A more efficient heat exchanger with walls of heat exchanger coils oriented at compound angles with respect to its associated heat exchanger fan. The bottom edge of each heat exchanger coil wall is oriented at an angle of between approximately 35 and 85 degrees to the fan, and each heat exchanger coil is tilted inward at an angle of between approximately 35 and 85 degrees relative to a plane connecting the two bottom edges of the heat exchanger coil wall. One or multiple coils can be provided in each heat exchanger coil wall and an optional top heat exchanger coil can be added to the top of the heat exchanger. The front of the heat exchanger, which is normally pointed for forced draft units, is replaced with a triangular shaped plate and a modified trapezoidal shaped base for induced draft units.