Ceiling-mounted air handling unit, including the housing, cooling coil, and fan, characterized by the housing being composed of insulated panels and anti-bridge cold junction connectors, the anti-bridge cold junction connectors comprising square tubes, card slots, sealing strips, tees, and cover plates, with rectangular grooves on the lower parts of the square tubes adjacent to both sides of the panels, one side having a small hat rim with chamfered corners, the other side having a long hat rim positioned lower than the small hat rim, the adjacent sides of the square tubes forming rounded corners, the rounded corner structure's right-angle structure folded inward and extended to form angle iron-type angle plates, the card slot plate being a panel with a supporting plate and a right-angle plate, the supporting plate structure being vertical downward from the back of the card slot plate with the bottom end outwardly curled, the supporting plate fixedly connected to the upper part of the panel to form a second small hat rim corresponding to the first small hat rim, precisely holding the sealing strip in place, the right-angle plate vertically downward from the upper part of the card slot plate and then folded inward to form a right-angle bend, the right-angle plate of the card slot plate fitting over the long hat rim on the other side of the rectangular groove, the supporting plate fitting against the bottom of the rectangular groove, the card slot plate and the angle iron-type angle plate forming a large groove on one side, a thermal insulation panel installed inside the large groove, the card slot plate and the side with the small hat rim of the rectangular groove forming a small opening groove with a sealing strip installed inside, the sealing strip being a circular tube of rubber, the first and second small hat rims holding the sealing strip in place.