[dsr70]

Is this a viable option? Assuming all other conventions of the install are followed of course.

Other details:

- The roof is parapet, so I'd be mounting on the inside of the parapet, with the unit above the roof, but it would sit higher than the top of the parapet. Hence I'd need some extended mounting fixtures.

- The gas, incoming cold, and outgoing hot lines would run about 3' along the roof and dive down through the attic, into a wall, and through the floor to the crawl space.

 

[md2lgyk]

As long as it's an outdoor unit, I don't see why you couldn't do it this way. But I would certainly check with the manufacturer of the particular unit you want to buy, just to be certain.

I installed our tankless myself while we were building the house. The biggest challenge to figuring out where to put it was the various code requirements for minimum distance from doors, windows, and other things. Those vary by location, so should be checked as well.

 

[bob22]

I can't imagine how this would work in a climate with freezing temperatures. It would seem to me that something would freeze.

 

[md2lgyk]

True that. OP doesn't say where he lives. And I didn't notice that the supply and return lines would be outside for 3 feet. Outdoor tankless heaters themselves are designed for freezing temperatures.

 

[dsr70]

I'm in southern AZ, hence freezing is not a concern. The unit is an outdoor model.

I'm weighing two install locations. The problem with the conventional outside wall location is distance to windows and such, as @md2 mentioned, but also the difficulty in getting plumbing from the crawl space to the wall mount. I'd have to drill through the stem wall. This is an adobe house with 12" walls and an equally thick concrete stem wall. The entrance to the crawl space, which is a concrete lined 2x2 well, sits just a few feet from the proposed install location. All three lines would be coming from the crawl space, so three 12" long drills would be needed.

The existing storage water heater is in the kitchen. That's coming out to give more room for the kitchen remodel. No other location inside works, and the outdoor unit is ordered.

I've read through the install manual and via googling, but I'm finding a roof install a very odd and unmentioned topic, therefore the post here. Thanks for the time and thought. Most basically, is the mere idea of having a gas fired and high volume water device on the roof just an unaccepted no-no?

 

[md2lgyk]

Have you thought about putting the heater in the crawl space? Though I ended up not putting mine there, the manufacturer told me it would work.

 

[dsr70]

I did think about the crawl space, but it's literally a crawl space. The unit would have to lie horizontal, but the install manual from rheem says a vertical mounting only.

How would you have managed that?

 

[md2lgyk]

We designed and built our house ourselves. Knowing we wanted to put the well pressure tank, backup furnace, and lots of ductwork in the crawl space, we built it to have 4 feet of headroom, a good-sized access door, and switched lights.