The Navien NR Condensing 98 residential tankless water heaters are available in three base models, the NR-180, NR-210, and NR-240. Navien offers a unique add on option for a built in tank and recirculation pump to each of these models by adding the suffix “A” to the model number with the NR-180A, NR-210A, and NR-240A […]