Hi,

I had a company come over and replace my return and supply flex duct because if was in very bad and dirty shape, original from 1964 probably. It was 14" flex. They also took the unit out (it is a package unit on the flat roof of my house) and cleaned the coil, tray pan, drain line. After they put back together, I notice after week or so that the air flow was less and less and the inside temperature was stating at 79 and not going down all day - A/C keeps running all day, at one point the AC froze up and I had to turn it off for 30 min to get the minimal air I was getting back (when the AC froze I had 3 of my vents closed to get more air in to my bedroom overnight, and I think this caused the AC to freeze). The temp would drop to 76 (Set temperature) by 4-5 AM! I had them come back and recheck everything. They took the AC out and check the return to see if there nothing blocking the air, they checked the freon, and everything else and they couldn't figure it out. I had another company come over and they mentioned that for 3 tones AC which I have the return should be 16" instead of 14" (but the original return was 14" and I didn't have any issues before this work - My house is around 1700 sq/f). The also checked the air pressure of the closes vent to the AC and they said it is around 30 and it should be anywhere between 15-20. Also, the closes vent to the AC keeps having water around it when it is running all day (Condensation I guess).

What could be the problem here?

Any help would be appreciated. I have 4 month old baby and we are using a portable A/C unit in our bedroom! :(

Thanks again.

PS. If you know of a good and honest A/C person around Fort Lauderdale/Boca Raton please let me know.

A 30 degree temperature is way to high it indicates not enough air flow, (ducts undersized or registers closed off ) condensation at the registers indicates no insulation on the sheet metal boxes the duct is attached to at the wall.

Thanks for the info Acetc. By "registers" do you mean vent? Also, since the pressure at the closes vent to the A/C is at 30 degree, could the supply duct they replaced from the AC to to main metal ducts be blocked? Also, I forgot to mention that I had the vent clean as well right after they finished the worked I described in my original question. Would this caused any air flow problem?

Thanks again.

You have an air flow problem and it may be a pinched duct or dirty filter, blower running to slow or it may be iceing up and blocking air flow, Look for any thing to restrict air flow. 30 degrees is way to cool for supply air, this just yells at you that it is starving for air flow, this is a process of elimination and it is very simple, you have cleaned the evaporator coil, replaced filter,checked the refrigerant charge (low on charge will cause it to freeze over) Checked all duct for blockage.My quess is it's the duct.
The registers are the vents on the wall or ceiling. Good luck.

The in side lining of the flex ducts made around the time of 1964 and a couple of years before and after had a bad reputation for coming loose and wadding up in the duct. So that would be one of the first things I would check.
If you check the temperature of the air entering the return air duct as close as you can to the blower and then check the temperature of the air after it has gone through the evaporator coil, as close as you can to the coil. This temp should fall in a range of about 18 to 20 degrees, if the temp is cooler than that it means that you have bad air flow over the coil, and you should check for blocked ducts, check for closed registers. ( For Cooling all registers should be open or they should be balanced by a technician. For a temperature higher than that mean that your air is either moving too fast through the coil or you might have extremely hot air getting into the air duct somewhere or the freon level could be low.

Acetc,

Thanks for all the info. I had a A/C guy come over and he mentioend that the retrun is squeezed in he return box and the opening for the return is 12" instead of the 14" which the flex duct is. There is beam in the way cusing the flex return duct being squeezed. He said to move the return duct so there is no obstraction or see if you can connect the return duct from top of the box insead of side.

Do you think this could be the issue?

Thanks all.

Absolutely, as an example a 14" duct will move about 1000 CFM and a 12" duct will move 600 CFM at the same static pressure, a three ton A/C requires 1200 CFM. Common sense will tell you it won't work.

So you recommand a 16" return duct for my 3 ton A/C or if I get the 14" doct placed righ I should be OK? Also, what is CFM stands for?

Thanks again.

CFM stands for cubic feet per minute, if you do not have the space for a 14"duct then a 16" duct would have the same problem, what about installing two 12" ducts so that they won't have to crush them?
A 14" duct is still undersized and should be replaced, by operating the system in this manner you shorten the life of the compressor and increase the operating costs due the inefficient operation of the a/c.
Bottom line is the duct system is a very important part of the air conditioning system.