Community Forums

MEWright · 06-22-2021, 04:54 PM

I just replaced my front AC unit on my 40G. We do have 3 units so my situation is different but they are all similar.

I am doing the following things to help mine cool better;

I am replacing all the ceiling grills and return grills, removing the old plastic junk ones and installing new 3 way metal vent supply grills. The factory plastic ones only blow air straight down, 3 way grills distribute the air better. I am cutting out the returns and adding 12x12 filter grills so I can use a 12x12 pleased filter media. I am also adding a few 4x8 supply locations to increase the circulation of the cold air. I will post pics of this when I am done.

I will remove the AC covers on the roof and use a product called "DUCT WRAP" to wrap the coil casings. This is a material like a water heater blanket that is made to wrap sheet metal ductwork and coils. Once installed I will cover it fully in a waterproof coating as I don't want it to get soaked during every rain causing the case to rust prematurely. If this does not work properly I will find another product to insulate the coil case to stop cool air temp loss and also help with condensation.

I am going under my coach and installing rigid R4 insul-board everywhere i can. The floor under the driver and passenger areas are just plywood and you can feel the heat and cold outside while driving. Insul- board and spray foam helped tremendously during my last few cold trips. I am adding more to help keep it warm/cool. You can buy sheets of insul board at home depot for about $15.

I am going to wrap my dash AC ducts with insulation. They are the same material as a dryer vent so they lose tempered air before it reaches the cab.

Lastly, as the AC units need to be replaced I am getting the most efficient units I can as the replacements. Its not much better but every little thing helps.

I saw a post years ago about a couple that took a tension shower rod and an insulated window drapery and put it across the cab right behind the driver and passenger seats to help separate the cab area from the coach living areas when they traveled. They only controlled the temp in the cab area and they said it worked very well. I never tried this as we travel with kids and they are everywhere...

Davidrvr · 06-22-2021, 05:32 PM

Get your interior window tinted with clear ceramic coat tint to help keep the heat out.. make sure you have 15k Ac as the 13k are just to small. Day and night shades help but the windshield is the main heater in the coach.. I added a 3rd Ac in my coach non ducted.. it’s working great so far and the mid and front Ac are ducted and the non duct helps cool the back which helps cool the front..

There is no reason to drive in any heat and not run the Ac off the generator.. it’s what they are made for

kenwyatt · 06-22-2021, 05:35 PM

Have 3 units but heres a couple things I did that helped and living and traveling in Texas it helped.
1 took all the internal grille’s off and made sure there was no leakage from the ducts into the roof area and all cooled air was going where it should. Second I took everything apart on the top and re-insulated the plenums on the inside and out. Doing the outside plenums helped the most. Just sitting in the rv port I am comfortable running 1 unit instead of 2. Here’s some pictures. Contact me if you want a better explanation. 817-715-0137

153stars · 06-23-2021, 07:43 AM

What he said and above...there a lot of info on tuning up HVAC systems in MH. Issues with ducts and foam in top cover creating cross flow issues. Someone shared these stick on big dimples that diverts air down out of round vents. A vid with air flow meter showed they actually work surprisingly well maybe a I piece of ranch molding might work in rectangle vent .

Quote:

Originally Posted by arcaguy

From what you've said the air conditioners look like they are doing their job. There is something called a design temp in any HVAC system. Air conditioning is designed to cool air a certain amount from the outside temperature. In the case of RVs I believe that is about 20 degrees. In your case you say that the outside air is 109 and the air inside the coach is in the low 90s. That's about right, maybe just a little short. You may pick up some additional efficiency by cleaning the AC units, but it probably won't be a lot I don't believe. You might also try sealing the interiior of the units with some foil tape. There are a couple of videos on youtube about this, one of them by Changing Lanes. I think maybe you need to adjust your expectations as to what the air conditioners can accomplish or maybe try and add a third AC unit. Good luck.

Garyaber · 06-23-2021, 08:12 AM

Dash air on my Entrega Vision, F53 Ford Chassis. Works well when first turned on but after about an hour of driving in HOT weather (florida), it shuts off and then blows only uncooled air. After a night and ready to go in the AM, the Dash Air works great for the first hour on the road.

As a note, I can run the generator and operate the roof airs, but they don't cool the front enough. However, during the hottest weather, the two roof airs when stopped cool well. I usually don't start the generator until parked and they will cool the coach just fine. It is a smaller class A, 27 or 29 feet depending how it's measured.

MrsChilerick · 06-23-2021, 10:13 AM

One other thing we do in really hot weather is to close the duct vents in the bedroom and close the door to that part of the coach to push the cool air from the rear air conditioner to the front of the coach where we are living. We reverse that at night to keep the bedroom cool while we sleep. When we do that we make sure the thermostat is set cooler than we want in the part of the house we are stealing cooler air from.

mlpeloquin · 06-23-2021, 10:30 AM

We had 103 degree heat in Las Vegas. The bedroom AC really cools the back end, but the front is fair. I put a fan in the rear to move the air from the rear to the front. I also have a small oscillating fan in front. 86 degrees is warm but tolerable. Only for five hours then things cool down slowly. If I had to live in this full time, I would put reflective film on the windows to help and get a portable AC and vent through a window.

https://www.amazon.com/dp/B08D7CM5YC...f_rd_i=1193678

ga traveler · 06-23-2021, 10:33 AM

As a camper since 1968 and a service manager for 15 years, I can tell you that your motorhome is normal. At over 100 degrees all rvs are hard to cool. As others have said, all the glass in the front makes it harder to cool. The best results ,according to my customers, is to place ridged bubble wrap over the windows when parked. I never did it myself but I have been told by many customers that it worked well.

ga traveler · 06-24-2021, 07:24 AM

Quote:

Originally Posted by Garyaber

Dash air on my Entrega Vision, F53 Ford Chassis. Works well when first turned on but after about an hour of driving in HOT weather (florida), it shuts off and then blows only uncooled air. After a night and ready to go in the AM, the Dash Air works great for the first hour on the road.

As a note, I can run the generator and operate the roof airs, but they don't cool the front enough. However, during the hottest weather, the two roof airs when stopped cool well. I usually don't start the generator until parked and they will cool the coach just fine. It is a smaller class A, 27 or 29 feet depending how it's measured.

Your dash air is low on Freon. When the Freon is too low it expands too much and causes the ice to form and the air conditioner no longer has air flowing through it.

rjsupersonic · 06-24-2021, 07:32 AM

Quote:

Originally Posted by Judge64

There are also several things you can / should do beyond general cleaning maintenance to make sure you get the maximum performance.

I have insulated the box around the evaporator on the roof along with the low pressure line coming out of the compressor to reduce loss in cooling.

I also make sure that the divider in the plenum is centered properly and sealed tightly with duct tape.

If the ductwork in your coach is styrofoam insulation, you want to remove the vent covers and use a utility knife to smooth out any jagged edges to improve airflow. Then at the end of the ductwork at the front and back of the coach, use insulation or spray foam to make sure the air stops at the end of the ductwork and doesn’t get pushed into voids in the ceiling where it is wasted.

You can also modify the cover on the toof and cut out the plastic louvres in front of the condenser to increase airflow and better heat dissipation.

If your A/C covers are brown or black, you can paint them white as well.

If you ever replace your AC covers get white, many rigs are painted black with black AC units. There is a substantial heat absorption difference in black vs white.

Garyaber · 06-24-2021, 07:43 AM

Quote:

Originally Posted by ga traveler

Your dash air is low on Freon. When the Freon is too low it expands too much and causes the ice to form and the air conditioner no longer has air flowing through it.

I hope it just that! I have it going into the shop next week to be checked out. As a note, the air still blows, but it's not cool air! Gradually gets warmer and warmer until it's just ambient air or even a little hotter.

arcaguy · 06-24-2021, 08:04 AM

Regarding the difference between outside and ambient air I believe my original statement is correct. Let me explain.

Assuming that we start with a coach that is 100 degrees inside and outside. You run the A/C for a half hour, or whatever length of time it takes, and the inside temperature is now 90. You continue to run the air for another half hour and the temperature is now 80. Thus the ambient air is now 80 degrees. If you continue this process since the ambient temperature is 80 degrees you should be able to run the A/C for another half hour and get the temp to 70 degrees and then another half hour and get the temperature to 60 degrees. Repeat the process and you can then get the temperature to 40 degrees. If the ambient air is the relevant temperature you could repeat this process until your coach would reach absolute zero. We all know this does not happen.
BTUs are linear, meaning that for every BTU you gain in the envelope (the inside of your coach) your A/C unit has to remove one BTU. The source of the gain in BTUs is the outside temperature, not the inside temperature of the coach. I hope this explains my statement. This is not an HVAC issue as much as it is a math problem and the answer I believe is obvious when you think about it.

MrsChilerick · 07-04-2021, 07:52 PM

Ok, so, I know better, but here’s my story.

In extreme heat which I will define as > 100 I always set the front thermostat at 74 and the rear thermostat at 72. During the day, I close the rear vents and close the bedroom door. At night I reverse it. It keeps the temp in the coach where we are, very cool. The other day it was 106 and we maintained 75 where we were in the coach.

Yesterday it was 106. I messed up and forgot to open the vents in the front and close the vents in the back and close the bed door until the front of the coach was already at 82. You’d think it just might take longer to get things cool, but it doesn’t work that way.
I couldn’t get the coach below 85 for the rest of the day. We were miserable, as I said, I know better. I messed up.

So, lesson learned. You have to keep the coach cool, rather than try to cool it in hot weather. Keep your thermostat set lower than you think you will be comfortable and make sure it starts cooling before the coach feels warm.

jacwjames · 07-04-2021, 08:00 PM

Been going through this the last couple of days. +100F weather. I have both the front and back temps set at 65. Yesterday it was too windy to put out the passenger side awning and that side got full sunlight until dark, you could feel the heat radiating from the walls. I did put some large windshield reflectors in the side windows which helped but coach still got +85F. Cooled down fast when the sun went down and I could shut off 1 AC unit.
Today a little better and not much wind so I could deploy the passenger side awning. Coach stayed comfortable all day.