got a combination boiler; works however when room heat valve turn on and the pump motor turn on; pressure is still zero; temp 130; at the pump pressure goes little bit up and then to zero fast fluxtuation. vent air is coming out from air vent.
did quick fill-water via bypass for 1 hour; still no change
expansion tank try to drain; no water out but hear air for a while, not any more but no water out from expansion tank drain.
expansion tank old style horizontal steel; tried open drain and air inlet from AIRTROL; nothing happen. expansion tank in bottom not hot;
at the pump; try to drain water through shut off valve water comes; so there is water.
any suggession ?