ASK THE EXPERTS..AC location preference. - Page 3 - Fiberglass RV


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Old 11-27-2010, 11:12 PM   #29
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Quote:
Originally Posted by Andy B View Post
I am not an expert, so feel free to correct me if I say something incorrectly. When the temperature of the air is lowered with all other things being equal, the % humidity increases. If I am interpreting the charts that I Googled correctly, using the example of 115 F at 7% humidity, if the air temperature is lowered to 70 F without removing any water, the humidity increases to 28%. That is still low humidity.
That's the crux of the matter; at 115 F a 5000 Btu "Air Conditioner" is incapable of lowering temperature; it ceases to have any effect. It just blows HOT until the outside temperature drops below 95. Then it will start to cool again.
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Old 11-28-2010, 07:23 AM   #30
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Quote:
Originally Posted by Andy B View Post
Yes, you could open a window with a larger than needed AC to reduce the temperature. Depending on the climate that would work to control temperature but maybe not humidity. It seems that using the right size AC is a better solution. A 5000 btu window unit may be a little larger than needed for efficient moisture reduction but a 9000 or 13000 btu roof mount would be much further from optimal.

I am not an expert, so feel free to correct me if I say something incorrectly. When the temperature of the air is lowered with all other things being equal, the % humidity increases. If I am interpreting the charts that I Googled correctly, using the example of 115 F at 7% humidity, if the air temperature is lowered to 70 F without removing any water, the humidity increases to 28%. That is still low humidity.

If the temperature outside is 95 F and 55% humidity, the humidity will reach 100% when the temperature is lowered to 76F. This shows that having an AC unit that cycles long enough to effectively remove water is important in a humid climate but may not be as important in a dry climate.

A larger AC unit still costs more to buy and to run, weighs more and would require a larger generator to run without a hookup. It is the rooftop air conditioner power requirement that causes some people to get a 3000w vs a 2000w generator resulting in even more weight and expense.

Andy
Hi Andy,

Not argueing with what you read or what you wrote, because that is one of those phenomenon that goes way over my head. No doubt the folks that wrote your read have done controlled experiments and their data is correct.

I'm thinking of humidity being the amount of moisture suspended in the air. Layman logic dictates that in an enclosed environment , the humidity level would remain the same until the temperture was lowered enough that the water vapor began to liquify. At that time the moisture is still present, but not necessarily suspended in the air. So humidity would drop in the cooler environment. On the flip side, when the liquid "water" is heated and turns to vapor, the humidity increases.

During a summer rain, the air cools. After the rain, the sun heats things and the liquid on the ground turns into a vapor and humity seems to rise.

However, my thinking is subject to be wrong, Big Time!

Agree that the correct size AC would likely be more benneficial in removing excess moisture. Generators or Generator/inverters in the 2K watt range can be lifted and handled fairly easily and can run a 5K-6K BTU AC with little noise and little fuel.
Honda and Yamaha both make excellent ones. Roof top units generally require a larger, thristier Generator.

I don't understand this from Fred. But, I would bet he is right! : That's the crux of the matter; at 115 F a 5000 Btu "Air Conditioner" is incapable of lowering temperature; it ceases to have any effect. It just blows HOT until the outside temperature drops below 95. Then it will start to cool again.

Thanks,
Kip
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Old 11-28-2010, 07:40 AM   #31
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Originally Posted by Matt in SV View Post
couldn't you crack a window if your AC is too powerful?

Kip, no insulation in the U-hauls unless you add it yourself. There us some access in some spots through bins and cabinets.


Thanks Matt!

Apparently they depend on the relatively dead air space between the walls for insulation. Seems to work well, judging from Cindy's comments!
Kip
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Old 11-28-2010, 08:14 AM   #32
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That's the crux of the matter; at 115 F a 5000 Btu "Air Conditioner" is incapable of lowering temperature; it ceases to have any effect. It just blows HOT until the outside temperature drops below 95. Then it will start to cool again.
A 5000 BTU AC is certainly capable of lowering temperature at 115 F. It may not lower the temperature as much as you would like. The heat coming in through the walls may be larger than the 5000 btu capacity in a uninsulated trailer so the overall temperature in the trailer may not go down, but the air temperature coming out of the AC has to be lower than the air temperature going into the AC unless the air conditioner is not working.

115F with very dry air is an extreme condition. A condition that most of North America does not experience. A far more common condition is heat in the 80's or 90's with plenty of humidity. One size AC does not fit all conditions. For most of the country 5000 btu is a better size than 13000 btu for a small trailer because it provides plenty of cooling and is better at controlling humidity.
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Old 11-28-2010, 08:26 AM   #33
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Originally Posted by Kip in Ga. View Post

I'm thinking of humidity being the amount of moisture suspended in the air. Layman logic dictates that in an enclosed environment , the humidity level would remain the same until the temperture was lowered enough that the water vapor began to liquify. At that time the moisture is still present, but not necessarily suspended in the air. So humidity would drop in the cooler environment. On the flip side, when the liquid "water" is heated and turns to vapor, the humidity increases.
The % humidity in the air refers to how much moisture as a percentage of the maximum amount that the air can suspend. The warmer the air is the more water it is capable of suspending. When the air temperature goes down without removing any water, the capability of the air to hold water goes down. Because the full saturation value is lower, the same amount of water in the air is a bigger percentage of the new maximum.
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Old 11-28-2010, 10:40 AM   #34
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Kip,

Just curious - are you looking at that Uhaul on ebay? If so, and you buy it, there are lots of posts on here, compliments of Bridgette and others, that outline repairs to the windows. That one looks like it has or has had leaks (Ours leaks again too #@*!).

CTs (the smaller Uhauls) do not have the strength to hold an air conditioner on the top although some people have put them there and others have added braces and then put them on top. The VTs were made for one on top.

(Just mentioning this after reading your signature line and the questions on the ebay ad.)

CindyL
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Old 11-28-2010, 07:29 PM   #35
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With regards to the value of the air between the double hulls (as far as insulation value) it does not add as much as you'd think. Using a small heater, there is no problem with keeping the UHaul warm, but the lack of any insulation between the warm inside and the colder outside air means that the temperature drops much quicker than a trailer with ratfur (which is lightly insulated). I camp with a friend that has a Scamp and her trailer will maintain a comfortable temp much longer than my UH. But I love the smooth walls much, much more than the fuzzy. Wish there was an easy way to install foam between the hulls - it would make the trailer pretty much PERFECT in my opinion!
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Old 11-28-2010, 08:43 PM   #36
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I have a UHaul 13CT and there isn't a lot of space to spare. The PO took out the original furnace and left a vacant hole for me to look at. I put a portable room heat pump (heat and air capabilities) in that spot. The exhaust/air input on the heat pump conects to the original exhaust port of the camper. The unit is out of sight, out of mind when not in use. The only real down side is that I must leave open the closet door to enjoy air or heat. I may put in a front vent so that i won't even have to do that. It can easily be taken out and used in the house if need be.
You mention your portable heat pump. Would that be one of those "Cool Cat" brand units? Or something else? I've been wondering if a Cool Cat (or your unit, if different) would be appreciably quieter when operating. It's hard for me to sleep with a noisy AC unit running that close to me, but I also can't sleep if I'm too hot!
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Old 11-29-2010, 05:40 AM   #37
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Originally Posted by CindyL View Post
Kip,

Just curious - are you looking at that Uhaul on ebay? If so, and you buy it, there are lots of posts on here, compliments of Bridgette and others, that outline repairs to the windows. That one looks like it has or has had leaks (Ours leaks again too #@*!).

CTs (the smaller Uhauls) do not have the strength to hold an air conditioner on the top although some people have put them there and others have added braces and then put them on top. The VTs were made for one on top.

(Just mentioning this after reading your signature line and the questions on the ebay ad.)

CindyL
Cindy,

Not aware of the Ebay U-Haul ad until now.
Gotta go look!

Thanks'
Kip
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Old 11-29-2010, 06:05 AM   #38
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Quote:
Originally Posted by Pam Garlow View Post
With regards to the value of the air between the double hulls (as far as insulation value) it does not add as much as you'd think. Using a small heater, there is no problem with keeping the UHaul warm, but the lack of any insulation between the warm inside and the colder outside air means that the temperature drops much quicker than a trailer with ratfur (which is lightly insulated). I camp with a friend that has a Scamp and her trailer will maintain a comfortable temp much longer than my UH. But I love the smooth walls much, much more than the fuzzy. Wish there was an easy way to install foam between the hulls - it would make the trailer pretty much PERFECT in my opinion!
Pam,

From the info gathered here, and some pictures that were posted, it appears that the Scamps have "Reflextic" glued on the inside walls and "Ratfur" glued to that. Checked out Reflextic at Home Depot and found it to be basically thin (1/4") bubble wrap with a layer of reflective foil on both sides. Apparently it works well.

Do the U-haul walls collect moisture when it is cold outside and warm inside?

Kip
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Old 11-29-2010, 07:08 AM   #39
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Here is the ebay one with 7 hours left:

U-Haul Fiberglass travel trailer vintage scamp casita - eBay (item 190473011618 end time Nov-29-10 12:13:07 PST)


Here is another one that is over on uhaulcamper.com. I don't think that you would be able to see it though without registering:

yep, gata do it,( medical and physical problems) so its for sale and as soon as i fix the leak on the fantastic fan on top and re glue the carpet back up a sign is going on it.
here is my link to it if you have not seen it before
The visual story of the "Cracked Egg"

The latter owner is in Texas, I believe, and uses a window air conditioner in his window but also has a fantastic fan.

CindyL
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Old 11-30-2010, 03:36 AM   #40
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Quote:
Originally Posted by Andy B View Post
The % humidity in the air refers to how much moisture as a percentage of the maximum amount that the air can suspend. The warmer the air is the more water it is capable of suspending. When the air temperature goes down without removing any water, the capability of the air to hold water goes down. Because the full saturation value is lower, the same amount of water in the air is a bigger percentage of the new maximum.
Andy,
Just to confuse myself even further, here are a couple of interesting
links. Looks like you were correct and I wasn't!
Kip

What is dewpoint temperature?

Temperature, Dewpoint, and Relative Humidity Calculator
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Old 11-30-2010, 03:38 AM   #41
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Quote:
Originally Posted by CindyL View Post
Here is the ebay one with 7 hours left:

U-Haul Fiberglass travel trailer vintage scamp casita - eBay (item 190473011618 end time Nov-29-10 12:13:07 PST)


Here is another one that is over on uhaulcamper.com. I don't think that you would be able to see it though without registering:

yep, gata do it,( medical and physical problems) so its for sale and as soon as i fix the leak on the fantastic fan on top and re glue the carpet back up a sign is going on it.
here is my link to it if you have not seen it before
The visual story of the "Cracked Egg"

The latter owner is in Texas, I believe, and uses a window air conditioner in his window but also has a fantastic fan.

CindyL
Thanks Cindy !
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Old 11-30-2010, 05:20 AM   #42
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Kip,

If you are wanting to contact the Texas owner and cannot get in touch with him through uhaulcamper, you can pm me.


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