Hi all,

I'm working on a small air drier that's dehydrates air for an air compressor. When there is no air flow through the drier it doesn't turn off , but has a hot gas bypass valve that comes into play if the suction drops below 3 degree c. This would prevent the coil from icing up. The only place I can measure the evap pressure is at the compressor. The hot gas bypass valve tees of the discharge line straight into the suction ( bypassing the evap ) on my first call there I found the suction running at 5c , quite superheated.but I could see frost exiting the foamed in place evap? The evap had iced and blocked the air flow generating alarms on the site. I have realised there is a leak and since recharging all is good. My question is : How can my evap ice up if my suction is running above 0c?
I understand the that the hot gas valve would be active raising the suction and superheat but shouldn't that pressure be constant down the suction? How can I have a lower suction in the evap than at the compressor?