There is a bit of confusion as to where this component is to be installed, it varies between an AC and a Heat Pump.


The vast majority of installers will position the LLFD outside with the condensing unit as it ships from the manufacturer with the condensing unit. This is the wrong application.
I can hear the question being asked “ Why is it shipped that way then ?”
Because the manufacturer wants to ensure the correct drier is used, uni-directional for AC, bi-flow for heat pump.

Regarding cooling only systems, the filter-drier should be installed near the indoor coil. This will be the best way to ensure there is no residue getting into the metering device.
On heat pump systems, the drier should be installed nearest the metering device being used first in commissioning. If the heat pump is installed in the winter the LLFD is to be installed by the outdoor unit, if the heat pump is installed in the summer the LLFD is to be installed by the indoor coil.

The LLFD should always be the last component installed in the line set as it has a hygroscopic desiccant in it. Once the caps are removed it will start to absorb humidity from the air. It is best practice to leave the caps on until the drier is ready to be installed.