Installation and monitoring of the first known cross-linked polyethylene (PEX) downhole heat exchanger (DHE) was described in previous work by Chiasson, et al., (2005). This article describes the second-known PEX DHE installation for direct-use heating applications. PEX is a material known for its relatively high temperature and pressure rating, durability, and chemical resistance. The PEX DHE described in this article was designed and installed as a retrofit in a geothermal well providing space heating and domestic hot water to two residences in Klamath Falls, OR. The DHE was installed in October 2006, and monitored for one heating season