Installing an AC System | Page 2 | Construction and DIY projects | Forums

I just thought it was high after having another fellow quote 6k and this guy saying he didn't even plan to pull permits. Figured it's time that I learned how to do it.

So I sat down today and ran the Manual J calculation based on my window sizes and knowledge of the building. Ended up around 22,000BTU for cooling needs and the same for heating. This supported the 2-ton need and I think I'm going with this unit. Slightly more expensive but it has a variable speed fan which I think should be more efficient and leave the system with a longer life:

I then started designing the duct work. I'm not sure if I'm overthinking this but it seemed worthwhile considering my lack of experience. 

Now that I know the dimensions I'm slowly designing the ducting. I know that it's not as critical as I'm making it but I'm trying to design with the following in mind:

• Unit comes pre-charged for 15' of refrigerant line
• Keep the return air register in a public area (no bedrooms)
• Maintain access to unit for maintenance of condensate line
• Put supply registers as close to the outer walls as possible (ultimately determined by roof pitch, 3:12)

The first run was very obviously a fail. Main trunk will be fiberglass duct board. 

It helps me to visualize what I'm planning, that way when I get to building I don't need to slow down. 

Came up with Layout B that seems more straightforward (less static pressure) but it requires slightly more ducting. It also complies with the four requirements that I mentioned earlier which makes it ideal. I'll just have to come up with a way to put in an attic door that's secure/lockable.

I wish! The new house was built in 1961 so it's not quite as nice. Trying to get my wife to pick a paint color at the moment. I was just looking for inspiration for the attic access door. It will be a lot easier to do what you mentioned previously: cut an access hole, load the equipment through there, and then close it back up.