This summary of the video was created by an AI. It might contain some inaccuracies.
00:00:00 – 00:19:13
Brian Orr from hvacrschool.com provides a comprehensive guide on adjusting expansion valves, also known as TXVs or TEVs, in HVAC systems to maintain proper superheat levels at the evaporator coil outlet. He stresses the importance of having fully liquid refrigerant with proper subcooling and sufficient pressure differential for the valve's effectiveness. Factors such as proper bulb attachment, insulation, and positioning follow manufacturer guidelines are emphasized to ensure accurate temperature readings. Orr discusses using liquid line filter dryers to prevent contamination and addresses common technician errors like focusing on suction pressure without measuring superheat.
The video also covers practical adjustment tips, illustrating adjustments due to factory defects, and emphasizes slow, measured changes (half-turns) to avoid valve damage. Key principles, such as the balancing forces of spring pressure, bulb pressure, and the external equalizer, are detailed, along with step-by-step guidance on how to adjust the valve to achieve the desired superheat. Orr concludes with reminders to monitor the system following adjustments, highlighting the need for accuracy and caution in critical systems like refrigeration and ice machines.
00:00:00
In this part of the video, Brian Orr from hvacrschool.com explains the importance of properly adjusting an expansion valve, commonly known as a TXV or TEV. He discusses the purpose of the expansion valve, which is to maintain constant superheat at the evaporator coil outlet. Key conditions for the valve’s proper function include having fully liquid refrigerant with the proper subcooling and sufficient pressure differential. Orr emphasizes that a fully liquid line and adequate pressure drop are crucial for the expansion valve to perform effectively. Additionally, he notes that the evaporator temperature should not consistently drop below 32 degrees Fahrenheit in air conditioning systems to avoid freezing issues.
00:03:00
In this segment of the video, the speaker discusses factors that ensure the proper functioning of an expansion valve in a refrigeration system. Key points include the importance of maintaining the correct evaporator temperature by managing pressure differences. The speaker highlights common issues that can arise, such as contamination by dirt or carbon flakes and stresses the necessity of installing a liquid line filter dryer to prevent contaminants from affecting the valve. Additionally, proper attachment of the bulb using a copper strap is crucial; it must be snug and in good contact with the suction line to ensure accurate temperature readings. The correct positioning of the bulb is also mentioned, with emphasis on following manufacturer guidelines and ensuring proper insulation, especially when the valve is mounted outside the cabinet.
00:06:00
In this part of the video, the focus is on the importance of insulating the bulb on the line to ensure it matches the temperature of the line rather than the air temperature. This helps maintain accurate superheat, which is the primary function of the expansion valve—not maintaining constant suction pressure. A common mistake by technicians is adjusting the valve to increase suction pressure without considering superheat, which should be measured first. The superheat is ideally measured at the outlet of the evaporator coil. The instructor explains that adjusting the valve without proper measurement is incorrect and emphasizes the need for accurate readings to ensure the expansion valve functions correctly. Additionally, there is a discussion about the practicality of installing ports inside systems like split systems for accurate superheat readings.
00:09:00
In this part of the video, the speaker explains the importance of accurately reading superheat inside the system rather than just outside, particularly at the outlet of the evaporator coil. They discuss that for shorter line sets, pressure differences might be negligible, but for longer line sets, one must account for possible pressure drops. They illustrate a scenario where an expansion valve needed adjustment due to a factory defect resulting in zero superheat, leading to liquid entering the suction line. The speaker demonstrates how to adjust an expansion valve, particularly an adjustable type from Parker, used for air conditioning units. This valve covers a range from one and a half to three tons and comes with various fittings and necessary components for easy replacement. They detail the process of exposing the stem to adjust the valve’s spring tension to correct the superheat setting.
00:12:00
In this part of the video, the speaker explains the balancing forces of the spring pressure, bulb pressure, and external equalizer that determine a system’s superheat. They highlight that most valves are set at 50% stem height by default. To decrease superheat, one should turn the valve counterclockwise (Lefty Loosey), allowing more refrigerant to flow. Conversely, to increase superheat, the valve should be turned clockwise to restrict the flow.
Important considerations include waiting at least 15-30 minutes before adjusting the valve, ensuring the system is running under proper conditions, and checking the superheat at the evaporator outlet. Adjustments should only be made if there is a significant deviation from the target superheat. Once an adjustment is made, allow the system to stabilize again.
To increase superheat in a heat mode system, turn the valve stem clockwise, starting with half turns and ensuring all other system parameters are correct before and after adjustments.
00:15:00
In this part of the video, the speaker explains the careful process of adjusting a valve to achieve the desired superheat in a system. They emphasize making half-turn adjustments at a time to avoid damaging the valve and recommend putting the panels back on and monitoring the system for about 15 minutes after each adjustment. They caution against making rapid or excessive adjustments, which can lead to valve damage. The speaker also describes common issues that can affect valve performance, such as foreign debris, mechanical sticking, or a loss of charge in the bulb. They note that fine adjustments are crucial in critical systems like refrigeration and ice machines.
00:18:00
In this part of the video, the speaker discusses adjusting the flow of refrigerant in an HVAC system. Key actions include turning a valve clockwise to reduce refrigerant flow to the evaporator coil, which speeds up superheating, and counterclockwise to increase refrigerant flow. The speaker emphasizes making these adjustments in small increments of half turns and allowing the system to run for an adequate amount of time before making further changes. The segment concludes with a reminder to be cautious and a sign-off from the speaker.