If you think you may have a TXV issue, there is a very simple test that can be completed using just crushed ice and a set of accurate gauges:
- With the system operating, attach your accurate/calibrated manifold.
- Detach your TXV's sensing bulb and submerse completely into crushed ice. (Caution: not just ice water, must be 32F). I recommend using an insulated cup!
- Your Saturation Temperature of the Evaporator should be (32F - TXV Superheat). Example: Your R-410A TXV has a desired Superheat of 8F. 32F - 8F = 24F Saturation Temp
- Using your Pressure/Temperature Saturation Chart, convert Temperature to Pressure for the refrigerant used (Fig. 1). The Suction pressure should be relatively close to this value.
|Sporlan Recommendations, Bulletin 10-9|
When adjusting TXV Superheat, remember that you make a single turn at a time. Changes to the TXV Superheat can take as much as 30 minutes of system operation to be measured.
To Reduce Superheat: Turn valve stem COUNTER-CLOCKWISE.
To Increase Superheat: Turn valve stem CLOCKWISE.
There are many possibilities that could cause high superheat, besides a faulty TXV. By using this method, you could save yourself some serious service time needlessly replacing a TXV during the busiest time of year!