How to check for AC duct leaks?

[disneyjoe7]

I had my duct's tested and repaired, but I feel something is wrong. Maybe what I'm saying is that the "Duct Test" couldn't test everything, and something is serious wrong. In fact I will move out come May to September due to what I feel is poor AC performance, something I will need to drug out, liquor out, or just move out.

Ok just to tell you how I feel about. It kills me thinking something is wrong, and nothing explains my electric bill being at times double of that of my neighbors.

What I feel is this there's a large leak in the return from the other side of house, this is allowing hot attic air in the system. How can I check this to be sure, before I hire or do something myself to check and or repair. If so I will require some sheetrock removal, so this WILL get ugly.

[treitz3]

Run your fan only [no A/C]. Put an accurate thermometer in your return duct and note temperature. Then move it to a register and compare temperature differences, there should be minimal or no difference. If the supply temperature is say 5 or 10 degree higher than your return ,then attic air is infiltrating into your return making your A/C work harder. Do this on a hot day.

Also, are you completely sure it is the A/C duct work and not possibly the house itself "breathing" too much? Windows, doors, trim work, thresholds?

[disneyjoe7]

No I'm not sure about anything at this point... But some idea's kicking around.

A.) Wrong thermostat or installed wrong (myself) It's a Honeywell Vision with Humidity control the control is causes the heat strip to go on. Per Honeywell is controls humidity by AC only lowering set point if needed to get where you're set point was set.

1.) but I don't think so as I felt it was cheaper to run AC then old thermostat.

B.) A door leak causing a heavy air leak from garage pass door then is forcing hot air into AC return #1 small 12"x 18" just under AC unit.

1.) I don't think so as I found air if anything is blowing out from this door not being sucked in.
This seems really odd and causing me to think this below.

C.) Improper installation of the large return #2 18" x 24" that's on the other side of house. This has to go from the 16" round duct to the fiber board I seen behind the wall.

1.) note here if this is true I made this worst by installing return filter AC grills to place a filter at the return other then the cheese filter just under the AC unit. Which was a cleanable 1/2" wonder which was broken / crack.

[Ricardo]

Another reason for higher electric bill could be low refrigerant; this would make your AC work harder/longer to reach the desired temperature.

[disneyjoe7]

Been checked / filled, and self test of small pipe / large pipe temp says A ok in this department.

The A coil had been do to being very dirty and was replaced prior to buying house so Freon was found to be down about 1 or 2lb.