heating/cooling question

[bazookaman]

I have gas heat and an AC unit. In the winter, I can set a 65 degree house to 70 and it heats up in about 15 minutes. In the summer, I can set a 70 degree house to 65 and it literally takes HOURS to cool down. Why the vast difference?

[space-time]

heating is easy and very efficient. Just burn some gas or run current through a resistor, you get heat. You get even more heat if you use a heat pump, for every kWh used you can get more than 1kW of 'heat" depending on how cold it is outside and how efficient the heat pump is. IOW a heat pump is over 100% efficient.

Now the other way around, to take heat from the house and dump it outside where it is even hotter, that process is always less efficient, it can never be 100% efficient.

[davester]

The furnace is probably oversized given that rate of heat increase. It is very common for fly by night HVAC contractors to oversize a furnace and not bother with the proper sizing calcs. It doesn't cost them anything and it ensures that they won't get call backs from cold customers. It also results in annoying short furnace cycles which will eventually kill the furnace.

Either the AC is undersized (or is broken...i.e. freon leak, etc) or you have an excessive heat gain problem, which could result from excessive south exposure windows with no low-e coating, lack of insulation, or too many heat sources (incandescent lamps, stove with pilot, etc) inside.

[rgG]

Also, make sure your coolant levels are good. If your coolant is low, it will take longer to cool the house down.

[tenders]

Also, the BTUs your furnace puts out are almost certainly several times the amount of BTUs your AC can remove. With the AC, the compressor is doing ALL the work. With a furnace, the heat from combustion is doing most of the heating; the fan is just blowing that heat around.

[MikeF]

Check the size of your cooling unit against the square footage of your house against where you live:

[Buzz]

Got fridge?
Got beer?
Got beer in fridge?
Then...
Got No Problem with AC!

Cold beer is well known to make up for most inefficiencies in any AC unit.
==


///

[Dick Moore]

I needed to check on proper sizing of a heat pump system when our church's package unit failed. I searched everywhere for free or very cheap software to do the calculations -- couldn't find anything that was reasonably effective and useful.

So I wrote two excel spreadsheets to do the calculations and annotated them, and made them available for download. People who have found them on my website tell me that they really help, especially as a check on what contractors recommend. They may help you to determine what's going on in your system.

Find them at: http://www.moorepage.net/heatloss.html

[bazookaman]

I guess I should check the AC Unit. The chart says I need a 2 ton unit. I have no idea what I have now. It sucks b/c the one side of house faces south...west I think. And there is zero shade on that side. And we have one window and a sliding glass door. So lots of glass. Sometimes it gets almost too hot to touch in the afternoons. We've tinted the windows on that side as well as hung some blackout curtains. There's just nothing else we can do...except suck it up.

[mikebw]

Awnings? Plant a nice shade tree?