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Old 07-24-2017, 09:34 PM   #1
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Air conditioning not cooling, part deux

OK, gang, I've come to accept that you can only get so much cooling from two 15000 BTU a/c units that are limited to 50 amp service. Our 38RD is still parked on our property in Central Texas, and sitting broadside to the afternoon Texas sun. We get up to 88 inside when it is 98 outside. I'm still trying to figure out ways to maximize a/c and trailer efficiency, and I'm game to try anything to cool things even just a degree or two, so I have some wild questions to pose of you all.

Inside, I've pulled the rear two ceiling vents out and taken pictures inside the duct. The ducts are 8"W X 1 1/2"H, are clear of debris, and appear to be sealed off at the aft ends. The vent flanges are cut to proper depth and are flush with the bottom of the ducts. Both of the ducts go 12" past the rear edge of the vents and look to be closed off and duct taped shut.
--Would it help to foam in that wasted area and build scoops directly over the two vents so that all air terminates at the vents instead of continuing past into the dead air space?
--What about adding two more vents butted right up against the rear of
the existing two (in that twelve inches of dead space), and foaming around them?

I got up on the roof and took off the a/c covers, but didn't see anything amiss at casual glance, like missing foam barriers.
-- The a/c covers are black. Would it help to paint them white?
--Would it help to add a layer of silver bubble foil insulation inside the a/c cover?
--I've added white Maxxair vent covers over the two ceiling fans. Would it make any sense to spray the tops of those covers with reflective metallic paint? They would still look the same from the sides, but would reflect some of the heat from the midday sun.
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Old 07-25-2017, 01:00 AM   #2
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Just removing the cover on the roof will not reveal the foam gasket separating the return/discharge, you'll have to remove the metal shroud by removing a couple dozen screws, be careful it's sharp, then use some aluminum tape to seal the foam back in place. On mine I cut a piece of 1" pipe foam insulation about a foot long & horseshoed it in the end of the ducts to block that wasted last foot. If you haven't remove all the vents & check the heighth of the collars.
May want to check out the posts on removing the shoe racks in the front closet & adding insulation, most have found what little is in there has fallen to a pile in the bottom.
We just left Laughlin Nevada with 112 degrees sitting broadside to the west & not a breath of a breeze & ours maintained about 85 degrees, running 4 extra fans, but never shut off til about 4am & back on about 9am.
Good luck, these things are not built for extreme heat or cold for that matter.
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Old 07-25-2017, 03:59 AM   #3
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there ha to be something in the system. either a fan is loose and not blowing(is the fan speed on high?)....low on freeon...do you have a pet and maybe the return fins in the a coil are blocked..the divider in the ceiling is not 100% divided? this might sound dumb, do you have full 220v? If you have low voltage the ACs will not run properly
we have been in 98 f for weeks and i can lower the unit to 72. and it cycles all day
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Old 07-25-2017, 02:05 PM   #4
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there ha to be something in the system. either a fan is loose and not blowing(is the fan speed on high?)....low on freeon...do you have a pet and maybe the return fins in the a coil are blocked..the divider in the ceiling is not 100% divided? this might sound dumb, do you have full 220v? If you have low voltage the ACs will not run properlyhin
we have been in 98 f for weeks and i can lower the unit to 72. and it cycles all day
I agree Ted. Sounds like something is either not working, or not working at peak efficiency! We were parked in the Dallas area in low 100, high 90's temps. Our coach is always comfortable...although it seems our AC's at peak times never shut off. Sounds like only one AC is functioning properly.

Bob
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Old 07-25-2017, 11:58 PM   #5
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AC

Randolf I will through my 2 cents worth in. I have a 2012 with 2/ 15000 BTU AC's. Both cowlings on the ac are white. I have also blocked off the excess aft ducting. I replaced all my ceiling vents with louvered types. As you enter our rig there is a closet to the right. Under our closet there is a screen about 3" tall by 32' L. Except for that screen there is nothing blocking the air flow from the storage area (where the converter and the heating ducts are) into the main RV living space. I blocked this off so no warm air would be sucked into the living space. Also at the base of the steps going to the bedroom was a vent plate to the same area with nothing connected to it from the other side. I blocked this off also. They may be air returns for the heater but they are blocked. I also took down the window shades that came with the unit and put up thermal curtains on the large windows. We live in Arizona (outside Tucson) and with the high temps it is very nice inside. In the mid 70's. One of the AC's blows air out harder than the other but perhaps that is because one has a heat pump. Both are on high fan. Just what I have done. Hope you get cooled off what ever you do. By the way only one ac was working when it came from the factory. It was not connected properly. Imagine that.
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Old 07-26-2017, 03:24 AM   #6
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While our '13 38gk took forEVER to cool down, once it had that first night to catch up, it kept it cool.

but in the interim, get the sun off the coach.... awnings, drop down sunscreens, reflectix on the windows... spray water on the roof and sides
bring in slides

anything to make it livable cuz the hot part of the summer is not here yet good luck
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Old 07-26-2017, 04:47 AM   #7
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Randolf I will through my 2 cents worth in. I have a 2012 with 2/ 15000 BTU AC's. Both cowlings on the ac are white. I have also blocked off the excess aft ducting. I replaced all my ceiling vents with louvered types. As you enter our rig there is a closet to the right. Under our closet there is a screen about 3" tall by 32' L. Except for that screen there is nothing blocking the air flow from the storage area (where the converter and the heating ducts are) into the main RV living space. I blocked this off so no warm air would be sucked into the living space. Also at the base of the steps going to the bedroom was a vent plate to the same area with nothing connected to it from the other side. I blocked this off also. They may be air returns for the heater but they are blocked. I also took down the window shades that came with the unit and put up thermal curtains on the large windows. We live in Arizona (outside Tucson) and with the high temps it is very nice inside. In the mid 70's. One of the AC's blows air out harder than the other but perhaps that is because one has a heat pump. Both are on high fan. Just what I have done. Hope you get cooled off what ever you do. By the way only one ac was working when it came from the factory. It was not connected properly. Imagine that.
Where at outside Tucson? We just bought a site in Picacho Peak Rv Resort.
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Old 07-26-2017, 01:35 PM   #8
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Danny,

Did you buy an RV site or a mobile home site?

I have driven by Picacho Peak Rv Resort several times in previous years when I was still working full time. One of my nephews lived near Willcox, AZ for 10 years. I went to technical conferences in Phoenix for many years and would drive from Phoenix down to Willcox to visit. That is a beautiful area but it sure is hot in the summer time.

Guy
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Old 07-26-2017, 02:08 PM   #9
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I got up early this morning and spent an hour drafting up a response to all your suggestions and describing what steps I've taken so far. But by the time I was ready to post I'd been logged out of the forum, and I lost everything I'd written. Rather than try to recreate it all, I'll try several shorter posts.

I got busy yesterday and removed each of the ceiling vents and took pictures inside of them and diagrammed the duct system. Now I have a MUCH better idea of what I'm dealing with. Suffice it to say, I am shocked and disappointed by what an inefficient duct design my 38RD has!

Travelin' T, I'm heading to town right now to buy some pipe insulation to make the horseshoe-shaped air dams that you suggested. Your way is so quick, clean, and simple that I'm embarrassed to think about the messy, time-consuming ways I was contemplating doing the job. As I mentioned earlier, the rear ducts go 14" past the rear edge of the aft air vents, but they ain't got nothin' on one of my bathroom ducts. It extends 46 inches beyond the bathroom ceiling vent!
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Old 07-26-2017, 04:36 PM   #10
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Guy, we bought a park model/modular home with an awesome view of the peak from,every window & the front porch. We weren't looking, but this just kinda grabbed us. The park is very nice & they've just remodeled 3/4 of the sites to,what they are calling "super sites". If in the area in the winter, stop by.
Randalf, glad I could,help, I'm sure any improvements you make can only help. Good luck!
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