yeah that's for sure I do like doing as much as possible I used to help build houses when I was younger. having said that I learned quite a bit and the house in Pennsylvania I laid out and build back in 2001 now I did not do the HVAC system for. my dad was electrician and I learned quite a bit from him that certainly helps on things I had a local company do the complete layout for the ductwork they did the calcs everything they told me where to put the return and only thing they did not tell me is how high up I have to go. the companies are contacted in that area they are either want to do the whole thing or Nothing at All fortunately I do have a couple friends that are HVAC and right now like most or extremely busy I figured in the meantime I could look around and possibly get some input on the returns. I will not attempt to do everything with this by myself I want to make sure it's right I hope my buddy will be able to go down to charge the system Etc he still has his license once I get to that point. it may be hard to see but this is basically why they figure it out for me the duck runs and the return size Etc

Assuming return is in only 1 or 2 rooms. For cooling,the higher the better. For heating,the lower the better. That mean's around the great Lakes,low return will be most efficient. In Texas,high will be most efficient. I live in Texas,I am a trained hvac pro,I installed my system and returns are in ceiling.

The diagram shows an 8 x 24 return. Is that the only return? That size will only support the air flow for 1 ton of cooling.

Returns installed at 10 feet for a 12 foot ceiling should be fine. It would good to have one high supply in order to get cool air near the top.

Hi Mike .. another friend of mine that is an HVAC he did the ductulator calcs and said I need to returns I had him to look over it so I would have another eye on it instead of going by what they are recommending in the picture I just put in red where I want to put them. I hope that makes sense I know it may not be the best picture but you get the idea I hope

Sam,

Let's back up a minute. What is you location? What type of system are you installing? What is the size of the system? Where is the system located?

You want to make sure your not under sizing the main return. I see one small return in your hand drawing. That is not sufficient for the main return. I would also recommend installing a correctly sized 4 inch media filter.

My father was an HVAC specialist back in the '50s and '60s and he always said that duct placement for heating and air conditioning weren't the same and he put dual systems in.

Mike the system is a Amana AMH 95 Series 70000 BTU propane furnace and I have a 3 ton AC unit I contacted Goodman gave them all the information . They said it will work it's being installed horizontal upflow. in the picture the second column is the model number.

here is where I'm at now.. I'm not drywalling the back wall I want to use it as accent putting up possibly reclaimed or another type of wood panels. once I confirm and determined for these returns I'm using underlayment Paint It Black on the wall therefore I could put the wood over top of that.