CAN AN A/C COOL A ROOM IF INSIDE IT ENTIRELY?

Factual Questions
1

OK, I was asked this question, and I cannot answer it. Here it is in the simple form:

Does an air conditioner - say a 14,000 BTU window unit, produce more cold air from the cooling side than heat from the radiator side (the section hanging outside)?

The question began as part of a bs session discussing the possibility of global warming getting quite severe. It is known that air conditioners use condenser/radiators to cool the freon by way of forced air blown through finned coils. It is also known that as the outside gets hotter, the a/c looses it’s efficiency – which is why most manufacturers suggest installing one out of direct sunlight or among bushes. (The condenser units of built in units are usually set on cement pads, surrounded by bushes, which are there for shade as well as aesthetics.)

Another form of a/c, used mainly on condos – and frowned on by ecologists and most other people – is water cooled. Water pours over the evaporator coils (and down the drain) carrying heat away. Not practical if there is a water shortage. That type is not discussed here.

Anyhow, it was resented that if it grew too hot for a 14,000 BTU unit to radiate heat, could the thing be pulled inside (the inevitable condensation drainage would be taken care of somehow) and run in a closed environment?

Would running such an a/c in a room work or would it produce more excess heat than could be acceptable? Would the cool air from the cooling side be able to not only cool off the radiant coils but cool off the entire room?

For you sticklers, lets assume the room temperature is at 100 degrees F.

I did not know. Does an a/c produce more cool BTUs than heat? A truly efficient a/c would produce more cool air than byproduct heat.

Some air conditioners today are designed to assist in expelling radiant heat from the extraction coils by either retaining some condensation water in a pit through which the lines run or even being designed to splash some water onto the coils themselves via the rear fan blade. (I don’t like those last ones. Outside dust and such can eventually mix with the water and gunk up the coils, requiring them to be cleaned more frequently. Plus, the lower section of the aluminum radiator fins can corrode away with time.)

Anyhow - could a 14,000 BTU window mounted a/c unit work if placed entirely inside a room? Would it cool the room down or would it produce too much of it’s own waste heat to be much good?

2

No, it is impossible for an A/C unit to produce more cooling BTUs than heat. If the A/C unit is completely inside, the room will get hotter. A 100% efficient A/C unit would produce exactly the same heating as cooling (an thus accomplish nothing), but no A/C unit is 100% efficient.

Arjuna34

3

It will produce more heat than cold air.
It is less than 100% efficient.

4

An easy way to think about it is that all the A/C unit is doing is moving heat out from room and throwing it outside. Since the front of the unit is inside and the back is outside, with a wall in between, the heat it throws outside generally stays outside. If you move the whole thing inside, the heat it throws out just mixes back in. A 100% efficient A/C unit would remove heat from a room without producing any additional heat of its own, but as I said, no unit is 100% efficient.

Arjuna34

5

If you’re considering global warming perhaps you might also think about the heat generated at power plant.
I’ve unfortunately have had the experience of trying to cool down a room with an AC completely inside of the room.
By coincidence it was close to the temperature you specified (about 100 F).
Don’t ask me why I was doing this, there’s a long boring story behind it.
Anyway, there was no noticeable increase in the coolness in fact it seemed to actually heat the place up.

6

I once tried to explain to an elderly woman why the refrigerator will not cool if you leave the door open. It pumps heat from the inside to the outside but if the door is open it is pumping heatr around for nothing because the heat you pump out the back comes right in the front open door. She still did not get it.

An AC is a heat pump just the same. How can it pump heat outside if it is totally enclosed?

But even if I were an 85 year old woman incapable of understanding the most basic concepts I would have to think they are built like this because they have to be built like this. Why would they all be built like this if they could work without any outside connection? Another conspiracy?

7

Maybe she’s old enough to remember how people USED to cool a room (or freezer), which didn’t require an outside connection: a big block of ice. Of course, the heat was removed from the water back at the factory, and dumped into the air there, but it’s not as obvious.

Arjuna34

8

>> how people USED to cool a room (or freezer), …a big block of ice

What do you mean used?? huh? What do you think I do with the icebox on my boat? I buy ice and pay like it was gold. (And everything is warm and spoils anyway). Ah, the pleasure of owning a boat!

9

Well, I’m repeating what’s already been said, but:

Heat is energy. It’s a thing. Cool refers to the absence of heat. So to cool the air in a room, the energy has to go somewhere. You can’t just destroy it - conservation of energy forbids it. So you have to have some mechanism for carrying the heat outside. Therefore, an air conditioner won’t work in a room where it has no place to put the heat but back in the room.

In fact, the machinery of an AC is not 100% efficient, so some of the electricity entering the room to run the thing would end up dissipating as heat and the room would actually get warmer! The same is true for an AC used the normal way: heat isn’t just carried from inside the house to outside, extra heat is made as well (and of course dumped outside).

10

If you are anything like me you fill it with ice in the morning to keep the fish fresh until you get them back and sell them.

11

ii once used an a/c to heat a room in the winter once i jumped it to run continously - it worked

12

That must have been one frustrated A/C!

Arjuna34

13

Where I work, in the data center, they got huge printers, tape drives and what not and their cooled by these indoor 20 ton Liebert Systems. Cool Air is forced through a raised floor, and the equipment rests on top of a hole to get cooled. We’ve got 3 to each room, and these are the coldest rooms I’ve ever been in. Probably not effecient at all but damn, it’s cold. I seen the inside of these things, they look like air conditioners, maybe they work differently. Does anyone know if these are actually air conditioners like window units??

14

These are not linked to the outside air at all. And they have water pipes going to and from it.

15

You’ve answered your own question. The water carries the heat outside, probably to a cooling tower on the roof.

16

An air conditioner is a net producer of heat, but that doesn’t mean the heat has to be released back into the air. You can trap the heat by heating water in pipes as was mentioned, and I suppose it would be possible to get rid of the heat through endothermic reaction, sinking it into a floor radiator that would conduct it away from the room, etc. You could use the heat energy in a heat pump maybe, and generate electrical power with it. There could be a number of ways to deal with the excess.

17

it may not cool the room, but what if you laid in front of the air conditioner? would you cool down while the rest of the romm starts to sear?

18

The air conditioner can still maintain a temperature gradient in the room, so it’s cooler in the front and hotter in the back. If the A/C were 100% efficient, the average room temperature would stay constant, and you would indeed be cooler if you let the cool air blow on you, to the extent that you kept the warm air from the back of the A/C off of you. (For example, if you had a big ceiling fan on, that would tend to mix the air up, reducing the effect).

But no A/C is 100% efficient, so as time passess it dumps more and more of its own extra heat into the room, which raises the average room temperature. You’d still be cooler in front of the A/C than in back, but you’d be hotter than the initial room temperature eventually.

So yes, at first you would cool down while the rest of the room got hot, but eventually you’d be hot also (and the rest of the room even hotter).

Arjuna34

19

If you do not vent the heat to the outside in some fashion, you have essentially created a dehumidifier. And as such you will have the same results. You may “feel” cooler due to the lower humidity in the room, but you are not actually removing heat, probably creating more with the use of the electricity. If you do manage to create such a unit, let me know. I can probably scare up enough investors to make us both rich!