Thoughts on adding a 3rd rooftop AC

[pasdad1]

Originally Posted by akeyzoo

.Now, which unit to get... Penguin 2 looks nice and low profile at 13.5K.

The Advent is made by the same company that produced carrier RV air conditioners a few years back.... Seems well made. 2 year warranty.

[TBS-POPS]

jax1911 hit the nail on the head!! Window coverings and cabinet insulation in the slides.Windshield is the biggest heat source and all the ac in the world won't cure it when its not covered on the OUTSIDE!. Cover the windows from the outside in the least tacky way and your rig will be much cooler.The dual pane windows are only marginally effective against heat.
On our old Dolphin we had the snap on mesh windshield and side window coverings and you could not believe the difference in how the ac would perform in temps above 90*.

[Peralko]

Chris,
I can't help but notice your coach appear to be mostly black--is your roof black as well? That could be a large part of your problem.
As far as temperature difference between ambient air and output air from the AC, a 20-25 degree difference is for swamp coolers. Our ACs are refrigerated air which is in a different ballpark. We have camped in Las Vegas with 120+ temperatures, and stayed quite comfortable, although we did run all three ACs. Also the top of our coach is light-colored, and of course we have no slides. In the heat we cover our windows with reflective insulated sheets.

[akeyzoo]

Peralko,
I have a white roof but 4 slides, dark paint and a decent number of windows...

:-)

Chris

[gemini5362]

Originally Posted by Mr_D

Me to! In 95° weather we can easily get the temps down into the 70°'s running only one of our 13.5 heat pumps. Running both of them gets the bedroom too cool so I usually set it for 76-78° and the front for 72°.
The specs for RV air cons or heat pumps is to cool the outlet air 20° less than outside ambient which may or may not be enough depending on the insulation in your rig. Ours is well insulated and has double pane windows too.

I am very impressed considering I have an allegro bus with double pane windows and 2 15k heat pumps. In 100. degree weather with both air conditioners running and the silver insulation over the front window. All the awnings over the windows out and I still cannot get the temp down below 80 degrees. I used an HVAC thermometer in the registers and the AC is working but not enough cooling for the unit. That seems to be much more of a recurrent theme than being able toget down in the 70s with only one unit running.

[gemini5362]

Originally Posted by Peralko

Chris,
I can't help but notice your coach appear to be mostly black--is your roof black as well? That could be a large part of your problem.
As far as temperature difference between ambient air and output air from the AC, a 20-25 degree difference is for swamp coolers. Our ACs are refrigerated air which is in a different ballpark. We have camped in Las Vegas with 120+ temperatures, and stayed quite comfortable, although we did run all three ACs. Also the top of our coach is light-colored, and of course we have no slides. In the heat we cover our windows with reflective insulated sheets.

All A/C units whether it is RV, Stick or dashboard only cool the air down 20 degrees. Basically they are in a closed room and keep cooling the air down by a 20 degree difference and that is how you get cooler temps. When the cooling load is too large for the AC to get that 20 degree difference is when you see what we are talking about.

[gemini5362]

Originally Posted by codgerbill

Just a suggestion, Buy a portable A/C (10,000-12,000-13,000 BTU) and exhaust it out a window. The upside is that you take it with you when you know you are going to hot weather climate, otherwise it is stored in the basement. We can also use it to cool our sun room at home. in hot weather We put ours behind the drivers seat and so there is negligible loss of space. We only bring it a couple times each year.

I am very interested in your post. How well does it really work. It seems to be the cheapest and easiest solution out there. I noticed the 10,000 BTU versions were only about 300.00 at Lowes. and the 13,000 were only about 500.00 I thought about it but was not sure if it would make enough of a difference to be worthwhile.

[Southpark]

I just want to caution that with dual pane windows the reflective heat barrier might be best used on the outside of the windows. Use on the inside surface may cause the window to overheat and the seal to break.

[codgerbill]

Originally Posted by gemini5362

I am very interested in your post. How well does it really work. It seems to be the cheapest and easiest solution out there. I noticed the 10,000 BTU versions were only about 300.00 at Lowes. and the 13,000 were only about 500.00 I thought about it but was not sure if it would make enough of a difference to be worthwhile.

We have the 12,000 BTU unit. We have not had the opertunity of using it in conjunction with the basement air yet. Currently our coach is in Shipshiwana Indiana having the basement AC/Heat Pump being replaced with a brand new unit. We have had 2 compressors replaced and it still was not working properly.

To answer your question, last year were were in 90-100 degree temperatures and going to the Winnebago GNR. The best the basement AC would do (with a blown #1 compressor) was about 5-7 degrees below the outside ambient temp. There was a couple in the adjacent lot that was also going to the GNR and thier AC was also not functioning properly. His temporary solution was to buy the portable unit. Inside his coach it was quite comfortable but not close ot "meat locker" temps. We immediately went to Lowes and bought the 12,000 BTU unit. In the box with the AC unit was a 6" hose for the exhaust and a window kit for the exhaust hose. The unit was able to bring temps down enough (I dont remember what the temperature numbers were) but it was enough so the "She who must be obeyed" was not vociferously complaining.

As soon as the basement air was supposedly fixed, the outside temperatures dropped to the low 80's/ high 70's so we did not have an opportunity to use the portable in conjunction with the basement air. As I mentioned we are currently having the the basement air completely replaced. there are some advantages (for me) with the portable unit.
1, It is portable so you only take it when you anticipate 100 degree temps
2. It can be placed close to any window that is able to be opened
3. If you are on a 30 amp service you can run an extension cord to the campground power post 20 amp breaker. You can run your coach AC on max settings and not trip the 30 amp breaker.
The disadvantage is that you have to store it somewhere when you travel and it does take up some space when you use it. For us we stored it in the commode room and when we used it I placed it behind the drivers seat and the space it took up was negligible.

[pasdad1]

Originally Posted by gemini5362

I am very interested in your post. How well does it really work. It seems to be the cheapest and easiest solution out there. I noticed the 10,000 BTU versions were only about 300.00 at Lowes. and the 13,000 were only about 500.00 I thought about it but was not sure if it would make enough of a difference to be worthwhile.

Need to get a "dual hose" portable. The single hose units are everywhere.....skip those and find the dual hose model.....I'll tell you why...

The single hose models suck air from inside the RV (air conditioned air) and use it to cool the condenser coils, blowing the hot air outside through the single hose. This creates a negative pressure, and so hot outside air is drawn back in.....not good.

The dual hose models bring in outside air through one hose, cool the condenser, and exhaust the hot air through the other hose......much more efficient.....no negative pressure created, and you aren't continually taking cool inside air and blowing it outside.

[pasdad1]

Here is a sample "dual hose" model so you know what to look for.

http://www.compactappliance.com/Edge...AP14001HS.html




Here are diagrams which detail how a dual hose model works vs a single hose model.

[Triker56]

Originally Posted by akeyzoo

Anyone made the switch from 13.5K units to higher capacity with success?

I replaced a rear 11K with a 13.5K and a front 13.5K with a 15K.
Now the rear 13.5K will keep the front MH section cool(75-78) up to the high 80's outside.
When it hits the 90's I need to turn on the front 15K for 1/2 hour or so to get front area down into the 70-72º range.

Then I turn it off until needed later.

[Peralko]

Originally Posted by gemini5362

All A/C units whether it is RV, Stick or dashboard only cool the air down 20 degrees. Basically they are in a closed room and keep cooling the air down by a 20 degree difference and that is how you get cooler temps. When the cooling load is too large for the AC to get that 20 degree difference is when you see what we are talking about.

But the ACs don't use outside air, they recirculate air from inside the coach, so it is a closed system. Even with 120 degrees outside, you can still get into the 70s inside.

[powerboatr]

Originally Posted by superlucky

Could you replace one of the existing A/C units with one that puts out more BTU's?

Just a thought

Bill

i just replaced my died on the roof carrier 13000 btu a/c in the rear bedroom with a coleman 15500 btu unit
WOW what a difference in cold air movement in the rear half of the coach
it has a bigger air intake and moves much more air, at near the same amp draw.
i had recently thought to add a 3rd in the kitchen using the fantastic vent opening...but when the rear a/c went south i upgraded btu capacity and it cured the heat issue
just waiting on the front one to bite the dust now....any day i expect.