TEV/TXV open/close

[Eric006]

We had an interesting discussion today about Airco TXV's. We left we two questions. Most TXVs are no-bleed types, meaning after compressor shut-off they close and block refrigerant entering the evaporator.

Question1: how can the TXV remain closed after shut-off? The suction line will slowly warm up to ambient temperature, the bulb will wam up and the bulb pressure will rise to open the valve.

Question2: is a typical TXV closed or open at atmospheric pressure and ambient temperature?

Any ideas?

 

[imok2]

1. The evaporator back prssure will go up as the temperature rises thereby creating pressure on the opposite side of the bulb pressure to keep it closed and if it goes hi enough it will make the low pressure switch and start the compressor.

2. Open; no back pressure to keep it closed