Ducted AC question

havasu wrote:
So my 95 Newmar has a ducted AC system with front and rear ac units

However the outlets only have directional grills and they cannot be switched off.

I seem to remember that my old Beaver had outlets that could be switched off as well as directed

Anyway, the bedroom is an ice box and the living room is an oven despite my window coverings, dyson floor fan etc etc

So I fashioned some vent covers from a cereal packet - cut circles and then cut them in half and attached one half to the ceiling half of the circular vent and one half to the rotating part so as I turn it, it opens up more of the vent, up to 50% of it's original flow.

I installed these contraptions into the 2 rear outlets and the one in the central bathroom area.

As this is a ducted system with everything connected to each other, can any ac experts see any issues with this? Is it likely to cause a problem with the rear ac which has to push a little harder now?

why not just do like I do and run the front AC and not the rear? bedroom stays nice and so does living/kitchen area?

I have a 2001 Mountain Aire same set up, two 2 A/c's we run the front A/C at night turn the rear one off. Cool/cold air makes it way to the bedroom thru the duct work.
Or you may use both but set the temp on the rear one a little higher than the front therefore the rear will only come on if it gets to warm.
Both are dometics and controlled by a single theromstate which shows front and rear zone. Good luck

Deadbat - Because the front AC is not sufficient to keep us cool when it's 107F outside like it is right now :)

Front vent temps have dropped 3F since trying this and I'm at 81F inside and dropping :)

1998 and newer Newmar motorhomes have 18 total round ducts. 9 intake and 9 exhaust. I do not see a problem with your modification, but I would add 3 more exhaust ducts in the living area. Your model probably has at best 10 or 11 total round louvers. Newmar found that with fewer than 18 total, when they came out with Dometic Heat Pumps in 1998, the original Heat Pumps could NOT have a freeze control, so Newmar Heat Pumps would freeze in hot weather due to lack of return and exhaust ducts. Dometic AC only units had a freeze control. Adding the extra ducts increased cooling capacity and flow. So, I would add the extra exhaust ducts up front and see if that would not help get a better cold air to the front. Your design has not changed much in 20 years on a Newmar. The only difference is later models (1998 to current) Dometic introduced a 15k AC/HP unit. If you get the chance in the future replace the front unit with a 15k and that will help also. 1998 thru 2002 under Newmars warranty, Newmar paid to have the extra round ducts installed. 2002 to current the 18 were standard. Doug

Any chance you can find replace grills that have adjustable louvers. Like you I find the air distribution better when the flow can be moderated in some locations.

Downside, DW is always asking for some to be opened or closed depending on..........pick a reason.

Just went to e-bay and found these: RV 4" Flush Mounted Rotating Ceiling Door Grille Vent AC Heat - New. They are available. JM2¢...

I don't know about yours but on mine the last vent in the front and the last vent in the back did not have a stopper ( for lack of a better word). If you took the vent off and looked down the duck work away from the A/C unit, it just kept going into the front and rear caps.
In my case I cut a paper bowl in half and it fit into the channel pined it in place and sprayed foam around it. So now all the remaining cold air comes out of the last vent in the duck work.

teddyu wrote:
Just went to e-bay and found these: RV 4" Flush Mounted Rotating Ceiling Door Grille Vent AC Heat - New. They are available. JM2¢...

Nice...except mine are 5" vents inside a 7" frame :)

But thanks!!

I had my inspection camera inside mine and they stop about 6" after the vent so not much to be gained from that.

I also have the overhead blower that blows extra air down from the top onto the driver and passenger if needed. I'm thinking it would be nice to be able to route the ac air to feed that and close off the rest of the outlets when we are driving to supplement the cab air.

I might have to be a little inventive on how to get the air routed through as it's all behind a ceiling panel.

There are many ways to make an "After market cover" as to possible problems....

The only one is that the restriction on air flow MIGHT lead to icing on the evaporator on SOME A/Cs.. Most A/Cs have anti freeze up sensors so this should not be a problem. Mine I can close the vents.. And do.. and have never had a problem such as that.

One problem I have had is water.. From time to time it sounds like it's gurgling and when I shut it off NIAGRA FALLS.

Turns out the cause is dirty inlet filters.

During the heat of the day (up to and beyond 100 degrees F) I run both front and back 13,500 BTU acnds. I put a 9" fan on the floor of the bath right by the bedroom and aim it straight ahead. I put another on the floor in the front of the coach and aim it high (45 degree angle) towards the rear. If I don't get too far behind it will keep the coach very comfortable. At night I raise the bedroom thermostat 3 degrees higher than the front and usually the back unit does not run or when it does it is infrequent. I believe one needs to move the air in a coach with ducted supply and return air in the ceiling. Otherwise I am convinced it short cycles-out the supply and right into the return.