Heat and home AC Units

HBombToo

It hit at least 100 degrees with a heat index of 108 if not more here in KCK. So the question is what is the best air temp inside a person can expect. The wife came running to me because the AC unit won't take us below about 77 degrees.Thats at least a 31 degree gradiant which seems pretty impressive to me.

OK Frank and the rest of you smart guys out there... whats the answer?

1/4twin

George Grand

That is pretty impressive. A long time ago, an engineering guy told me that maintaining a 10 degree difference was work for a normal system. That may have been with yesterday's technology, I don't know.

I've found about the same thing here, at the worst of times, I'm still able to maintain 76-78.

George Grand (of the Jersey Grands)

amulford

Well, that's not too shabby. It's only 5`F warmer than I allow mine to get set to, under any circumstances.

Do you have a single system? (I run two split systems. One for the downstairs and one for the upstairs. ) Alot of times split systems are sized to square footage, a ton (12,000 BTU) to 500 sq. ft. of living area. This has to do with the exchange rates of the coils (surface areas), blower capacities, compressor capacities, etc. If you are close to that ratio, then of course it will be hard for the system to keep it cool. Multiple intakes may help, but ultimately the exchange rates will have the final say. The faster the exchange (whole house volume) the easier it will be to keep it cool. Then the air dosen't have time to heat up as much. But the condensor and blower coil have to be able to handle the rate also.

That being said, you can't have to high of a rate either. The system won't run long enough to dehumidify if the exchange is to rapid.

If I size them, I normally go an extra ton. It helps the unit to not work so hard, and you have the reserve for times like this.

Another thing that helps alot is to keep the attic temp down. I run a thermostat controlled attic fan, set at 90`. If the temp reaches 90`, the fan is sucking out the hot air. I lose some of the cool air too, but the gain outweighs the loss.

Polkersince85

With a heat index of 108, there is a lot of humidity in the air, lower blower fan speeds helps the unit run longer and removes more moisture. Try going naked.

HBombToo

The exchanger looks like everybody else's... a few feet high with about a 3 foot diameter or so. The roof is wood shake and there is no way heat is trapped looking at all the vents and stuff. I just figured I was at the system limit with the heat index but am totally clueless with these systems.

The lovely Sherry gets nervous about everything and when I through out there that the intense heat will only last a couple more hours, I just wanted to check my thinking.

This is just interesting to me and thanks for the response.

twin

Frank Z

Keep in mind that higher humidity levels will cause the A/C to use a lot of its capacity to dehumidify and that means less cooling capacity.

Based on your discription I'd say it's doing pretty darn well for the conditions.

MacLeod

Wouldnt a lot of it also depend on the insulation?

My apartment seems to be well insulated cause we can get this place cold enough to hang meat! And we're in the 100's with heat indexes.

Frank Z

Yes insulation does make a difference. An A/C system is sized based on every aspect of the construction of the space to be cooled.

MacLeod

I guess it was a good thing this place was built back in the 80's. It seems to be well done with ample HVAC. And it seems to have decent soundproofing...at least I think so cause nobody's complained on me yet.

Frank Z

They're scared of you.

George Grand

Unless you are in an end unit, the apartments on either side of you are providing pretty good insulation. If your apartment is on the bottom floor, the people above are taking a bullet for you too.

George Grand (of the Jersey Grands)

McLoki

In the summer alot cooling has to do with solar gain as well. The A/C in my house is marginal most summers (3 ton unit, 2550 sq ft house) and it does ok if I close all the curtains on any windows allowing in direct sunlight. If I leave the curtains open, the house temp will rise and the A/C will never catch up.

It is supposed to be over 100 here today, I will let you know how it goes.

My St. Bernard is hating this weather, make sure your pets are inside or can at least get out of the sun and have plenty of water.

Michael

dorokusai

I have a Trane XE1000 30KBTU for a <2000 sq ft house, and it will rock out 68deg at 100+deg outside temperature easily...which makes the downstairs an icebox. The digital thermostat is set at 72deg year round.

This was installed prior to buying the house, otherwise I would have went with a split AC for more efficient cooling within the house.

F1Nut just has a couple small window units, and it's always comfortable on the main level....but he's also nestled in some nice trees. The basement is perfect.

MacLeod

"Nothing runs like a Trane!"

madmax

In cars when you set to "MAX" a door opens up inside the car, draws the cooler air in and cools it again instead of pulling in the hotter air from outside. This allows the air to be much cooler. I wonder if there are home systems that use the same approach?
madmax

Frank Z

All central A/C systems cool the air thats in the home. Newer homes do have a make up air duct that brings in fresh air to replace the air that is being used by any gas burning appliance, dryers, **** fans, etc.

madmax

I see. You can tell I have portable units.
madmax

jdhdiggs

Just my experience, in Tejas, we had some 115+ days (HI in the 130+ range) and we could keep it in the 68-72 if we wanted to ($$$$).

But our AC was sized for a house about twice as large and we had numerous attic work done for effieciency.

Current house, no issues but no really hot days to speak of (HI peaked around 95-98)