Sometimes welding procedures specify downhill root and other times uphill is specified. It is great to be able to do both so you will be ready either way.
uphill root voltage and wire settings are a bit lower but is really not more difficult than downhill once you nail the settings
The problem with tig welding carbon steel square tubing is that is is easy to melt thru and pull oxides into the puddle. When that happens, the puddle gets weird. Pulse settings can help.
In this video, I go over mig welding settings for short circuit mig welding in horizontal and vertical uphill. Also a quick tip for vertical uphill settings. Arc shots and techniques are shown in detail.
12 inch pipe with 35 degree bevel.
Open root welded with 5/32" XX10 electrodes
fill and cap with 3/16"