A/C cooling on a hot day

[richfaa]

Been reading post on how good or bad the A/C does on a hot day. Well today was a hot and Humid Ohio day. We hade done these checks on our 06 3400 bit never on the 13 302 Big Sky.
The Montana sits on the property . The nose faces due North so we get the sun on both sides all day. There is no cover.

Outside temp was 93 Degrees. Temp on the roof was 112 degrees. Both A/C's on set at 68 degrees. The best inside temp we got was 82 degrees. Pulled the A/C return air vents on the ceiling at the rear of the Montana and laid a digital thermometer on the ceiling material. The temp was 85 degrees. 112 on the roof and 84 on the inside of the roof...Not bad???? Taped a Digital thermometer to the outlet vents of the A/C. Reading was 62 on the rear A/C and 59 on the front A/C. It did not feel bad as the humidity was low inside as water was pouring off the roof but IMO those numbers are not all that good. The A/C's ran all days and could not keep up. For those in the really high temps....good luck. This thing is black and gray the perfect colors to reflects the sun......Not..

[andylparish]

I feel your pain, we are on a semi permanent assignment in bossier city, Louisiana. The temps are 100 to 102 and it's terribly tough to stay cool. Reason I have been asking about adding a 3rd ac to the fantastic vent in the galley. Do you know who to contact at keystone about this?

[richfaa]

keystone will tell you to contact your dealer or a dealer.

[NCFischers]

Darker colors absorb heat, light colors reflect heat.

[DQDick]

We hit a heat index of 115 today, temp was 102, I didn't go up on the roof but the inside temp never went above 78. We worked with some folks with a Class C the color of the Blue Sky's and the AC would kick on over an hour in their rig before one of ours would kick on. Color does matter. I also have my concerns about the whisper quiet AC's. If I get the cool in this heat I'll live with the noise. Two more reasons I'm not currently looking at new ones.

[swanny]

this helps a lot, cover and or block EVERY place cold air can escape. heating duct ( very critical area), stair vents , holes in floor in cabinets, you know the 4" holes for 1/2" tubing and especially cover the windows on the sun side with the silver reflective material just slide it in behind the shades.

kevin

[Artemus Gordon]

We routinely get 115-117 during summers in Redding. This year it hit 116 in June. I learned to put both units on "high Fan" during the day. We get RV down to 74-78 depending on which end you travel. Here the units freeze up and just blow hot air if left on Auto. With AC unit fans on high, the units run full time and no icing issues. Also learned that setting thermostats below 70 rarely makes a difference. We also bought exhaust vent insulation inserts for all four fantastic fans, and one for skylight in bath. Along with shades pulled completely down we survive. That said I just bought a free standing AC for front living room and vent it out the basement. This will be first time I use it later this week, will report results.

[DonandBonnie]

We are currently in the same heat as you, Rich. About 10 miles south of Ashtabula. We only have the front A/C, but are getting roughly the same temps as you report. Two things that help - pull all of the night shades down and stuff a pillow in the fantastic fan openings. Both will aid in keeping things cooler, but won't eliminate all of the inside warmth that we are experiencing.

[JandC]

Our newer unit (oyster, tan, or whatever it is) doesn't cool as good as our old 3400RL. There isn't a huge difference but there is a difference and I attribute it simply to the exterior color being slightly darker.

Where I think most RV's really fail is in the windows. Regular dual pane RV windows are a joke and not worth the month IMHO. Maybe is there was a RV window with argon gas sealed between panes and extra UV protection gased in it would help in both hot and cold areas.

[richfaa]

Darker colors absorb heat, light colors reflect heat'...Thats what I am saying the black and gray were the perfect colors to reflect heat.But they sure are pretty. Except for blocking off the furnace cold air return we did nothing else and that did not seem to help. It is going to be near 100 today and I will do some more checking.

Fortunately we manage to stay in moderate temps all year. The furnace is rarely used as the fireplace does the job most of the time in Florida. The A/C is used more. We would normally not be here this time of year .We should be in Wyoming. 100 degree days are not common in Northern Ohio and by the weekend it will be in the 80's thanks to Canada.

[DQDick]

quote:Originally posted by Artemus Gordon

We routinely get 115-117 during summers in Redding. This year it hit 116 in June. I learned to put both units on "high Fan" during the day. We get RV down to 74-78 depending on which end you travel. Here the units freeze up and just blow hot air if left on Auto. With AC unit fans on high, the units run full time and no icing issues. Also learned that setting thermostats below 70 rarely makes a difference. We also bought exhaust vent insulation inserts for all four fantastic fans, and one for skylight in bath. Along with shades pulled completely down we survive. That said I just bought a free standing AC for front living room and vent it out the basement. This will be first time I use it later this week, will report results.

Should do ok. At the COE lake here there are a number of those being used in tents and a number of tents that are set up for AC. Freaked me out when I first saw them, but who could stay in a tent in this weather without one?

[richfaa]

We have a IR thermometer and I have been shooting temps on the outside of the pretty mostly dark color Big Sky both in and out of the sun. Very interesting and somewhat scary readings. No wonder we can't keep these things cool in hot weather. It is just 91 degrees now and 4 hours away from the high heat of the day temps.

We do have all the shades pulled and the furnace return air blocked, We have been pulling the A/C ducts and so far there is a lot of debris in there.

Wonder if those ladies in that QC film pulled the ducts...

[bethandkevin]

I don't know about residential A/C, but in automotive systems a temperature differential of 30 degrees is the benchmark for an efficiently working system. Rich's system hit that mark 93 outside and 62 outlet temperature inside. Rich and Helen's is not the darkest color combination on a Big Sky, but I think the A/c is doing what is expected of it. The only way to get more out of the units is to install higher BTU units-that means more money. Just my opinion, but sometimes I think we expect more than we should out of our rigs. They are tested for average conditions and short term extreme ones. The heat wave many of us are experiencing is neither of those. Rich, you gathered some great information there. You prepared yourself with pertinent information to call Keystone with.

[bigskyjimmy]

It is 89 degrees Today and will be 98 Thursday but low humidity here in Western WA and so far so good we are keeping nice and cool,we really like the Whisper Air in ours ,have both A/C's on low-Med fan and 55,one thing I did do that helps is cutting every other Vent/Slot/ louver in the ceiling covers and the air comes out better down below instead of angled sideways toward the ceiling

[Clemson1881]

High humidity is the enemy of A/C efficiency. The wetter the evaporator fans get the less they can cool because the water insulates them from the air passing through them. That's why 90 degrees at the beach is harder to cool than 98 degrees inland. Best tactic is do the step vent mod, cover your heat vents, and allow your A/C to get a head start (get it cool early). Also avoid lighting the stove/oven.

[stungjoe]

One thing to consider is the lights. Today I finished installing LEDs in all of the 12V ceiling lights. You may be amazed at how hot they can get. Plus the brightness is amazing with the LEDs. Another heat source would be the television. My 55" Sammy puts off a good deal of heat.

I second the humidity aspect. I moved from Midland, TX to Houston. Although the actual air temp is lower the THI for this area is insane. The moisture streaming in off of the gulf intensifies the heat. It's kind of like a steamer.

I also open the vent directly into the living room instead of running it though the ducts. I keep the bedroom A/C on medium when I'm home and shut the pocket door to the bedroom at night. This park charges 15 cents/KW so I expect my electric bill to be close to $200 this month running both A/C's and my washer/dryer.

[richfaa]

Yes Kevin the A/C was doing the job we expected that. Other factors contribute to them not being able to keep up. What we have is a large square box in a Oven and trying to keep it cool.

Did some more checking and got some better results. BTW we are doing this because Helen and I are grounded for the summer due to some health issues that needed to be addressed(all fixed) and I am bored. If anyone has one of those IR thermometers shoot some temps you may be surprised.

Pulled the A/c vents in the Rear ceiling and they were fill of construction debris. I was disappointed but not surprised. I guess those QC ladies missed that also. Had the shades down, furnace return vents blocked and the skylight in the shower blocked.
The temp was 97 today at the high point 4 degrees higher than yesterday.

I found this interesting I shot the black and the white color in the direct sunlight Black was 114 degrees and white was 110 degrees only 4 degrees difference I expected the difference to be greater. We have a lot of black and dark color and not much white.

Outside window temp slide was 112 degrees, window inside 108 degrees 4 degree difference single pane. With blinds drawn 94 degrees .Now the outside wall right under the same window 119 degrees (color black) inside wall under same window 83 degrees. we would be better off without a window.

That big rear window is a killer window outside 114 ..inside window 110..shades drawn 94.That is a lot of window and a lot of heat.

The best insulation was the entrance door. Door white 102..door black 108..door inside anywhere 84 ..great door.

Oh. at the heat of the day outside gray at the bathroom area 124...Bathroom wall 96.If you have that IS thermometer shoot some outside then inside wall
temps/You will be surprised.

Temp inside the side compartment with the outside temp at 96 and the gray door at 124 was 86 degrees. Lower than expected but remember that hot air rising is going right up and through the Furnace return vents if not blocked.

Also if you have dual pane windows do the outside and inside window check if you have the IS thermometer, I have on another RV..you may be shocked

Also setting the rear temp 5 degrees lower than the front keeps them both running. The front Ac is more efficient and cools a smaller area. The cold air spills down into the rear and if set at the same temp will shut the rear A/C off.hanks someone for that tip. The best inside temp I was able to keep today was 74.6 degrees..Big improvement over yesterday..Know what..Maybe the Arctic package works better.

[Dam Worker]

You got to love those IR thermometers. Usually very accurate and they provide useful information. Remember like it was previously stated that the AC's have a certain amount of max cooling capacity. Last unit we had utilized a 15K unit. Not much better than a 13.5K but when it is hot I will take any help I can get. Remember it is easier to cool something than to heat it. I can't remember what the heater BTU's are on our units but I would imagine they are higher than the combined BTU's of our AC's. I am curious how other owners rigs perform with keeping their Montana's warm in the winter?

Tom Marty

[richfaa]

This is a follow up to the post made previously my myself. http://www.montanaowners.com/forums/...84&whichpage=2

A couple of days after the measurement were taken the outside temp was 81 and the humidity was at 36 %
That happens here in Northern Ohio. However the temps inside the Montana were almost the same. Nothing changed, It was a clear day not a cloud in the sky and the same sun was beating down on the Montana. Shooting temp with the IR thermometer showed little difference between outside skin temps and the inside wall temps. The issue is that the high skin temps are being transmitted to the inside walls and ceiling of the Montana. The temp of the inside wall of the bathroom was still at 89 degrees where it was 92 a couple of days ago.

The insulation can only do so much and if you look at the difference between skin temps and wall temps it is not doing bad. There are a lot of hot spots and the A/c must overcome them no matter what the outside temp is. The more out of the direct rays of the sun you are the better you will cool IMO.

Funny thing. We plugged all the holes . skylights, entry window, puled the blinds, etc and the A/C kept us cool. So there we are huddled in a dark Montana can't see a thing.. but we are cool.

[dieselguy]

This will sound a bit off beat, but remove the inner lense from above your shower ... put a layer or two of say 1" bubble wrap against the outer lense ... reinstall the inner lense. You'll be suprised at the reduction of heat in the shower area that used to spill out in the bedroom. The little retractable blinds attached to the ceiling are an alternative.