Omni air conditioning

[chunker21]

I've started this thread because it's a topic brought up on another thread about a/c not keeping up. Here's what I found. First there are lots of threads, videos, etc. discussing ways to improve the output of an RV a/c. Some very expensive, some cheap but none of this work like desired or claimed if the ducting in the ceiling/attic has problems. Second this is what I found working on my Omni XG32 and I suspect all other models of this nameplate are similar.

I took the ceiling plates off both a/c and while the divider box panels was pretty good, I secured them with a goodly about of foil tape and also streamlined the air going to the ducting with more tape. The big issue I found was the integrity of the styrofoam ducting itself in the front. Several reports of the duct is open to the front cap, not true in my case. BUT the duct is badly compromised by the installation of the non-powered ceiling vent between the 2 front a/c front vents. Either when the a/c ducting is installed or when the ceiling vent is installed, the styrofoam a/c duct is cut away on the inside edges. That leaves gaps that apparently go into the attic area. Additionally when the styrofoam ducting was assembled in the attic, the parts don't come together leaving gaps in the duct to the attic. I found that situation on both sides aft and outboard of the a/c vents about 4". Looks like a top top bottom gap of about 1" or so. Both sides. On the inboard side of the a/c vents, there is a gap with no styrofoam ducting both in front of and behind the ceiling vent aluminum box. That just loses cold air to the attic.

What I did there. I had a can of expandable foam, large gap, and inserted it to the gaps in the front edge along the box and filled in the gaps. HINT; shoot some foam in, let it settle and harden some then shoot more in. Otherwise it piles up and falls over. On the inboard rear I tried the foam but it's about 12" in from the a/c vent opening and I couldn't get the foam far enough in. For that I got some fiberglass insulation bats and tore off small pieces, used a section of #12AWG as a "ram" and pushed it in the gap. Did the same with the outboard gaps aft of the a/c vent holes but could reach in to get it started.

Another hint, if you have big fat hands you can't get them in, or far in, the ducting. Maybe wife or GF could help. Use disposable gloves to keep the glass out of your hands.

I then turned the a/c on, closed all the other vents and let the debris blow out and yes I made a mess. Glad she's not here to see it.

No I don't have pictures, access tight for lights, camera or inspection mirrors. Frequent inspections to see how it's going. I now have the 2 a/c going and it seems like a pretty robust flow from the open holes of the system. I didn't measure any airflow before so no idea how much it's improved. Perhaps Thor thought that air conditioning the attic would keep the coach cooler but I prefer it inside the house part.

[RCS]

Chunker,

I did the same, closed up the voids that I could get to with insulation up front. Have not tackled the back yet. But air flow is definitely better and I notice the ACs are not running as much (but it is partly cloudy here today, so that may have more to do with it than what I have done). Also, I found another void in the Styrofoam duct just in front of the vent fan opening - plugged both sides. I suspect that was letting air into the area above the ceiling. That is 4 large gaps in the duct so far that I have closed up.

[chunker21]

Originally Posted by RCS

Chunker,

I did the same, closed up the voids that I could get to with insulation up front. Have not tackled the back yet. But air flow is definitely better and I notice the ACs are not running as much (but it is partly cloudy here today, so that may have more to do with it than what I have done). Also, I found another void in the Styrofoam duct just in front of the vent fan opening - plugged both sides. I suspect that was letting air into the area above the ceiling. That is 4 large gaps in the duct so far that I have closed up.

I haven't pulled any of the a/c vents other than full forward and aft. Later I'll insect what's beside the rest of them. The styrofoam ducting in the back of the coach looks good on mine. But I can only see a short bit up to where the aft a/c dumps into the ducting and that part is OK. RCS, the 4 large gaps that you fill, are they all associated with the non-powered square vent in the front, or are there other locations you found?

It's 90 and humid outside and the RV is under a cover so no direct sun on it. I have a thermometer in one of the central a/c vents and it was showing 52, the intake to the front a/c 68, the tablet shows 71 in front and rear. Units are cycling.

[RCS]

Kinda hard to describe where the gaps were, but here goes. Two gaps were a couple of inches toward the back of the rig from the left and right front duct openings (the round vents up front) on the outboard side of the plenum. They opened a gap that ran all the way out to the outside walls (checked this with my snake camera).

The other two gaps that I found were also from the front (round) ducts also, but just in front of the 14 inch roof vent opening. There is a styrafoam plenum that runs between the two front (round) ducts and just behind this plenum, towards the back of the rig, was a gap one each side. Filled these with insulation.

Clear as mud?

[chunker21]

Originally Posted by RCS

Kinda hard to describe where the gaps were, but here goes. Two gaps were a couple of inches toward the back of the rig from the left and right front duct openings (the round vents up front) on the outboard side of the plenum. They opened a gap that ran all the way out to the outside walls (checked this with my snake camera).

The other two gaps that I found were also from the front (round) ducts also, but just in front of the 14 inch roof vent opening. There is a styrafoam plenum that runs between the two front (round) ducts and just behind this plenum, towards the back of the rig, was a gap one each side. Filled these with insulation.

Clear as mud?

Actually yes those were the same gaps I had. Hard to believe that Thor considers this an acceptable design or execution of an HVAC ducting. Sadly the more I am looking at the details on how this was built I see absolutely shoddy work and even poorer design and materials. It's like if I look closely at something, what am I going to find? Ignorance would be bliss but I can't operate that way.

[Gmthrust]

This https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
is extremely helpful when looking inside the walls and ac ducting.
Be forewarned as to what you will see throughout the coach.
I found that one side of our ducting was "interupted" by one aluminum spar running across the roof. I went in through one of the ducts and LED lights in the bathroom to spray some foam. I do like the idea of some batting insulation, might give that a shot.

[LarryD]

did you remove the slats inside the vent. I know the vents are 2 pieces because I had to snap one in when I took delivery. I just cant figure out if there's a trick to snapping them back out for better access.

[chunker21]

Originally Posted by LarryD

did you remove the slats inside the vent. I know the vents are 2 pieces because I had to snap one in when I took delivery. I just cant figure out if there's a trick to snapping them back out for better access.

If you are talking about the adjustable pieces that let you direct the air, no I didn't remove them. I want to be able to direct the airflow. To remove them place a table knife between the outer ring and the ceiling. I would push it in a bit so it's on the inner piece, twist the knife or pry down. Gently move around the vent and pull it down or snap it off. The outer trim ring clips on the inner part with 4? small clip edges. Not sure if this is what you are asking though.

[LarryD]

Thanks. the inner part snaps down into the outer ring. I did as you instructed but put the knife in the slight separation between the two and pryd upwards into the vent. Poped right off. Thank you for the advice.

[Judge]

I’ve posted about some of my A/C upgrades and modifications. I just wanted to relay some information from my current trip.

I said that I’ve been very pleased with my A/C. I’ve also posted that you can’t judge performance based in the temp reading in the thermostat display panel because the sensor is very close to the wall where it is going to be the hottest.

Today was a sunny day and temps hit 80 with clear skies. We have no shade and the passenger side of the coach is facing west so it’s getting the most intense sun of the day.

We were outide and the sun was very warm to hot. When I came inside the coach it felt like an ice box. The FireFly Panel said the front was 82 but I knew it was much cooler than that temp.. So I got out my digital thermometer and placed it on the kitchen counter. It read 66!!!!

Now the passenger outside wall was hot enough to cook an egg and the wall on the inside near the sensor was very warm so I can see how the thermostat was reading 82.

Obviously I couldn’t be happier with my A/C and I think I have the system working as good as it possibly can based on its design. Last weekend in Nashville with temps at 95, the coach never got warmer than 78 based on the thermostat (wish I would have checked with my digital thermometer at the kitchen counter like I did today) and today with the temp at 80 and direct sun beating on the coach the actual air temp in the coach was mid to upper 60’s.

If you truly want to check the performance of your A/C system, check for the 15 - 20 degrees delta between the air return temp and the air output but also measure the ambient temp in the center of the coach and don’t rely on the thermostat sensor reading…. at least if there is sun beating on the wall near the sensor.

[LarryD]

66! wow! that would be perfect. will need to search for your mods. hope youre having a great trip so far!

[chunker21]

Originally Posted by Judge

I’ve posted about some of my A/C upgrades and modifications. I just wanted to relay some information from my current trip.

I said that I’ve been very pleased with my A/C. I’ve also posted that you can’t judge performance based in the temp reading in the thermostat display panel because the sensor is very close to the wall where it is going to be the hottest.

Today was a sunny day and temps hit 80 with clear skies. We have no shade and the passenger side of the coach is facing west so it’s getting the most intense sun of the day.

We were outide and the sun was very warm to hot. When I came inside the coach it felt like an ice box. The FireFly Panel said the front was 82 but I knew it was much cooler than that temp.. So I got out my digital thermometer and placed it on the kitchen counter. It read 66!!!!

Now the passenger outside wall was hot enough to cook an egg and the wall on the inside near the sensor was very warm so I can see how the thermostat was reading 82.

Obviously I couldn’t be happier with my A/C and I think I have the system working as good as it possibly can based on its design. Last weekend in Nashville with temps at 95, the coach never got warmer than 78 based on the thermostat (wish I would have checked with my digital thermometer at the kitchen counter like I did today) and today with the temp at 80 and direct sun beating on the coach the actual air temp in the coach was mid to upper 60’s.

If you truly want to check the performance of your A/C system, check for the 15 - 20 degrees delta between the air return temp and the air output but also measure the ambient temp in the center of the coach and don’t rely on the thermostat sensor reading…. at least if there is sun beating on the wall near the sensor.

That's good performance. Wednesday I had north, sort of, WV and KY for a couple weeks. Still warm part of year so hopefully I'll see some improvements too.

[Gmthrust]

Originally Posted by Judge

... So I got out my digital thermometer and placed it on the kitchen counter. It read 66!!!!

Ok Judge, enough already, stop pressuring me, I'll buy a digital thermometer. Stop being so relentless! Geesh, I'll go to Amazon right now!

[cupajoe147]

So I assume if the Firefly shows an inside temp of 80 degrees and the digital thermometer shows 66 degrees, I should set the Firefly auto a/c thermostat to 80 - 85 degrees?

[kwplot34]

Not sure about the other models, but on our XG32 the front a/c temp sensor is above our theatre seating mounted under the cabinet, the bedroom a/c temp sensor is mounted underneath the cabinet over the bed.
One cool thing about them being easily accessible is, if you are feeling a little warm and want the a/c to come on, put your thumb on the sensor and hold it there for a few seconds, the a/c will come on.

[LarryD]

thought it mostly looked good until I got to the front.. Found I have a couple gaps, one seems to be a channel maybe. I took pics with a borescope, maybe some of you can make sense of it. The most "illuminating" discovery was that the Bathroom shower skylight is responsible for my vents being lit up. I'll probably try to stuff some fiberglass batting in and around some of the gaps and uninsulated places to see if it changes anything.

[chunker21]

Originally Posted by LarryD

thought it mostly looked good until I got to the front.. Found I have a couple gaps, one seems to be a channel maybe. I took pics with a borescope, maybe some of you can make sense of it. The most "illuminating" discovery was that the Bathroom shower skylight is responsible for my vents being lit up. I'll probably try to stuff some fiberglass batting in and around some of the gaps and uninsulated places to see if it changes anything.

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I'll take a stab at it from what I saw on mine. Not sure which model you have, mine is the XG32. The first picture looks like viewing the outboard part of the ducting looking aft into the front vent. I had the same gap that looked like it just dumped into the attic. I stuffed that with some fiberglass batting. I presume the middle is the passenger side looking aft. The last one appears to be the metal box of the non powered ceiling vent. Mine is just like that where they apparently just tore the ducting when the vent was installed. If you had looked forward and inboard you probably would have seen the front corner of the vent box and more gaps in the ducting. On mine the front "bulkhead" of the duct was about 8" forward. But gaps where they tore the ducting with the vent install which would also leak a/c air into the attic and potentially front cap. I stuffed some batting and shot in expanding foam in those areas because the foam nozzle would each those gaps. Absolutely sloppy negligent installation making the Thor branded RV junk.

[chunker21]

Originally Posted by LarryD

thought it mostly looked good until I got to the front.. Found I have a couple gaps, one seems to be a channel maybe. I took pics with a borescope, maybe some of you can make sense of it. The most "illuminating" discovery was that the Bathroom shower skylight is responsible for my vents being lit up. I'll probably try to stuff some fiberglass batting in and around some of the gaps and uninsulated places to see if it changes anything.

Attachment 33232

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LarryD something I thought of. Reference the 1st picture with the gap. If you still have the vent covers off can run the scope to that gap and look around the corner to where the gap leads. I suspect it's open top the attic but I don't have a scope to know for sure. The only other way to know would be remove the roof and that's a bit extreme in this case.

I looked at the other passenger side a/c vents with the lights off inside and don't see any illumination like you have. I didn't remove any of the other vent covers though. Thanks.

[LarryD]

Originally Posted by chunker21

LarryD something I thought of. Reference the 1st picture with the gap. If you still have the vent covers off can run the scope to that gap and look around the corner to where the gap leads. I suspect it's open top the attic but I don't have a scope to know for sure. The only other way to know would be remove the roof and that's a bit extreme in this case.

I looked at the other passenger side a/c vents with the lights off inside and don't see any illumination like you have. I didn't remove any of the other vent covers though. Thanks.

Thank you chunker. I'll scope it again over the weekend if I can. For additional context, the pic with the gap is forward vent drivers side. 2nd is pass side, I think you are right, thats gotta be the metal box of the ceiling vent, last pic is second from front pass side looking back toward bathroom. It's the same view looking from bedroom forward as well.

[chunker21]

Originally Posted by LarryD

Thank you chunker. I'll scope it again over the weekend if I can. For additional context, the pic with the gap is forward vent drivers side. 2nd is pass side, I think you are right, thats gotta be the metal box of the ceiling vent, last pic is second from front pass side looking back toward bathroom. It's the same view looking from bedroom forward as well.

That gap you showed on the first picture exists on both sides of mine and can be seen from the front vents looking aft outboard. I am curious to see what you see when you do get a chance to look into that gap. I used and inspection mirror and small LED "headlight" to see into mine. A scope might just be in my future.