Thread: Iced line and coils in HVAC forced air system.

Looked at a Forced air system today that when turned on the cooling cycle the refrigeration line started freezing up and then after a while the coils or fins started icing up. The owner was there trying to tell me that with the icing the unit was properly functioning. I told him he was wrong and it needed to be serviced by an HVAC techinician. I am really dumbfounded though as to what was going on. I need to write it up but I also need to know what was happening. A very old unit. In fact the ID plates could not be read. A repo house. Here are a couple pictures.

Jim Murphy

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Looks like you might have caused the issue if the unit was running while the panel was off. I can only guess by the photos, but IF it is a unit with the coil on the suction side of the fan and you pull the cover off, then you reduce the amount of air drawn through he coil and the unit will start icing due to lack of air flow through the coil the same as if the filter is clogged.

Most likely caused by low refrigerant or a blockage. It's not normal so it needs service.

Thanks, they may be it. The owner had the cover off because he had a bad relay switch and turned the unit on to demostrate that the unit would cool when I was outside inspecting the exterior. I came in and it was already icing up.

Jim Murphy

Agree with what Jim said. Its typical to see the refrigerant line and capillary tubes on the coil ice up if the cover panel is removed.

rick