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.

[greenrvgreen]

Again, the name-calling. Oldman tried it with an IR gun, and tried it with thermometers, and both times his methodology is wildy inaccurate, although the two methods agree precisely--and disagree with the accepted wisdom. I ask again, what can the "experts" tell us about this?

When I hold my hand up to the AC vent, it sure feels like more than a twenty degree drop. My unscientific method agrees with Oldman. Since the experts have the accurate measurement tools, can they post their own readings? Have they even measured it?

[dougrainer]

greenrvgreen wrote:
Chris, I guess I haven't understood one bit of it either, especially the part where you resort to name-calling, instead of explaining clearly what you see as the problem with Oldman's temp readings.

AFAICT, he has a thermometer at the intake vent, and again at a remote outflow vent. If you're saying the cooled air is short-cycling and re-cooling, how is it doing that? The two readings are remote from each other.

While Oldman hasn't been easy to deal with here, his assertion is clear and no one has yet made a clear answer to it: Why is he getting these readings, is it a clear case of insanity?

So, you would be fine with your Doctor using those type Thermometers to gauge your health? WE cannot answer his question because we have no idea how his system is installed and what may be happening. A Blind Hog will eventually find the Acorn. But, not ALL blind hogs will find them in the same amount of time:B Doug

[greenrvgreen]

Chris, I guess I haven't understood one bit of it either, especially the part where you resort to name-calling, instead of explaining clearly what you see as the problem with Oldman's temp readings.

AFAICT, he has a thermometer at the intake vent, and again at a remote outflow vent. If you're saying the cooled air is short-cycling and re-cooling, how is it doing that? The two readings are remote from each other.

While Oldman hasn't been easy to deal with here, his assertion is clear and no one has yet made a clear answer to it: Why is he getting these readings, is it a clear case of insanity?

[dougrainer]

Chris Bryant wrote:

2oldman wrote:
Here's some incorrect data and misconception for you. Yeah, I probably just made it up.

Good grief- are you insane? Have you not understood one bit of what we have said?

Hello, hello... anyone there....

Those Thermometers are the Most ACCURATE you can get:S Doug

[tempforce]

so how much moisture is in the air? more moisture, means it feels hotter.
are all of your vents open?
what's the btu output of your a/c unit and how large is your r.v.
how hot is it outside and what are your walls made with. aluminum sides and studs will transfer more heat than wood walls.
it does look like the unit is cooling some air, that's why i asked if all of the vents were open..
when i was in arizona. it took a 11,000 btu window unit and the 15,000 btu roof unit to lower the inside temp of a 32' trailer below 80'f. it was over 115'f outside, i had no shade over the r.v.
both a/c units were running on high. i could get colder air from the vents on low, but that resulted in less air getting cooled. so it was hotter with the a/c units on low.
ok, the difference between the two air conditioners. the higher btu unit can cool more air.
the larger btu unit uses a larger capacity compressor, evaporator and condenser. they may fit into the same sized a/c body as a lower btu unit. thus saving manufacturing cost.
just like the roof units all look the same from the outside.

[Chris_Bryant]

2oldman wrote:
Here's some incorrect data and misconception for you. Yeah, I probably just made it up.

Good grief- are you insane? Have you not understood one bit of what we have said?

Hello, hello... anyone there....

[2oldman]

Here's some incorrect data and misconception for you. Yeah, I probably just made it up.

[Bob_Landry]

Anyone who understands air conditioning would understand why 2oldman's numbers are not right. He has probably never even used a set of gauges and it would do no good to refer him to a refrigerant pressure/temperature chart because he wouldn't know what he was reading. Some people are best left to their own misconceptions since they aren't really interested in what anyone else has to say. Don't confuse them with facts.

[smthbros]

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

Properly designed and installed air conditioners should move about 400 cfm air per ton capacity over the evaporator. They will function well at cfm as low as 350 and as high as 450. Lower cfm promotes latent heat removal and higher cfm promotes sensible heat removable. The dry bulb temperature differential of the air entering versus leaving the evaporator is dependent on the volume of the air and the latent heat of the air. The dry bulb temperature gives no indication of latent heat in the air.

So a larger btu unit should move more air. Of course this depends on the quality of design and construction of the AC unit as well as the quality of design and construction of the duct system.

[Cloud_Dancer]

On this one, I'm dismissing 2oldman, and going with Doug and Chris. These are 2 guys who have been working on RVs for many, many years,.....and always willing to share their experience in order to give all of us a hand.
They are two of 4 RV technicians who I would trust working on my motorhome.

[Chris_Bryant]

2oldman wrote:
Take your own measurements and stop dismissing me.

Do you really not understand what we are saying? You don't understand why you are getting those temperatures, or why that means your air conditioner is not cooling your rig as well as it should be?

Serious question, though just for my curiosity, as I have zero interest in explaining further- an apparent waste of time.

[2oldman]

Take your own measurements and stop dismissing me.

[dougrainer]

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

There is nothing sadder than a person who refuses to LEARN something and will go by his own wrong assumptions. According to YOU, EVERBODY (trained Technicians) are WRONG, and you somehow have the insight on what is correct. Doug

[dougrainer]

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?

THIS IS YOUR PROBLEM. YOU CANNOT USE A IR THERMOMETER TO MEASURE ACCURATELY THE TEMPS. Doug

I DON'T JUST STATE THIS. BOTH DOMETIC AND RVP WILL TELL YOU THIS.

[Strabo]

15,000 Quick Cool, ducted. Works well in a 32' fifthwheel toyhauler. I like the adjustable main vent that adjusts air flow between main vent and the rest of the hauler. Works well for one unit.

Coleman makes it.