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Discussion Starter #1
I live in central Texas and today’s high temp was 103 with a heat index of 109. My brand-new PM 2500 159 Hi Top is sitting in the drive and the inside was like an oven. To keep costs down my hope / dream was just use a roof vent fan such as the Maxxair 7000K for draw through air circulation. But after trying to work in the van today I am thinking that perhaps an A/C such as the Coleman Mach 8 might be wise also. Granted I have not insulated the van yet as I am literally just getting started on my conversion.
For those who live, travel, spend time it hot locations. Will insulation and a vent fan alone be enough to make the van livable or will I need A/C also? If you have both a vent fan and A/C where did you locate them on the roof and why?
 

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Welcome. Definitely insulate and install a vent. Then see if you still
need AC for your use. AC takes some power so running it on 12VDC
is possible but expensive. Most practical is to use it on shore power only.
Coleman mach 8 9000 btu is enough for a well insulated van. We have one
on our Sprinter.

Insulation is essential. We recommend and sell Thinsulate(TM). It is acoustic
and thermal insulation; safe and installs easily. You wont need Dynamat or
anything else for noise.

All the best
Hein
DIYvan.com
 

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When you are working on it in the heat, wrap the OUTSIDE 360° with Tyvek. Either from Lowes or HD with logos, or you can get plain white from Amazon for $4/yard. I attached with magnets, but tape will also work. Make an awning for the side door with a tarp attached to the nubbins on top. With Hein's Thinsulate in the ceiling, this will at least keep your interior temperature close to ambient and pretty much avoid the "oven" effect. I tested and measured this method near Death Valley last year.

One measurement I remember in particular, the sun was on the driver's window. I draped the Tyvek to cover half the window. Measuring the temperature of the glass from the inside with a laser thermometer, the exposed glass was 135° while the covered glass was 102°, which was about ambient.
 

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The insulation will help but it will still be crazy hot in there. The West and maybe Northeast can get away with no AC. No possible way to go without it in the humid South. A major function of an AC is removing the humidity from the air. That is possibly more important that cooling the air.

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Discussion Starter #6
Excellent suggestion / idea! Thank you MsNomer, I've got some Tyvek in the work shop I will get it out an see what kind of temp shelter I can rig with it.
 

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Discussion Starter #8
The the Web is a wonderful resource when looking for ideas or information on a project. Although sometimes you are left scratching your head when you find conflicting information. Specifically I am talking about Vent Fan and A/C placement on the roof. I have seen convincing arguments for differing placements ie: Fan to the rear of the roof and A/C forward or the exact opposite, with varying reasons being touted. I even found one advocating for the A/C to be located in the middle of the roof. I want to use my roof real estate wisely as my goal is to: A) Do it right the first time! B) Get the most efficient utilization of the vent fan and A/C as possible. C) Leave as much real estate open as possible for solar panels. The old adage of "measure twice and cut once" really applies here.
Many of you have already been down the road that I am now starting on. I am interested in and would be grateful to hear why you located your vent fans and A/C units where you did and also how it has worked out for you over time. Then there is the hypothetical question - If you had to do it all over again would you change things around and why?
 

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I live in central Texas and today’s high temp was 103 with a heat index of 109. My brand-new PM 2500 159 Hi Top is sitting in the drive and the inside was like an oven. To keep costs down my hope / dream was just use a roof vent fan such as the Maxxair 7000K for draw through air circulation. But after trying to work in the van today I am thinking that perhaps an A/C such as the Coleman Mach 8 might be wise also. Granted I have not insulated the van yet as I am literally just getting started on my conversion.
For those who live, travel, spend time it hot locations. Will insulation and a vent fan alone be enough to make the van livable or will I need A/C also? If you have both a vent fan and A/C where did you locate them on the roof and why?
I agree with Josh. Insulation only delays getting hot.

When it's 103 F in shade, you can move all the air you want with a fan, and without A/C it's not going to be very comfortable. When cooling media is 103 F, it's hard to get below that temperature unless it's dry enough for evaporative cooling to work (a swamp cooler), and those don't work adequately in humid and hot conditions.

My only suggestion is to also evaluate the 11,000 BTU/hr Power Saver in addition to the 9,200 BTU/hr mentioned above. It has greater capacity and specs indicate it uses less power (in case you want to run off generator in future).
 

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Ours is insulated and we have a roof fan located near the front.

When we are in the van it is either moving and we have the van AC on or we are sleeping at night and its generally under 80F and the roof fan and another fan blowing on us keep us cool enough.

Since you are in Texas, your summer nights may not get as cool as in Montana.

If you are planning on hanging out in your van during the day in the sun with the engine off, I would think you would want AC.
 

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Hi,
The Coleman Mach 3 PS (Power Save) seems like an interesting one. It produces 13.5K BTU/hr cooling on at 1075 watts -- EER about 12.6.
http://www.airxcel.com/coleman-mach/products/air-conditioners/medium-profile

The Mach 8 cub produces 9.2K BTU/hr at 1270 watts -- EER about 7.2.

Apparently it takes less power to run the Mach 3 Power Save at 13,500 BTU than it does the Cub at 9,200 BTU.

It seems like the Mach 3 Power Save model would produce the same amount of cooling on about 40% less energy than the Cub.

Its kind of a high capacity unit for a van conversion, and not sure how well it would handle a cooling load that is quite a bit lower than its capacity??
Its also taller than the cub, so some aero drag penalty.

But, the efficiecy is impressive -- especially if you want to run off batteries.


Gary
 

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I spent two weeks in Utah recently where it was getting up to 100 everyday, but a dry heat. The nights were nice and some mornings required a jacket, but by mid-day it was too hot to be inside. I have two ceiling fans but no roof mounted A/C. The fans were of very little if any benefit towards cooling things off inside, very little noticeable air movement.

Most of the days I was inside somewhere studying but some days I would just go to the van for a couple hours, until the evening session started, and turn on the cab A/C. The cab A/C made the front part of the van nice but the bed all the way at the back was just ok. This was dry air. Humid air down in TX or the south would have been worse. I'm wired for an A/C and may install one but typically try to avoid hot areas in the middle of summer unless I'm driving across them to get to the mountains. And I usually camp off grid so an A/C wouldn't be usable unless I was able to run it from the battery bank and panels.
 

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Ours is insulated and we have a roof fan located near the front.

When we are in the van it is either moving and we have the van AC on or we are sleeping at night and its generally under 80F and the roof fan and another fan blowing on us keep us cool enough.

Since you are in Texas, your summer nights may not get as cool as in Montana.

If you are planning on hanging out in your van during the day in the sun with the engine off, I would think you would want AC.
I take it from your message you live in Montana?

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I spent two weeks in Utah recently where it was getting up to 100 everyday, but a dry heat. The nights were nice and some mornings required a jacket, but by mid-day it was too hot to be inside. I have two ceiling fans but no roof mounted A/C. The fans were of very little if any benefit towards cooling things off inside, very little noticeable air movement.

Most of the days I was inside somewhere studying but some days I would just go to the van for a couple hours, until the evening session started, and turn on the cab A/C. The cab A/C made the front part of the van nice but the bed all the way at the back was just ok. This was dry air. Humid air down in TX or the south would have been worse. I'm wired for an A/C and may install one but typically try to avoid hot areas in the middle of summer unless I'm driving across them to get to the mountains. And I usually camp off grid so an A/C wouldn't be usable unless I was able to run it from the battery bank and panels.
Here in Mississippi when I walk out at 6am is hot and sticky. I rode 13.5 miles on my mountain bike at 6:15am last week and it was terrible. Humidity was suppressing. So thick. Definitely not going to want a jacket in the morning. The last couple of days we've had lower humidity and it's been nice. I've really got to get out of Mississippi

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Discussion Starter #16
Hi,
The Coleman Mach 3 PS (Power Save) seems like an interesting one. It produces 13.5K BTU/hr cooling on at 1075 watts -- EER about 12.6.
http://www.airxcel.com/coleman-mach/products/air-conditioners/medium-profile

The Mach 8 cub produces 9.2K BTU/hr at 1270 watts -- EER about 7.2.

Apparently it takes less power to run the Mach 3 Power Save at 13,500 BTU than it does the Cub at 9,200 BTU.

It seems like the Mach 3 Power Save model would produce the same amount of cooling on about 40% less energy than the Cub.

Its kind of a high capacity unit for a van conversion, and not sure how well it would handle a cooling load that is quite a bit lower than its capacity??
Its also taller than the cub, so some aero drag penalty.

But, the efficiecy is impressive -- especially if you want to run off batteries.


Gary
Great info - 40% less power consumption for the Mach 3 is pretty impressive. You mention the aero drag and I am wondering if the penalty would make enough difference to really worry about. Thanks Gary - this is definitely worth digging into and doing more research.
 

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Regarding what Gary said comparing PS 3 & Mach 8 Cub. I wanted to be able to use any 15A circuit. Specs indicate get the PS 3; however, I chose the Cub because it is lower, 8.25" vs 13.8". Not sure it was best selection. The 9.2K btu Cub is marginal above 95F in full sun. If you really need AC I just don't think 13.5K btu would be too much capacity. These things are LOUD on High. It's mostly the fan not the compressor. I want to experiment reducing the air vent vanes.
 
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Discussion Starter #18
I spent two weeks in Utah recently where it was getting up to 100 everyday, but a dry heat. The nights were nice and some mornings required a jacket, but by mid-day it was too hot to be inside. I have two ceiling fans but no roof mounted A/C. The fans were of very little if any benefit towards cooling things off inside, very little noticeable air movement.

Most of the days I was inside somewhere studying but some days I would just go to the van for a couple hours, until the evening session started, and turn on the cab A/C. The cab A/C made the front part of the van nice but the bed all the way at the back was just ok. This was dry air. Humid air down in TX or the south would have been worse. I'm wired for an A/C and may install one but typically try to avoid hot areas in the middle of summer unless I'm driving across them to get to the mountains. And I usually camp off grid so an A/C wouldn't be usable unless I was able to run it from the battery bank and panels.
Thanks El Guapo for sharing - this is exactly the kind of real world experience that I was hoping to get. I ordered a MaxxAir 7000k fan this evening and will install it when it arrives. As already suggested my intention is to insulate well, install the fan and then see how how it feels. I like my comfort so I am fairly certain that an A/C will be on my list of things to do. I am still wondering about fan & location my gut instinct is to mount the fan aft so that I can draw air through the from the front windows. I bought a pair of air vent window inserts from EuroCampers.com. They are made of louvered aluminum and have a metal screen mesh on the inside for bug protection. They seem well made and are held in place by raising the window into a slot in the bottom. With fan the located aft the A/C will have to go forward it should be able to cool all the way to the back and also draw out some of the humid air. Does anyone have an opinion / experience with fan and A/C location?
 

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I put a maxxair 7000 in at the rearmost ceiling section, as close to that sections forward ceiling spar as possible - and am disappointed with the fan-off but in-motion air flow, tobacco smoke haze sticks around longer than I'd like.

I was hoping there would something like a vacuum draw from the square back of the van but it seems to be dead air space, not much slipstream across it to pull huge amounts of interior air out passively - yet that reduces wind noise so it's really quiet. Also I pulled the factory gnat-proof screen off the inside to help it passive smokestack vent better standing still or driving slow, I've still not enabled the house battery.

If I were to do it again I think I'd jump to the second or third ceiling bay from the back, with it in the rearmost location I can't swap it out for an A/C unit since there isn't 26-30 inches from front of roof cut for A/C support, and I've still not made my mind up about rooftop A/C but prewired at the factory cutout just behind the cab.
 

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I have no personal experience but AC in the center for and aft is often recommended by the AC manufacturers.

Here is a quote from Coleman for the Mach-8

"Vans – location should be in the center of the roof (side to side – front to back)."
 
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