Air Conditioner Issues

[GetGone]

Hello again. We have a brand new 2023 Montana 3793RD. It presently has 2 Coleman Mach Q A.C.'s which are ducted. This is our first camper with ducted A.C. Our others had the roof mounted units that were so loud you could barely carry on a conversation. However, they definitely blew out the cold air!! My concern with my new unit is the AC's aren't working efficiently. The camper is out of direct sunlight parked in a pole barn. Yesterday I set the thermostat to 68° Hi-Cool Auto for the den AC. After running for over 2 hours the thermostat still read 78° which is the same as when I turned it on. The camper really didn't feel any cooler than it did before I turned on the AC. When pointing a laser thermometer directly into a vent it reads 68° but when I move the beam over a couple of inches it reads 77°. When I put my hand directly up to the vent the air that is coming out is definitely cool but there is very little air flow coming out of the vent. All the vents are like this. I closed up the bathroom and bedroom to reduce the area being cooled. Is this normal for a ducted type AC? Should I go ahead and add the 3rd AC in the kitchen? I'm all ears. I look forward to reading your thoughts and hopefully solutions. Thank you all for your information.

[bshgto]

all a/c the fixes are useless. Go to walmart and buy 2 6000- btu window a/c`s and put one in the bed room window and one in the living room window and remove while traveling.. That`s the only fix that will bring the temps down. The temps out of the window a/c`s is far lower than the first vent from the ceiling units. A third a/c is useless because you can`t run all 3 time a time anyway unless you have electrical knowledge to defeat the control box. Compaire costs and hassle.

[SonnyP3]

Originally Posted by bshgto

all a/c the fixes are useless. Go to walmart and buy 2 6000- btu window a/c`s and put one in the bed room window and one in the living room window and remove while traveling.. That`s the only fix that will bring the temps down. The temps out of the window a/c`s is far lower than the first vent from the ceiling units. A third a/c is useless because you can`t run all 3 time a time anyway unless you have electrical knowledge to defeat the control box. Compaire costs and hassle.

I have run all three of my A/C’s since day one. I own a 2023 3763BP. As long as I have shore power, I run all three day and night.

[Bourbon County]

Having the rig parked in a pole barn definitely reduces or eliminates the solar gain heating, but what was the ambient temperature inside the barn? Are you seeing condensate drip off the roof?

If you have a 2023 model, you should still be under warranty. I believe I would do some further testing and depending on results, file a warranty claim before buying additional air conditioners.

You were on the right track with your laser thermometer, maybe not the best instrument for this measurement. Those are meant to read surface temps, not air temps. A digital BBQ thermometer will work or if you have a thermocouple with an air sensing probe even better. The laser thermometers are all an aspect ratio instrument, some are 10:1, others are 12:1, they are normally stamped on the side of the instrument. What that means is however many units (inches, millimeters, feet) you are away from the target the circular area it's reading is either 1/10 or 1/12 the size of that distance. The red dot just happens to be the center of the target area, it averages the temperature of the entire circle it's measuring.

For the test: Turn on both ACs and let them run for 8-10 minutes so the evaporator coils get good and wet; that's when they are at their peak performance. Stick your thermometer into the supply vent furthest from the unit, record your reading and work through other supply vents doing same. Next, remove the grille and filter on a return, stick your thermometer into the return air stream and record. If you use a BBQ thermometer, make sure the probe is not touching a surface, just air.

If your delta T, or difference between the return (higher) and supply (lower) is in the 18-22 degree range, your AC is doing it's job. This will vary some depending on outdoor temps, the hotter it is, the less efficient an AC is. If the AC is performing, the next thing to check is airflow. Does your unit have the blade diffusers? I don't have those, but have read some horror stories about them.

Coleman's are regarded to be one of the best RV air conditioners on the market and are widely used on higher end units; of course this doesn't mean there's not a problem with yours. If yours isn't performing after your test, you have some very good data to give your dealer for a warranty claim and it's not just based on your perceptions.

I think we as campers expect to park our RV, turn the AC on and it cool almost instantly; fact is they just don't work that way. If everything is working properly, they can only pull the indoor temperature down by about 2 degrees per hour.

[C&P RV]

You don't mention where you are located and the outside temp. It's a stretch to expect the temp to come down much more than 20 degrees from the outside (even under some shade) but there are things you can do to mitigate.
1- close off the vents under the stairs that allow heat from the front basement area to come into the main living space. This is especially important if you have either of the front basement doors open.
2- cover the floor vent in front of the loveseat. That vent also has an opening in the rear basement over the pullout drawer
3- Adjust the direction your vents are blowing. You have the "Blade" AC vents. Many on here on the forum don't like them. They are adjustable to direct airflow. You can remove one by grasping it firmly and pulling straight down. You'll find that the part that goes up into the ductwork has one side higher than the other which you can use to aim the airflow. The "theory" behind the Blade design is that the cool air will spread more evenly throughout the RV. I've adjusted ours so that they work fairly well to cool the space.
4- Do something to block out the skylight in the bathroom. We used J-channel and put foamboard in the slot, which still lets some light in but blocks most of the heat.
5- Pull down as many of the shades a possible
6- Check the temp difference between the return air (center of the ac unit) and one of the Blade vents. If you're lucky you will get 15-20 degrees of drop. If less than 15 degrees your unit may be freezing up in the evaporator because of high humidity or your AC unit is faulty.

Some on the forum recommend running HI Cool, without the Auto. I've tried both and usually run High Auto. It will freeze up on Low Auto in areas with high humidity.

Finally, our 2022 came with the 3rd AC installed. I am able to run all 3 ACs at the same time with zero issues. The Bedroom AC, water heater, washer, dryer and 3rd AC are all wired to one of the 50 amp legs (in ours it's the leg on the right side of the breaker box or closest to the bedroom). I would expect your 3793 to be wired the same way. The 3rd thermostat is adjacent to the thermostat for the den area. The 3rd AC dumps into the kitchen area where the MaxAir Fan is on your unit. It is not ducted and it is much louder. Because of where it blows, I have to set both the den and 3rd AC temps much lower than the bedroom to keep all 3 running until the space cools. Once it's cool I usually set the 3rd AC a couple of degrees higher than the den AC.

[bshgto]

I f you manage to run all 3 a/c`s I can imagine what it sounds like in the camper. The window units are 1/3 the the noise level and produce far cooler air and use less amps than one ceiling unit combined, to each his own.

[SonnyP3]

Originally Posted by bshgto

I f you manage to run all 3 a/c`s I can imagine what it sounds like in the camper. The window units are 1/3 the the noise level and produce far cooler air and use less amps than one ceiling unit combined, to each his own.

My three A/C’s are as quiet as church mice, even when running all three. They are no louder than the central air in my home.

[GetGone]

Originally Posted by C&P RV

You don't mention where you are located and the outside temp.

We are in hot humid Georgia!!!

Thanks for the information.

[1retired06]

My AC units (dometic) work fine. I swapped out the vents. I found the ducting to be collapsed and used PVC to open then up, and placed some short pieces of PVC at each end of the ducting to prevent collapse and the air flow significantly improved.

[Bourbon County]

If you have tested and confirmed the units are actually cooling, the next step is to check airflow.

I don't have the blade diffusers, but looking at them, they look restrictive to airflow. I understand the idea and the logic behind the design, but see potential problems. The first potential problem would be an air "short circuit", which means there is a short distance between the supply and returns and a portion of the air is simply blowing out the supply and being pulled straight into the return doing nothing to cool the space. The blades are supposed to offer 360 degree air diffusion, which theoretically sounds good. The way the supplies and returns are arranged in an RV ceiling, you're never far away from a return and I suspect might be an issue.

The blade diffusers have a small semi-circular piece that sticks into the duct. I believe it's meant to be a scoop to direct air down through that diffuser. If it's turned so the inside radius is turned into the airstream, it should work. If it's turned so the outside radius is turned into the airstream, it would likely deflect a lot of airflow around that supply diffuser. This is supposed to be the adjustment they speak of, you can experiment by turning the blade to different positions and check airflow afterwards. I seriously doubt there is any thought or standardization that goes into the adjustment at the factory.

It would be very easy to remove a couple of these and see what that does to your airflow. I don't know if they just snap into the collar or maybe has a couple of screws. Another place to look is the filters in the returns. Keystone advertises MERV 9 filters in their "Blade Pure" system. That is also somewhat restrictive to airflow. Most any air conditioner can cool the air; the secret to comfort is delivering the right amount of cool air to the right place in the RV. There are a number of things in a system that can restrict airflow: duct design, filters, diffusers and grilles, evaporator coil, etc. Obviously you can't change some of them, but there are obvious ones you can.

[GetGone]

Originally Posted by Bourbon County

If you have tested and confirmed the units are actually cooling, the next step is to check airflow........

Okay, I went to home depot and purchased the BBQ thermometer. When used to test the air temp in the vents it was 55°. I had the rigs thermostat set to 68° During the heat of the day the thermostat read between 78° and 80°. The outside temperature was in the mid 90s.

Without the blade vent covers in place the air flow is much better. One vent in particular is noticeably better than the others.

So there's the reading that you suggested I take. I'm interested in the $100 fix you mentioned in one of your post. I sent you a DM with my email address.

I truly appreciate the info and thoughts that you and everyone else has offered.

Scott

[BB_TX]

As 1retired06 mentioned, check your ducts. There have been a number of posts over the years about collapsed ducts. That would definitely cause low air flow and prevent proper cooling. Don’t remember all the remedies.

[texas05]

We run 3 ACs without issue. Much quieter than our previous Grand Design.

[GetGone]

As a couple have mention that I check, the vents that are being used significantly cut the flow of air. I removed a few of the vents and had a definite increase in the amount of air. Oddly enough the two vents closest to the unit seem to have the least amount of air flow.

[Foldbak]

The Keystone blade vents are horrible. I replaced with the old school louvered vents! Much better air flow.

[GetGone]

Originally Posted by Foldbak

The Keystone blade vents are horrible. I replaced with the old school louvered vents! Much better air flow.

You are absolutely correct. Right now I have nothing covering the vent openings. It may be a little unsightly but at least air is moving into the living space. Thankful to those on the forum that mentioned this.

[Toma-in-TX]

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

[Foldbak]

Originally Posted by Toma-in-TX

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

This is what I used. It snaps into the collar. The screws show a bit so I painted them white.



https://www.amazon.com/dp/B082FYRYBH...roduct_details

[Bourbon County]

Originally Posted by Toma-in-TX

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

I bought the Valterra A10-3359VP from etrailer.com for everywhere except bath where I used a Valterra A10-3354VP. You'll find there aren't a lot of choices on the market. They are larger diameter which is a really good thing and you have to cut the hole in the ceiling out a little. I used an oscillating saw which worked very good.

With the racetrack duct system, the highest air pressure is in the middle of the coach halfway between the 2 units. I ended up closing the vents off quite a bit on those. The A10-3354VP is an old school spin to adjust model; the bath is a very small space and doesn't need very much airflow. If you're going to be in there for an extended length of time it's easy to reach and open it up a little.

Since the A10-3359VP is directional, try to point them away from a return as much as possible to prevent an air "short circuit". When installing the sleeve inserts, carefully check the height, they need to be flush with the duct insulation or slightly below; trim them down if needed.

[skippydoo]

Valterra A/C Vent Spaceport 4" White

Hi, we purchased a bunch of these on Amazon to replace the vents back in 2020. Amazon sells them for abt 6.50 each.

https://www.amazon.com/Valterra-A103...%2C164&sr=8-19