I'm adding a new 007 Circulator Pump for closed loop system. Problem is that one of the radiators on a third floor does not heat- tried purging air (it's a new added radiator). It gets hot when I continuously release air/water from return pipe, but it just doesn't seem like there is enough pressure to do it on its own. In the basement I have one 1" loop pipe and out of it 1/2" branches coming out to radiators. Correct way would be to use manifold, but it is financially not viable right now.
So I want to add new Taco ciculator pump just for that line (new radiator on the third floor since it doesn't have enough pressure). Do I mount the pump on return or supply? Which direction should the arrow point?