Author: clidzbarski@fieldpiece.com

Fieldpiece is always looking for innovative ways to make tech’s job easier, faster and better, and the combination of Job Link Probes and the Job Link System App do just that. Did you know that you can now use these tools to conduct a temperature compensated, nitrogen pressure leak test? Let’s walk through when to run a pressure test and some of the key steps in the process.

If you’re conducting a service call and have made repairs on a system, it’s important to make sure that it’s a clean, dry, and tight system – especially if you brazed new copper, added flared connections, or repaired other mechanical connections. A nitrogen pressure leak test is an excellent way to ensure that the system doesn’t have any leaks before charging it.

It’s recommended to run a pressure test, also called a tightness test, after a leak has been detected and repaired, or on new installs before charging with refrigerant. The test fills the system with nitrogen under pressure to determine whether it can hold that pressure over time, verifying there are no leaks. Nitrogen is an inert gas and is much safer and cheaper to use than refrigerant.

Before adding nitrogen and conducting a pressure test, record the initial pipe temperature and determine the length and volume of the tubing that is being filled to calculate the amount of nitrogen you will need. Then, make sure there aren’t leaks at the Schrader cores. You should also test your hoses and anything else connected to the system during the test.

Start by purging the system with nitrogen. This is different than flowing nitrogen – that’s at a much lower pressure. Purging allows nitrogen to flow into one side of the system and then out the other. This displaces all excess oxygen and air in the piping. Since you’re working with gas under pressure, be sure to work safely. Any gas under high pressure should be handled carefully and transported per the Department of Transportation guidelines.

After purging, replace the valve cores if you removed them, and attach a pressure regulator to the nitrogen tank and a charging hose to the service port. Be sure to use a regulator that is made for nitrogen and properly sized for the target pressure. Attaching a Job Link® System JL3PR Pressure Probe to the system can offer additional accuracy compared to the standard regulator dial. To monitor temperature, connect a Fieldpiece JL3PC Job Link® System Pipe Clamp to the system. Note that you can also use your Fieldpiece SMAN® digital manifold to run a nitrogen pressure test.

Once the system is prepared, start to slowly pressurize the system. Start with 100 psi and let the system sit for a minute. Then add another 100 psi and let it sit again. Typically, the recommended test pressure range falls within 200-600 psi, but check the system manufacturer’s specifications. If you’re pressurizing the low side of the system, use the manufacturer’s rated test pressure. Note that a stepped process that gradually increases pressure is not only safer, but it can also prevent wasting time and nitrogen.

Once the system is under pressure, isolate it by removing the charging hose and capping the Schrader port. If you’re working on a residential system, let it sit for 30 to 60 minutes. Some larger, commercial systems require a nitrogen pressure test to sit for 24 to 48 hours. Check with the manufacturer’s recommendations for the exact time needed.

If the system needs to sit for an extended period, temperature fluctuations in the environment will affect the pressure of the nitrogen in the system. Make sure to compensate for these changes in pressure before concluding that a system is leaking. Note that the new pressure test feature in the Job Link System App compensates for temperature fluctuations, as does the Fieldpiece SMAN digital manifold.

If you see a drop in the temperature compensated pressure over time, it means there is a leak. Bubble test every fitting and connection to find the source of the leak. This includes every field-fabricated joint in the system. Any of these could be a potential leak point.

When performed correctly, a nitrogen pressure test is an easy and safe way to determine if a system can be charged with refrigerant. Download the latest Fieldpiece Job Link ® System updates from the app store to include the nitrogen pressure test features. Learn more at www.Fieldpiece.com.

Now that we’re in the middle of heating season, we bet you’re making more and more service calls for malfunctioning or under-performing furnaces. During these calls, it’s important to make sure that the furnace pressure switch is functioning as intended.

The furnace pressure switch opens and closes to prevent harmful combustion gases from entering the living space and to prevent furnace fires and potential explosions. An elastomeric diaphragm within the switch remains open when the furnace is off. When the furnace is turned on and functioning correctly, the diaphragm operates under the correct pressure created by the draft inducer motor. This completes an electrical circuit that allows the furnace to ignite for the heating cycle. If the pressure conditions are outside of manufacturer specifications the switch will open to initiate a shut-down to prevent the creation of an unsafe environment for residents and technicians.

When examining a pressure switch, start by using a CO detector to check for harmful gases to ensure you can work safely. Then, run the furnace through its cycle. If you notice erratic ignition cycling when there is a call for heat from the thermostat, that may indicate that the diaphragm or the pressure switch is old and could need replacing. Also, check to make sure that the furnace is properly vented.

If the furnace tries to cycle but stops during start-up and then shuts down, it may be because of a faulty pressure switch. In this case, check for a clogged hose port, a blockage in the flue, corrosion or debris blocking the switch. A bad spring could also be the culprit. All of these should be examined.

To test a pressure switch, an ideal tool is the Fieldpiece SDMN6 Manometer Dual Port w/ Pressure Switch Tester. This versatile manometer allows a tech to use the ports to quickly connect to the switch while it’s still in place, confirm that it’s operating correctly and even verify it is performing within manufacturer specifications.

When a pressure switch is faulty and requires replacement, a good piece of advice is to keep a supply of universal pressure switches in the truck. This quickly helps get a furnace back to operating properly. When replacing a faulty switch with a universal switch, it’s best practice to notify the property owner. Given the importance of the proper fit and setting of a pressure switch, some owners may be willing to wait for the procurement of an OEM part for additional piece of mind, or even request a future update from a universal switch to the OEM. This will allow for their system to be operable until a follow-up call can be made with the requested pressure switch.

The pressure switch is an important piece of every heating system and knowing how to examine, test, calibrate and replace them is a critical job for techs and the Fieldpiece SDMN6 is the best tool for the job. Learn more about the SDMN6 at Fieldpiece.com.

Measuring a system’s static pressure is a bellwether to HVAC system performance, similar to measuring your blood pressure to determine overall health. Static pressure is the resistance against airflow in an HVAC system that must be overcome to deliver warm or cool air to a conditioned space. Manufacturers of air handlers and furnaces design their systems for optimal performance at or below a specified Total External Static Pressure (TESP). And measuring TESP with a digital manometer is just one way to help techs diagnose and troubleshoot HVAC systems. 

How to Measure TESP

TESP is measured using a dual port manometer with probes inserted at the return side, typically after the filter, and the supply side of the furnace or air handling unit. Test ports will likely need to be created, so it’s important to be cautious and drill outside of the manufactured box in order to not puncture the coil, blower or heat exchanger. While the optimal TESP will vary based on the equipment, a typical system will run most efficiently at or below 0.5” water column (w.c.). What that means is that you don’t want to see a static pressure buildup in the return and supply that is higher than the specified TESP because it’s harder for the blower to work as designed and effectively move air. 

Zero and Align Probes

Before inserting the hoses or probes into the test ports, hit the “zero” button on the manometer to make both port 1 and port 2 equal relative to each other and to the atmosphere. Insert the manometer hoses or probes so that the openings are perpendicular to the direction of airflow. More repeatable and accurate results can be achieved with static pressure probes instead of hoses. The probes with a magnetic base and arrow marking that aligns the probe tip into the airflow provide the highest guarantee of successful placement. 

Taking Measurements

Once the probes are inserted and the system is operating at the highest airflow speed, wait approximately three minutes for the system to stabilize before taking measurements. Note that after a few minutes field manometers will drift, so it’s also important to reset with the “zero” button before each use. 

Add the absolute value of the port 1 and port 2 measurements together to determine the TESP and compare to the manufacturer’s specified TESP. Some manometers will only provide the differential value, rather than a supply and return value. Fieldpiece manometers, such as the SDMN6 and Job Link® JL3KM2 Probes have independent sensors for each port so that if the TESP is not in compliance, you can troubleshoot more quickly by targeting the side of the system with the largest variance. 

Diagnostic Tips

If the TESP exceeds the manufacturers specification, some common causes include dirty filters, blocked ducts, closed dampers, an unbalanced system, undersized ductwork, kinked flex duct or too much airflow. Under these conditions, fixed speed and variable speed motors will not operate optimally and experience premature failure.

With a much lower than specified TESP, common causes include leaky ductwork, separated duct connections, missing filters and low fan speeds. Resulting poor system performance typically means that a space is not being cooled or heated appropriately and the customer is not comfortable. 

Using a digital manometer, techs can see the results of irregular maintenance and poor installation practices reflected in an out-of-spec TESP measurement. Whether you’re servicing a furnace, air conditioner or heat pump, airflow analysis and measuring total external static pressure is a critical indicator of a system’s health.  

During heating season, the threat of carbon monoxide (CO) poisoning is at its peak—for homeowners and the HVACR pros making service calls. Because CO is an odorless, colorless and tasteless gas, it’s critical to practice CO safety and be armed with a reliable carbon monoxide detector, proactive in its use, aware of the steps to take if CO levels are detected and able to recognize the symptoms of CO poisoning.

Sources of CO 

Fuel-fired appliances, like furnaces, use combustion to create heat. Since combustion is never perfect, dangerous byproducts like CO are produced along with heat. Performing combustion analysis helps HVAC techs precisely regulate the fuel and airflow, optimizing system efficiency and safety by delivering the most heat while minimizing harmful emissions.  

CO Symptoms and Effects 

Common symptoms of CO exposure include headaches, dizziness, and nausea. Exposure might also lead to weakness, confusion, and shortness of breath. Anyone having these symptoms on the job site should immediately notify occupants, leave the area, and begin proper ventilation procedures. If the symptoms do not stop, seek medical attention immediately. Higher levels of exposure lead to chest pain, blurred vision and loss of consciousness. In severe cases, CO poisoning is fatal.  

Check for CO 

It’s impossible to know if CO is present without a proper CO detector. Use a “walk-around” carbon monoxide detector like the SCM4 Carbon Monoxide Detector, which features a fast, electro-chemical sensor to measure CO levels from zero to 1000 parts-per-million (ppm) in real time. For reference, 9 ppm is considered the maximum safe level of exposure over 8 hours for indoor environments and 200 ppm or greater will cause physical symptoms and can be fatal.   

Keep a CO detector and other combustion analysis tools in your HVACR toolkit for every job, regardless of the equipment being serviced, as other fuel-fired appliances may be present. Wearable CO detectors provide continuous monitoring for added safety. Home-installed CO detectors are also crucial for early warnings of elevated CO levels.

Get Certified 

Any tech working around furnaces should obtain certification in combustion performance and carbon monoxide safety. Many organizations offer certification for HVAC techs to learn about CO hazards, testing procedures using a carbon monoxide detector and an overview of the combustion process. For example, learn more about the courses offered by the Carbon Monoxide Safety Association.  

CO is a serious and frequent danger to both techs and occupants. Always practice CO safety, ensuring that fuel-fired appliances meet safety standards, keeping you and your clients safe.