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TXV Troubleshooting – Short #245

By Bryan Orr

In this short podcast episode, Bryan walks through some common thermostatic expansion valve (TXV) troubleshooting scenarios. Many of the same principles apply to troubleshooting electronic expansion valves (EEVs). These dynamic metering devices maintain a constant superheat.

Troubleshooting does NOT start and end with the TXV. First, you need to inspect components (especially filters, ductwork, and filter-driers) and confirm the airflow and charge. You can use measureQuick to monitor superheat, subcooling, static pressure, and other key measurements, and the TrueFlow grid can give you a true idea of the CFM your system is moving. Keep in mind that superheat and subcooling values can vary by system.

Airflow problems and filter-drier restrictions may mimic failed TXV conditions. Ideally, the liquid line filter-drier will be located indoors, and you can check for a pressure drop across it by looking for temperature differentials. You need a full column of liquid going into the filter-drier, and you can use a thermal imaging camera to see the desuperheating, condensing, and subcooling phases inside the condenser coil.

The TXV has a bulb that can be loose, improperly mounted, or improperly insulated; when there is an issue with the bulb, there will likely be low superheat. The bulb should be on a clean and [ideally] horizontal portion of the suction line, and it should be strapped with copper or stainless steel straps. Insulating the bulb is especially important when it's externally located and when low superheat or flood back is a concern.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

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Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android

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#EEV #hvac #thermostatic expansion valve #troubleshooting #TXV #txv bulb

Author:

Bryan Orr

Company: HVAC School

Position: Founder

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this engaging episode of the HVAC School podcast, host Bryan Orr sits down with Leo and Paul Sharkey, a father-son duo of mechanical engineers who made the leap into the HVAC business. Leo and Paul share their remarkable journey of purchasing an HVAC company in September 2020 and quadrupling its revenue within five years. Their engineering backgrounds bring a refreshing, data-driven perspective to an industry that often relies on rules of thumb and outdated practices.

The Sharkeys operate in the challenging Northeast market, where homes can date back to the 1600s and 1700s. They discuss the eye-opening discovery that traditional HVAC sizing methods—like the simplistic “one ton per 400 square feet” rule—fail dramatically in older housing stock. Their commitment to running thousands of Manual J calculations has transformed their approach, often resulting in smaller, more efficient systems than competitors propose. The conversation dives deep into the unique challenges of working with centuries-old New England homes, including extreme infiltration rates, non-linear heat loss curves during harsh winters, and the complications of mixing modern additions with ancient construction.

Beyond sizing, Leo and Paul tackle the practical realities of heat pump installations in cold climates. They explain why turndown ratio is critical, how they handle homes with heat loads that triple their cooling loads, and when backup heating systems are truly necessary. Their consultative approach rejects the “one-size-fits-all” mentality that has flooded the market with incentive-chasing installations. They candidly discuss the problems created by Massachusetts’ generous rebate programs, which have attracted fly-by-night operators who prioritize rebate qualifications over proper design and long-term performance.

The episode also explores the balance between ductless and ducted systems, revealing when each approach makes economic and technical sense. The Sharkeys share fascinating case studies, from a 1748 house with the equivalent of a full-size door’s worth of air leakage to underground concrete dome homes requiring specialized dehumidification. Their willingness to take on complex projects that other contractors avoid demonstrates how engineering thinking, combined with trade expertise, can solve challenging HVAC problems. This conversation is essential listening for anyone serious about understanding cold climate HVAC design, building science principles, and what it takes to deliver quality comfort solutions in real-world conditions.

Topics Covered

Engineering background transition to HVAC – How mechanical engineering experience in semiconductors and manufacturing informed their HVAC business approach
Manual J calculations and proper sizing – Running 7,000-9,000 Manual J calculations over five years and why they typically specify smaller systems than competitors
Old New England housing challenges – Working with homes from the 1600s-1700s, extreme infiltration rates, and heat loss characteristics of ancient construction
Heat load vs. cooling load imbalances – Managing homes where heat loads can be triple the cooling loads and how this affects system design
Heat pump turndown ratios – Why equipment turndown capability is critical for shoulder seasons and preventing short cycling in cold climates
Cold weather performance and derating – Equipment capacity loss at low ambient temperatures and the importance of proper backup heat sizing
Ductless vs. ducted system economics – When to choose multi-zone ductless over ducted systems based on home layout, infrastructure, and cost
Retrofit complications in mixed construction – Dealing with homes that combine 200-year-old sections with modern additions on the same heating system
Massachusetts incentive programs – How Mass Save rebates (up to $25,000 financing + $10,000 rebates) have impacted market quality and contractor behavior
Installation challenges at low temperatures – Field issues including undersized ductwork, poor equipment placement, defrost cycle complications, and electric backup heat requirements
Building science fundamentals – Blower door testing, weatherization impacts, infiltration effects on heat load, and wind loading considerations
Consultative sales approach – Rejecting one-size-fits-all solutions and customizing system recommendations based on home characteristics and homeowner needs
Backup heating strategies – When and why fuel-based backup systems are necessary, including power outage considerations and client comfort levels
Complex project examples – Case studies including underground concrete dome homes, storage closet air handler installations, and severely under-designed retrofit corrections

Learn more about Leo and Paul’s business, Jay Moody HVAC, at https://jaymoodyhvac.com/.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

Subscribe to our YouTube channel.

Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

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