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

[Minivanmotoman]

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. 

 

[Jmel]

It is inefficient to go from 12v to 110v, so the actual amount of usage the fan will incur will be more than 45w.

That being said, if it works for you and you have the battery power for it ---

Personally, I bought a manual vent for the roof of my van for about 40 dollars, and a 200mm pc case fan for about 20, and called it a day.

 

[deadwood]

You can also just buy a quality 12v fan. No reason to convert form 110v power. I have one that I couldn't live without. I have a Maxair fan in the roof but when it's warm I need more air moving.

I think people really like the roof fan because it works great to exhaust the warmer air in the van up and out. Most people don't use it to blow air into the van. With a window cracked open and the fan on it creates a nice breeze through the van.

But you are right. If you had windows open then a 12v fan moving air around will work great. And if you are camped out with nobody near you even better. But if you are doing any urban camping in cities where privacy is desired then a roof fan is hard to beat.

As with everything in van life there are always compromises. But I don't think I'll ever regret the roof vent/fan. I use it every single day. Even when not in the van I'll leave it open and running on low so that the van is much cooler when I come back to it.

 

[John61CT]

Because personal comfort is just one issue.

Sure opening all the windows is fine in moderate weather, but fine CFM control over flow of outside air exchange is better in more extreme conditions

And is what's required to prevent condensation: smelly musty damp, rusting, maybe mold.

 

[Trebor English]

So why is a uber expensive DC vent + expensive install required?

My MaxxAir exhaust fan is about a foot away from being directly over my propane 2 burner stove.  If I am cooking inside the whole back gets unpleasantly hot and humid.  The fan on low keeps it from getting hot.  After the sun goes down and it cools off outside the exhausting out the back draws cooler air in through the front windows.  This actually changes the temperature and humidity.

By the way, I installed it myself so it wasn't expensive.

 

[jacks18614]

45 watts at line voltage is 4AH at 12vdc. A CF-18 Dometic 12vdc draws 4ah 12vdc but runs only 6-8 mins/hr for a total per hour draw of about .5ah.

 

[Spaceman Spiff]

jacks18614 beat me to it.  IMO 4 amps is not 'low power drain', running it for 8 hours will consume as much energy as my refrigerator in 24 hours on a hot day.  By comparison my MaxxFan consumes about 1 amp where I usually run it and 0.2 amps on low.  I also have a O2Cool fan ($16 on clearance at WM) that consumes ~ 0.5 amps at 12 volts or runs on 8 D cells.

An exhaust fan serves a different purpose than a portable fan: to remove hot air up by the ceiling so cooler air can replace it.  By strategically opening windows I can have a nice breeze where I want it, usually at the head of the bed.  The MaxxFan has the added advantage that I can leave it open during rainstorms.

 

[user 37446]

look on Amazon for usb powered personal fans, or 12v ciggie plug fans as well.  If you are a careful comparer, you'll find a couple of usb fans that get pretty good reviews. 

 [size=small]Desk Personal Fan USB Table Portable Fan(2 Speed, 4 Inch,Quietness)(Black)

[size=x-small]4.5 out of 5 starshttps://www.amazon.com/gp/registry/wishlist/2SV1XPZTT6I7V/ref=nav_wishlist_lists_1#(147)
$12.99$12.99
In Stock.Offered by DAOTS.[/size]
Add comment, quantity & priority
Item addedNovember 5, 2017
Add to Cart
MoveWish ListMove
Delete[/size]

---

[size=small]OPOLAR 9 Inch Metal Desk Fan, Enhanced Airflow, Lower Noise, USB Powered ONLY, Two Speeds, Perfect Personal Cooling Fan for Home Office Table

[size=x-small]4.5 out of 5 starshttps://www.amazon.com/gp/registry/wishlist/2SV1XPZTT6I7V/ref=nav_wishlist_lists_1#(179)[/size][/size]

 

[John61CT]

Just know that fans blowing inside the living space are not required.

They can only **supplement** a fan that exchanges air with the outside.

 

[highdesertranger]

because hot air rises. and all the other reasons people have mentioned. highdesertranger

 

[akrvbob]

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.

 

[jonsun]

12v fans are horrendous interference emitters. I'm 100% 120v now.

 

[Minivanmotoman]

As I see it, boils down to air movement, cost and convenience. Or $/cfm. Air flow equates to blade size, rpm and location/ direction.
A Maxxair creates more air flow than a comparable fan at 10x -20x the cost? More convenient of course.
Vent do the job?
Air flow/ vent reduce temperature? In an enclosed greenhouse van in the sun? yes. But not lower than outside temp. But if cfm directed upon the body, can maintain and enhance cooling. Maxxair do that?
Roof vent better to exhaust air than open windows?
Maxxair quieter and more stealthy? Necessary?
Possibly, situational, dependent upon many factors. Would think marginally at best.
There was a thread on here where the poor woman was overloaded with ALL the things she thinks she has to buy, install, setup to get properly setup and necessary. Using the KISS principal, can reduce a lot of stress for many.
Keeping in mind that shade, opening a window, cross flow, wind are relatively simple, easy and cheap.

There are many on here looking for guidance, alternatives.
Opinions based upon bias perspective, group think or presumptions doesn't necessarily help reflect better options.
This is cheap RV living after all.

 

[GotSmart]

On my first build, I found a fantastic fan shell and installed it. Instantly the ambient temperature inside went from 135 to 80, the outside temperature simply by venting from the high point in the van. No more hot box van. Once I put in a working fan, even better. 

I disagree with Bob in that I think venting is more important than moveing hot air around.

 

[Minivanmotoman]

Almost sure, Bob meant moving air in conjunction with opening a vent, window or door. Doesn't have to be only one or the other.

 

[highdesertranger]

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

 

[John61CT]

For effective air exchange you need openings for both intake and exhaust.

Effective placement is at opposite ends of the living space, one or more up or near the top, other(s) down the bottom.

Whether it is better to push the stale air out or pull the fresh air in will depend on several changing variables, so you want reversable direction as well as variable flow rate.

If the incoming flow can be directed across your body, bare skin or wet t-shirt, then no "inside only" fans are needed.

Obviously all the above is just an ideal, perhaps the effort required not realistic for most and unnecessary in moderate weather conditions, not worth the trouble for those following the 70's.

So, in some cases just opening windows and a USB fan clipped to a shelf is "good enough" or all that's possible.

Your van your choice.

 

[Minivanmotoman]

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

^^^
True, but why limit yourself to the vent for argument's sake?
Maxxair vent= 14"*14" or <1 sq.ft. with vent cover restriction. Double it with two vents < 2 sq.ft. $200-$500+.

Open van side door= ~48"*48" or > 16 sq.ft.
Double it with two side door open or > 32 sq.ft. Priceless.
Or any window for that matter >.
They are both pretty close to the highest point/roof to be just as most effective.

Air flow through larger surface area of opening, greater cooling. Linear increase?
Thermal dynamics.
Add white roof coating for more passive cooling.
Park in the shade for even more.

 

[jacks18614]

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.

 

[jimindenver]

I had a O2 12v fan. I gave it away and you can see why in the video made about it. The person puts it up to her face and said that it was a nice little breeze. What I replaced it with is a 20 inch box fan that I can feel from a distance. Once you have the excess solar and battery you will find the variety of what you can use to be greatly expanded.