No, it is not required that the NPE condensing tankless gas water heater be the first appliance off the gas meter.
It can be installed using the existing infrastructure and can go in place of a traditional tank water heater so long as the gas line is size appropriately and can delivery sufficient gas supply to the unit.
The NPE is approved to be vented with 2”vent material (maximum length of 60’, maximum of 6 elbows, and reduce 8 linear feet per 90° elbow). 3” vent material can also be used (maximum length of 150’, maximum of 8 elbows, and reduce 5 linear feet per 90° elbow).
ComfortFlow technology is a proprietary system that incorporates a buffer tank and recirculation pump.
The buffer tank will reduce “cold water sandwich” effects commonly found with tankless products and the recirculation pump will minimize the amount of time required for delivery of hot water to fixtures.