thinking of changing my 13 year old water tank (propane heated) with a Rinnai tankless water heater (wood floors next to it in basement, dont want to chance a failure/flood). Are there any concerns of using this type of heater in the North East with our cold winters, etc...? (someone mentioned more popular in southern states due to weather not so cold...is this a valid concern?)...are there other down sides to this type of heater vs a typical water tank system?
quite a few tankless water heaters in New Hampshire. The only "concern" I would have is the hot water output. The incoming water is colder he than say in Fla.... Most of the manufactures (like Noritz) give you a hot water output guide for the south and the north. Make sure that is taken into account. Generally speaking I install a unit that has a gas input of 175-199,000 BTU. that takes care of most of my applications....
have a few tens of thousand Rinnai tankless water heaters. You simply use the interior direct vent model. The recommendation of the 180-199 kbtu units is correct. At a 70*, 50-120F, you will get 4.3 to 4.7gpm for the .82 EF units and you get about 4.8-5.4 rpm with the .95 EF units. It is not a direct correlation but water heaters are tested to an Energy Factor rather than an Efficiency %. Frankly, for my modest hot water needs I went with the .82 and have been happy with it. Get an experienced contractor. There are many in your area.
My disclaimer for this info is that I was Rinnai's manuf Representative for 21 years in the New England States, so my bias is noted...but well deserved;)