Arrived on site to diagnose relief valve popping on new install. We saw that the boiler was flat when we arrived. We refilled the boiler and test ran it. The boiler quickly climbed to 25+ psi. We then found that the valve to the expansion tank was closed so the extra pressure had no where to go. It may have been bumped closed but we opened it up and the boiler pressure went back to normal. Watched unit run for 10minutes with no more pressure issues occurring. System is operating properly