16 Navien gas tankless units in three series, from the $1,005 NPN-160U at 160,000 Btu/h to the $2,910 NPE-240A2 at 199,900 Btu/h. Every unit takes 3/4" on cold inlet, hot outlet and gas, runs on 120V AC, and carries a stainless steel heat exchanger. Water pressure range is 15 to 150 PSI across the line.
The NPE-2 series is the condensing line and the reason to specify Navien. It runs 0.93 to 0.96 UEF on a dual stainless heat exchanger, primary and secondary, and vents through 2" or 3" PVC, CPVC or polypropylene at 0" clearance to combustibles. That clearance figure is what lets the unit go in a tight closet or a finished utility room where a hot-vented heater cannot. The NPE-2 is also rated to 10,100 feet, is certified to SCAQMD 1146.2 at under 20 ppm NOx, and every model except the NPE-150S2 is Energy Star certified.
Read the model number, not the suffix, for capacity. Navien numbers the NPE by nominal size, not by input: NPE-150S2 is 120,000 Btu/h, NPE-180 is 150,000, NPE-210 is 180,000 and NPE-240 is 199,900. Flow at a 67°F rise runs 3.4 GPM on the 150 up to 5.8 GPM on the 240S2.
S2 or A2 decides whether you buy a pump. The S2 is the base condensing unit and carries the higher efficiency number, 0.96 UEF. The A2 is ComfortFlow: a built-in recirculation pump and buffer tank inside the same cabinet, 0.95 UEF, and a minimum draw that drops to under 0.01 GPM instead of 0.5. On a retrofit the A2 removes the cost of an external pump, a crossover valve and the labor to mount them, which usually beats the $292 to $585 cabinet premium.
NHW700 and NPN are the mid-efficiency line. Both run 0.81 UEF on a single stainless exchanger and are Ultra Low NOx, and both are considerably lighter and smaller than the NPE: 55 to 65 lbs and 14" wide against 68 to 77 lbs and 17.3" wide. The NHW-SU and the NPN-U install indoors or outdoors, the NPN-E is exterior only, and the NHW700 AI models carry the same built-in pump and buffer tank as the A2.
Two things to confirm before ordering. The 3/4" gas inlet is the fitting size, not the supply sizing: a 199,900 Btu/h unit on an undersized or long gas run will fault under full demand, so size the pipe to the load. And on the NPE, the 0" vent clearance applies to approved vent material only, so budget the PVC or polypropylene run with the heater rather than after it.
Navien venting kits, recirculation components, isolation valve kits and repair parts are stocked separately.
