First, thanks to all of the very helpful people I have heard from on this forum on a variety of posts! You have really helped me out on a major purchase!
Finally, maybe my last question. I recently had a Rheem Modulating furnace installed in my home. In the install, they patched into an existing 2" vent. The setup is 3" PVC from the furnace through an elbow to a 3"-2" contraction, then into existing 2" pipe. All looks very nice, except I noted from reading through the installation manual (I am a nerd about such things), it is stated that there should be no longer than a 10' run of 2" pipe when there are 5-6 elbows (for the 75,000 BTU furnace). Due to an awkward location of the furnace in my home, the exisitng 2" vent run has 6 elbows and runs for a total of at least 20 feet. So, the new vent line has about 12 feet of 3" pipe including one elbow then about 20 feet of 2" pipe with 6 elbows.
I asked about this and got answers I didn't like. I was told (1) that they had installed far longer 2" runs for this furnace with no problems, (2) that the pressure-limiter switch would keep the furnace from running if there were a venting problem, and (3) since most of the run is vertical it's not a problem.
I worry that (1) the existing setup, though easy to install, clearly violates the guidelines in the manual, (2) will this shorten the vent blower life?, and (3) is this a safety hazard?
Am I being too concerned? What is a good way to proceed?