Also, vent temp should not drop below 32°F. One of the most common causes of a frozen evaporator coil is lack of system airflow. If there isn't enough air blowing over your evaporator coil, the coil won't have enough heat to absorb.

 

Of course, however the conditions were set to produce the lowest possible temperature, purely as a reference. Obviously a freshly charged system H2 system, done to the book, under the same ambient temp and humidity conditions, is capable of sustaining this, don't think its a fault or anything to worry about.

 

26 degrees that's impressive. Some vehicles I've worked on it's hard to get to 40