Best AC practice May 27, 2020, 09:48:49 pm I'm right now in Dead Horse Ranch State Park in Cottonwood, AZ. This is a very nice place - but it's was damned hot here today with at least 105 °F in the late afternoon.My rather old Dometic Penguin AC blows still out air that is only 51 °F cold directly at the outlet. I think that is impressive (although newer units might be even better and are certainly less noisy). What I'm not really sure about is whether I should have the roof vents closed or open and whether the fan in the back should be running or not running when the AC is on such hot days running for hours.What is the "best AC practice" here?Klaus
Re: Best AC practice Reply #1 – May 27, 2020, 10:04:29 pm Klaus, here are some strategies:How to Stay Cool in Your RV, Camper, or Motorhome | AxleAddict
Re: Best AC practice Reply #2 – May 27, 2020, 11:13:45 pm At 105 outside, you're going to need to close everything - windows, vents, shades. Consider a reflective windshield cover and consider the orientation of your RV if possible. Keep the fridge side in the shade in the afternoon if you can. Best practice is to drive somewhere cooler!Kidding, but only slightly. Rich'03 MB in NC
Re: Best AC practice Reply #3 – May 27, 2020, 11:27:17 pm Quote from: rich - May 27, 2020, 11:13:45 pmBest practice is to drive somewhere cooler!No doubt, that's the way to go (or better: to drive). However, I had no choice due to special circumstances.On Saturday I go for some days to Zion National Park where I will have a shadowy riverfront site (with electricity). From there I go to Bryce Canyon National Park - where I will most likely (and to my greatest pleasure) have to use the furnace a little in the morning.
Re: Best AC practice Reply #4 – May 28, 2020, 01:36:04 am As Rich said, seal it up tight and let the air conditioner do its work. Don't forget a cab blanket to block off that hotspot.Keep the air conditioner's fan on high, but don't set its thermostat to maximum. Running it on max for hours, and/or running it on a lower fan speed, can lead to the internal coils icing up. The sound will become muffled, and airflow will be greatly reduced. If that happens, shut it down for half an hour or so to let the ice melt off. 4 Likes
Re: Best AC practice Reply #5 – May 28, 2020, 09:16:04 am Quote from: Andy Baird - May 28, 2020, 01:36:04 amAs Rich said, seal it up tight and let the air do its work. Don't forget a cab blanket to block off that hotspot.Keep the air conditioner's fan on high, but don't set its thermostat to maximum. Running it on max for hours, and/or running it on a lower fan speed, can lead to the internal coils icing up. The sound will become muffled, and airflow will be greatly reduced. If that happens, shut it down for half an hour or so to let the ice melt off.A mobile RV tech I've used before told me that setting the thermostat to about 5/8ths will help diminish chances of icing up on the older A/Cs. That has mostly worked on mine. Also, fan on high, as you say, Andy.Chris 1 Likes
Re: Best AC practice Reply #6 – May 28, 2020, 12:13:41 pm Quote from: Klaus - May 27, 2020, 09:48:49 pmI'm right now in Dead Horse Ranch State Park in Cottonwood, AZ. This is a very nice place - but it's was damned hot here today with at least 105 °F in the late afternoon. My rather old Dometic Penguin AC blows still out air that is only 51 °F cold directly at the outlet. The best one can hope for is a 30-35 degree drop in the interior temperature, compared to the outside temps.A 51 degree output is not as low as a new A/C would produce.Larry 1 Likes
Re: Best AC practice Reply #7 – May 28, 2020, 02:08:47 pm Right now (11 AM) we have here 97° outside and I have 75° inside in the back with the AC running on low and the temperature set to medium between cold and warm. The air coming out of the AC has 47° and the registers are pointing kind of down. I have no fan running and the rear vent is open just a little bit. Other than that there are no windows open.For now I'm quite happy with that - it will be interesting how the inside temperature is this afternoon with 100° or more on the outside.After reading more carefully through the previous posts I changed the thermostat setting to 5/8ths and the fan to medium. When I go shopping in a little while I will put the fan to high - right now I prefer it a little less noisy. Thanks for the detailed tips!Klaus
Re: Best AC practice Reply #8 – May 28, 2020, 02:23:02 pm Klaus,When the weather is really hot (e.g. above 95), it makes a big difference to have all the vents closed. But when the temps are lower (e.g. 90), we will sometimes have the back vent open with the fan turned off. It helps with air circulation and we don't find it is a big difference in coach temps. Fan on high makes a big difference.It can help a lot to aim the AC vents to put the air where you are. I don't know if you have directional vents, but even some cardboard (or maybe paper) taped up could help direct air - if it is blowing directly on you/pets, it will feel cooler even if the rest of the coach is not at that temperature. [They sell plastic vent air direction devices at home improvement stores but they are meant for houses and so you will have to jury rig them and IMO they are not worth getting for only a day or two of use.]As others have said, covering up where the sun is coming in helps a lot! I was surprised when we moved to AZ and I was told that shading so the sun doesn't shine into windows was more critical than attic insulation in houses (stick and bricks). I had never heard that in any other state where I had lived. Tarps outside can help, that blanket between the cab and coach others mentioned helps, keeping the bathroom door shut can help, and reflectix on windows (for a couple of days this might not be worth it - but foil might be worth doing). The south side is most critical, and cab windows if they are not facing north.We typically leave the north side windows uncovered as that doesn't make as much difference in temperature to cover them and we get to see outside.Be aware inside cabinets get warm so don't put your chocolate (or other things you don't want to melt) on the north side upper cabinets. A new AC would work better (not worth it for a couple days) - our current AC is typically not turned above the 10-15% lower end of the temperature setting or it gets too cold - even on 110-120 degree days. Jane
Re: Best AC practice Reply #9 – May 28, 2020, 02:49:14 pm Hi Klaus. Unless you are cooking a lot, close that roof vent, all of them! Also close the outside vents at the dash A/C before you shut off the engine. Any place for air from outside to get in, especially if it is humid outside, is just making your air conditioner work harder. Air conditioners are one speed only, well two if you count 'off' as a speed. The compressor is on or not. Run it at full cold setting. It is harder on the compressor to have it start and stop, just leave it on full. If the air is coming out at 47 degrees, you aren't going to develop ice in the cooling fins. If it does freeze up, the noise of air flow will be muffled. Just turn up the fan to high, and cycle the compressor off (temperature control just a little anti-clockwise) until it clears out. Keep the fan on high to melt the ice faster. Otherwise you can leave the fan set low or medium. For me 'Hi' is too loud. Make sure your washable air filters are clean. If you habitually camp in hot places, you can upgrade the capacity of your roof A/C from 13,500 btuh (what the Penguin is rated at), to 15,000 btuh of the Carrier brand roof A/C. The extra 1500 btuh isn't worth replacing the A/C until it needs replacement. IIRC the Carrier sticks up higher, and of course uses more power. Reflectix sheets inside your windows, shade awnings on the windows outside, blankets to close off the cab area, etc. I remember when the upstairs A/C failed at my mother-in-law's place in FortWorth, I would shut off the downstairs A/C compressor for 15 minutes early in the morning to give it some rest, otherwise it never cycled off. (two weeks before repair people could get there) RonB 1 Likes
Re: Best AC practice Reply #10 – May 28, 2020, 03:47:59 pm Quote from: RonB - May 28, 2020, 02:49:14 pm Run it at full cold setting. It is harder on the compressor to have it start and stop, just leave it on full. If the air is coming out at 47 degrees, you aren't going to develop ice in the cooling fins. If it does freeze up, the noise of air flow will be muffled. Just turn up the fan to high, and cycle the compressor off (temperature control just a little anti-clockwise) until it clears out. Keep the fan on high to melt the ice faster. Otherwise, you can leave the fan set low or medium. For me 'Hi' is too loud. Make sure your washable air filters are clean.Our A/C has not frozen up more than a few times in 17 years, usually later in the day when the outside temps drop Our normal weather is warm and dry, not much humidity to freeze up. As Ron said, if the outlet temp is 47 degrees, it shouldn't freeze.When it's hot, the fan is on High and thermostat to set to Max. Other rig's A/Cs may react differently.Experiment with your A/C to see how it works in various climatic conditions.Larry
Re: Best AC practice Reply #11 – May 29, 2020, 12:37:51 am Klaus,Living in Tucson, I have found a few things that help considerably with heat during the summer.1. Installed a covercraft windshield cover. These are very well made and quite thick with insulation and work well during the summer and even in the winter. Yes, it does get cold in Tucson, especially in February.2. I bought several rolls of reflectix and cut it to fit both side windows in the cab. I had the edges bound by my upholsterer and they look great and stay in place.3. I had covers made for all interior vents and put reflectix on the "up" side. These covers snap into place.4. I had a interior cover made for the skylight in the shower. Used a 2" piece of foam and had it upholstered and put reflectix on the top. It dramatically cuts the heat in the summer, and once again the cold in winter.5. I made window shades from reflectix for all large side windows and put against the glass under the pull down shade.6. I had a heavy fabric shade made for the cabin that attaches to the overhead and goes all the way around from side to side and goes down to the floor. This really works well in the cold times as it keeps the cold from the unheated front cab out of the rest of the RV. 7. I added two 12v fans that are attached to the underside of the cabinets in the front of the RV just behind the cab. These help keep the air moving.8. I replaced the original barely working 12k dometic a/c with a larger 13.5k Coleman unit. I think LD should put 2 a/c units in the 31ft LD because it is too difficult to keep entire interior cool when you only have one central unit. Thats all for now. 4 Likes
Re: Best AC practice Reply #12 – May 29, 2020, 12:51:13 pm Quote from: parussky - May 29, 2020, 12:37:51 am4. I had a interior cover made for the skylight in the shower. Used a 2" piece of foam and had it upholstered and put reflectix on the top. It dramatically cuts the heat in the summer, and once again the cold in winter.I should have mentioned the shower dome, as it has made a big difference to us. We used reflectix and HVAC foil tape to create a reflectix panel just smaller than the shower dome. It gets held in place by some tension rods we picked up years ago to hang wet things in the shower for drying.Another option, if you're staying in one place, is to toss a towel or something over the shower dome from the roof side. Rich'03 MB in NC
Re: Best AC practice Reply #13 – May 30, 2020, 06:49:13 pm This is an idea that came from a spring-backed picture frame. On an 85 deg day, the shower dome was 115!I put a double layer of reflectix held in place by these clips. Left is in place, Right hanging off to show how the bends go. 5 Likes
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