Wow,,, I just can't believe what strange things are happening....... so you're saying the upholsterer shop needs to get their guys more training / licensing...
Was your shop in Canada? you probably meant to write ,typo?, 600/347 ... instead of 300.. and 208 equip doesn't last very long on 600 Volt... remember,, the 208 is line to line.. as the 600 is also line to line... so any 208 stuff would be connected 600.. and the 120 would be connected to the 347...... it SMOKES in a big hurry!
happens somewhat frequently .. as trained licensed people don't seem to know the 550 , 575, 418, 208 220 240 .. it seems all the same to them three phase right...
The old split receptacle trick!
but here is a story for you..... licensed electrician.. doing homes for years... picks up a couple 208/3 phase jobs... runs his circuits 2 hots per neutral.. and a ground ... so the 1" emt conduit with 9 hot, 5 neut, 5 bond conductor was confoooosing to me .. tillI realized where his training was from
then I saw beautiful wiring in the main.. red wires.. black wires.. blue wires.. white ... into the splitter.. then 3 disconnect wired in.. for 3 machines.. so he put 3 red wires in first disconnect... 3 black wires in the second disconnect.. then 3 blue wires in the last disconnect..... ,,, it looked really good.... ! His supervisor missed it.. ESA missed it...