Upgrade from 13.5K to 15K AC?

[KST-184BH]

I pretty much know the answer, but figured I would see what other folks think about this scenario. Maybe others have already made the switch. My Melbourne 24K AC just doesn’t seem to keep up after outside temps hit 80+. I believe a large issue is the dark paint scheme which likely isn’t suited for this Texas heat. I did add black out blinds in most windows, full wrap around front windshield cover, cleaned filters, etc. However I was wondering if it’s worth the money to replace the 13.5K unit with a 15K unit. I doubt if the extra 1500 BTU will make much of a difference but perhaps someone else has done this when their old AC was going out and they upsized. Was there any noticeable difference? Thanks all!

[oldmanAZ]

Before replacing the AC, I suggest trying a couple of other things if you haven't already:
- Weather permitting, use the awning to shade the side as much as possible
- Get a Non-Contact Infrared Thermometer ('laser thermometer' less than $20)
- Slide toppers (my interior slide roof was significantly warmer than my TT ceiling)
- EXTERIOR shades for your windows (once sunlight gets into and through the windows, it turns to interior heat)
- Begin using the AC early in day, before the interior heats up
- 'Raise' your expectations (we OK with 10degF cooler inside, but it reduced humidity inside by a ton)
- Use a breeze box or other fan to blow on the people (at the last minute we decided not to take one and regretted it)

Hope some of the above helps you, it helped us.

[CampNow]

Agree, a 13.5 to 15k a/c upgrade is not going to make any significant difference. OldmanAZ offered up some good suggestions.

I'd suggest applying some quality window tint (with a high UVA/B rating) to all your windows---that'll block a lot of heat. Don't go with cheap tint---most provide very little UVA/B protection. The large windshields on Class A/B/C rigs let in a lot of heat. Some tint installers sell nearly clear window tint that is still capable of blocking significant amounts of UVA/B in windshield applications---being almost clear they're legal to use in most states.

Our last trailer was a 5th wheel toy hauler with very high ceilings (lots of interior volume to cool) and lots of windows. Two 15k a/c's were having trouble cooling below 80 when ambient temps rose above 100 (desert SW). Tinted all the windows with some quality ceramic tint and was able to maintain 78-79 degrees with ambient temps of 110+.

[glamisbound]

What many owners don't know, especially if they are new to the game, is that RV A/C do NOT cool as efficiently as a household unit does. The fact is that you shouldn't expect much more than a 15 degree difference between outside and inside air temp in most RV's with the A/C going. I'm camping right now as I type this. It's 111 outside and 91 in my RV. I'd rather it be 75 in my RV but I know there is no way in heck that my 13.5 is going cool my RV down that much. So it's about expectations and reality.

[Magnolia Tom]

Another tip would be to check all of your vents to see if any of your cold air is leaking into the attic space. Remove the collar on the vent, then use some foil tape to seal the gaps between the duct and ceiling. It did wonders for my fifth wheel

[KST-184BH]

My laser thermometer shows the system is pretty much doing what it is designed to do. Just didn’t know if the extra 1500 would make a difference. Guess that’s like adding one more 4” duct to the system. We don’t use the top bunk so using the built in curtain to close it off. Same with the bathroom and both spaces are warmer than the main living quarters I installed ceramic tint in the front cab windows but I could still feel heat getting in. I guess no way to possibly block it all. Not sure about having even darker windows in the back by adding more tint over the Jayco factory tint. Guess I could try the minimum, just not sure how the ceramic tint works. Assumed the darker the tint the more ceramic used? Good idea on the ducts, sure feels like some air could be escaping. Did purchase a 35 pint dehumidifier for my next “humid” trip. In the Big Bend this week so no need to bring to the desert. Wouldn’t you know, it’s starting to rain....ahh the smell.
Yep, guess it’s all about expectations. 85% of my camping has been done in Texas, so the heat is just something you either love, tolerate or.....well that’s about the choices.

[jlechmanik]

Originally Posted by KST-184BH

My laser thermometer shows the system is pretty much doing what it is designed to do. Just didn’t know if the extra 1500 would make a difference. Guess that’s like adding one more 4” duct to the system. We don’t use the top bunk so using the built in curtain to close it off. Same with the bathroom and both spaces are warmer than the main living quarters I installed ceramic tint in the front cab windows but I could still feel heat getting in. I4 guess no way to possibly block it all. Not sure about having even darker windows in the back by adding more tint over the Jayco factory tint. Guess I could try the minimum, just not sure how the ceramic tint works. Assumed the darker the tint the more ceramic used? Good idea on the ducts, sure feels like some air could be escaping. Did purchase a 35 pint dehumidifier for my next “humid” trip. In the Big Bend this week so no need to bring to the desert. Wouldn’t you know, it’s starting to rain....ahh the smell.
Yep, guess it’s all about expectations. 85% of my camping has been done in Texas, so the heat is just something you either love, tolerate or.....well that’s about the choices.

FYI for measuring air temp a laser thermometer is not what they use in the industry. Lasers measure the surface temp which you can't do with air.

Now with that was said I had a 15k on my prior class c. Wasn't doing crap. Hotter inside than out! Took it back to CW and they said it was performing to specs. Did some research and found the industry minimum standard is 15 degrees difference between the intake and the cooled air. My old one had 8 degrees. So much for CW's warranty reliability.

I wanted to stay with Coleman since that is what I had. Found a new Coleman (mach 5?) that was $650 shipped to my door. Installed it with the help of a few friends (I did the install, they helped me get it on the roof. Then I made sure the air was only going where it was supposed to go with Refletix (same stuff most put on windows). Sealed it up nice and tight and made sure no air was leaking between intake and the cooled air coming out. Turned it on for the test and got 25 plus degrees and a more powerful fan. A HUGE difference.

But I noticed the temperature of the slideout area was hotter than the rest of the RV. And even with Reflectix in the windows the window frames are hot to the touch. Being in direct sun really challenges RV AC systems with solar heating.

[wabirch]

Get as level as you can, keep bubble between the lines.

[CampNow]

Originally Posted by KST-184BH

. . . Not sure about having even darker windows in the back by adding more tint over the Jayco factory tint. Guess I could try the minimum, just not sure how the ceramic tint works . . .

How dark a given tint looks to you (the visible light) does not necessarily correlate with how much UVA/B it reflects back. There's visible light, ultraviolet light (UVA/B), infrared light, and so on. They make almost perfectly clear window tint that reflects back quite of bit of UVA/B.

For instance, there are sunglasses (usually cheap) that are very dark, which reflect little to no UVA/B. Because the sunglasses are dark, your pupils open up to let in more "visible" light, which, unfortunately, at the same time subjects your eyes to even more damaging UVA/B. It's a terrible lose/lose situation.

[oldmanAZ]

Originally Posted by jlechmanik

FYI for measuring air temp a laser thermometer is not what they use in the industry. Lasers measure the surface temp which you can't do with air.
..snip

But what you CAN do is see what interior surfaces are heating the interior air.

For our TT....
The slideout ceiling was significantly warmer than the other parts of our TT ceiling. A slide topper took care of that heat source.

Our interior shades were a heat source when the sun was shining on them through the factory tinted windows, but the interior surface of the tinted windows - and their metal frames - were even warmer (the interior TT side walls were not warm). We strung a clothesline outside just above the windows and hung beach towels from them, shading the windows. That took care of those windows as a heat source.

[CampNow]

Originally Posted by glamisbound

What many owners don't know, especially if they are new to the game, is that RV A/C do NOT cool as efficiently as a household unit does. The fact is that you shouldn't expect much more than a 15 degree difference between outside and inside air temp in most RV's with the A/C going. I'm camping right now as I type this. It's 111 outside and 91 in my RV. I'd rather it be 75 in my RV but I know there is no way in heck that my 13.5 is going cool my RV down that much. So it's about expectations and reality.

Does your 31FS have 50 amp service? If you camp regularly in temps like that I'd seriously consider a 2nd a/c. IMO, that's an awfully large rig to cool with just one 13.5k a/c unit.

Our Jayco Eagle is 33 ft. long (not including the tongue area). We have two 15k a/c units. As long as we get both a/c's operating early in the day when temps are in the 80's, later in the day when temps reach, say ~110 degrees (with low humidity), it'll keep the interior around 78-79 degrees---pretty comfy for us. If we attempt to cool down a hot trailer in ~110 degree temps---it does take quite a while to get temps down to 80 with both a/c's running.

IMO, if an RV is longer than 25 ft. and one intends to camp where ambient temps are higher than 90 degrees with high humidity or higher than 100 degrees with low humidity, IMO, 50 amp service to support a 2nd a/c unit should be seriously considered.

[vcbice]

When we see over 105 the inside gets over 80. It used to get higher. I added tint to all the windows. I just picked the stuff that blocked the most UV. I thought about slide toppers, but, those do not do anything about the ends of the slides. I got reflectix and put a layer around the entire slide (yes it blocks the window that faces SW).

Yes, if you can leave the awnings out it helps, but, winds in our area do not permit that. A couple of rigs in the RV park here have even had awning toppers ripped off.

And, yes, I have two 15k AC units that run all day.