Is my AC unit cooling properly?

[Bird222]

This unit is a 14 seer American Standard unit that is about 1 year 9 months old. The temps have been between 100-102 for about a week. The thermostat is set to 78 and it gets down to about 83 during the hottest part of the day and runs constantly. The thermostat is in an area where I think it gets alot of sun also it feels cooler than 83-84 degrees in the house. However for the unit to be running all the time I would think it would be cooler than it is in the house. What are your opinions?

 

[Rockinacoustic]

Last time it was serviced? Had the filter changed?

 

[meister]

All things being equal. Ie your house is insulated properly. No. It is not working. Most likely is your a coil is dirty and perhaps froze up.

Your system should put out 25-30 degrees cooler than the return air temp, thus keeping the place cool.

 

[Red Squirrel]

No AC works properly unless it can bring the temp down to at least 23C (73F).

 

[postmortemIA]

No AC works properly unless it can bring the temp down to at least 23C (73F).

on my AC's manual it says it might work beyond 78F, but it is not guaranteed. Obviously it depends whether you are cooling mice den or 5000sq ft house.

 

[MagnusTheBrewer]

The most critical component of whole house a/c is the duct work. Proper sizing, sealed joints and, balance of zones are very important.

 

[Raizinman]

Need temperature readings at hottest part of day and again at night when cooled off a bit.
1) Outlet vent temperature
2) Temperature outside
3) Temperature of attic

 

[lothar]

The most critical component of whole house a/c is the duct work. Proper sizing, sealed joints and, balance of zones are very important.

Checking for mice is just as important as those if not more important.

 

[Bird222]

Thanks for the responses. I did just change the filter (again). Coils were cleaned. We do need to seal around the front and back doors, but I don't think that is the total story. I dug out the papers and the model is 4YCY4042B1096AA 3.5 ton unit btw. The house is 1890 sq ft.

 

[QuantumPion]

A/C's are most efficient when running constantly. Every time they start and stop they have to cool down before working, just like your car's A/C. Most systems are designed so that in the hottest weather they will run at 100%. The only issue is if your system is low on refrigerant, or if your ducts are constricted, the coils can ice up. If this happens the A/C won't cool at all while running due to the insulation of the ice. Turning off the A/C for an hour or so will allow the ice to melt and the A/C to resume normal operation.

Also if your A/C unit is oversized for your HVAC system, that can also cause the coils to ice up.

 

[mshan]

Is this a sudden, new change?

If it is (i. e. cooled very effectively during hot days last summer), does it feel like the system is suddenly just blowing warm air around? If so, go listen and see if it sounds like compressor is on. If not, perhaps your start-up capacitor has gone bad, or system doesn't have one and needs hard start kit installed.

Is air flow out of vents as strong as it was when brand new, or much reduced (possibly suggesting air handler isn't getting enough return air now?).

On another thread, someone commented that max temp drop ac that can be expected (from intake of air handler to outtake) is about 25 - 30 degrees. If you can measure temp at main return duct and at vent that is pretty close to air handler, maybe you can get some coarse sense of whether it is cooling properly or not.

 

[Squisher]

I would say something is wrong.

Like Magnus said it might not be the AC unit itself. I have 3.5 ton unit on a 2400 sq ft. house and I could get it down to maybe 74 or 73 on 100 degree days.

 

[Josh123]

We had guys come in to blow more insulation in our crawl space this morning. Apparently we only had about an inch worth so they went in and blew another foot. We'll see if it actually helps cause our A/C usually runs all day and can't stay cooler than 86 degrees on hot days.

 

[Bird222]

We had a new unit and new vents put in at the same time. One HVAC guy that I use for maintenance said if a bigger unit was put in and the return is not big enough it could cause a problem. However, I don't remember last summer having this problem. I have the original HVAC company coming back to check it. I don't really don't know what to think at this point.