Thanks Brian, you just answered half of the question I was going to ask (170 vs TK-1). I had previously surmised that the TK-1 was 'probably' the better of the two for my needs. Highly efficient single family house with pretty large flow requirements (2 showers at once is almost guaranteed). I'm located in Michigan.
Now for my second question. Looking at the TK-1 what do I need to do to vent it? I would like to vent it the same way as my high efficiency furnace with PVC pipe. The unitl will be wall mounted approx 8-9 feet from an outside wall. Can this be done? Does the TK-1 include a power vent?
Thanks, Dave you can email me with info if you like (firstname.lastname@example.org)