HVAC Training - TXV

Six Steps – Checking a TXV

By Ron Walker

Troubleshooting a TXVIf you suspect you have a bad TXV, the first thing you must ensure is that the system has a proper charge. You can do this by checking that there is some subcooling happening in the condenser. If possible, check the manufacturer’s specification for the proper superheat for that particular model. As a rule of thumb 8° – 12° is considered normal. If you measure a superheat somewhere in this range, regardless of what is happening in the system, the TXV is most likely working.

1. Check the sensing bulb, make sure it is properly connected to the suction line. If you can move the bulb, it is not securely fastened.

2. If the bulb has been insulated by the manufacturer, make sure the insulation is intact.

3. Check the equalizer line for restrictions, kinks, or signs of frost. A frosted equalizer line will require the replacement of the valve.

4. Some manufacturer’s have an inlet screen that can become clogged with debris. The only way to check the screen is to pump the system down and physically examine the screen.

5. If you are not sure, you can always add some refrigerant. If you add a pound or so and the pressure comes up, the problem was a low charge. If the pressure remains unchanged you have a bad valve or a liquid line restriction.

6. If the TXV is flooding the compressor (little to no superheat) check that the sensing bulb is securely fastened, check that the sensing bulb is insulated, check for proper charge, and check for proper air flow. If everything checks good, change the TXV.

That”s pretty much it. This should give you a good starting point for troubleshooting a TXV.

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About The Author

Ron Walker

After retiring from the U.S. Marines and achieving his B.S. degree, Ron Walker entered the HVAC field. He has been an HVAC technician, service manager, and business owner. Working as a service manager, he spent many years training HVAC technicians to be more technically competent and really understand their trade. His passion for teaching and helping others resulted in the creation of HVAC Training Solutions, LLC.