AC expectations

[tomthyme]

Hey folks,
We hope all is well with each of you.

While in Colorado Springs on vacation we had our main AC unit replaced on our 2011 Cameo. It had stopped cooling altogether, then started tripping a breaker. Thankfully the extended warranty will show some value here. The real question is what should we expect from our new 15k btu unit. We live in the Dallas area and struggle to keep the rig cool on those few super hot summer weeks. Our 13.5k unit kept us at 78 at best when in the sun with temps reaching 99. Of course that is awesome cooling, but should I expect more? Does anyone's rig really stay at 72ish in the north Texas heat?

We would live to pick up those few extra weekends of rig-time if we an get it comfortably.

Thanks so much!

By the way, Cheyenne Mountain State Park is great, but that is another forum.

Tom

[Gearitis]

We found something better than tinting in this Texas sun. We have taken a roll of Reflectix and cut it to match the window size internally. It fits snug in the windows and comes out easily if needed. It travels well also and is just like the window shade you put in your windshield in the cab of your truck. We have 1 15k air conditioner in our 32 ft Cougar. On Monday, some shade, awning out, it stayed at 85or abouts inside during the day with shades closed and the vents were insulated. After fitting the Reflectix, Wed, Thurs and Friday it was 103-108 outside. It stayed a comfortable 78 and by 10:00 pm it was 72 and air conditioner was cycling normally. Saturday, I thought I would just do something different and put the remaining roll across the front cap. It made it too 103 on Saturday, and it never got above 74 inside. I am sold on the Reflectix. Yea, you feel like your are a little close, but it sure makes the heat more bearable.

[Cummins12V98]

The biggest thing you can do to get max cooling is to remove the AC shroud and look to see if the foam is sealing to the cover or the foam is sealing to the unit. I had a hard start go bad a while back so I had a cover off and noticed the foam was not sealing. I bought two foam kits for the Dometic Penguin ac units. The factory had the foam attached to the covers and one was 50% sealed and the other was about 75%. The directions said to attach the new foam to the unit and clean off the old foam off the cover.

After I made the covers seal like they should be at well over 100 the RV stays cool even at medium speed on the AC fans.

[Cummins12V98]

squeakkos wrote:
what about the people that don't have ac?

Sucks to be them!

[C_Schomer]

It should be noticeable. It's not only 1500 btuh (11%) more but it will have new unit efficiency again - that's a biggie. Tight windows/doors/vapor barrier are paramount in a humid climate. Latent load is a b___h! The more latent load there is means the less the sensible load can be reduced but reducing the latent load is also just as important for comfort, to most people. Craig

[sayoung]

tomthyme wrote:
So sorry I wasn't clear, we have a front AC at 13.5 and a rear AC at 15k btu.

Our Jayco has same setup with the extra insulation & good day solar screens.it will keep you cool here in North Tx when in low 100's but you have to have a 50amp space
Keep the condensers clean is the key.i fix more ac's that for a little cleaning would hold up better

[thomasmnile]

tomthyme wrote:
So sorry I wasn't clear, we have a front AC at 13.5 and a rear AC at 15k btu.

As others posted, you can expect a 20 degree difference between the ambient air in your trailer and the "conditioned" air discharged through the ducts. With two units operating, you may see interior temps around 80-82 degrees at midday, maybe more if your campsite is not shaded or when the sun is at its highest angle. That was my experience with our HitchHiker LS when we foolishly decided to spend a week in mid August at St. George Island SP in the Panhandle and the temps were hitting the mid to upper nineties. I didn't think that was too bad considering the trailer is nowhere near as well insulated as our stick n' brick. FWIW: Even a residential AC system is going to produce a 20 degree temperature differential between interior ambient and discharge temps at the plenum.

[squeakkos]

what about the people that don't have ac?

[rtazz17]

ScottG wrote:

hmknightnc wrote:
About a 20 degree drop from outside ambient temperature is all you can expect

This is a commonly confused point with AC. You can expect about a 17~20 degree drop in temp from the input to the output of the AC. In other words the AC should drop it that much as it goes through it. The 20 degree thing is not between the inside and outside temps and a strong AC system should be able to drop the inside temps much more than that.

Good point.Air in is coming from the inside of your camper,as the temp drops in your camper the air output temp should drop colder as well.Not related to ambient outside temp.

[jjj]

I am camping in california and yesterday we had temps at 109 where we are at and we saw max cooling in the afternoon at 85. Our trailer is not the best of brands. We have a 05 Keystone Challenger with tinted windows but not double pane and a single ducted A.C. and in 75% shade. It wasn't great but not too bad for what it was out side. Only bad thing is AC never stopped running from about 10 am until about 10:30 pm and was set at 78.

[tomthyme]

Thanks all for your support! Happy trails!

[Atom_Ant]

I think what you were asking is how much more cooling are you going to get from your new 15K btu AC than your old 13.5K btu AC you replaced. I would say that given you have a second 13.5K btu AC already, you probably aren't going to notice any measurable difference. That is only a 5% increase in capacity and there are many other variables that can impact you well beyond 5%, such as the sun reflecting off a portion of the rig.

[ScottG]

hmknightnc wrote:
About a 20 degree drop from outside ambient temperature is all you can expect

This is a commonly confused point with AC. You can expect about a 17~20 degree drop in temp from the input to the output of the AC. In other words the AC should drop it that much as it goes through it. The 20 degree thing is not between the inside and outside temps and a strong AC system should be able to drop the inside temps much more than that.

[SailingOn]

Keeping cool:
- Shade. Awning, slide awnings.
- Remove covers and check for obstruction in ac vents (sawdust, peeling duct tape, faulty installation)
- Keep the door closed: limit traffic, pets, kids in and out.
- Find and fill all those air leaks: corners of the slide, entries for pipes, vents, wiring, esp inside cabinets; old seals around outside storage doors.
- Foil window insulation (Reflectix): cut to fit, Velcro or may stay in place itself. In August, made an 8-10 degree difference in mine. While the trailer’s in storage, limits sun fading the upholstery. Blocks the view, though, and is bulky to carry around.
- window film (Gila, at HD, Lowes, etc.): Tedious to put on, needs 2 people, but once there needs no upkeep. adds some privacy. Helped ours enough that we no longer bother with the Reflectix except in long term storage.
- Small fan or two, esp for the bedroom and that favorite chair. With a breeze, and the AC removing humidity, 88 can feel pretty good when it’s 108 outside.

[JCZ]

hmknightnc wrote:
About a 20 degree drop from outside ambient temperature is all you can expect

In the HVAC industry we don't measure the split from outside temps. The temp. is taken at the fresh air return (where it goes in) and then at the register. You should have an 18F to 20F split for optimal performance.

While my 27' 5er is new (probable operating a maximum effiecency)with dark tint thermal pane windows and the heavier insulation in the floor, roof and walls that Northwood Mfg. is known for...two weeks ago it was 110F here in Sacramento and my trailer maintained a constant 76F inside (with the shades closed and parked in the shade)....although it did cycle often througout the afternoon.