Cool Room Evap Icing Up

[passandscore]

From the sounds of things, I question the design.

Why have 2 evaporators, 2 TXVs and 1 liquid line solenoid. How are you controlling defrost?

How can 1 evaporator go into a defrost while the other one stays running? It couldn't happen as you would have a call for cooling (liquid solenoid open) and a call for defrost! You would certainly ice up the coil!

Do both evaporators defrost at the same time?

How old is this system? Any recent changes?

Muiltiple Evap Diagram.jpg

This diagram shows individual thermostats for individual rooms. Your application would require individual defrost time clocks on each evaporator with 2 independent liquid line solenoids utilizing 1 thermostats.

[stoljc05]

It is also a very old system and nothing has been changed recently.