What is the difference of the 2 models. Here is my experiance with a
Bosch 117000 btu unit and my take on what you need to know. You can`t
guess at Ng supply it needs to be measured with a manometer with
competing apliances on, if you dont get the flow you wont get 100%
output when you need it when in winter water is at its coldest. This
means knowing main input also. A Ng 3/4" line, im guessing you are
thinking 190000 btu Rinnai, My 117000 btu Bosch needs 3/4 at 10 ft or
more run, as I mentioned competion affects flow, I measure 2f drop in
water temp with my furnace competing.
Inlet water temp in winter for me can be 33f at -15f, you need to
knows your lows and take off 5f for saftey in sizing, but you probably
don`t know your low incomming temp as now is mid March.
Now measure output temp at your HWH and at a furthest shower, mine
drops 6-10f with insulated pipe in 30ft. I have no problem with a 112
shower temp with 33f incomming with unit not even on high so the big
Rinnai can handle most everything unless your gpm is to high or Ng flow
to low, I only have 4gpm. For a tub it will be fine, it will fill a
swimming pool. What is your Gpm incomming, tankless are rated at a temp
rise of a gpm. So sizing everything is critical.
Get a unit that keeps output temp even, my bosch monitors rise, not
output temp. A remote thermostat is nice to, the better Takagi and
Rinnai keep an even output temp. Takagi makes Bosches better unit.
Ive only heard you have no Rinnai Warranty unless a Rinnai certified
installer does the job, and a "plumber" that just says, without
checking, that your Ng supply is great is a, well, maybe, might be, a
hack. Poor testing, poor planning, you might be unhappy.