how long to lower temps When living quarters at 100

[mrad]

We did a two hour pool today in 90 to 97° weather. When we got to our destinations the interior of the fifth wheel was pretty much 100° all over according to my infrared heat gun. After two hours it only dropped a couple of degrees. I have two 15,000 BTU air conditioners. One in the bedroom, one in the garage of the toy hauler. At first I had the turbo cool closed so it was using the ducts. But after having a little success cooling it down. I open the turbo cool in both the bedroom in the garage hoping to cool them down and pull the heat out of the walls and then try to cool down the living room dining room area later this evening when it cools down.

Just wondering if this is normal for two 15,000 BTU air conditioners in a 43 foot unit, or if there might be something wrong with the units

[Mike134]

2oldman wrote:

Mike134 wrote:
this guy has your answer, I'd take the same measurements on your home's A/C to see if it's cooling correctly.

If any of my a/c are blowing 75° air for more than a couple minutes, they're not functioning properly.

You misunderstood you want a 20 degree temperature drop across the cooling coil. If your house is at 95 to start you want 75 discharge, start at 75 want a 55 degree discharge. Hopes this helps.

[MEXICOWANDERER]

For personal comfort, I'd much rather have an eighty-degree environment with thirty percent relative humidity than a seventy degree room with seventy percent relative humidity.

But dehumidifiers really shine in cool clammy climes where they not only remove moisture but add some heat to the air.

Having an instrument set on the wall, thermometer and hygrometer allows me to instantly analyze my comfort versus climate modification performance.

Inversely, in the winter when a room was at 80F and I felt chilled, I found the relative humidity at five percent or even zero percent.

When neither the temperature nor humidity falls, I know the problem is within the machinery.

[azdryheat]

I have all my windows covered with silver insulating pads that are cut to shape. Works great at keeping the interior cooler when the trailer isn't in use. One thing about our trailers, the builders love to put in huge windows to let in the heat and cold.

What I had to do to my toyhauler was to properly seal the air vents to keep the cold air from going into the attic area. They did a terrible job of taping at the Voltage factory but once I corrected their sloppy work the A/C works a whole lot better.

One thing I've seen at the RV shows I work is the higher-end 5th wheels are much better insulated. The Tiffin Beacon has thicker walls and double pane glass. Also the Redwoods are very nice in triple digits but you're going to pay for the comfort.

[smthbros]

For what its worth, a 20° temp drop for the air over the evaporator is not, in and of itself, proof of a properly functioning system. The temp drop is a variable commodity based on a few factors, primarily:

1- The latent heat load of the air across the evaporator.
The greater the relative humidity of that air, the less the temp
drop. As the AC removes the latent load, the temp drop will
increase. As MEX posted, latent load takes priority.

2- The volume of air across the evaporator.
The greater the CFM of air, the less the temp drop. A dirty coil
or filter would increase the temp drop.

If you have not done so lately, now would be a good time to clean the condenser as well.

[2oldman]

Mike134 wrote:
this guy has your answer, I'd take the same measurements on your home's A/C to see if it's cooling correctly.

If any of my a/c are blowing 75° air for more than a couple minutes, they're not functioning properly.

[wintersun]

AC units for buildings are usually size so that there is a 20 degrees of cooling from the ambient temperature. With an RV the problem can be that the AC units are not sized correctly or have too short a cycle time. It takes time to remove the moisture from the air and cool down the interior spaces and sometimes a lower BTU rated unit that runs "continuously" works better than a high BTU AC.

Most RV's are built for "3-season" use and so not insulated for temperatures below freezing and so also not going to be great when temperatures are over 100 degrees. The advantage of an RV is that it can be moved to where the outside temperatures are warmer or cooler.

I grew up without air conditioning in my houses or my cars and trucks and it was not something that bothered me all that much. Friends with homes in the desert did not have AC either. Now AC is considered a necessity in the USA and so we use more electricity and add more to global warming which is not a good cycle to be in for us or for future generations.

If one is planning to spend months in the desert then building a structure to provide shade is worth considering. I see this often with trailers in areas where there is a snow load to worry about and the similar protection could be provided against solar loads.

On a more immediate basis if you can locate the RV so the rear is to the south then there will be less wall area exposed directly to the sun and having the side with the awning facing southwest would also help, if you have an awning.

[Mike134]

wildtoad wrote:
Measure the air temp at the return side of the unit versus the output side. If the return temp is say 95, and the output side is 75ish then the units are doing all they can do.

X2!!

this guy has your answer, I'd take the same measurements on your home's A/C to see if it's cooling correctly.

[lwbfl]

I've lived in Florida my entire life, camping for 35 years. The inside of my camper is usually higher than the outside temp once we stop. Here is what works for me: Travel with the vents open whenever possible (vent covers with lots of ventilation area!) As soon as we stop, I open the doors, windows and vents to let the heat out. Fire up the A/C and a fan if you have one and let it push out the heat while you finish setting up. Once set up, close everything back and let the A/C work. Sit on front of a fan with a cold drink until you cool down from all that hard work!

[time2roll]

If that 43' RV had a generator... the A/C should have been running in transit.

[JoeH]

dougrainer wrote:
43 foot RV whether 5th or Motorhome requires 3 roof AC units in hot weather. Doug

I agree ! --- a few things you might want to do is to put insulated coverings on all the windows and to travel with vents open . That way the inside will be close to ambient temp vs a closed box with sun coming in the windows which will heat it up past ambient temp. Then when you stop and plug in you are at least starting out with ambient temp interior , but 2 AC's are going to struggle in a 43' rv

[Acampingwewillg]

Your right Doug...I wouldn't begin to compare my 37' to a longer slide coach but I only posted this because getting a coach/RV cooled from a standing 100+ degree interior is a task for any cooling system. My reasoning is that it's a multi prong approach to get max cooling....the more you RV in heat, the more you learn!

[dougrainer]

Acampingwewillgo wrote:
Just to dispel some myths....37' non slide well insulated motorhome, two 15,000 btu roof top airs, awnings out, shares down, exterior window shades and a misting system on patio awning. The place, Pahrump, Nevada, the outside temp, hovering at about 115, inside RV, 68 degrees!

I've owned our motor home for close to 20 years and I travel in hot months....so it's not a one time occurrence!

The myth dispelled....that air can only cool down 20 degrees below outside temp! The accepted rule of thumb is 20 degrees less than the Ambien air entering your return air duct of your unit( up to its max cooling ability). That's my real world experience and my I understanding as to how it all works....your results will, in fact, vary!! LoL

You are correct BUT, you cannot compare your RV and length to RV's built LONGER (43 versus your 37) AND you have no slides Which is a GOOD thing because slide rooms are big air leakers even if they do not leak water inside. Doug

[dougrainer]

20 degrees refers to the output cold air in relation to the input hot air NOTHING TO DO WITH AMBIENT OUTSIDE AIR TEMP. So, you get your hot RV and it is 105 INSIDE. You start your AC units and the air running thru the evap will be 105 degrees and the output at the vents after running 15 minutes will be 85 degrees. AS the RV cools down the input and output temps will be 20 degrees. The RV starts to cool down and it is now 100 degrees in the RV. Odds are the 100 degrees is now the INPUT and the cold air output will be 80 degrees. The downward COLD progression will continue at this 20 degrees until the unit has reached its max low cold air output depending on the outside Heat and Humidity and how well the RV is insulated. Doug

[time2roll]

Some RVs are magical at cooling. Most however have poorly installed ducting etc.

Otherwise why does cool air come out of the electrical outlet if I have the cover off? Takes a lot of energy to cool the ceiling cavity and have it pushed down the walls :R