I won't bore you with the details, I'll just say that there are dozens of other HVAC companies out there and you should avoid Heatmaster like the plague.
Basically they don't know Chicago code so don't trust that their work will pass inspection. If it doesn't you'll have to pay them extra to change it... if you hire someone else it "void the warranty."
If you have them come out to do any maintenance -- even as simple as replacing a fuse. You'll need to pay. If you do it yourself it will "void the warranty".
And god forbid you actually to hire them to fix the mistakes they originally made. They're too busy screwing other people to be bothered to call back with an estimate.