What configuration is used for a heat pump installation added onto an existing system?

What configuration is used for a heat pump installation added onto an existing system?

• A. Horizontal coil in ductwork
• B. Vertical coil in room units
• C. A coil in the return air plenum
• D. Split coil installation

Answer: (C)

When adding a heat pump to an existing central system, the typical setup is to install the indoor coil in the return air plenum of the current air handler. The outdoor heat pump works with that coil, and as the blower pulls air from the return, it passes over the indoor coil to be heated or cooled before traveling through the existing supply ducts to the rooms. This retrofit configuration uses the existing blower and ductwork with minimal changes, making installation simpler and less invasive. It also supports heating and cooling by reversing the refrigerant flow. Installing a coil in the return plenum is preferred over putting a coil in the supply ducts, using room units, or deploying a separate split-coil arrangement, because it integrates smoothly with the existing system and avoids substantial ductwork changes.

When adding a heat pump to an existing central system, the typical setup is to install the indoor coil in the return air plenum of the current air handler. The outdoor heat pump works with that coil, and as the blower pulls air from the return, it passes over the indoor coil to be heated or cooled before traveling through the existing supply ducts to the rooms. This retrofit configuration uses the existing blower and ductwork with minimal changes, making installation simpler and less invasive. It also supports heating and cooling by reversing the refrigerant flow. Installing a coil in the return plenum is preferred over putting a coil in the supply ducts, using room units, or deploying a separate split-coil arrangement, because it integrates smoothly with the existing system and avoids substantial ductwork changes.