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Old 03-03-2013, 10:56 AM   #1
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Any air conditining pros here?

Other than the btu rating, is there another formula for calculating the cooling capacity of a roof air conditioner? I needed to replace one of my roof air conditioners and they replaced a 15000btu with a 13500btu. They told me that the new unit has more cooling capacity because of new technology. The old unit is a 5 year old unit and they said that the new unit, even though lower in btus, has more 'cooling capacity'. Is this possible and as I said earlier, is there a way to calculate the cooling capacity of each unit?
Thanks
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Old 03-03-2013, 12:04 PM   #2
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Ok, I know a little for every 550 sq ft is = to 12,000 BTU,s which is = to 1 ton of cooling, for every 1 ton of cooling there is 400 CFM's...so for a one ton unit you should have no more then 5 supplies as a rule of thumb...and for RV's there not much you can do to stop the heat gain other then some other Ideas the I had posted in other threads.

The new refrigerants R-410 A is a very good and works much much better in Heat pumpand A/C units then R-22 and the chance out for R-22 is R-407 C.

Yes, the new units are better, and are smaller in some cases.
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Old 03-03-2013, 12:16 PM   #3
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rockwood,
thanks for the info. Also, what suggestions do you have to stem the heat gain in an RV?
tom
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Old 03-03-2013, 12:33 PM   #4
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I know nothing, but it seems like a BTU is a BTU regardless of the refrigerant. Seems like a better refrigerant would make the unit consume less power, but that is all. Replacing a 15K with a 13.5K makes no sense to me.
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Old 03-03-2013, 12:37 PM   #5
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Originally Posted by lbrjet View Post
I know nothing, but it seems like a BTU is a BTU regardless of the refrigerant. Seems like a better refrigerant would make the unit consume less power, but that is all. Replacing a 15K with a 13.5K makes no sense to me.
That was my feeling as well but they claimed that for some reason, the new 15000btu units wouldn't work with my thermostat and wiring. I think that they are just trying to convince me of this fact that it wouldn't work and didn't want to admit they made a mistake. Will need to research further.
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Old 03-03-2013, 12:40 PM   #6
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Quote:
Originally Posted by lbrjet View Post
I know nothing, but it seems like a BTU is a BTU regardless of the refrigerant. Seems like a better refrigerant would make the unit consume less power, but that is all. Replacing a 15K with a 13.5K makes no sense to me.
Same here - I have always smiled whenever I see the term "BTU" defined. The definition I have always known is " The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit ."

Why couldn't they say One quart or one gallon of water?
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Old 03-03-2013, 12:52 PM   #7
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I did some testing in Mytle Beach and there are a few things you can do.

1. install insulated curtains at your windows and keep them closed during the day, we used spring rods and place them in the window valances.

2. If you have day/night shades in your RV close only the day shades and leave the darker side up, dark shades attract heat and increase the heat load at the windows, if you leave the shades open completely the windows magnify and increase the heat load as well by closing the day shades it helps break up the sun and the heat.

3. Set the fan control to the A/C system on "ON", this will help eliminate hot spots in the camper, the air is always moving.

4. Pre cool in the am if possible, set stat low while the heat load on the camper is low in the moring.....I don't know if you have noticed this or not but as the sun go's down the a/c system will begain to cool off your camper faster, this is because the primary heat load on the camper is being reduced as the sun disappears.

5. Install insulated foil in all sky lights and vents.

I will go back and see if I can fine the test that I had posted. The temp where around 90 to 95 degrees for the two weeks we where in Mytle beach and this was the 4th of July. My T-stat was set at 72 degrees and the system maintaned set point.
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Old 03-03-2013, 12:56 PM   #8
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rockwood,
Thanks for the suggestions. I think I remember someone posting about getting an insulated, bubble foil some where, I think it was Lowes. Do you know what it is called?
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Old 03-03-2013, 01:01 PM   #9
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That was my feeling as well but they claimed that for some reason, the new 15000btu units wouldn't work with my thermostat and wiring. I think that they are just trying to convince me of this fact that it wouldn't work and didn't want to admit they made a mistake. Will need to research further.
I don't understand, the T-stat is nothing more then a switch, the only time a standard T-stat will not work is if you have a heat Pump, this requires a "Heat Pump Stat because there is more then one stage of heat.

Is the unit on your roof just A/C only????? or is it a Heat Pump????? or is it an A/C system with Heat Strips????
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Old 03-03-2013, 01:06 PM   #10
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rockwood,
Thanks for the suggestions. I think I remember someone posting about getting an insulated, bubble foil some where, I think it was Lowes. Do you know what it is called?
I think it is called "Flextrix"
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