The sophomore forward was spectacular in the season-opening series at Arizona State.
Seifarth spent just one full season with the Nittany Lions.
Koebel will replace Rick Kaluza, a 1986 Penn State graduate who has served in the role since spring 2009.
Dunn scored 15 points in his club debut on Friday.
Penn State women's volleyball's matchup against Northwestern on Saturday, October 11, has been moved back an hour.
The Nittany Lions dropped three spots.