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

It will take a long time to cool the inside of an RV if the inside temp is that hot especially since the outside temp is still hot and working against the ac units. 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. Not sure where you are, but find some shade!

Hi,It generally takes a long long time. Consider starting the generator, and running the roof air for an hour before you stop for the day.

Heat soak.....Walls, floors, cabinets, ceiling, furniture etc etcDumping the cool air directly downward will bring temps down quicker due to the volume of cool airTHAT is why when we are traveling in HOT temps......our A/C is on via our generatorNice to have cool 5vr when stopping for lunch and when setting up at CGWinter travel...furnace is on

Having a veritable environmental lab's worth of recording instruments on a wall I notice that the humidity must drop before the temperature starts to move downward.The temperature starts dropping very slowly once humidity reaches 60%. If enough BTU extraction is provided, the temp drop increases once the humidity reaches 50%.But ceiling and wall Delta T will offset temp gain. The main. Benefit being a reduction in humidity. After I connected an 80-pint dehumidifier the cooldown was faster. But that Delta T and percentage of humidity makes simple calculations difficult.My casita under construction is going to be firred out in 2x4 with closed cell foam. It's all shaded under a large Parrota tree.When living in the tropics in a bare concrete dwelling life means the school of hard knocks. My bus cools down much faster at night. I parked it cross ways to the tradewinds.

For a heat soaked RV it is common to take an extended period to cool down. I figure four+ hours after sundown before you feel a chill. Never turn the A/C off in those conditions.

how long to lower temps When living quarters at 100

dougrainer
Nomad
Jun 05, 2021
43 foot RV whether 5th or Motorhome requires 3 roof AC units in hot weather. Doug
opnspaces
Navigator II
Jun 05, 2021
2oldman wrote:
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.
At 75 it will take forever. Mine's 55, constantly. I measured it.

What he's saying is that at the best of times the temperature difference between the incoming air and the treated air is 20 degrees F. So if the incoming air is 95 the air back out is 75. As the RV starts to cool down the air cools. So incoming air at 90 conditioned air is 70.
Lwiddis
Explorer II
Jun 05, 2021
20 degrees is about tops.
2oldman
Explorer II
Jun 05, 2021
opnspaces wrote:
What he's saying is that at the best of times the temperature difference between the incoming air and the treated air is 20 degrees F.
I've heard this before, even from HVAC guys, and it's just not true. 20 degrees difference refers to the best an RV air can do is keep the *entire coach* at 20F below ambient.

Unless I have some sort of magic a/c, yours should also measure 50+ degrees or so at all times. I measured mine with 90+ ambient. Put your hand on your car or RV a/c vent. It's a lot colder than 75.
jjrbus
Explorer
Jun 05, 2021
Not an AC guy Delta T of 20 is considered normal. First thing to do is make sure filter and more importantly evaporator and condenser coils are clean. I have seen good AC units replaced because of cruddy coils!

What I do is open a roof vent to give the hot air someplace to go, I leave one open for 20 to 30 minutes and sometimes when I forget a lot longer!
dtappy3353
Explorer
Jun 05, 2021
Didn't know you could cool the trailer by plugging it into the generator. If I start the generator and plug the electrical cord into it...this will have no impact on my truck connection for brake, directional or marker lights?

Sure would be nice to have a cool trailer to stop and have lunch like others....
Acampingwewillg
Explorer II
Jun 05, 2021
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
time2roll
Nomad
Jun 05, 2021
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
dougrainer
Nomad
Jun 06, 2021
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
dougrainer
Nomad
Jun 06, 2021
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

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how long to lower temps When living quarters at 100

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