NO!!!!! You need to vent this heater in the
same manner as a tank water heater with the proper slope.

Steve, Dr home is incorrect. Manufacturer supplied vent kits are available for all Aqua-Star gas tankless units, and may be vented through a wall. My company can supply both. Call Brian at 800-851 9891
E-mail me at hotwater@structurex.net
I was glad to read your query, cheers, Brian.

I do not wish to start a debate, but, I
stand by my position on venting all water
tanks by the traditional method. The
reliability factor for these "kicker" fans has not been outstanding. You are placing
another maintenance item into the system that
is not necessary. If you do opt to install
this system, then I strongly recommend a smoke detector and a carbon monoxide detector
also be installed in the general vicinity.
GOO LUCK!!!!