what might be the issue if getting frost (icing) on narrow freon pipe ?

what might be the issue if getting frost (icing) on narrow ***** pipe ?

what might be the issue if getting frost (icing) on broader ***** pipe ?

What do we call the narrow pipe ?

and what do we call the broader pipe ?

thanks

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here are the images for your info

Small pipe = liquid line (High pressure to medium pressure fluid)
Big pipe = suction line (Low pressure gas)
orifice = expansion device (Transision of high to low pressure)

depending on make of system some frosting can be called normal mode of opperation, if there is lots of frost forming while system performs poorly, some gas may have leaked.

from your images it looks like normal opperation, and the expansion device is inside the out side unit.

I would recomend you repair the insulation on the narrow pipe with new insulation, as with any places needed ont he wide pipe.

Is the inside coil making cool air?
Is the wide pipe cool feeling as it leaves the coil?

If no then you need a technicition to test the system and possibly add gas(you called it *****) to it

Sog..........

The small pipe on an ac unit is the expansion line, the expansion valve on most splits is inside the condenser, usually frosting of the expansion line is sog or EEV problem, that's if it is a split type system. Judging by the pictures both lines are insulated which indicates it is an expansion line not a liquid line

You are evaporating your unit below 0degC. investigate:
1. Low load on the evaporator which can be due to factors including fan not circulating enough air through the coil, blocked filters and clogged evaporator
2. low refrigerant charge which may be due to leaks