Air conditioner not cooling much

[FirstGene]

I have been running the A/C in our new to us 2027 ACE 27.2. The temps here have been in the 90's most days lately. I checked the output of the A/C with an infrared thermometer and the A/C is pumping out air in the 40's and low 50's, so that is ok. But the MH only gets 3-10˚ below the outside temperature.

Is the insulation that bad? When we had an Airstream, it cooled much better and had poor insulation, so this is hard to understand. Is this a 2 season MH?

When the chassis A/C was running at the dealer, the MH was cool, but they weren't using the chassis A/C and since it is cooling fine, this is a mystery to me.

I have seen people claim on the Airstream forum that an A/C can only cool 20˚ below outside temps, but I never known that to be true.

 

[paulwadley]

If your air coming out is in the 40-50 degree range, that is good. As far as insulation, you need to add additional to cool it down inside on hot days. A lot of heat transmits through the windshield. People usually set up a drape or blanket to cut off the cab area from the back of the coach which helps greatly in keeping the heat in the cab area from going into the back of the coach. All windows may need to be blocked as well as the inside of the cabinets with insulation. Parking in a shady spot helps reduce the heat from the sunshine.

Paul

 

[FirstGene]

Yeh, this thing has a lot of windows plus the windshield.

 

[dkoldman]

Read this thread.

https://www.thorforums.com/forums/f4/ac-not-cooling-mh-37287.html

Also it is important for us to know the inside return temperature to compare to the output of 50 degree temperature which is fine. You may have same issue with divider as the thread I sent you too.

Also, what year is the RV, I assume 2027 is a typo.

 

[FirstGene]

Also, what year is the RV, I assume 2027 is a typo.

It is a 2017. Will look at that thread.

 

[dkoldman]

It is a 2017. Will look at that thread.

Great. Without focusing on outside temperature, take the temperature at the return to see what it is. The air coming out (output should be about 15 - 20 degrees colder.

I think you may have the same problem as other thread which is good news and easy fix.

Let us know what you find out.

Good luck

 

[FirstGene]

I explored the A/C today after watching the video. The divider was properly placed. The way the screws for the plenum were in told me I was not the first person to remove it. The last one replaced the screws so tightly the plenum was cracked around the screws. I used aluminum tape around the divider to better seal it and put the plenum back.

It has cooled down and I can't give it the supreme test—95˚ and above temps. I will go out and check the temp now, but had to stop for a while. Even at those afternoon temps, the output was in the upper or mid-40's.

I also discovered the ducts are always open to output whether or not the vents on the plenum are open. I shut down some of the registers on the ducts to increase flow to the others but it makes little difference—there are about 10 registers, too many to cause much flow through any individual one. I guess the A/C mainly cools the roof.

 

[FirstGene]

The temp at the output is now about 15˚ cooler than it was when it was in the upper 90's outside. It was 72˚ outside when I checked.

If I close off one output off the side of the A/C so only half of the registers on the ducts work, maybe that will help. I'll wait to when the outside temps are well up in the 90's so I am comparing apples to apples.

 

[macdaddy1111]

Have 2 1500 btu ACs and it could barely keep up in 90s temp.

I covered my roof in solar panels and made insane difference. 2 in clearance from RV roof to panels.

I also installed AirFlow mods.

Another option for you in desert is https://www.shaderv.com/

 

[FirstGene]

Thanks macdaddy. I'm am going to try simple solutions one by one. Getting hot again here, so I will have an opportunity to test it.

The cover over the MH is a good idea, but costs around a grand, so not an economical solution. Solar panels are also a good idea, and not as expensive, but not sure we will be doing enough boondocking to make that a good idea for us.

My first thing to check will be to see if sealing the separator made a difference. I doubt it, but if it works, I will not complain. Next I will seal off one group of ceiling registers. The A/C fan is not strong enough to blow air quickly through the ducts, so it heats up and comes out weak and warm. I may have to seal off both ducts, but one at a time is a start. When we had an Airstream the A/C was very noisy, but this brand is not as loud. Ducts reduce noise, but cooling is more important than noise.

 

[FirstGene]

A few simple fixes have made some improvement. Today it is 85˚ outside and 74˚ inside the MH. I have to wait until it gets to the mid-90's to compare with the bad results last week. The separator between hot and cold sides is fully sealed. It was in the proper place (I was hoping it would be thoroughly dislodged because that would have been the easiest fix). And I closed all the ceiling registers on the street side. That means less air is going through the ducts which have little or no insulation. The furthest register, in the bedroom, is blowing out little particles of foam insulation. I guess it has never had so much air blowing through it. Now I can feel decent air flow tab the register. Before I closed off the other side, it was so gentle a breeze I would not have noticed it had I not known the A/C was on.

The temp at the plenum is around 40˚ and about 50˚ at the registers with the plenum vents closed. With the vents open the registers are at upper 50's to lower 60's. I'll check again later this afternoon when it should get to 90˚. I expect I'll seal off all the street side registers as that will keep increased air flow at the curb side registers and the plenum vents.

If not for the tip about the separator plus the info about the lack of insulation, I would have not gotten this far so easily. Thanks again guys! When I joined the Airstream forum years ago, fellow owners educated me fast about what was going on. Eventually I was returning the favor to other newbies.

And an amazing thing—the thermostat was set at 74˚ and a thermometer inside said 74˚. The same controller for A/C and heat was in the Nash trailer and was off by about 5˚. But I bought a cheap clock to put on a cabinet door over the sofa. It came with a thermometer too—a bargain, except the temp on it is 10˚ too high. At least it is an easy subtraction.

 

[FirstGene]

After I sealed off the curbside ceiling registers, things got cooler right away. The temp is 73˚ while it is 88˚ outside. To seal it I cut a piece of scrap wood about 3/16 thick and placed it where the hole that goes to the curbside registers is and used aluminum tape to seal it. Some air is still coming through the curbside registers, so there must be a leak between sides—it is possible there are really no ducts, just a space between the interior ceiling and the roof that gets pressurized by the A/C and then the air exits through the 9 registers. Tomorrow is supposed to be 94˚ so that will be a better test.

I suppose I could blow a bag of cellulose pellets into that space to insulate it properly, but I'll not yet consider that.

 

[16ACE27]

After I sealed off the curbside ceiling registers, things got cooler right away. The temp is 73˚ while it is 88˚ outside. To seal it I cut a piece of scrap wood about 3/16 thick and placed it where the hole that goes to the curbside registers is and used aluminum tape to seal it. Some air is still coming through the curbside registers, so there must be a leak between sides—it is possible there are really no ducts, just a space between the interior ceiling and the roof that gets pressurized by the A/C and then the air exits through the 9 registers. Tomorrow is supposed to be 94˚ so that will be a better test.

I suppose I could blow a bag of cellulose pellets into that space to insulate it properly, but I'll not yet consider that.

Something covered in the big A/C thread that you may have missed:
In many cases Thor does not terminate the ceiling channels - they continue past the last vent into empty spaces like the front and rear end caps. Many people have blocked the channels past the last vents with good results.

 

[FirstGene]

Thanks—is there is channel for the registers on each side, are they connected, is the whole roof open? I thought of spraying foam in there, but don't want to make this a major project.

 

[MLP-THOR]

Look at this video.

This works, I did this. You also need to seal off the side vents to your roof distribution. The manufacture does not seal them up and a lot of cold air gets pushed through the gasps and not into the duct system. Add bubble insulation to the inside of your sunny side windows. Then get the magnetic windshield screen. It all makes a big difference.

 

[FirstGene]

Thanks MLP. I have a different A/C, though the principles are the same. The intent of the Youtube guy was to use the ducts and ceiling registers and to do so, he closed off the registers/vents on the A/C itself. By the way, one of the things that perplexed me was that the chassis A/C easily cooled the MH but the house A/C didn't even though it was producing 55˚ air before I modified it.

Since the A/C is not as noisy as the older ones, I am ok with using the vents or registers on the A/C because I lose less cold that way and increase the efficiency of the A/C. It certainly makes sense to reduce turbulence with the baffles and decrease the space (that increases the velocity of the air flow through the air handler part of the unit—these A/C's are not built to build up enough pressure in the channels). It looks like he didn't have a separator between the hot and cold sides originally. I did.

In my most fevered thoughts, sometimes at 3 am, I imagine a major project. I remove the registers and run true ducts through the ceiling to each register. Given the space available and poor access, that would be a major project (yeh, I could remove the ceiling, but that's worse and indication of extreme insanity).

At present the curbside duct—better described as a channel—is closed off and there's more air flow elsewhere. It is 91˚ outside and 76˚ inside—a 12˚ improvement from the day before yesterday. My more pragmatic options:

1. Leave it and hope that's ok.
2. Seal off the street side channels and send all air through the unit's vents—using the Youtube baffles.
3. Close off parts of the ceiling channels with spray foam.

#1 will be ok for today as the heat increases. More modifications may be necessary.
#2 seems too drastic—the A/C works more efficiently not using the ceiling channels, but the cool air may not distribute well, especially in the bedroom.
#3 I have a can of foam, so I may try it if the can is still good. Looks like I can remove the registers and look around up there to see how the innards of the ceiling are built.

Before the clouds come in and temp is still in the 90's, I can experiment with the vents open and closed, the ceiling channel registers open and closed. In the meantime I can set up the soundbar and blue tooth transmitter and figure out how to store more stuff.

I sure hope someone who has explored the ceiling channels chimes in—just what is actually up there? Are both sides open to each other? Is the whole ceiling getting the air, or are the channels only a foot or so wide? That's as far as my imagination goes. Maybe I will be energized to take off a register or two and feel around up there—I may find dead things and trash as well.

 

[jawzilla]

I have used this little handy device to explore new wiring routes, but it could be used to look at your ceiling ducts as well. It’s for an iPhone, but I’m sure they make one for an android if thats what you have.

https://www.amazon.com/dp/B0BRYV2HFL?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[FirstGene]

Jawzilla, that is a good idea, but my problem is I can’t get to the channels except right close to the registers in the ceiling. I took one off and saw that they used foam board for insulation, but they never sealed it. Thus it leaks around the whole ceiling/roof. If you don’t seal insulation it lowers the R value significantly. I had a can of spray foam, but it seems to have taken a walk somewhere without a forwarding address. The foam at the front of the main cabin accessible from the front register does not reach another piece across the front, so there are gaps of about an inch. Those I could seal, but will have to get some new foam unless the can comes home.

Now that it is in the low 90’s the A/C is keeping the cabin 16 degrees below outside temp. Before I sealed off the curbside channel and taped the separator it was running 3 degrees cooler. If I seal off the street side registers at the A/C I could get a much better result, but I think I’ll try spray foam where ever I can reach into the ceiling by removing the registers. The A/C vents seem to cool the entire MH pretty well, but I’d rather have one side of the ceiling registers working so cooler air can blow into the bedroom and the always hot kitchen (bedrooms can be hot too, although that is another topic).

Those cameras used to cost around $150, so $20 is a good deal and the older ones had their own screen, so this saves money since you can use a phone. If I can get a can of foam with a 3’ straw, that would enable me to spray the entire channel and the camera would be handy, but first I have to find a can of foam with an extra long straw.

 

[ducksface]

Brown Gorilla glue is essentially spray foam. It dries to the same color as spray foam and swells almost as well (3x expansion.)

Pump it where you need it with this.
https://www.amazon.com/gp/aw/d/B0C5QPJ2W3?psc=1&ref=ppx_pop_mob_b_asin_image

Do not buy the Bluetooth endoscope. The lag was horrible and the wireless when dealing with a16ft cable was ridiculous.

I use my android endoscope all the time.

 

[MLP-THOR]

One of the biggest improvements is to use metal ducting tape to seal the connections between the AC and the ceiling ducts. There is usually big gaps there. Most of the air pressure is as well and cold air leaks through them. In doing so, my air flow from rear to front was greatly increased. The same with front to rear. I have 44 degree air at the front duct from the rear AC and 47 degree air from the rear AC in the front duct. If I now use both AC's, one will freeze up unless it is 95 degrees or better outside. Note the rear AC is 15k and the front one is 12.5k. It pays to clean the AC coils. I used Dometic non rinse coil cleaner. The coils went from dark gray to shiny aluminum and the AC output went down 5 degrees. Put rags around so as not to have the stuff run across your roof.