Basic Home AC question

[bigboost]

This isn't about my garage, but I figure there were some knowledgeable HVAC people on here. Sorry for the length.

This is our first summer in our first home, and it's been getting into the mid 90's this week and I noticed the AC is struggling to keep the house cool, used to just leave it set at 78, and it had no problem keeping it there, now I come home from work and its sitting at 80-81 and will not drop until it cools off in the evening.

I had the AC checked by a technician and he told me that nothing was wrong with my unit/system, said the high pressure side was a bit high, but nothing he could do about that.

It's a 10 year old 3 Ton Carrier unit, our house is 1500sq feet, was build in the mid 80's and has R19 fiberglass batts in the attic.

After some reading I think the unit is large enough for my square footage, so I'm going to blow some more insulation in the attic and pray for the best, do you guys think its just poor insulation, or should I really be saving for a new unit?

 

[Rookie2]

check the air filter, is the registers flowing enough air ? sometimes the 'A' coil will get plugged with dust etc. and the air flow slows down. My friend charges my old house 3 ton using a 'superheat chart'
hvacsalesandsupply.com/Linked%20Documents/Tech%20Tips/Proper%20...

When my unit can't keep up and I can't find my A/C friend i'll sneek a little R-22 in the system till he gets here. But too much can be as bad as too little .

That's all the confusion I can think of. my farm house has no wall insulation and R19 in the attic. and anything over 85 outside and she never turns off.

 

[BJ42LX]

Check the condenser and make sure the cooling fins aren't clogged with stuff. I have to disassemble mine every year and clean it. It gets covered with lint-like fuzz from trees and stuff in the area.

OP: presumably your AC guy checked this already, but maybe the tip helps others.

 

[Mustang51js]

Look into a attic fan if you don't have one allready,not a house fan but attic fan that has a tstat and exhausts the heat from attic.

 

[bigboost]

Thanks for the input. The AC guy checked the amp draw from the blower and the unit outside, checked the coils and condenser, and I've changed the filter, all is working properly.

I did a bit of reading on attic fans, from what I gathered they weren't all they were cracked up to be, but I don't have any first hand experience.

I'm going to blow another ~R19 on top of my current R19 next weekend and see if that helps, just after blowing almost 20K on my garage I really don't have 4K to unload on a new unit lol.

 

[Mustang51js]

I install attic fans all the time and they work,but depends on the size of the attic. With the right one you could drop the temp about 5-10 degrees on the floor below. As long as you get one big enough to keep up with the heat it doesn't let it soak through the ceiling and your ac works better. Usually set them at 95 degrees

 

[bigboost]

I install attic fans all the time and they work,but depends on the size of the attic. With the right one you could drop the temp about 5-10 degrees on the floor below. As long as you get one big enough to keep up with the heat it doesn't let it soak through the ceiling and your ac works better. Usually set them at 95 degrees

This is what I read, and given my house is 30 years old, i'd assume it may not be sealed up as well as a newer house, but I have no idea.

Attic fans are intended to cool hot attics by drawing in cooler outside air from attic vents (soffit and gable) and pushing hot air to the outside. However, if your attic has blocked soffit vents and is not well-sealed from the rest of the house, attic fans will **** cool conditioned air up out of the house and into the attic. This will use more energy and make your air conditioner work harder, which will increase your summer utility bill.

 

[Jackfre]

I would avoid the blown in insulation. As you all ready have batts I'd suggest batts on top of batts. Do it early in the day and you can have it done in a few hours. You may not anticipate having to do anything in the attic, but batts are easier to move if you do have to get up there.

Or, I have found our local insulation company to do a complete install for about what I can buy the material for.

 

[brewchief]

Did the tech clean the condenser or just throw gauges on it?

Even if it looks clean it can be pretty dirty and reduce the capacity. A half hour with a nut runner and a hose can make a big improvement.

Is your ductwork in the attic? If so spend some time inspecting it for leaks and missing insulation, fix these before adding insulation to the attic. If it's all flex you might consider replacing it with new flex with a higher R value insulation.

I would bring the attic insulation up to R-50 regardless.

 

[The Cobbler]

about 4 yrs ago I added r-50 to my attic which was r-12 when build in 1950. long story bu I removed most of the original insulation and installed batt fiberglass . also changed the A/C to a high seer but the same size unit as the previous was. replaced all the windows
Prior to that work the AC would run non stop and just barely keep up. now it cylces on and off.
I'm toying with idea of an attic fan too.

bottom line, Insulation is your friend .