Weak cooling, help!

kevintabb

While Atlanta is experiencing an unusually hot summer, I feel like the AC is very weak. It will run non-stop 3 till 9 to maintain 78 inside. My last electric bill was $200. I suspect a weak blower as the airflow out of the registers is weak. If I prop a fan against a register, that room will be several degrees cooler than the rest of the house after a while.

The blower motor is rated 1/2 HP, 10xx RPM, 10 FLA. The current draw is 8.5A while in cool mode. Is there any other test I can do to test its effectiveness?

Temp drop at the furthest register in the house is 20F. That's enough proof the compressor is fine, right? By the way, I did take the hour or so to open the unit and inspect the cooling coils. They were spotless and I noticed no icing at all. I don't suspect blockage.

The ductwork is 60s-era steel and there's 12 registers and 3 returns for 2000 sq ft. I can't find a noticeable leak anywhere, although one section in the crawlspace has condensation on the insulation (old aluminum sided fiberglass, btw.) I suspect a small leak might be to blame there, but I can't hear or feel anything.

Is it worth ripping off the old insulation on the ductwork and retaping the joints? Has anyone had any positive experience installing a faster blower motor? Any more advice? Thanks in advance.

yuri

Have you had the unit professionally serviced/freon level checked etc? A weak blower can mask symptoms of a low refrigerant level and there are other variables for poor cooling which only an EXPERIENCED tech can find out. Just because you are getting a 20 deg drop does not mean it is cooling 100%. The compressor valves can be worn/poor compression ratio/loss of capacity. Hard to find someone when it is that hot and they are busy but it is worth a try and will pay for itself in electricity savings and extend the life of the unit.

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beenthere

Did you look on both sides of the coil to see if its clean. Thee can also be dirt in between the fins that you can't see.

If your duct is lined. You can add insulation to the outside. Use a foil warp, so you have a vapor barrier.

What size are your 3 returns?

kevintabb

Yeah, its not dirt-free, but definitely no clogs on both sides.

I'm up for redoing the insulation, but I think I should strip the old so I can fix any bad taping (if there is any.)

Two are "regular", maybe 16", and the one in the hallway is very long, maybe 32".

@Yuri, I agree 100%, it needs a service and a professional opinion, but I was trying to avoid that in this heat wave. I would imagine they are charging extra right now.

beenthere

A chemical cleaning of the coil will help. The dirt you can't see is hindering air flow some.

You don't get much air through those returns. So your short on return air also.