Tankless water heater question

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Hello,
I am considering going "tankless" with a Rheem RTG-66XN (http://www.rheemtankless.com/content/resources/documents/tankless/RH66IndoorDV.pdf), which is an outdoor gas-powered tankless water heater. I live in Minnesota, and I'm interested in the outdoor unit primarily so that the unit won't consume the indoor air that I paid to heat or cool, I'd rather it consume outdoor air and so I don't need to run new venting.


What is the typical installation cost for an outdoor tankless unit?
Where would people typically install the tankless unit? Is it built to be directly exposed to the elements?
Rheem says their heaters are safe to -30F. Can anyone comment how it's freeze protection works?


Thanks!

[Ladiesman271]

Just a typo. Protect the unit from freezing!


http://www.rheemtankless.com/content/resources/documents/tankless/Tankless66X_UC.pdf

[jimbo]

What is your demand for hot water. Note that in your Minnesota winter, where you will need at least 70º rise to get barely hot enough for a shower, the flow is only about 4 GPM, and if you wanted 80 or 90º rise, your max flow will be even less.

[gregsauls]

My indoor Rinnai R75 uses outdoor air for combustion. The single vent to the outside has an inner steel pipe for exhaust gas out, and an outer pvc pipe for combustion air into unit. All in a 5" tube.