Adding AC vents or opening ceiling vent

[Cecilt]

We have a 36' TT that is pre-wired and braced for a second AC and is already 50 amp. Bought last September and even on a fall night felt hot in the MBR with our existing 15k AC. I found a good deal on a new Dometic Brisk Air II unit and will be installing this in the spring.

The unit is a Keystone Outback bunkhouse. The entire unit has 4 AC vents. One in the bunk room, LR, MBR and bath. In campgrounds where we have 50 amp I plan to use both AC's. I will need to close off the vent in the MBR as there is certainly no need to have air coming through the vent when I am running the AC I just installed in the ceiling of the MBR. The new unit is non-ducted.

My question is I think I need to add additional vents since I will be closing off 1 of only 4. Was thinking go adding a second one in the bunk room. For the LR I am not sure if I should add a second vent or just open the ceiling plenitude ducts( not sure if I said this right). Is this okay and or recommended.

Here is a link to our unit:
http://www.keystonerv.com/outback/models/323bh/model-mobile

[Rubber_Ducky1]

I think some of you are confused. As I read the OP, he is talking about ductwork vents for the air conditioner not through the roof vents.
We have a Wildwood Lodge 394FKDS Destination trailer. We ordered it from the factory and had them install the 2nd air conditioner in the MBR. There is a ductwork vent in the ceiling of the MBR from the main air conditioner. When we run both air conditioners I don't worry about that main air conditioner vent being open in the MBR. I just run the 2nd air conditioner on a lower setting. Problem solved!!

[handye9]

Some tips, if you go ahead with the vent addition.

1. Find the spot where you have clearance both inside and out. Mark your spot on interior ceiling.

2. Use a saw that has blade depth set to cut slightly less than the 1/8" ceiling panel. You don't want to cut any wires that may be laying above it. A vibrating saw works best for this. Some thing like a MultiMaster or Dremmel Multi-tool.

3. Once the inside hole is done, use a small diameter drill bit to drill up through the roof, one small hole in each corner.

4. Up on roof, use a razor knife to cut an "X" in the roof membrane, connecting the four drill holes.

5. Fold the roofing membrane out of the way and cut your hole in plywood roof.

6. Fold the membrane back into the hole (cover the edges of the plywood).

7. The vent kit will come with putty rope and screws. Apply that putty to lip of the vent and set it over the hole. Make sure your interior trim piece will line up, before you fasten the piece on the roof. When you fasten the vent, a small amout of putty should squeeze out from the screws.

8. Inside, trim and tuck the roof membrane out of the way. Install interior trim piece.

9. Go back up on roof, caulk around the vent with Dicor Lap sealant. Don't be shy with the amount.


Note: If you are going to install a Maxair vent cover, wait for caulk to dry.

[Cecilt]

ReferDog wrote:
Adding the ducts could be a tough one. The 2nd A/C unit was for the air to flow out of that A/C.

Not sure I follow. The second AC will be installed as a non ducted unit in our MBR. I figured when running it I would subsequently close off the vent in the ceiling that is pushing out air from the first AC. By doing so, I would now be down to just 3 ceiling vents for the original AC and to me that just seems like too few vents to push air out effectively. That is why I figured I would add 1 or 2 new ceiling vents just for the first AC.

Wonder if keystone would offer up any advice. My guess is If they add this second unit at the factory they probably just install it and not worry about the existing design and leave it up to customer to figure out, if there is anything to figure out. Might be thinking about it too much.

[ReferDog]

Adding the ducts could be a tough one. The 2nd A/C unit was for the air to flow out of that A/C.

[prichardson]

How the A/C is ducted will dictate how easy it is to add outlets. Some newer units have channels in the foam celing insulation. On those you can remove a register and probe with a tape measure and find where it runs then drill a hole for additional registers. If there are actual ducts it could be problem since you would need to run a new duct for additional registers. Opening the register on the plenum is an option; however that is usually noisy.

[handye9]

It is possible to add a roof vent. Would be a big help, if you could get drawings (showing framing and ductwork) from the manufacturer.

Since the bath vent is so close, I would first question the need for a fourth vent. If manufacturer had installed the second A/C, would they have cut another vent?

I added a vent on a Starcraft 25' TT, but, I did it because it only had one (bath) vent in the entire trailer. Starcraft was very helfull in sending drawings, however, their drawings did not show any wiring. With the drawings, I was able to locate roofing structure and ductwork. While cutting, I did find wires for 12 volt lighting. Luckily, I didn't cut them, and there was enough slack to move them out of the way. Very few, if any, TT manufacturers include wiring in their drawings.

[byrdr1]

CecilT as long as you know where the duct runs, I don't see why you cant add another vent. In my TT I wanted to add a vent, I spent several days looking and thinking and thinking some more. I found the duct work in the ceiling and found where I could add it. I looked at hole saws and then round vents from Home depot. Found everything I needed to do this and then backed out of doing it. Decided to trade it. NOT for this reason just was at that point. NO need to do the work and then trade it in.
BUT I think its very doable and would add AC to the main area or the bunk house area. The main thing careful planning with the right tools.
This is why when we went to the 5er we got the 13.5 unit installed in our bedroom and it has been nice with NC/SC temps and humidity. ITs direct blow intot he bedroom but catches the bathroom also. I did not close off any of those vents do to the fact that during the night we turn the bedroom AC off and just run the main unit as needed.
randy