Mine works good as long as I leave hot water running when it gets this cold...the only downside to tankless outside the house...usually in Bama it's not an issue

Y’all are correct on a small flow on hot water side flowing. Water heater only fires when the appropriate GPM is flowing.

Brannon I don’t know how your drain line froze on your tankless if no water is draining? Are you talking about your relief line? It shouldn’t freeze unless it’s relieving on temperature.

You would be correct on the latter

Mine didn’t freeze up, but I’m on a crawlspace that I had encapsulated and sprayfoamed. It has a supply and return from hvac running to it.

Mine didn't freeze up,under the house and the central unit kept it warm.

Mine did fine during the extreme cold . It's mounted on the interior wall of my basement and had hot water the whole time .

My tankless is in a closet in the house vented out the attic by pvc.

No regrets. Went with the navien and it’s been awesome.

Your tankless new construction of a replacement for a traditional tank unit?

Mine is an inside, vented unit, no issues

My tankless froze up on Christmas Eve in south Alabama. Didn't realize the the supply and return lines inside the unit (mounted outside) were NOT insulated. Damned previous owner.......I got it thawed out with a torpedo propane heater and promptly insulated the pipes. Worked great the following night!

Mine, like others said above, will not fire the heater if the faucet is just a trickle. I needs closer to 1/4 open before the heat fires on mine, so I can if needed run it at a small trickle to maintain flow but not burn gas. Mine is also rated to -22 degree where it will randomly fire in cold weather to keep the heating element warm enough, but if water isn't flowing the pipes can still freeze (exactly what happened to me).

Good to go now - hopefully won't see weather like this for a LONG time. I'm a damned yankee and moved south for a reason.

Mine is on the outside of the house on south side. I didnt realize it but it is completely open on the bottom. It got down to 0 wind chill here Friday morning but it never froze. Then Friday night, we lost poser for 3 hours from 8p to 11p. After that, it was frozen. I put a regular flood light bulb on it and covered it with a canvas tarp, all but the exhaust vent. Left for three hours and came back and it worked fine. Now I know what to do in the future.

If it's exterior, wrap the pipes with an electric heat strip. Insulate the attic lines and if you have to open a door to allow heated air into the attic to prevent freezing. I had a couple of buddies have freezing issues, luckily with no leaks.

My buddies froze up too. Had a hell of a time getting it going he has had problems with it brand new.