Air Conditioning - Trane 3 ton question

I recently had a Trane 3 ton 10 seer central air conditioner installed. My apartment is 1500 square feet, in a mixed use commercial property with a flat tar roof. Yesterday the temperature here in Chicago was 84 degrees. I ran the unit all day but the temperature in my apartment only reached 74 degrees. (I like my apartment cool). The temperature today 78 degrees, the unit has been running all day and my apartment is 72 degrees. I called for service and the tech tested the unit and said everything is working fine. I am afraid that this unit is not large enough or it is not working like it should. It can get pretty hot and humid in Chicago in the summer and I am afraid that if this unit does not get my place any cooler than 72 degrees on a 78 degree day then it will not be cool enough when it gets 90 degrees. I told that to the tech but he assured me that the unit functions according to the outside conditions. So my apartment did not get any cooler today because the unit sensed that it was cool outside. That sounded like a crock to me. Is he correct? Is this unit large enough for my apartment. Any advice would be appreciated.

hard to say about sizing, do a load calc online to determine if the unit is properly sized

what is the temp drop from return to supply?

is the unit condensating?

When the load calculation was done, you told the contractor that you wanted it cooler than normal inside? Systems are normally designed for about 75 inside on a design summer day. A heat gain calcualtion WAS done, right?

hard to say about sizing, do a load calc online to determine if the unit is properly sized

what is the temp drop from return to supply?

is the unit condensating?

I am sorry but I am totally new to this forum and to air conditioning. No load calculation was ever done. The company came in and measured and told me that I needed a 2.5 ton unit. That unit was defective so they replaced it with a 3 ton. I did not tell them that I wanted the place colder than normal I just figured that the right size unit would be cold. What recourse do I have if this unit is too small? I can't afford to get a larger furnace and air conditioner.

I work for a Trane Dealer and believe me they are a great system. At home I have 3-Ton Carrier that is almost 16 yrs old. I have learned to put in my own blower wheel & motor after 5 motors and 3 wheels. It wasn't easy but I stuck with it.

I am like you I like to keep it around 68 to 70 degrees on those hot days. I live in Southern California and recently it has been up to 105. My system takes it real good.

Anyway back to your Trane. How long ago was it installed? How much did you pay for it? Is it a split system or a packaged unit? 3-Ton sounds just about right. But as for the part where someone said it depends on the outside air I don't believe that to be true.

Say if outside air is 78 and you want the temperature to be 70, it should reach 70, however the temperature is pretty close to each other that might be why it won't get any cooler. Now if the temperature is 70 outside and you want the inside temperature to be 65 (for example) now that could a problem. Because you trying to get the temperature lower that what makes sense. Your compressor will freeze up in this case and you could burn up the compressor which will damage the condenser and coil that will trigger an down the line situation.

If you have access to a computer and can get online go to Trane's website:
(www.trane.com or www.comfortsite.com) and they list of various situations that you can possibly try to resolve this problem yourself. If that does not work than I would call back the people that sold you the system and don't give up until you get what you paid for.

I had my system installed about a month ago. I had 2 90,000btu furnaces and 2 10seer air conditioners installed.

Do you have 1-3 ton unit or 2-2 ton units?

Are you using a programmable t-stat and shutting it down during parts of the day or do you leave it at one set-point?

Take a temp at the return and a temp at the supply and post what you get.