs diagnose and identify potential airflow problems across entire systems.

Airflow is critical.

It’s easy to forget how important airflow is to an efficient HVACR system. The next time you’re on-site troubleshooting an HVACR system, before you gauge-up or perform other tedious and invasive tests, check for evaporator performance and correct airflow. It’s relatively easy to do and it’ll give you a quick snapshot of system performance. You’ll learn how well the system is transferring heat, and you’ll get a better idea of what could be causing the problems.

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Walk-Ins: The Importance of Equipment Placement

If you’re installing a walk-in cooler or freezer, it’s critical to make sure the condenser unit and evaporator coil are installed in the correct location. Choose the wrong spot and your customer could be looking at a difficult and expensive installation as well as performance issues from the entire system. No one wants those.

To avoid problems during and after the installation, discuss with your customer the ideal location for the condenser and evaporator coil. If it’s installed indoors, the condenser could take up valuable retail space. And if it’s outdoors, the ideal location for the unit could be inconvenient for maintenance or simply unpleasant to the eye. Choose a location that allows the customer to take best advantage of their space while not interfering with day-to-day operations.

If an indoor location is chosen for the condenser unit, keep ventilation and airflow in mind. It’s critical for operation. Plus, energy savings requirements have changed evaporator design. Newer evaporator motors ramp up and down, and this could create warm spots in walk-ins; also recent manufacturing requirements have changed as they relate to the distance from the back evaporator to the wall. Airflow requirements vary, so check with the manufacturer of your specific model. Most low-temperature units need around 200 CMF per 1,000 Btu/hr. A medium-temperature unit will call for 165 CFM per 1,000 Btu/hr. That means you’ll need a space that offers ample airflow — especially for a larger, more powerful unit. Indoors, the condenser can also generate heat. The presence of this extra hot air will need to factor into your decision-making process.

If installing outdoors, adequate ventilation shouldn’t be a problem. However, if you’re in a climate that often has very low temperatures, the condensing unit may need additional components such as a cycling control or a head pressure controller. These will help keep the high-side pressure above the minimum values when it’s cold out. Also, you can set up the system to use a pump-down method to control condensing unit operations and then add a crankcase heater, so refrigerant doesn’t migrate when it cycles off. Finally, your outdoor unit should be covered to protect it from the elements. You should check with the manufacturer to determine the best way to cover it.

As we all know, condenser units don’t work forever, so no matter if you install it indoors or outdoors, keep in mind that a tech will need to access it for service and routine maintenance. Make sure all parts of it are easy to access — after all, you may find yourself being the one performing the service on the unit.

Inside the walk-in, the location of the evaporator coil has a direct effect on its ability to keep the whole space at a consistent temperature. It’s critical to understand the total distance the evaporator needs to cover. This directly affects its performance. Check with the manufacturer of the evaporator for specific instructions, but don’t overlook the fact that the air pattern must envelop the entire room. Don’t install the coil where product could be stacked against it and block airflow. Make sure there’s enough space for storage and for normal business operations. It shouldn’t be in the way. Also, don’t install the unit over a door because it could draw in warm, humid air each time the door is opened—potentially leading to frost build-up.

Choosing the right location for all of the critical components of a walk-in cooler can help it run more efficiently. It can also make it easier to service or repair. Make sure to keep all of these things in mind for your next project to improve your HVACR technician skills.

 

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Vacuum Pump and Vacuum Gauge – The HVACR power couple.

The use and placement of tools are critical to the success of maintaining or repairing HVACR systems. One misstep can lead to another, ultimately putting any system at risk and customers at a disadvantage when it comes to paying higher costs.

Whether you’re installing a whole new HVACR system or making repairs to an existing one, you need to evacuate the system before you can add new refrigerant. This means lowering the pressure down to a deep vacuum to ensure all moisture and non-condensable gasses are removed. If you don’t evacuate the system properly, moisture and non-condensable gasses that remain in the system will adversely affect system efficiency and may potentially lead to acid formation and critical component failure.

The best way to make sure that you pull a 500-micron vacuum, an industry-standard, is to use the ultimate power couple in HVACR service – the vacuum pump and vacuum gauge. Separately, they are amazing, powerful tools. Together, our best HVAC vacuum pump and best digital micron vacuum gauge offer a level of speed and accuracy that are truly game-changers for techs in the field.

To ensure that you’re using these tools correctly, keep these tips in mind:

1. Location, location, location: Choosing the placement of the vacuum gauge is key to pulling an accurate vacuum. Ideally, the vacuum gauge should be as far from the vacuum pump and connected at the system, preferably the service port, for a more accurate reading of the vacuum in the system. For a good single hose set up, consider installing the vacuum gauge on the liquid line and connecting the vacuum pump to the vapor line for optimal performance.

2. Clear every restriction: From small diameter hoses to valve cores, anything that restricts flow can slow down your evacuation. Before you start, remove the valve cores from the service port and use larger diameter vacuum-rated hoses to attach the pump. These will help speed up the entire process.

3. Know your readings: Today’s digital micron meters or vacuum gauges display instant, accurate data about pressure changes. When you’re pulling a vacuum, fluctuations in pressure are normal. Systems can take a while to equalize because there could be some outgassing or trapped moisture could be evaporating. Give the pump some time to work before you react to these minor fluctuations.

4. Use clean oil: If you’re removing a lot of moisture from a system, remember to replace the pump’s oil when it starts to look milky due to moisture or dirt. By always keeping the oil clean and dry, you allow the pump to maintain a greater pressure differential and pull a faster, deeper vacuum. Premium vacuum pumps allow the oil to be changed while the vacuum pump is running.

Pulling a vacuum to remove moisture and other impurities is part of life as a field technician in the HVACR industry. To thrive as a master of your trade, you need to know the right way to use a pump, the right way to place a vacuum gauge on your system and how to make HVACR’s power couple work best for you.

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Fieldpiece Salutes the Women of HVACR

For women working in HVACR, it can be hard to carve a path in the industry; but these women are doing just that each and every day. They are working hard and proving themselves as technicians, contractors, service providers, business owners and beyond.

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The Fieldpiece Family of Tools

Fieldpiece Instruments, the leader in HVACR tools, has everything the HVACR professional needs to get the job done right. From manifolds and multimeters to vacuum pumps, clamps, and tool bags, these HVACR tools offer speed, precision, efficiency, and reliability.

Using the Fieldpiece Job Link® System App, HVACR professionals can view readings from most of the recent generations of HVACR tools on their smart phones up to a range of 1,000 feet. And Fieldpiece Instruments’ proprietary technology in its Rapid Rail Sensor™ and Run Quick™ Oil Change System brings valuable innovation to its family of HVACR tools. HVACR professionals, Fieldpiece Instruments has you covered!

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Job Link® System App and Tools 1000′ Wireless Range

Fieldpiece Instruments, the leader in HVACR wireless tools, knows the value of timely data to the productivity of the HVACR professional. From clamps to probes to digital manifolds, the Fieldpiece Job Link® System App connects all wireless HVACR tools within 1000 feet. Delivering dynamic, real-time readings to smart phones or tablets, technicians can make precise repairs that get it right the first time.

With a subscription to the Job Link® System App, customers can view professional reports that define and clarify any problems. And the Live Look-In feature lets professionals at the office confer on an issue without traveling to the job site. HVACR technicians count on the Job Link® System App for connectivity, productivity, and efficiency.