Community Forums

IC2 · 07-02-2016, 07:09 AM

I believe I've owned some sort of RV for more years then most but think that something new was just learned. Again

Talking amongst us folks at the CG, someone mentioned that they leave a hatch open then turn on the a/c. By doing this, it supposedly drives the hot air near the ceiling out and allows the cool air to, for no better explanation, pool in that area and eventually lowering the temperature. I tried it and it seems to work.

Now, the question - does it really work that way or are those folks full of - ahem - hot air, and my experiment was only wishful hoping? I didn't use the MaxxAir exhaust fan, but would using that for at least a while help too? Or more wishful hoping?

Roger G · 07-02-2016, 07:21 AM

Yes it seems to work but there is a point where it is sucking the cool air out too. I generally do it for about five minutes and shut it down. I also open a small window that is high off the floor with the idea of starting a flow across the ceiling. Could be my imagination.

Smitty77 · 07-02-2016, 08:55 AM

Traditional roof top AC's of course cool the coaches air, and do not use outside air. Sort of like putting our car on recirculation, vs vented to the outside.

So just like in a car, the quickest way to cool things down is to get as much of the built up hot air out as possible.

When we enter a really hot RV, we open the kitchen window, and run middle of the coaches fantastic fan roof vent on high for about 3 minutes. Will sometimes also open the front drivers side window, and rear bedroom window, enough to allow more sucking in of outside cooler air into those zones as they are being pulled to the center by the fantastic fan roof vent.

After this short timespan, we fire up both AC's on auto (High for our units) with all vents opened. Once they kick on and are running, close the windows, and close the roof vent.

We also, if not already done before we head out in the AM, close the shades on the side with sun coming in. And, we use window awnings when able to do so based upon winds.

IMO, running the AC and opening the roof vent, may help some by the air being stirred and up by the AC and then up and out the roof vent. But I've tried it that way a few times, and then the other way (Mentioned to me from a fellow Escapee, so for sure not the first one to do this

!), and it seems to me that getting the hot air out faster with the windows opened and roof vent sucking it out, then allows the AC to cool cooler air, which ends up in a faster overall cooled coach.

Sorry if I did not write that very well, but hope the idea came thru!

Best to all, stay cool,
Smitty

Lv2Roam2 · 07-02-2016, 09:00 AM

Agree with all...same as our experience over many years and different rigs...

timetogo · 07-02-2016, 09:12 AM

Been leaving a vent cracked with the AC on for 30 years or more.

HR2004 · 07-02-2016, 09:24 AM

Kind of like our convertible. It is black on black and gets really hot when it is locked up in the sun.. I raise the top a few inches for less than a minute and you can feel the heat just fly out..

IC2 · 07-02-2016, 09:29 AM

It sounds as though I learned something this past week and really contradicts the way I had been instructed when we bought our first 5er in 1975. I'll have to experiment more as to the best way for our 5er along with the best way to use the two a/c units when we are somewhere that we can actually use the 50 amp service this RV has instead of the 30 that we are hooked up with for most of this summer.

Ray,IN · 07-02-2016, 04:17 PM

If we forget to leave the A/C running while away, I don't even turn on the A/C first. I open both fantastic fan vents, turn on the fans and open a window at each end of the coach for 10 minutes. Then I close everything and turn on A/C.
We almost always leave the A/C on continually. When windows are opened for a long period, everything stuffed-sofas, pillows, mattress', etc absorb humidity to equal ambient air humidity. Then the A/C must work harder to remove humidity from that stuff.

MtnTrek · 07-02-2016, 06:18 PM

Quote:

Originally Posted by Ray,IN

If we forget to leave the A/C running while away, I don't even turn on the A/C first. I open both fantastic fan vents, turn on the fans and open a window at each end of the coach for 10 minutes. Then I close everything and turn on A/C.
We almost always leave the A/C on continually. When windows are opened for a long period, everything stuffed-sofas, pillows, mattress', etc absorb humidity to equal ambient air humidity. Then the A/C must work harder to remove humidity from that stuff.

Ray brings up a very good point in regard to Humidity. Be it relative, or dew point. The Psychrometric properties of air and water vapor and our comfort levels are complex. There is a little more to comfort than just the temperature of the air as well as the effect on efficiency of our comfort control equipment removing this "latent heat". That condensate water drip, drip, dripping off the roof.
If the open vent allows infiltration of more water vapor into the controlled space you'd be loosing efficiency and in effect comfort. Remember if there is air going out, there is air coming in, somewhere. Perhaps slide seals, cracks, windows. Crack the door in the deep south 84%RH you know what I'm talking about. In contrast, look how you can cool a dwelling in the arid SW desert 6%RH with a swamp cooler (fan pump & water only).

Smitty77 mentioned the auto A/C and the use of recirculating and flow through ventilation. Bear in mind that the average auto A/C 's are in the 36k-72k BTU output each of our rooftops 12k-15k max. Yeup, a lowly minivan probably has more A/C capacity that 3ea. 15k penguin11s.
Note that large puddle of water under the car idling at the bank drive through.
Often you can cool that dry bulb temp in a matter of minutes. It might take hrs. to lower the wet bulb temp (dew point) of that same volume of air.

Happy motoring.