yesterday, I posted a thread about having much higher than expected gas bills with our new Rudd 92% furnace and possibly having my back contractor out to check the performance of the furnace. In looking though the archives here there are numerous posts about the importance of following mfg venting guidelines to the letter (especially for Rudd/Rheem), which my contractor really didn't.
Rudd Achiever 92% upflow 100k btu single stage. For both the intake and exhaust, he ran 3" schedule 40 from the unit. He used two long sweep 90's and 4 foot straights to get up to the joists and about 8 feet of straight out through the rim. This looks like it is to spec. However he ran the 3" out through the wall and then used two more long sweep 3" 90s to place the exhaust a foot above the intake. He did not reduce to 2" as the manual requires and didn't use the vane kit on the intake. Could this reduce the efficiency of the unit?
Thanks for any advice. I appreciate it very much.