13.5K BTU vs 15.0K BTU Air Conditioners -- HOW????

[TenOC]

Question for my RV Air Condition Experts.

What is the difference in 13.5K BTU and 15.0k BTU? I know what a British Thermor Unit is. My question is HOW does the A/C achieve the difference in the RV? What is the real effect to the person inside the RV?

Given the same outside and inside temperatures.

1. Does the larger BTU unit blow more volume of air? More CFM?

or

2. Does the larger BTU unit blow colder air? I thought that under ideal conditions the A/C should cool the air only about 5 to 10 degrees.

[Old-Biscuit]

2oldman wrote:
Of course not, so what's the only other thing I could be measuring?

Infrared Thermometers measure reflected infrared light
Distance and Emissivity (reflectivity of object measured) are 2 factors that greatly influence measurements.

The 'laser' does not measure anything..it is just a pointer used for aiming

The infrared thermometer does NOT measure air temps

And the surface temps you are measuring can be/are deceptive due to the 'emissivity' factor


Believe it or not...........

[2oldman]

Of course not, so what's the only other thing I could be measuring?

[Old-Biscuit]

2oldman wrote:

CJW8 wrote:
2oldman, with the numbers you are giving you are recirculating cold air. In otherwords, a lot of your cold air is getting sucked back into the intake.

I'll do it again. Not that anyone is going to believe me. It's a new infrared themometer.

That's why I asked, why don't some of you do this?

You can NOT measure AIR TEMPS using an infrared thermometer.

[Kayteg1]

2oldman wrote:
There's nothing more I can say except take your own measurements.

My refrigerator takes 80F outside and blows -10F via freezer vents.
Why I am still hot in the kitchen?

[2oldman]

There's nothing more I can say except take your own measurements.

[Chris_Bryant]

2oldman wrote:

Chris Bryant wrote:
Asked and answered- you have air recirculating- a bad installation, and from the figures you gave it isn't doing a great job cooling the rig.

Right - a bad installation. They should all be this bad. 47 degree air isn't doing a good job? WTF are you talking about?

I don't think this is a horse I've ever seen beat before...unless you think questioning what a bunch of people are saying is beating a dead horse.

Measure your own air con temperatures. Then we'll have something to go on, not just a bunch of statements.

I apologize, but you just don't understand. The temps you are getting are because the air is recirculating. This makes the air coming out much colder than the air going in. What it does NOT do is make the air in the rig cooler. What we are saying is if the unit was installed properly, and the air wan NOT recirculating, giving you those high split numbers, the inside of the rig would cool much faster.

This is simple science- as out of vogue as that has become.

[2oldman]

CJW8 wrote:
2oldman, with the numbers you are giving you are recirculating cold air. In otherwords, a lot of your cold air is getting sucked back into the intake.

I'll do it again. Not that anyone is going to believe me. It's a new infrared themometer.

That's why I asked, why don't some of you do this?

[CJW8]

2oldman, with the numbers you are giving you are recirculating cold air. In otherwords, a lot of your cold air is getting sucked back into the intake. That is the only way your indicated delta T you are stating is possible. Or your measuring device is incorrect.

The difference between a 13.5K and a 15K is 1.5K. An air conditioner really is a heat remover. So the 15K will remove more heat. (BTU is a measure of heat) It does this by moving more air across the condenser and the evaporator, having bigger tubes and a larger compressor and probably a different orifice or expansion valve. I am certain many things are different between the two units. The temperature difference (delta T) between the intake and the outlet will always be 18-22 degF on a properly functioning unit with the technology we use today. The air mover in the larger unit will probably move more air.

[2oldman]

Chris Bryant wrote:
Asked and answered- you have air recirculating- a bad installation, and from the figures you gave it isn't doing a great job cooling the rig.

Right - a bad installation. They should all be this bad. 47 degree air isn't doing a good job? WTF are you talking about?

I don't think this is a horse I've ever seen beat before...unless you think questioning what a bunch of people are saying is beating a dead horse.

Measure your own air con temperatures. Then we'll have something to go on, not just a bunch of statements.

[TexasChaps]

TenOC wrote:

tempforce wrote:
the 15,000 btu unit can cool a larger space than that of a 13,000 btu unit.

My question was HOW?. More CFM (the fan blows more air) ? or bigger Temp difference?

could be either or both of these.. basically the larger unit has the capacity to remove more heat.. more BTU's = more energy moved..

[Chris_Bryant]

2oldman wrote:
82F and 47F. I better hang on to this air con.

Asked and answered- you have air recirculating- a bad installation, and from the figures you gave it isn't doing a great job cooling the rig.

[TenOC]

tempforce wrote:
the 15,000 btu unit can cool a larger space than that of a 13,000 btu unit.

My question was HOW?. More CFM (the fan blows more air) ? or bigger Temp difference?

[ScottG]

To answer your question, when I was buying parts for my Dometic 13.5, I compared the parts list for both it and the larger unit. I found out there were many important differences not the least of which was the compressor. I think the other critical parts were different as well but dont remember precisely.

[tempforce]

the 15,000 btu unit can cool a larger space than that of a 13,000 btu unit. so if your in a very hot climate the preferred unit would be the one with more btu's. now if you have a small camper and used too large of a a/c unit. it would cycle more and would not remove as much moisture from the air. the cycling of a large a/c unit, uses more electricity. than leaving a smaller unit running continuously.

[2oldman]

82F and 47F. I better hang on to this air con.