Installing central A/C?

[Zeya]

Originally Posted by marcopolo666

No, there are two "things" : the "compressor" which is usually outside, and the "condenser" (the thing that makes cool air) tied into the ducts (generally next to the heater unit and the fan). They are connected by a line that contains either freon or some other gas.

Right, okay. The condenser is what I would be worried out fitting by an existing attic furnace. For installation, are the condensers small enough to fit through a typical pull-down-ladder attic entry?

On that note, your previous comment...

Originally Posted by marcopolo666

I just don't understand the "Heaters/furnaces are installed in attics" comments. I have *never* lived in a house in CA with either heating or A/C installed in the attic. I've lived in houses built in the 50's, 60's, and 70's.

My house (prepping to sell and move soon, hence the questions) has the furnace and condenser in the attic. (Compressor is in the back next to the main circuit breaker panel.) House was built in 1958. My house might be odd in this way. I think the previous owner had it all done when he replaced the roof. Good move; that's the time to do it.

I guess I'll take note as I house shop where their furnaces are located. A lot of the ones I've seen have the furnace in a little hall cubby, on floor level. I wonder how the heck you would install air conditioning in a house like that. Can you put the condenser elsewhere, or does it have to be hooked up to the furnace (for the fan or whatever)? I should study some diagrams or something.

[Ultrarunner]

I did a complete install in a 1950's ranch style home for my brother.

He had lived there for years with just the original wall furnace... that didn't fly when he got married.

Estimates for a quality install, including ducts, gas and power were 10 to 12k...

We did all the work for less than 3k in materials... including a custom full size drain pan under the entire unit in the attic and piped to daylight should a leak ever occur... this was in 2003

Ten years of wedded bliss now... so it was worth it.

Hardest part was all the crawling around in the hot dusty attic.

I was able to go in from the garage high up on one wall.

The building inspector commented it was the cleanest install he had seen.

No expossed refrigerant lines, concrete pad for the compressor, plenty of plywood decking in the attic and lighting...

Highly recomend two stages for gas heat and variable blower speed along with a quality air filter box.

Home being on concrete slab did not have the option of a crawl space.

[fashionguy]

It depends on people but if you live in South Bay, Central Air is highly recommended. The hot days are few and far between but in those days it is REALLY hot. Having the option is worth the cost for the long term. If you don't turn it on often, you don't spend much on electricity bill anyways.

North of Millbrae it is OK to not have Central Air. When people say San Francisco is cold during the summer, they mean San Francisco only. For most part of South Bay the climate is actually much more similar to LA than SF.

Originally Posted by Azmordean

I know it's not your question but do you think you'll need central air? I was concerned about not having it in my apartment (it has a "through the wall" hotel type window unit in the living room) when I moved here, but I've found I actually use it about 3-4 days a year. Otherwise, windows open and fans seem to do fine around here.

And I've found during heat waves, it is super dry outside, so the window unit tends to cool down the living room very quickly.

[MediocreButArrogant]

Since we're going through a record heat wave, I thought I'd bump this thread and share some information I learned in adding A/C to a 40+ year old house which previously only had central heat.

The problem with adding A/C to an older home built 40+ years ago is that the ductwork is likely inadequate for A/C. The heating/cooling balance in San Jose is such that you will need to flow more air during cooling than heating, so ductwork that is adequate for heating is undersized for cooling.

Ductwork under the house and in the attic can be increased in size, but the limit is often the chase that brings the air up to the attic (not applicable to all homes, but many/most two-story homes). Unless you're willing to tear out walls and ceilings and do some structural work, it's usually not feasible to increase the size of the chase or move it, to get more air upstairs. So given the limitation of bringing cool air up to the attic, you want to put some effort into reducing the heat load, so you can get away with a smaller A/C, and avoid trying to push too much air through undersized ductwork.

The problem in our house is that while the downstairs remains very comfortable (it took until 5:30PM for the temps to rise to 76F and for the A/C to run), my office upstairs feels 3-4 degrees warmer (doesn't help that I have a fairly powerful workstation-class PC running 10hrs/day when I work from home). I was considering zoning the system in my home, but after talking to a rep from Sandium, he really discouraged me from doing anything to restrict the supply (my A/C is already oversized - bad decision on my part to not challenge the decisions of the company who installed it). So the thinking is that reducing the heat gain through the attic into the second floor may be the most important thing to help the temperature imbalance. The insulation is totally inadequate, not even coming to the top of the 2x6 ceiling joists, so we think there is a lot of improvement possible. A radiant barrier might help too. The house already had new energy efficient windows installed, so those don't need replacing.