i am going with what has been said. 1200 sqft and two systems sounds like over sized and not albe to remove enough moisture and inproper drainage
the smelk of smoke may be the moisture building up on the motor windings and burning off, You will be replacing a motor soon
forget any fix for now
have a man-j load calulation done. Find out for sure how much cooling is needed for you condo. Then make an inteligent dicision about fixing the problem once and for all
you may find the new system you just had put in is big enough to do the intire condo and just some duct modifacations are needed to make it work
IMO forget about wat has been done and start at the begining Man-j load calc.
you can do your own by hitting the calc marker at the top of the page here. works great and is easy to do
The only way to solve this problem is to get a ducted return to YOUR air handler from your condo. I lived in an apartment two years ago that had this EXACT same problem...the neighbor next door smoked and whenever she lit up, my place reeked...I don't smoke. She also sometimes cooked nice smelling meals, other times it was awful and I had to hide in my bedroom with the air cleaner running full blast...or leave the apt.
The cause was the air handler, mounted over the bathtub like yours, used building fur down and wall stud cavities for return air to the air handler. BAD, BAD, BAD...should be outlawed! Although there was separation between my apt. and the smoking neighbor, it was just a thin sheet of drywall and studs...electrical wiring penetrations and other leaks were not hard to spot. My solution...we got a house and vacated the apartment. I didn't own it, I wasn't going to fix it.
In your case, the only way to resolve this problem is to provide a sealed return to your air handler so it draws air ONLY from your condo!
Just a few questions
Is this a heat pump? If so you may have a bad sequencer or control wiring problem which is keeping the electric back up heat running with the cooling. This would attribute to smoke smell.
Do any of your neighbors have these same problems? If they did, what was their solution?
Could your unit be returning from the attic, or from another apartment? Do any of your neighbors smoke?
Is your filter covering the entire coil area, do you have a filter in the unit?
Just a quick comment, you have mentally put yourself into a condition which will cause you to make a quick decision which could financially be a disaster.
I know, I buy homes from frustated homeowners, believe me I get their homes a steep discounts sometimes for $1. Then I take the time to calmly figure out what the problem really is and then resell these houses for full price.
Since I am in Phila, PA and cannot buy your house. I am advising you to call an established HVAC company, not the one you have used, this is the one that you always see in your development (the cheap guy). Don't look for a free estimate, ask for an analysis of the problem, you are paying for the service ask for a explanation of the problem in English, with a guaranteed solution.
When this is all over you will come to love your condo again, and will not want to walk away from its equity.