# Does cooling require more BTU/hr than heating to maintain same temp difference?

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Well, my 5,000 BTU(1.5kW cooling) air conditioner struggled to maintain 75°F when it was 100°F outside. The compressor ran continuously and it simply will not pull down a small room below 75°F and it took a long time to get down to 75°F.
My portable space heater which is also 5,000BTU/1.5kW can maintain 72°F just fine when it's 30°F outside and it doesn't have to run continuously.
How come my A/C struggles to maintain 25°F difference running continuously whereas my heater can maintain 40°F+ difference without running continuously even though they both have the same BTU performance?
Both results were with the central HVAC turned off.
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AC/DCdude17 wrote:

No, but you are failing to consider the heat gain that normally takes place winter and summer.
Winter or summer you have lights (all add heat as well as light), water heater, adds heat inside you home, windows generally create a net gain of heat both summer and winter, almost all electrical devices from the door bell to your computer add heat all year, even you add heat when you are home. During the day in both winter and summer, the outside of you home (roof and walls) are heated during the day and that increases heat gain. Now add to the fact that your A/C not only cools the air, but dehumidifies it and you can see why it takes more BTUs to keep you home cool in summer as it takes your heater to keep it warm during the winter, with equal temp differences.
Generally a good install will call for a closer match of A/C size than heat because the A/C will dehumidify less well if over sized.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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You have only once source of heat removal (cooling) with the AC, but you have many heat sources helping the space heater.
The AC is pulling down the air temperature and heat is still getting into the room from various sources. The walls not only tot he outside, but to the rest of the house are transmitting heat into the room. The crack under the door. Lights, TV, even your body. IIRC, an average adult gives off 400 Btu per hour just sitting in a chair.
The heater is getting help from all of these sources. Daylight hours it is getting solar heat. While the outside temperature is 30 degrees, what about the rest of the house? Are all the walls at 30 or are they closer to maybe 60 giving a lesser differential and thus lesser heat loss?
While 5,000 Btu is still 5,000 Btu, the heating and cooling loads are not necessarily equal in the particular room. Ed
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And specs for heating equipment are more straightforward than specs for cooling equipment. An AC may only make 5K Btu/h of cooling under rare operating conditions.
Nick
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AC/DCdude17 writes:

Heat load is more than just temperature difference.
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performance?
Only sorta slightly related, but Im running a water source heat pump, cooling house and heating swimming pool concurrently......
Water flow rate is ~7 gpm, incoming water is at 84 deg F, outgoing at 96 deg F--so I'm figuring it's moving roughly 40,320 btu of heat--this is a 3-1/2 ton unit.......
Anyone care to double check my numbers or have any questions / comments ???
--

SVL

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in message

struggled to

compressor ran

small room below

5,000BTU/1.5kW can maintain

have to run

difference running

difference without

same BTU

Good grief, there are certainly a lot of "logic" answers here, most with some but not much merit. Simply stated, it takes a LOT more energy to drop the temp a degree than to raise the temp a degree, because of the methodologies. The technology for increasing temperature is simply much more efficient that that for lowering the temperature.
Pop
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If you have a mass and remove 5,000 Btu or add 5,000 Btu, it is still the same amount of energy it is still the same mass. Since Btu is really an expression of Btu PER HOUR, the same amount of energy is being moved in the same time period.
Take the window AC unit and mount it backwards so it exhausts from the condensing coil the heat into the room. Would the effect of running it raise the temperature more or less than a heater that gives of 5,000 Btu of heat? If two rooms were the same temperature and one had the heater, the other h ad the AC (assuming the outside air is at the temperature used to get the 5k rating), which room would be heated more?
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wrote in message

the
of
Doh!!!
Stop it NOW.................
Your gonna confuse them all with this talk of "btu's"....
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SVL

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I'm afraid you are incorrect, Mr. Rivet. Think "COP = 3."

In wintertime, with the cool side in a damp basement stairwell...

About 30% more than 5000 Btu/h, given compressor and fan motor powers.
Nick
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wrote in message

the
=== I'm afraid I don 't understand: After making that comment, youthen proceed next to agree with it by offering a related analogy. ?!?

exhausts from the

stairwell...
or less than

motor powers.

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wrote in message

it is still the

Btu is really an

being moved in the

exhausts from the

of running it

gives of 5,000 Btu of

the heater, the

temperature used to

True, but the LOSSES (efficiency) of causing that are grossly different. Your analogy is sound, but it ignores the losses involved in makng that change occur, which is what the OP was asking about. I'm afraid getting into a technical debate, especially one with the lossless descrip you're trying to use would be futile and take way too much ether and time. Keep reading; it's there.
Pop
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I'm not looking to get into a debate, but I'm looking to learn something. Guess you don't know enough to teach me so I'll look elsewhere. Thanks anyway. Ed
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This is an embarassing thread. No one learns science any more.
The two processes are different because of the Second Law of Thermodynamics. It's not just a good idea...
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X-No-Archive: Yes
PopRivet wrote:

So, Newton was wrong?
The technology for increasing

This is the biggest non-sense posted in my thread.
Space heater can only output as much heat as the electricity going in and this will not change. Simple law of conservation of mass.
Cooling is more efficient. You can take about three units of heat from inside and take it outside with one unit of electricity. The condenser will spit out three units taken from inside + one unit used by the compressor.
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What does Newton have to do with this? Possibly you're confusing the three laws of thermodynamics, with Newton's three laws of motion.

Not at all -- he's absolutely right. You need to go back to school.
Heating is more efficient than cooling for two reasons: First, *all* mechanical processes eventually dissipate *all* their energy as heat. Thus the energy input into a heating device is all converted to heat. So is the energy input into a *cooling* device.
Second, the laws of thermodynamics work in favor of heating, and against cooling. The temperature gradient is downhill for a heating system, and uphill for a cooling system. Simply put, a heating system transfers heat from a warm object (e.g. a furnace) to a cool object (e.g. a room); this transfer occurs spontaneously. A cooling system, OTOH, transfers heat from a warm object (a room) to a *hot* object (the outdoors -- obviously it's hotter outside than inside, otherwise why are you running your air conditioner?). This transfer does *not* occur spontaneously, and requires additional energy to force the heat transfer uphill.

Actually, that's "conservation of *energy*".

Speaking of nonsense... you just won the prize. Cooling is *far* less efficient than heating.
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No. The electrical energy into an AC moves about 3X more cooling energy.
Nick
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So you're saying that air conditioners operate at an efficiency of 300% ?
There isn't any such thing as "cooling energy" anyway. "Cool" is the absence of heat. An air conditioner does not create "cool". It moves heat from inside the house to outside the house. This is an uphill temperature gradient, and is guaranteed to be a less efficient process than heating a home, which moves heat on a downhill temperature gradient from a warm furnace to a cool room.
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wrote:

Then suggest you look at the nameplate ratings then--and note that while the heater draws ~ 1500w, while the A/C likely only draws ~ 500w
I run heat pumps here year round.......when the outdoor temps drop below 40 deg F, heat pumps drop off in effeciency, and so the backup electric heat strips kick in--when this happens, my electric bill also about triples..........
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SVL

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500W at 240V = about 2 amps. That's not much of an air conditioner. Even at 120V, it's only about 4 amps, not even a decent window air conditioner.
Better check those nameplate ratings yourself; I think you're missing something. Maybe you're looking at the rating for the blower, instead of the compressor.
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