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AC not cooling enough....

Posted by mystique (My Page) on
Thu, Sep 13, 07 at 13:39

Our 2-storey house gets really hot in the summer, without the AC. At least the second floor does - the first floor is not bad at all. Our master bedroom faces west and from 12 noon to almost 8 the sun beats mercilessly against our window, which is pretty big by the way.

I don't remember it being this mad last year summer but this summer our room got really unbearable. Even with the AC on, we hardly found any relief. It would take about 5 hours for it to cool down say about 2 - 3 deg. When I switch it on it would be around 80 and 5 hours later it woul dbe 77 or something like that. We bagan wondering if our ducts need cleaning. When I stand near the vent in the bedroom, I can feel cool air but it doesn't seem all that cool. And it takes forever to cool the room.

Now I know nothing about AC but our house was brand new when we bought it in Nov 2005. It was built just then after tearing down an existing structure. Does anyone know if ducts need cleaning in less than 2 years? I think the AC is Ducane if the brand is important. I thought ducts need to be cleaned only every 4-5 hours.


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RE: AC not cooling enough....

What size is the house? What size is the a/c unit? If you provide the model# from the condensing unit (outside), the size can be determined. Are there return vents in each room on the second floor? If you put your hand on a return vent, can you feel air being drawn in? Where is the air handler - attic? basement?

There will be a 5 to 7 degree difference in temperatures between floors as heat rises to the top floor.

"I thought ducts need to be cleaned only every 4-5 hours"
- I think you meant "years", not hours. And no, as long as the filter is changed regularly (monthly), the ducts should be clean.

If you have a digital thermometer, and open up the air handler (where the a/c coil is located on the inside unit), you can measure the temperature of the air just before the coil, and just after the coil. This is called the "split" temperature, and should be 18 to 20 degrees on a dry day. Having cool air is one thing, getting it to the rooms is another story.

You may also have leaking ducts, either supply or return, especially if they run through the attic. A supply duct leaking will reduce the volume of cool air flow while a leaky return duct in the attic will draw hot attic air into the system.

A 2 year old house should not have these problems.

Ducane is a builders grade unit made by Lennox.

You could always install a window unit in the master bedroom to help cool the room while you figure out what's going on with your central a/c. Curtains/blinds/shades - anything to reduce the radiant heat gain in the bedroom windows will help.


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