A Quick Primer on Furnace Pressure Switches

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




Measuring HVAC Total External Static Pressure with a Digital Manometer

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.  

Press Releases


New VCRTs Help Technicians Recover Refrigerant Faster and with Confidence Every Time


ORANGE, CALIF. (January 22, 2024)Fieldpiece Instruments, the leading manufacturer of tool and test instruments that enhance the work of HVACR professionals, introduced three valve core removal tools (VCRTs) designed to improve system charging, recovery and evacuation tasks. VCRTs remove the valve core from service valves in air conditioning, heat pump, and refrigeration systems to replace defective cores and provide an unobstructed flow of refrigerant for faster servicing. The Fieldpiece VCRTs represent a significant leap forward in valve core removal technology, overcoming the limitations of existing tools.

One of the game-changing features within the Fieldpiece VCRT lineup includes an integrated sight glass that allows technicians to verify at a glance that the valve core is captured prior to removing it and confirm when refrigerant is flowing. Fieldpiece eliminated the frustration that techs face when it takes multiple tries, and lost refrigerant, before the valve core is captured with current competitive products. The Fieldpiece VCRT capture tip also includes an interior gasket that the valve core pin presses into to secure it for removal. No more fishing around for lost valve cores – a solid grip guarantees that the job is done right the first time, every time.

Another Fieldpiece exclusive feature is a comfort spinner, a free-spinning, rubberized cap that makes removing and inserting the valve core, while under pressure, easier and more comfortable. Like the sight glass, this comfort spinner is available on the VC1G and VC2G models. All three VCRT models, including the ultra-compact VC1, include a magnet in the cap to keep the removed valve core on hand during service.

All VCRT models are equipped with a 1/4” service port fitting that can be swapped in the field with an optional 5/16” service port fitting for mini-split systems, conveniently reducing the number of tools to carry. Replacement capture rod assemblies also streamline the maintenance process. Techs can say goodbye to deep-buried O-rings, as these simple replacement kits reduce downtime and expedite the repair process.

The premium VC2G tool features a dual ball valve design that protects attached vacuum gauges and pressure probes and adds versatility for connecting hose lines and isolating system service ports.

“Our VCRTs offer benefits that current VCRTs on the market do not have,” notes Jeb Ball, vice president of sales and marketing at Fieldpiece Instruments. “We collaborate with techs to understand the pain points and develop solutions that enhance their jobs. The VCRT line expands our arsenal of tools built for efficiency, versatility and durability, and underscores our commitment to innovations that allow technicians to work faster with more reliable results.”

The new line of A2L compatible VCRT’s is being showcased at AHR Expo, January 22-24, in Fieldpiece Booth #S9334. Wholesalers are purchasing inventory now and product will be available to techs in April. To learn more about the benefits of Fieldpiece VCRTs, visit

# # #

Press Releases



Fieldpiece to Award $25,000 in Scholarships to Support Emerging Talent in the HVACR Industry

ORANGE, CALIF. (Feb. 01, 2023)Fieldpiece Instruments, a leader providing cutting-edge HVACR tools and test instruments for over three decades, today announced the launch of its third annual #MasteroftheTrade Scholarship. Fieldpiece will distribute $25,000 in scholarship funds in 2024, with the support of SkillsUSA, which will collaborate on the program’s administration. The initiative underscores Fieldpiece’s continued commitment to uplifting the HVACR industry community it proudly serves.

The #MasteroftheTrade Scholarship will support 12 individual recipients with funds earmarked for their education in a college or postsecondary HVACR technology program. Among the winners, six $2,500 criteria-based postsecondary education scholarships will go to SkillsUSA HVAC students and a total of $10,000 in scholarships will go to the six gold, silver and bronze medal-winning high school and college/postsecondary students who top the leaderboards of the National Leadership & Skills Conference (NLSC) in June.

“As a dedicated champion of the HVACR community, Fieldpiece is committed to fostering the growth of both arising and seasoned professionals in the industry,” said Tony Gonzalez, technical training manager at Fieldpiece. “Fieldpiece empowers tradespeople with innovative test tools, unique programs and free online resources like Fieldpiece University. Its commitment extends to providing scholarship opportunities, along with the creation of a growing body of educational and informative content designed to equip HVACR professionals with the skills, knowledge and opportunities needed to excel in their field.”

According to the U.S. Bureau of Labor Statistics, the HVACR industry is growing faster than average with more than 300,000 job openings expected by 2032 thanks in large part to a retiring labor force. Fieldpiece aspires to play a role in closing this gap with scholarships that give back to the industry it proudly serves.

“SkillsUSA is thrilled to partner with Fieldpiece Instruments to help roll out its generous scholarships,” said Chelle Travis, executive director at SkillsUSA. “Empowering the next generation of HVACR professionals is vital for the ongoing prosperity of the industry and Fieldpiece’s scholarships play a significant role in shaping the workforce of tomorrow.”

To apply for the #MasteroftheTrade Scholarship, applicants must be SkillsUSA members enrolled in its HVACR or general construction programs who plan to study HVACR at the college or postsecondary level in the class of 2024-25 (high school seniors) or 2025-26 school year (high school juniors). The scholarship application must include a resume and either an essay (300 words or fewer) or a video (1-3 minutes) answering the question: “Why have you chosen a career in HVACR?” The scholarship opened on Jan. 1 and applications must be submitted by April 15, 2024. Scholarship recipients will be announced on May 16, 2024 and will be awarded based on the merit of the application including the essay or video and the proficiency of the SkillsUSA Framework skills demonstrated in the application materials. To receive the funds, scholarship recipients must provide an acceptance letter from their postsecondary education program or their first semester tuition invoice. The funds will be distributed directly to the school.


The SkillsUSA Championships are the nation’s largest workforce development event for middle-school, high-school and college/postsecondary students enrolled in public career and technical education programs. The contests are designed to test the skills needed for successful entry-level performance in given occupational fields. SkillsUSA represents 130 different occupational areas and adds contests to the SkillsUSA Championships each year to meet the demands of new or expanding careers. In 2024, the SkillsUSA Championships will feature more than 6,000 competitors in 110 hands-on skill and leadership contests. Each contestant is a state gold medalist.

Visit #MasteroftheTrade Scholarship webpage for more information.


ABOUT SKILLSUSA: SkillsUSA is a nonprofit partnership of education and industry founded in 1965 to strengthen the nation’s skilled workforce. Driven by employer demand, SkillsUSA helps students develop necessary personal and workplace skills along with technical skills grounded in academics. This SkillsUSA Framework empowers every student to succeed at work and in life while helping to close the skills gap in which millions of skilled trade positions go unfilled. Through SkillsUSA’s Championships program and curricula, employers have long ensured schools are teaching relevant skills, and with SkillsUSA’s new credentialing process, they can now assess how ready potential employees are for the job. SkillsUSA has nearly 400,000 members nationwide in high schools, colleges and middle schools, covering over 130 trade, technical and skilled service occupations. SkillsUSA is recognized by the U.S. departments of education and labor as integral to career and technical education. It has served nearly 14.2 million members since 1965. For more information, visit:


# # #



During heating season, the threat of carbon monoxide (CO) poisoning is at its peak, for home residents and all the HVAC pros making service calls. Because CO is an odorless, colorless, tasteless gas it’s critical to be armed with the proper CO detection instruments, proactive in their use, aware of the steps to take if CO levels are detected and recognize the symptoms of CO exposure.  


Sources of CO 

Fuel-fired appliances, like furnaces, use combustion to create heat. Because combustion is never perfect, some dangerous byproducts like CO are created in addition to heat. Combustion analysis helps HVAC techs precisely regulate the fuel and airflow to optimize system efficiency – safely delivering the most heat to a space and minimizing the harmful byproducts.  


CO Symptoms and Effects 

Some of the most 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 for a tech or an occupant to know if CO is present without proper instrumentation. To know if there’s CO on a job site, use a “walk-around” carbon monoxide detector when entering the building. The Fieldpiece SCM4 Carbon Monoxide Detector features a fast, electro-chemical sensor that measures zero to 1000 parts-per-million (ppm) CO 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.   

Keeping a CO detector in your toolkit is essential and should be used on every job site, regardless of what equipment you’re servicing because you may not know what other fuel-fired appliances are present. A wearable carbon monoxide detector also provides convenient and consistent monitoring to keep you safe. Carbon monoxide detectors are also recommended in homes to provide an early warning of elevated levels to occupants. 


Get Certified 

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

CO gas is a frequent danger to techs and occupants and should be treated seriously. Ensure all combustion appliances are within safe levels of CO emission and take continuous precautions while on the job.  


HVACR Tool & Test Innovations Designed for Techs!

Fieldpiece products are tough, versatile, innovative and can handle the demands of working in HVACR. That’s because they were designed with the idea that every HVACR professional in the field deserves the best tools possible. Here are just a few highlights of some innovative features and technologies we developed to make your jobs easier, faster and better!


Stop Recovery on a Dime with Zero-Stop™

When recovering refrigerant, the Fieldpiece MR45 Refrigerant Recovery Machine has the ability to automatically stop the recovery at 0 psig, with additional auto stop levels of -10 inHg and -20 inHg. Stopping the recovery at 0 psig is an industry standard when recovering A2L refrigerants to prevent air from contaminating the refrigerant in the recovery cylinder.

Change Vacuum Pump Oil on the Fly with RunQuick® Oil Change

Regularly changing the oil in a vacuum pump is crucial for maintaining optimal performance and  longevity. The oil in a vacuum pump reduces friction and wear between moving parts, and over time, the oil can become contaminated with debris, moisture, and by-products of the pumping process, making clean oil an essential part to maintaining peak pump performance. To make these oil changes as quick and easy as possible, Fieldpiece vacuum pumps utilize the RunQuick Oil Change system, which allows technicians to change their oil while the pump is running. In as little as 30 seconds technicians can swap out their old oil without losing vacuum, saving time on the jobsite and increasing the life of the pump.


Eliminate the Water Trap and Extend Sensor Life with HydroCycle™ Pump and SensorVault™ Technology

The Fieldpiece CAT85 and CAT45 Combustion Analyzers feature cutting edge improvements like no other combustion analyzer. The CAT85 showcases the HydroCycle Pump, which condenses and returns water to the flu. This eliminates the need for a water trap, as well as the need to buy water trap filters, lowering the cost of ownership for technicians.

The Fieldpiece CAT85 and CAT45 Combustion Analyzers also feature SensorVault technology that help sensors last longer. SensorVault  automatically seals the sensors when the unit is powered off – isolating them from ambient oxygen, thus reducing sensor degradation when they’re in storage. If the sensor needs to be changed, they’re field-replaceable and come with a four-year warranty. This means maximum uptime on the job site, and lower cost of ownership for techs.

Measure System Temps in a Flash with Rapid Rail™ Sensor Technology

The JL3PC Job Link® System Pipe Clamp Probe, allows techs to get accurate temperature readings in seconds. By incorporating Fieldpiece’s patented Rapid Rail Sensor Technology, these clamps utilize the pipe itself as part of the sensor to immediately react to changes in system temperature. They provide accurate readings on wet or damp pipes and are not affected by wind, ambient temperature, or any other outside influence. Instant readings make it easier for a tech to get a superheat and/or subcooling measurement.

These technologies are just the tip of the innovation iceberg that Fieldpiece brings to tools and test instruments.  Fieldpiece doesn’t just introduce products, we introduce solutions designed for HVACR techs, like integrating a dual port manometer into our combustion analyzer to save space in your tool bag and color tags for hoses so you can easily swap for a spare rather than purchase a whole set.  We’re on the job with you, discovering your pain points and finding solutions. These are just a few examples of the innovative features and technologies we’ve brought to you, and there’s more coming!

To see more innovations, visit