I'm almost ready to begin my install. Still trying to cleanup from the old oil furnace which seems to have left the basement black and smelling like oil. I'll be pressure washing soon and making the area look all nice and pretty.
I have some questions based on my readings and watching the scrutiny on this website. Now, before I get into it, understand that I will indeed get a licensed contractor to finalize my work. The brazing, evacuation and final termination of wires and gas lines will be done by a licensed contractor. I'm just doing the setup to save costs.
I'm installing a Goodman GMS9 which is a 93% AFUE furnace in my basement with a 3-ton 12 SEER condensor and coil outside, about five feet above the height of the basement floor.
I'm understanding that I will have to run two separate drains for the coil condensation in order for there to be a true secondary backup in case of failure of the primary. Is that correct?
I'm also understanding that there will also be a vent/flue condensation drain that will now be a third drain. To be on the safe side, I plan to run this as a separate drain and make sure it does not drain to the outside air due to the potential to freeze up. Actually, I plan to tap all of these into the washer drain near the floor and install a tee in each of them in case I need to monitor or inspect the flow of condensation.
All three of these pipes I plan to run to the wall with a proper pitch and then along the wall making two turns to get to that drain I mentioned close to the floor. I plan to maintain the pitch along the wall to maintain the drainage.
I've seen and read all your critiques in the hall of shame and everywhere else you have commented and I have learned a lot. I plan to take my time with the running of the exhaust/combustion pipes and connect them into a concentric vent for a neat exterior appearance. Yes, I will clean up the pipes and make them "pretty" because I'm like that too.
I've paid close attention to the warnings in the install guides and on this site as to properly shield the wires (on the proper side, opposite of the drainage). I also plan to use that more rigid electrical pipe/shield to come down to the furnace rather than the flexible stuff; I think it looks neater and more professional. Yes, I plan to install a shutoff switch.
One contractor suggested that I remove the tin ductwork I have in the basement that runs up through the walls and install flexible ductwork for its insulation properties. I need your opinion here. I have noticed that some ducts are 4x8 and some are 4x12. The ones that are 4x8 are where there are multiple registers in one room and the ones that are 4x12 are where there is only one vent in that room, usually a smaller room. There seems to have been some serious craftsmanship and some scientific thought in the way this ductwork maintains the same width throughout all the twists and turns through the basement and up through the walls. And to think this was done in 1940 or earlier.
Remember, I have returns in EACH room of this two-story house. I'm not as experienced as the rest of you in HVAC, but I think that the fact that there are so many returns and the fact that I'm using 100% tin throughout, my airflow resistance will be as low as it can possibly be with this number of ducts and returns, compared to insulated flexible ducts. I don't want to add registers unless I have to.
So my thought is to have the contractor fire up the unit when I'm done, check the load, resistance, return, rise, and all that jargon and make sure air is flowing optimally. As long as it is, then I'll just seal the tin joints with mastic, insulate them and go from there.
My whole point was to verify my understanding of the number and configuration of the drainage pipes needed for that unit and about the general preferance to attempt to keep the custom tin-job for its generally better and lower airflow restriction in this home that could possibly be discovered to be under-ducted. I just think that knowing and fearing that it can be under-ducted, it would be a bad idea to install insulated flexible ductwork without planning to add ducts (yet).