$7 120v AC personal fan vs $200 MaxxAir DC vent

[user 37446]

A vent on the roof is critically important, I wouldn't be without one.

But, I agree with you that portable fans inside are as important, or more important than a fan in the roof.

A portable fan can be aimed to blow in or out at the roof vent, and another one can be pointed at the open door or window, pushing more air in or out. A third one can be very close to you, cooling you off.

The ideal is both, but if you can only do one, portables are more important.

That's well said, if you have the option install a roof vent. My soon to be bought minivan isn't going to get butchered (resale) so for me it's opening the wing vents and using the 2 usb powered fans. Course I selected a model with a sunroof so I have a non-powered roof vent of a sort - just doesn't work well in the rain...

 

[Minivanmotoman]

If your $7 45 watt fan draws as much energy in one hour as EIGHT 18L compressor refrigerators how is that cost effective when you need a $1000 solar system to operate that $7 fan?

My $15 12 volt single speed clamp on auto fan on the fixed mode uses .2ah as per the charge controller when the fan is the only load on the system.

If a fan (not mine, didn't invent it, let's not get personal, )
takes that much power, agreed. Is that math correct?
Heck, sounds like we should have 8 fridges cooling the whole van interior. Will need my parka.

 

[bullfrog]

There is another alternative which I use. Since I already use Ryobi 18 volt batteries with a 12 volt charger for tools and lights they have a bucket / floor fan which I use in conjunction with a roof vent and floor vents to circulate heat and prevent condensation which is totally portable and can even be used with a mister attachment.

 

[akrvbob]

the most effective vent is the highest point of the van.  physics.  highdesertranger

This is only true if is there is hot versus cold air in the van. I don't think there is. I think it's all the same. If it's all the same temperature, why does it rise? I don't think it does.

The most important thing is simply square inches of opening and that 14 x 14 on the roof is pathetic. Open the back door and the side door, put a portable fan blowing in from one and out the other, with you in the middle--NOW YOU'RE MOVING SOME AIR!!  Put two of them in both places and there is just no comparison.

 

[John61CT]

Of course in nice warm weather, but that doesn't work too well in an all-day sideways rainstorm though.

Much less a blizzard living in a ski area carpark.

Or on a busy street downtown.

 

[tx2sturgis]

With my Fantastic roof fan and a decent sized computer fan blowing over me in the bunk, I can sleep comfortably when the outside temps after dark are up to about 85 degrees when I turn in. At that temperature I don't have any kind of blanket or sheet over me at all. Sometimes I spritz with a water spray bottle for extra cooling. 

75 to 80 is comfy, maybe with a very light blanket just for comfort, and the night normally cools down in most places I would ever spend the night, so after a few hours I might even get chilled and turn off the roof fan or pull up a heavier blanket. 

Below 70 outside and I dont need the roof fan at all, just leaving the lid popped open and my bedside fan and I'm good!

Below 60 or so and the vent lid is closed and I rarely use the bedside fan. 

Point is, the combination of the two means I rarely need night time A/C...the fans work very well as a pair. 

I need them both equally.

 

[Spaceman Spiff]

This is only true if is there is hot versus cold air in the van. I don't think there is. I think it's all the same. If it's all the same temperature, why does it rise? I don't think it does.

The most important thing is simply square inches of opening and that 14 x 14 on the roof is pathetic. Open the back door and the side door, put a portable fan blowing in from one and out the other, with you in the middle--NOW YOU'RE MOVING SOME AIR!!  Put two of them in both places and there is just no comparison.

There will always be a temperature gradient, the question is how big and that is very location specific.  A van sitting under a dense canopy will have a  negligible gradient.  A van sitting in the desert sun will have a significant gradient, so the air at the roof will be noticeably hotter.

You are correct that the size of the opening is the biggest variable in the amount of air you move, but that is not the only consideration.  Weather, insects, critters, personal safety, privacy, stealth all have to be considered.  And it is unfair to compare one fan in one opening with multiple fans in multiple openings.  I can open doors or windows and add fans to increase air flow, but I find I seldom need to add fans.  The roof vent fan will push out 920 cfm on high and by strategically opening windows or the door I can direct the air flow.

I can run my MaxxFan on medium, open a window by the head of the bed and have ~ 400 cfm of directed breeze costing 1.5 amps, and I can do it in a driving rain or in a swarm of mosquitoes or while using the bucket with lots of people around.  The volume of my camper is ~300 cu.ft. so I can change the air in the camper quickly to drive out those putrid beagle farts.

 

[bigskybob]

We use a box fan in the camper,but I can see where a ceiling vent with a fan would help a lot in a van.

 

[BinDerSmokDat]

I'm using a $270 maxx fan on my build for the following reasons...

10 speeds, so you don't have to have the roar of a B-17 buzzing all night when you just want a draft
Thermostat, so it has the ability to come on when needed to cool things when you aren't around
Self contained shroud so no rain worries
Designed to be sturdy enough to remain open at road speeds, providing passive venting while driving
Electric opening and remote so I can turn it on/off or close it without getting out of bed.
Maxxfan comes with mounting hardware and trim ring for a nice clean hassle-free installation inside and out.

Converting any 12V or 110V fan to do all that would take my time which is worth more than the difference in cost and not come out early as nice aesthetically.
When you consider that your fan is basically the heart of your HVAC system in any build, I don't see the benefits in skimping.

 

[Minivanmotoman]

All great valid points. Boils down to ones budget and value preferences. Like a/c, great to have but if you have budget restraints, make do basically. Do we consider a/c a necessity or a luxury today, in general, because it is so affordable? Depends upon ones situation, like everything else.

 

[musicman]

So why is a uber expensive DC vent + expensive install required?
Why can't I just use a small personal fan cooling across the torso with open windows, when required? At 45 Watts, low power drain, couple hours for a lot less money not do the job?
Just bought this 9", $7 clearance at Walmart, rated at 45 watts. 

It might do the job and it might not. It's sll about air flow. The more air flow  you have the better. A cheap one may not produce the same airflow as the maxfan

 

[frater secessus]

I had a O2 12v fan. I gave it away and you can see why in the video made about it.

One of these?

[img=150x150]https://sep.yimg.com/ay/yhst-115455...-indoor-outdoor-fan-with-adapter-18.png[/img]

I bought two, both at garage sales / thrifts.  They blow so hard I often wished there was a lower setting.