They may have used a Marshall 290 instread of the 299. I have a 290($15
verses$30). The difference is the direction of the vent. The vent needs to
point down.This,for condensate to drain. It will freeze and influence the
proper functioning,otherwise.Even in less than fridged air. The 290 can be
installed this way,but it is on its side.No sweat.Like I say, I'm cheap.