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Old 06-15-2017, 02:44 PM   #1
twvette
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Air conditioners only hold low 80's on Fuzion 420

Ironically don't use AC much here in AZ as mostly up north in summer but got my first chance to use it recently. I was on shore power and both AC's ran all day. Temps were 90-92 outside with not any shade/clouds and my thermos in living room and garage (literally two feet away from each other) were reading high 80's. Felt a little cooler than this so put a thermometer in kitchen and it was about 82-84. I thought with ducted A/C's I would still be good but one is at very end of rig in garage and other is at very front in master bedroom so now see it as an issue with placement. I did have the garage, bedroom, and bathroom doors wide open to try and get some flow to living/kitchen. At first the main vent on these were not open (seems would direct more to the ducts) and was even worse so temps listed are after opening these up. The air was good and cold but just too much trailer/not much bulk air coming out all the ducts. So, the center of trailer (living/kitchen) were not very comfortable. Maybe I should have got the option for 3 but then there is the whole issue of which two are running as max at once per my understanding. Anyone else experiencing this?
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Old 06-15-2017, 08:52 PM   #2
Rick52
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My 2016 fz371 does the same thing my ac's are in the bedroom and the loft area and ducted. It's hitting a high 90's in So. Cal right now and I played with mine yesterday. I checked the ducts for proper seal throughout and all seemed like they were doing the best they could. I really think there are just too many losses in the the walls and windows for these kind of temps. It's not a house with dual pain windows and 6inch walls..... It feels better than outside and for camping what else can you expect....
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Old 06-16-2017, 06:56 AM   #3
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Rick52 has touched on the biggest consideration about air conditioning in RV's. That's energy use and insulation. Going to Lowes.com and looking at window air conditioners, an 8000 BTU unit is rated to cool 350 square feet of space and a 15000 BTU unit is rated to cool 850 square feet of space. Even with slides, the biggest RV's are less than 500 square feet and most 30 to 35 foot RV's are around 300 square feet of floor space. Even with 30,000 BTU's of capacity, many RV's are "hot inside when in the sun". It's "difficult to understand" why such a small space doesn't cool well until you consider that the walls are R-9 and the ceiling/floor are typically not much more insulated than that. Then consider that the "roof A/C ducting" runs directly under the 3/8" roof membrane/decking (with virtually no insulation on that R4 foam ductwork which is being bombarded with the sun's heat, and the roof is often too hot to touch or to walk on with bare feet with that ductwork "less than 1" under it. It's a miracle that we get any cooling at all. With 2" wall construction, 5" roof construction and 1" slide construction, single pane windows that are "overly large to give a sense of bigger interior space, you can only get so much "heat resistance".

Should we be able to cool better? It would be wonderful, and how we position the RV (shade, big walls not facing east or west, etc) makes a significant difference, as does the color of the RV. But if you could imagine putting a window unit air conditioner in one end of a 8x20 vinyl tent pavilion, blowing into the space, imagine the BTU's it would take to make that dark green tent feel comfortable.... I wonder if the A/C in that tent would cycle off/on much differently than our RV? ie: run almost continuously. RV's are better insulated than that tent, but when compared to a "S&B" structure, not by much.

I don't think we'll ever see an "energy star" rating on an RV. It's just the nature of a "temporary house" that is so "under-insulated and uses so much energy to try to make it comfortable"....

When you get right down to "brass tacks", the "carbon footprint" for one of our RV's isn't that much "less impressive" than the "carbon footprint" from Al Gore's private jet.
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Old 06-16-2017, 08:42 AM   #4
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Thanks for the detailed info. Its just a bummer that nobody else in my my group with similar sized fifth wheels was having problems cooling theirs and their A/C's were actually cycling vs mine running non-stop. This was even with all shades down and nobody going in/out during day. Mine is black and lots of windows compared to the others so know that can be a big difference but was hoping if has the "Blizzard" package it could also insulate better than other much lower end models. Its manageable just expecting more and its even a downgrade from my old Weekend Warrior AC abilities. I do have to say the bedroom was plenty cool but it was the only cool area ... still good as that is really about the only place I truly care when trying to fall asleep to be a bit below 80. Going to try some fans to get some circulation next time.
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Old 06-16-2017, 09:45 AM   #5
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Just to add to John's post, many a time our rigs are also sitting on hard surface slabs like concrete ensuring that we get heat from all around. This heat sink will continue to provide continued heat as the sun goes down. at least on my Raptor and I think on most TH that garage area is not a covered belly area. Basically the back side of the garage floor is the outside. So I think this is another reason that garage is harder to cool. The R rating of the floors in the other areas of my Raptor are in the high 30s.

My walls are R9 and ceiling if I recall in high 30s like maybe R39. think these R values help me survive with one AC.

Another big asset is my large paddle Fan, cooling the air is one thing moving it is another. My unit is white which again helps. As I stated in a previous post after examining and repairing all tapped interfaces in the AC system, I noticed a big difference. My registers are the type that shoot air along the ceiling rather than straight down
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Old 06-18-2017, 03:55 PM   #6
mbjam359
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AC

We have a Raptor 412RP. We have 2 ac one in the bedroom and one in the living area. The Br cools down rather quickly and it takes a while for the living area. The living area will cycle in the evening but stays on for the most part of the day. With the technology we have it surprises me this is the way it is. The dark colored coaches look really nice but its got to be harder to cool them. I was thinking today a plain white coach might be the way to go.
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Old 06-18-2017, 05:42 PM   #7
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We have a Fuzion 371 with the blizzard package and it was comfortable this weekend even in South Louisiana...temps were in the low 90's with high humidity and it was actually too cold for me!
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Old 06-18-2017, 06:36 PM   #8
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Have you checked the air filters and looked for any obstructions in the ducts?
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Old 06-19-2017, 04:26 AM   #9
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Long time stalker, 1st time writer. We have a 2016 Fuzion 420 with 3 a/c's. We live in northern lower Michigan, and the dealer had two 420's. One with 2 units, the other with 3. Salesperson said she did not see the need for 3, unless you live in Arizona. That sold me, I like it cool. However, the first 1st time we camped with high heat and humidity, the 3 units struggled to keep our camper cool. Prior to this 5er, we had a 1986 35' Jayco 5er, with 1 a/c unit, no duct work, and that baby got cold. When we got back home. I started the investigation, using the knowledge I acquired from this forum, thanks everyone. 1st stop, vent ducts, everything good. Next, bottom cover of center a/c, above loft, awesome location I might add, thanks Keystone. The divider had been blown out of position, so a little aluminum duct tape and good. Well, so so good, that increased the air movement slightly, and I mean slightly. My thermostat is set up as zone heating/cooling, mine has 3 zones. Zone 1 is the living/kitchen area. Zone 2 is the bedroom/bath. Zone 3 is the garage. When I turn on zone 1, to cool just the living area, the center a/c is the only one that comes one, but is connected to the entire duct system, so essentially, I have 1 a/c trying to cool the whole 43' beast. I then taped off the vent in the bedroom and the one in the garage. It made a big difference, and I can actually zone cool by opening up the louvers on the bedroom and garage a/c units, so the air stays out of the vents, and cools the desired area. Sorry for the long post, like I said 1st time, hopefully I'll get better.
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Old 06-19-2017, 05:30 AM   #10
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Welcome to the forum curtthegreat. I think you've touched on one of the most significant factors in satisfactory (or is it unsatisfactory) cooling. The ductwork is in the attic space. It is surrounded by "superheated, unconditioned air".... What that means is that the cold air being produced by the rooftop units is actually being "warmed to near room temperature" as it leaves the rooftop unit and passes through the ductwork. Most of the ducting in the trailer's "central air delivery system" is actually 3/8" or 1/2" aluminum foil covered foam. Next time you're in Lowes, look at the R factor printed on their rigid foam sheeting. It's typically around R2 for 1/2" thickness. Add the foil backing and maybe it will insulate to about R3. Now add (at most) 1 or 2" of spun fiberglass insulation on top of that, and you'll have around R4 insulation between the cold air and the "superheated" attic air. What comes out the ducts is already "close to warm" rather than the cold temperature that's leaving the rooftop unit.

One of the "resistance factors" from buyers in the early 90's when ceiling ducting was being introduced was the inefficiency that came with it. Before that, one A/C unit, 15K BTU in size would cool a 32' travel trailer and keep it comfortable. The problem was that you couldn't close any doors or the "down-spout air" was blocked. So manufacturers introduced a ceiling delivery system. DISMAL FAILURE !!!! It was (back then) a thin aluminum ducting that ran through the rafters and by the time the air got to the bedroom, it was hot, not cool, but hot. Through "trial and error" the system evolved to what's available today, foam ducting and shorter runs from rooftop unit to vent. So to minimize the heat gain, two, three or even four rooftop units are needed. And, it's still not as effective at removing heat as the old "air dump" system.

So now, for the past few years, most manufacturers use a "combination system" that has ceiling ducting for "moderate temperatures" and an "air dump" that they call "quick cool" or some other "gimmick" brand name, but it's not "new technology". Actually, what it is, is a reversion to the older "air dump technology" from which RV air conditioning started.

Unfortunately, most RV manufacturers, RV dealers and PDI "introducers" don't even touch on the most effective way to cool the RV on hot days. That's to just eliminate the air movement through the ducts (where it gets hot before entering the cabin) and use the "air dump system". It's "not what they told us we had" (central air) but it is "cold air into the cabin" and it cools much more effectively than the ceiling ductwork.

We find, typically, that we can keep our 31' fifth wheel much cooler with the air dump and a fan to blow air up the stairs, even in 100F temperatures. When using the ceiling delivery ductwork, maybe 85F cabin temp, when using the dump, we can keep inside temps around 75 or so. Sure it's loud, no such thing as a quiet place to read a book, but much more comfortable than the elevated temps we get with the "central air".

Your experience, opening the "dump vents" to deliver cold air directly into the room by avoiding the ductwork is the same as what we've found to be true. Sometimes "the old way of doing things" is still the most efficient... It may not be the "best or the most quiet, but the most productive.....
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