My wife and I have a disagreement. We own a kennel for dogs which we have to keep it reasonably climate controlled for the comfort of the dogs. Now with that said let me describe the building the dogs are housed. A concrete block structure with the only insulation in the attic. The kennel does have sliding run doors of clear plexi that can open to the outside, thus allowing a breeze if any to flow or allow in heat from heated concrete run floors.
In this structure, we have one small window ac unit that can cool the entire space of 10 kennel rooms. It is programmable in the sense that I can adjust the thermostat to only turn on the ac and fan if the temperature gets above my setting, in other words, if I set it at 75 and leave it, the ac and fan will kick on at 76 and stay on until it has lowered it to 73, then it turns off. Then after the heat of the day breaks and at night it doesn't have to or rarely runs at all because the building is already cool as it is outside. My logic is because it keeps the inside surface of the block walls cooler during the late afternoon sun warming them up, I figure it takes less energy to keep the temperature regulated.
My wife thinks this is spending more money than if you just leave the ac completely off and use it only when the outside temperature reaches 90 to 95. The inside of the kennel can be 80 to 85 degrees at that point, and can continue to get warmer until the heat of the day breaks. I feel that my wife's approach allows the structure and any items within to warm up and that adds to the problem of trying to cool everything down. So that's my dilemna, which way of climatized wind is is the most efficient and cost effective?

Sincerely,
Logically challenged

PS - please state your credentials also when answering this.

I could go into a long explanation but it is easier to say let the unit run. Cutting it off does allow heat build up and the build up will have to be cooled down so the cost is just about the same.

I had kennel for years on this property. English Bull Terriers (spuds) have been in our family since my father brought some over after WW2. As a HVAC person I always let the A/C run just to keep the excess moisture out of the air.

If you let the heat rise in the building it will cost more money to cool it back down. The higher the temp inside and out side the building makes the amps go up on the compressor. It has to work harder to catch up. Not to mention the run time and energy used to cool the block work down. The blocks will absorb the heat from the sun and it takes it awhile to get it back out. Your A/C works its hardest in the later part of the day.

Your wife's line of thinking is correct it takes less energy to cool it down than it would to keep it cool longer. The heat is of the day is still the same you have just been removing it all day long instead of all at once. Think of this way does it use more energy to boil a pot of water all day long or just to boil it when you need it. However there is one more factor here though is that the cost of electricy goes up in the middle of the day. So her way will use less electricy but your way might cost less.

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Originally Posted by michealb

Your wifes line of thinking is correct it takes less energy to cool it down than it would to keep it cool longer. The heat is of the day is still the same you have just been removing it all day long instead of all at once. Think of this way does it use more energy to boil a pot of water all day long or just to boil it when you need it. However there is one more factor here though is that the cost of electricy goes up in the middle of the day. So her way will use less electricy but your way might cost less.

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I have to ask... Her way will use less KW but his way might cost less. So why is her way of thinking better? If you turn your A/C off when you go to work and then turn it back on when you come home not only do you have the air in the house to cool but all of the furniture, walls carpet, etc. It all has heat and now it needs to be transferred to cool the room down. Your A/C will run overtime trying to catch back up. The higher the temp inside and or out side the compressor works harder and that = a higher amp draw.

Actually it has nothing to do with the cost of electric. It is the dogs health that matters.

I said her way is correct cause I didn't see that he also asked which would cost less. Of course I didn't take into account the fact that the air conditioning isn't as efficient when its hot out side either. Eh let the thing run your probably only talking about a few buck either way a month.

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Originally Posted by NIKADIMEZ

My wife and I have a disagreement. We own a kennel for dogs which we have to keep it reasonably climate controlled for the comfort of the dogs. Now with that said let me decribe the building the dogs are housed. A concrete block structure with the only insulation in the attic. The kennel does have sliding run doors of clear plexi that can open to the outside, thus allowing a breeze if any to flow or allow in heat from heated concrete run floors.
In this structure, we have one small window ac unit that can cool the entire space of 10 kennel rooms. It is programmable in the sense that I can adjust the thermostat to only turn on the ac and fan if the temperature gets above my setting, in other words, if I set it at 75 and leave it, the ac and fan will kick on at 76 and stay on until it has lowered it to 73, then it turns off. then after the heat of the day breaks and at night it doesn't have to or rarely runs at all because the building is already cool as it is outside. My logic is because it keeps the inside surface of the block walls cooler during the late afternoon sun warming them up, I figure it takes less energy to keep the temperature regulated.
My wife thinks this is spending more money than if you just leave the ac completely off and use it only when the outside temperature reaches 90 to 95. The inside of the kennel can be 80 to 85 degrees at that point, and can continue to get warmer until the heat of the day breaks. I feel that my wifes approach allows the structure and any items within to warm up and that adds to the problem of trying to cool everything down. So that's my dilemna, which way of climatized wind is is the most efficient and cost effective?

Sincerely,
logically challenged

PS - please state your credentials also when answering this.

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This question is essentially identical to one my girlfriend and I constantly disagree over. I am an engineer, but no expert on heating and cooling. However, here is how I look at the question -- it takes energy to lower the temperature of an environment below the outdoor temperature. The bigger the temperature differential you want to maintain, and the longer you maintain it, the more energy it costs. You are paying to maintain a "degree-hour" differential. I think her position essentially is this: it costs more (energy) to maintain an almost-constant (low) temp over a period than it does to maintain a variable but somewhat warmer (on average) temp over the same period. Frankly, it seems extremely difficult to argue with her position. Michaelb's analogy with the boiling water seems to describe this situation perfectly.

That said, however, I agree with hvac1000 that the health and comfort of the dogs should be the primary consideration, particularly since they can't sweat to cool themselves efficiently.

On a related note, a couple of answers mentioned that the AC would draw more amps when it's hotter outside. I always thought an AC was either "on" or "off" at a particular moment, and that the amp draw would be constant when the unit was on, no matter the outside temp. Anyone care to comment further on this issue?

Yes the A/C will draw little more current when it is hot outside. The compressor has to work a little harder because of the higher discharge pressure and temperature.

The best thing you can do if you have the tools and knowledge is to run the blower inside at a slower speed till the humidity level hits a predetermined percentage. At that time the control will set the speed of the blower back to the normal setting for the rest of the cooling cycle.

I actually never recommend turning the A/C on and off I prefer to see it run. This way the moisture is always under control and the A/C system does not have to run for 2 hours to get the moisture out before it can really start to cool. You can always look up latent heat on Google to get a partial explanation of this.

It has been a long day playing in my work shop with my experimental toys. Time for a movie and some sleep. Good night.