Ventilation Fan/Vent ThinkTank - Calling out SternWake!

[Lafnbug]

I'm interested to see what you Dwellers have done for ventilation in your rigs - particularly full size contractor vans with no or few opening windows... I have NONE.

I read elsewhere here about SternWake's set-up, where he claimed he had "MANY" fans, and had gone so far to customize his 12v refrigerator with more of the same for increased electrical efficiency. He said he was able to achieve, or perhaps dip below, ambient outside temperature. SternWake, can you shed some light on what you did here?

My questions are:
1. Fresh intake air - it seems like a vent UNDER the living space (through the floor) would be ideal, as it could be used in all weather conditions, not to mention no visible vents on the exterior of the vehicle. Has anyone done this?
2. Symbiotic fans - One blowing in, one blowing out, for faster, more efficient air change. Worthwhile? Old news?
3. Two exhaust fans, both blowing out - The intake would be through the dash vents (you would have to leave your dash control settings in the right position for this to work, at least on my vehicle). The nice thing about this is:
a. some vehicles have a dash air filter in place from the factory
b. if you left your controls on 'defrost', maybe it would help with 'Fogged Windshield Syndrome'
c. the downside is most contractor vans have a steel partition door that may not allow this method to work very well, not to mention that good airflow would mean your night-lights are visible as well.
4. 24/7 fans - other than being passive, why would this be desirable? SternWake...?
5. Thermostatically controlled fans - is there anything commercially available in 12v other than the Fantastics? I'm exploring possibilities other than roof mounted, as my project is not leaving much room up there...
6. I'm thinking about hiding an exhaust fan behind my rear license plate - the plate could be mounted on stand-offs to give it room to breathe.
7. Like others, I am looking to keep the amp draw low.
8. A/C units and generators are NOT an option on mine... looking to do the most with the least - aren't we all =:^)

Do's/Don'ts? Successes? SOURCES?

---

9. Has anyone rigged their dash blower to run from their house system? Just a thought...

 

[SternWake]

Oh boy, fans!

My name is SternWake, and I am a muffin fan addict.

I only have 5 running as I type this.

Haha.

This post will detail how my ventilation has evolved over the years, and it is not done yet, as they keep making better fans which move more air for less noise made and less electricity used. Skip to the end if your eyes cross as it will be a long post.

First thing I did, back in 2001 after purchasing my Conversion Van, was cut an ~ 4 inch hole in my fiberglass roof to accommodate a Nicro marine solar powered fan similar to this:

http://www.marinco.com/en/n20704s.

Hardly a massive air mover at ~1000 Cubic feet per hour but it was sooo much better than nothing, and at the time I did not spend much time inside, and the goal was to keep from baking the wax off my surfboards strapped to the ceiling, and it worked well at that.

For some reason, probably ignorance, this was all I had for the next 6 years

Late in 2007 I had acquired some 120MM computer muffin fans, but never really put them into use for regulating internal temps until the next year, when I started feeding my growing addiction to them

One day I rigged up one of the slower muffin fans onto the Nicro vent, even though it was bigger than the Nicrovent, and I opened my door on a hot day expecting the usual hot temps, and found they were not as hot as expected. At this point I had 130 watts of solar on the roof and battery depletion was not a concern

Later on I made a step down ring from 4.75"(120mm) to 4" so the fan could better push air out the ceiling. it worked well, but the fan I was using was rated at only 50 CFM. I had purchased another fan of a different design and noticed that it spun in the opposite direction to the fan blades of the other fan. When I put the second fan to feed the first fan, the airflow increased by a large margin, and the noise decreased as well.

I tried putting 2 fans whose blades spun the same direction inline, but the noise increased greatly and it did not really move much more air, if any more at all.

So at this stage I had the 3 fans exhausting air through the original Nicro Mushroom vent. I then removed the Nicro fan blade from the nicro vent and noise went down, air movement increased. I then would up removing the Nicad battery from the Nicro vent, cutting the wire to the motor from the battery, and covering the solar panel on the Nicro vent and now it turned into a passive mushroom vent.

Now I had good air flow with just the one fan blowing, if I needed more airflow, I plugged in the second fan. I will guess it was combined, about 90 CFM. Each fan was about 50 CFM blowing through the somewhat restrictive Nicro Mushroom vent.

The great thing about the Nicro was that it is rain proof, no worrying about opening or closing it.

But 100 CFM could surely be improved upon. So began the search. What I wanted was an Adjustable Speed fan, and what I found was the Silverstone FM121

http://www.amazon.com/SilverStone-FM121-Control-Designs-120X120X25mm/dp/B000BWEIFU

This one moved upto 110 CFM and had a dial for any speed desired between 37 and 110 CFM. When I put this on my ceiling and fed it with the feeder fan the airflow dwarfed the previous setup, and all was well, temporarily in muffin fan addict land.

My conversion Van has the sliding windows at the bottom of the conversion van windows, and opening one of these and cranking both fans would have a good airflow entering the van through that screened window. I also have a tight mesh Chicken wire over that window for security. Painted flat black.

So this was good, but not enough for an Addict, so I started trying other fans, but none really could compare to the Silverstone. They might cost less but they made more noise, consumed more juice and moved less air.

I still have that original Silverstone on my Ceiling, but I have replaced the impeller as i damaged it. I Almost Never turn it off. I put the speed control dial where I can easily reach it from bed, or from my 3rd chair.

Now the counter rotating Feeder fan is pretty key for when more airflow is needed. My original fan suffered some abuse but I jury rigged it, and it still works but it is retired. Here is the Updated version I replaced it with.

http://www.amazon.com/Arctic-Coolin...=1401070970&sr=1-9&keywords=Arctic+cooling+12

It had a unique vibration dispersion method and is very quiet. I have it held to the Silverstone with magnets which hold the provided screws together and holds the fans about 1/4 inch apart. These two fans together, I will estimate, move 150 CFM and draw .55 amps with the Silverstone on high. Turning the Arctic fan on when the silverstone is on high reduces the noise made by about 35%, and moves a LOT more air.

Here is one Pic I already have Uploaded with the two inline fans connected to my Step down ring. I have some Oak Tongs that basically hold the step down ring tight to my Ceiling. they were a temporary solution I made in 2008, which are still there.

Basically with a window open and these fans on High, i can cook pasta without fogging the windows. The fans have suffered no ill effects from exhausting cooking fumes/ gasses/ vapors and I have no fear of CO poisoning. I basically cook on a single burner propane stove placed on the floor directly below these fans and have done so exclusively for the last 7 years.
So this covers my roof exhaust fans. I have plans to further improve this area which I will go into later.

That Sliding conversion van window with the chicken wire, well that obviously needed fans too. I made a plywood shroud, painted it flat black, and stuck 3 120MM fans in it. Sadly the Silverstone fans do not prove to be very durable in this location. The moisture at night eats away the solder joints on the circuit boards, and the speed control seems to fail first.

Also the Silverstone's quality seems to have degraded as the replacements do not seem as well made to me. My current one is now ticking at slow speed. I have spare bearings and impellers for it, from old fans which failed, but have not swapped parts yet.

I think my Current Silverstone is ticking, because i apinted the White Impeller black, and through out the balance. previous fans I darkened with a Black Sharpie to make them less visible from the exterior.

The other two fans besides the SS in the photo above are among the first fans I bought. They move a lot of air but take .7 amps and make a lot of noise, and will slice the tip off of ones finger.

Basically the hotter it gets, the more I slide the window open and the more fan I turn on. I had all three on earlier today when Lying in bed reading. they are right next to my head.

At night in hotter weather, I will leave the non clicking SS fan running on low all night long, inches from my ears. I have a black curtain which redirects air away from me if I so choose. I really like the White noise factor and often will crank the fans just to drown out ambient noises from screaming kids or such.

So Those are my Primary Exhaust and Intake fans, and they, along with A white paint job, insulation over the windows keeping sunlight out, and radiated heat suppressed, can keep my interior cooler or no hotter than Ambient temps, at least until late afternoon when temps fall faster than the van can radiate the heat from itself.

Those are not my only Fans. I have a small 60MM fan in the passenger side footwell currently sucking air out. Generally I hang my Wetsuit in this area so this assists in drying it.

Now I also have fans to blow directly at me inside the Van. The Intake and exhaust fans make a slight breeze inside, but sometiumes one just needs a fan blowing right at ones body.

For this I still wanted variable speed so I Employed a variable voltage Ciggy plug adapter and mated it to a fan.

Vantech was the brand of the first Muffin Fan I acquired, and it was efficient and quiet but fragile.
Here is the Fan blowing air nearly silently at me at 3 volts as I type. At 12v it is a screaming Banchee can move a dense narrow column of air directly across my whole van. On a smooth table at 12v, it will claw its way across the table just from the airflow. I love it!!

http://www.amazon.com/Vantec-TD9238...401072634&sr=1-1&keywords=vantec+tornado+92mm

This was the first voltage controller I used. I modified the dial to turn with fngers.
http://www.amazon.com/12V-2A-DC-To-Converter/dp/B000KGIDOY/ref=pd_sxp_grid_i_1_2.

I no longer use this voltage controller as it burnt out after a few years. My fault as I did not tighten the internal heatsink properly with some loc-tite. Its same model replacement failed for no Discernable reason.

I went with this model instead and So far so Good. Much easier to switch voltages/speeds too, and without modification.
http://www.amazon.com/PowerLine-Universal-Adapter-Compatibility-90305/dp/B0042X8XOQ/ref=pd_cp_e_1

I mounted the Fan onto an 8" Adjustable Gooseneck, and mounted that to a 2 inch Metal Spring Clamp. So I can clamp in in dozens of different positions and plug it into several different ciggy plugs all around my Van and aim the airflow pretty much anywhere.

This Fan is awesome. I also have the 80MM version too. In fact I'd recommend the 80mm over the 92mm version as it moves nearly as much air but it is quieter and consumes less juice.

The following photo is not exactly representative as to how the fan is today. I got a new Clamp, painted it black, put rubber cushions on the business end and cleaned up the wiring. The 92mm version draws 1 amp on 12v and somthing like 0.08 amps at 3 volts. It will not run a 1.5 volts, and sometimes does not want to start at 3 volts. In general I use it most at 7.5 volts. Anything higher, and I must be super hot.

Currently I am not using the 80Mm version. But I have plans for it. and they include a longer gooseneck and a PWM motor speed controller. More on that in a bit.

Now My fridge is another matter. My first fridge A Norcold DE 0040, had a passive condenser. that portion which transfers heat sucked from the interior to the atmosphere. I built my cabinet to house this fridge so that this passive condenser was right below my middle conversion van sliding window. I attached a Louvered vent to the window exterior, painted it black to allow the heat to escape.

While the cabinet was still in the planning stages, i was running the fridge in my parents garage, in Florida in Summer time, and was Dismayed by how oftern the compressor was running. I did not think my yet to be installed 130 watt solar system would keep up, So I went a little overboard in my attempts to make the fridge more efficient. And you guessed it, more muffin fans. Actually this is where my Muffin fan Madness started.

I wound up adding insulation to the fridge body and adding a small fan to blow cool air onto the condenser from below and another fan to the interior, and when I finally got everything hooked up, I realized the 130 watts was more than enough and I likely did not need to go through the extra efforts, but I am glad I did.

That Norcold was a loud SOB though. It lasted about 5 years before it ran low on refrigerant and failed. I had made improvements to the insulation for both noise and temp insulative purposes but it still was loud enough to annoy me greatly.

I replaced it with A Vitrifrigo, and was glad I built the cabinet to accommodate the extra insulation as it made it easier to accommodate the slightly larger Vitrifrigo and it's extra insulation too.

The VF fridge comes with a Danfoss compressor and a Forced air condenser. Forced Air with a Muffin fan. A condenser designed to have A muffin fan attached to it. I was in heaven.

But I could not just have any Muffin Fan, and certainly VF did not research the most efficient quietest fan they could, surely they just slapped on whatever they could find for a good price in bulk right?

Anyway when the Fridge was delivered, first thing I did was take a Pic of the120mm fan so I could determine its specs. I found it was rated for about 72 CFM and had a .22 amp rating. and had a simple sleeve bearing. Intolerable!!!! ( to a muffin fan addict)

So I researched all I could, I found similar 'made in china' fridges with danfoss compressors came with 92 mm fans rated at 37 CFM.

I found This one Noctua Fan that moved ~53CFM, made less than half the Noise and consumed only 0.05amps!!

http://noctua.at/pdf/infosheets/noctua_nf_f12_focused_flow_web.pdf

Sold. At first I installed it in the same location as the provided fan, pulling air through the condenser, and it was not really much quieter in that location.
http://s557.photobucket.com/user/wrcsixeight/media/VFCoolingUnit_zpsfdc171ea.jpg.html?sort=3&o=171

For grins I placed it to push air through the condenser, and it got no Louder, So I relocated it to that side and made a cooling unit tunnel to force all the airflow through the condenser and shrouds so this single fan forced this air out my previously installed louvered vent in the conversion van window without any chance of being recycled through the condenser. My extra insulation allowed enough clearance to mount the fan in this orientation.

When All was said and done, the performance of the fridge increased. It got colder faster, used less electricity, made less noise, and expelled the heated air out the van body, all with the one fan which consumed les than half the electricity as the fan provided with the fridge.

And My Muffin fan Addiction felt justifiable.

The Fan provided with the fridge did not actually consume .22 amps, that was what it consumed when first spinning up. Running current was .12 amp, but still the Noctua consumed less than half of that.

What is neat is that this Noctua fan actually is capable of increasing the amount of air which passively gets pulled in through the open windows. On cooler nights when I do not power the intake fans by my head, and the fridge compressor kicks on, the slight breeze coming in through the window increases when the fridge runs. I love it.

One thing to note too is that I can close the window with the louvered vent behind the fridge. I took the electric motor and actuator from my conversion Van sofa bad and made it so it can open and close the window with a simple rocker switch. I do not want to drive in the rain or dusty roads with the window open. I also made another vent (closable) into my adjacent cabinet so that in winter time, the condenser warmed air is not expelled into the outside, but into the adjacent cabinet. In this cabinet, which houses my Electrical wall , I have another vent, with, you guessed it, another Muffin fan exhausting air from the compartment but into the passenger compartment, just behind the drivers seat.

This particular fan is the fan which came with my old Norcold Fridge. It was designed to be turned on when the back of the Norcold cooling unit exceeded 115F. I relocated it so that it ran 24/7 on that fridge. It is a 24v fan. It runs silently on 12.x volts. It has been running nearly continuously since late 2007.

So One might think with all these fans that A muffin fan addict might be satisfied. Hardly.

What I am working on now is a new intake system for my Sliding conversion van windows. Instead of Wood, I am using 1/4 inch plexiglass I've painted flat black. Instead of 3 120 MM fans I will use 2 120mm fans, and one 180mm fan. The plywood, even painted has been a bit susceptible to moisture.

http://www.amazon.com/SilverStone-p...ie=UTF8&qid=1401075875&sr=1-1&keywords=fm+181

Another Silverstone fan with a Speed controller. This fan on Slow speed moves 65 CFM for only 0.05 amps!! I cannot hear it on slow speed.

At full speed it draws over 1 amp and moves 150 + CFM.

I am a bit concerned how it will respond to the moisture it will have to deal with overnight, but I have to do it. No choice. I did paint it black too. I should have just spent the hour or 2 with a Sharpie as no doubt it is not balanced as good as it was before painting and might develop the tick that my Fm121 has.

Live and learn.

Now my Ceiling Exhaust is limited by the Silverstones max speed, and the resistance of the Nicro Mushroom vent. Well for grins one day I was seeing what the most powerful 120mm Fan is, and it turns out to be an abosolute Monster.

http://www.amazon.com/Delta-Electro...UTF8&qid=1401076510&sr=1-1&keywords=delta+fan

252 CFM and sounds like a Jet engine. No Speed control included, but I have my methods.

http://www.amazon.com/Converter-12V...m_sbs_e_4?ie=UTF8&refRID=04X9D8PM9FTJSDXGPVWR

This PWm controller can handle this fan , probably 2 of them if it had to.

This PWM controller operates at 25 khz. I have another one which is 15 khz and it make my tornado Fan whine annoyingly at slower speeds That one I use to Dim my LED night reading light. The 25khz PWm controller is inaudible to most humans ears, but will bother some pets no doubt.

I so fan have managed to refrain from purchasing the Delta Fan, but I don't know how much longer I can hold out.

Well to finish off this novel, most people with vans would be better off getting a Fantastik Fan and perhaps making a screened vent in the floor to allow cool air to replace what the fantastic fan sucks out the roof.

http://www.amazon.com/Fan-Tastic-Ve...&qid=1401077178&sr=8-1&keywords=fantastic+fan

 

[Reducto]

I have a fan-tastic fan and it's been great for 2+ years but I have a couple of issues:
1) It takes up valuable roof space and sticks out like a sore thumb
2) It lets sun in which can be in my eyes while I'm trying to sleep in

I'd love something that is either smaller like the round ones or something hidden on the back door somehow. They are hard to beat in terms of reliability and airflow, though, which is why they are so popular. If you do something in the back you'll need to incorporate ducting of some sort so people won't be able to see in through it.

I have a vent in my floor and it is great - my van had a rear heater and it is what was left over when I removed that. I glued some screen door material over it to keep the bugs out. Any sort of large hole with a screen over it will do - no need for a filter.

 

[Lafnbug]

SternWake, I had a feeling about you and The Fans! I personally owe you some beer for that magnum opus... You had me laughing out loud! I think we are all flailing in your wake!

Thank you so much for taking the time to post all that, AND provide links; you have inspired me to undertake some experimentation. I now have a full shopping cart at Amazon!

You, sir, are THE MAN.

---

Reducto, yes these are the reasons that I'm trying to find another way. I've been thinking about multiple fans and ductwork, with all intakes and exhaust UNDER the van. Quiet, clean, stealth. SternWake has convinced me that it is possible!

Once I put a tangible idea together, I will post some results!

 

[SternWake]

Nice when My efforts are appreciated.
And I'll have to take you up on that beer someday.

About my username, it is not really about how my path effects others, it is more about momentum and timing.

You know how in a boat with a planing hull there is a point at which the throttle must pass for the boat to get up onto a plane, and after that point, after planing speed is achieved, the throttle can be backed off tremendously yet the same speed maintained?

Well I've been a surfer for nearly 35 years now, and surfing is 95% paddling. I'm pretty heavy so it takes a good amount of effort to get the board moving at an acceptable paddle speed, but the same planing hull boat analogy applies too, slightly. I cannot get up on a plane when paddling back out or through incoming waves, but at some point I can achieve say perhaps 60% of my max paddling speed, then drop my paddling effort to say to 30%, and my own sternwake catches up to me and I can then accelerate with it and maintain that 65%+ speed at the 50% energy level by timing it right, and seeing all the little chops coming, and using my body weight to adjust the board to break through or pass over them and allow my Sternwake to again catch up and allow me to accelerate.

Sometimes I can get overexcited after a wave when paddling back out, and forget to wait for my Sternwake assist, and just keep going at 65%+ effort, then Chide myself for forgetting. Often times if there is little wind I can see my wake I created when riding the wave. Passing through that is amusing, especially when one weighs 230 Lbs and creates a fairly impressive wake during a hard turn.

Basically expending some effort, then waiting for it to catch up, allows me to go faster for less effort.

And when I turn toward shore and combine the floatation of my board with my Sternwake and with the incoming swell at the right time, well sometimes I do not even need to paddle to catch the wave, and few people who witness me do that will ever consider trying to catch the same wave as me and I can achieve uncontested domination of a surfbreak, sometimes. And that, on a good day, when it is crowded, is like no other feeling I've experienced. Those other surfers can flail in my Sternwake, but that's the only time that particular analogy of my username applies to or affects others, as far as I know anyway.

But it is always better to surf with just a few friends, or even a few strangers, as long as the vibe is good and we take turns and share the oceans bounty.

 

[Lafnbug]

A quite poetic and insightful treatise. You have a knack for articulating your breadth and depth of knowledge in a fun, easy-to-read manner. The all-important Good Vibe is there!

The beer WILL flow...

---

I'm sure I could punch a bunch of holes in the van, plug in some fans, and get acceptable results; I'd rather take a more calculated approach and learn from others if possible. How many fans, what size, where to place them.

Sometimes, I guess, you just have to say WTF and dive in! Maybe I'm missing out on all the fun =:^)

 

[akrvbob]

Sternwake, if you don't mind my asking, what part of the country are you in?
Bob

 

[SternWake]

I'm about 60 miles North of the Mexican border and a mile from the ocean. A pretty benign climate.

 

[GrayWhale]

Sternwake, so all of your fans are sucking air from inside the van and exhausting it out?

I tried your muffin fan idea and hooked up 3 of the 120mm side by side, to one of the conversion van sliding windows and they're not very effective. Of the three, 2 are sucking air from outside and 1 is pushing air out. http://www.newegg.com/Product/Produ...cm_re=120mm_fan_4_pack-_-35-103-052-_-Product

On the opposite sliding window, I have 2 of these USB fans pushing air in: http://www.bedbathandbeyond.com/sto...city-dual-powered-fan/3249300?Keyword=usb+fan

and they are blowing a lot more air in. Great post btw, thanks.

 

[SternWake]

My ceiling fans are exhaust fans.

My fans in the side windows are all intake fans, sucking outside air, into the Van to replace the air sucked out by my ceiling fans. The Shroud is Key, without the shroud a significant portion of the air is just being recycled through the window. With the shroud, the fans have no option but to suck cooler air from outside and push 100% of that air to the interior

Your link indicates each Muffin fan moves 47 CFM.
While My Silverstar fm121 is about 33 CFM on its slowest speed, it moves 110 CFM on high. So my 3 fans can simply move more air than yours. Also, some fans are much more effective than others, even if rated the same, depending on the restrictions in front of, or behind the fan. Static pressure readings as another way to measure a fan's effectiveness.

Like The Noctua Fan i linked to above, has a higher static pressure rating than a different fan that has a significantly higher CFM rating. This is part of the reason I believe my Noctua fan on My fridge condenser is Significantly more efficient than the Vitrifrigo provided fan.

My other fans in my side window currently are 72 CFM( the Vitrifrigo provided fan) and the other is, I estimate about 120 CFM So all three of them move a significant amount of air into the Van. In fact I can hook my bed sheets to my shroud and block the edges, and my lighter weight blankets will hover off my bed with all three fans on, and on high.

While the door seals and window seals cannot be considered perfect, air sucked out has to be replaced either passively or forcefully and air pushed in needs to be allowed to escape or forced out. So if you have a single 47 CFm fan pushing air in, you need a window open to allow 47 CFM of air to be pushed out elsewhere, or a fan of 47 CFM sucking air out. Better is the latter so the 2 fans work in tandem at replacing air within with air from out.

Does not have to be perfect, but shrouded intake and exhaust fans should be rated similarly and work in tandem, and the further away the fans are from each other in the van, the better too.

Fans next to each other in the same window should be blowing in the same direction, in or out, not both at once, otherwise effectiveness is reduced greatly. the goal is to replace the air within from cool air outside, not just recycle hot air within, and the shroud is key, so that it cannot recycle the air the fan just moved.

So if I had all my fans were exhausting fans out, and all my doors and windows were closed, the fans would not be able to exhaust much air at all, as they would lose the battle with atmospheric pressure. They would be fighting each other and not be effective, at all, except as noise makers consuming battery power.

 

[SoulRaven]

This was posted on another board by their resident Guru The_Camper_Van_Man.

<b>The_Camper_Van_Man Wrote:</b>

Here is what I did for a friends cargo van before he switched to a window van.

In the side step well, right behind the passengers seat, I installed a 4 inch PVC pipe running to the ceiling, topped by a double elbow which could rotate to basically send the air in any direction. The bottom of the PVC is screened to keep bugs/critters out. And a shut off valve is located at a comfortable reaching level.

In the very rear drivers side, is another 4 inch PVC pipe, with a single elbow at the top. At the bottom is a Tee in the vertical pipe. going back to the living area. Both the outs on the Tee'd end have shut off valves, with the one coming out under the van being screened. An exhaust fan is positioned in line just above the Tee.

You now have the ultimate in heat circulation and fresh air ventilation technology. For fresh air, you open the front, and the out in the back, keep the recirculator valve closed, and turn on the fan. With the double elbows up front you should be able to direct the fresh air breeze to where you want it.

In the winter, close both front and rear to outside valves, and open the Tee'd recirculater valve and turn on the fan to draw the heated air at the ceiling back down to floor level in the living area.

Since both pipes go to the ceiling, you will never lose heat in the winter, yet it will draw out the hottest air, replacing it with cooler air in the summer.

Sometimes it is better not to try to reinvent or over complicate simple yet tried & true technologies.

 

[GrayWhale]

Thanks very much for another thorough writeup. I knew I was doing something wrong. Didn't know that keeping it tight with a shroud was so important. I'm going to redo everything like you say including getting better fans.

So when you've got this one sliding window open with the fans running, you keep all other windows and doors shut in order to cause airflow towards the fan on the roof pushing it out right?

 

[SternWake]

Pretty much. I've got my Ceiling fans running near full blast now, and one fan running on the side window, but have the side barn door open too. Mostly for light, not heat.

But it is not even 70 degrees, and the ceiling fans are on high because I just made Coffee and forgot to turn it back down.

But in general I keep all other windows and doors closed, and the fans on high when it is hot out. Like if I go out surfing, everything is locked up, the van baking in the sun, my Sunshower on my dashboard warming and at least one of my 3 intake fans is running.

All my cargo door window can be opened, and I almost never do open them.

With my sun shower on the dash I do not put up my front window shades, but I do pull the curtain behind my front seats, so the front area bakes, but behind the curtain is basically the same temp as outside.

I consider the fan shroud in the back window to be a bit of security too. Somebody thief might notice the fan spinning, see the open window, but with the chicken wire and the fan shroud in place, it would take as much effort, or more, to break into that window than it would any other.

Also, Thieves can't be sure whether someone is inside or not. The fan running probably makes it more likely that someone is.

I'd highly recommend fans with variable speed. Two fans spinning at half speed use less electricity, make less noise and move more air than one fan spinning at full speed.

That 10 amp motor speed controller in my first post in this thread works well for this duty. As the fans that have built in speed controllers like the silverstone fm121 and fm181 are pricier, and susceptible to moisture and need be be thought of as having a limited lifespan.

But they are well designed fans. in general the fans with the more curved, scythe like blades are going to be better at their job.

I know Antec makes a fan that has 3 user selectable speeds, but I think the max CFM is only like 80, where as the fm121 is 110cfm.

Newegg and Amazon have a good selection and prices, but I like shopping/ researching at this site:

http://www.frozencpu.com/cat/l1/g36/Fans.html?id=VadTcmZB

 

[Lafnbug]

Thanks for the ideas gentlemen. I think I have enough to go on; I am currently researching insulation. Once I start the build process I will document the entire thing with photo's and commentary.

Speaking of which: How do I upload photo's to the forum?

 

[loess]

This week I removed the rear half of the headliner, seats, trim panels and carpet from my Toyota Previa in preparation for the insulation phase of my build and for installing the solar rig, but it's been quite warm outside and while I've been in there dismantling things and cleaning up the headliner residue I've been reminded of how rapidly the temperature rises in there without any A/C or air exchange. So I am glad to run across this thread and am thankful for you folks who are fanatical about your fans.

My van has an aftermarket moonroof that was installed by the previous owner, it measures 15" x 30" and can be manually tilted partially open and closed (but not fully retractable like a sunroof). I am thinking I could build a shroud and mount it up there with several fans, like SternWake's sliding conversion van window. Theoretically with the driver and passenger windows cracked that would help with the climate up front and can serve as an intake vent or exhaust vent for cooking (and heating in the winter). As for the rear living space, there are five windows total, three of which are quarter glass windows that only crack open a few inches (see pics below of the sliding door window as an example of this). Covering those windows with large foam inserts that I made to fit in the frames helps a bit, but even with all three windows open those little vents don't really do a thing to help lessen the sauna-like atmosphere. Perhaps they could be used with fans for air intake or for pushing air out but I'm not sure how that would work considering the odd shapes and angles when they are cracked open? Like you Lafnbug I'm hesitant to cut any new holes in the body of the vehicle without careful planning and research...will be interested to see what kind of solutions you come up with.

 

[Lafnbug]

I will hazard a guess or two here; however, I would defer to other more knowledgeable and experienced folks here!

Assumptions:
You have very limited solar/battery capacity
You wish to use this ventilation system in all weather conditions
You wish to maintain stealth

I would think that even though the quarter window openings are slim, they still seem to provide for a fair volume of air to pass through. Building two fan shroud mounts to fit any of these openings should be doable, and I would pick the two that were furthest apart for maximum air change. I would have one intake fan, and one exhaust, working together. As SternWake noted previously, it is both quieter AND more electrically efficient running two fans at 50% capacity vs one at full blast.

I think the trick here is to somehow have the fan(s) oriented inline with the window, rather than just blasting air straight at the glass. I would perhaps mount the exhaust fan near the window hinge and aim it straight at the center of the rear opening. Building a shroud for this could maybe be accomplished with some Lexan if you wanted to retain usable light through the window. I guess the real trick with this set-up would be access for opening the window! Two of these exhaust fans, one on each side in the very rear, using the sunroof as a passive intake MAY produce acceptable results. Obviously a symbiotic intake fan in the sunroof would help tremendously with air exchange.

For me, the real problem lies in wet weather. I don't know where you are geographically, so this may not be a huge issue. I have to face sudden, unannounced torrential downpours, so that is a HUGE design factor for me. If I need to leave the van, I want to have it passively vent without me being there. I plan on using thermostatic controls once I finalize my design. Rain is one reason I want to incorporate vents underneath my van. It just makes sense for me, as I don't have any windows to make use of.

Perhaps doing a mock-up with a fan or two and some cardboard will shed some light on the possibility of using your existing windows. Are there any aftermarket replacements for your van, something more like SternWake's windows? Just a thought...

 

[SternWake]

I bet you could do the shroud multiple fan thing in that moonroof. if you've got the headliner off, run some wiring up there to leave yourself some options. Make it 18awg or thicker wire just in case you become addicted to such fans and want to run some hideously powerful fans.

But if fan diameter is not limited, and it will not be in that moonroof, the larger the fan, the more air it can move for less noise, and if it has a speed control like the FM181 then you can dial it in for every temp you come across.

Also give thought to the shroud seal, and vibration/noise dampening.

Enough can't be said about the speed control, and a fan that can move lots of air on high speed.

Opening those side windows with a series of fans in that moonroof will do wonders.

I've limited my roof exhaust to the original 4 inch vent diameter, which pretty much requires the intake fans in the side window, but if I could exhaust significantly more air out the roof vent, I bet I could forgo the intake fans, as long as there was a passive source to replace the air that the exhaust fans removed. My inline fans do pretty good, for pushing hot air through a 4 inch vent, but are limited in how much air can actually be forced through that restriction.

One other thing I must mention is the possibility of airflow when driving causing the fans to move. Not an issue with fans with no speed control, But I had one Silverstone in my roof vent, but with the mushroom vent removed.

I had the fans speed controller on low, but did some highway driving, and the fan apparently spun so fast it ovewhelmed the speed controller, frying components on the circuit board.

I've had no issues with the Nicro mushroom vent in place and slow fan speeds.

There are passive roof vents that are more low profile than my Nicro vent, that are also rain proof, and the air/ wind over them, the more air drawn through them.

http://www.defender.com/category.jsp?path=-1|6880|2290139&id=2290143

Never forget the products designed for boats. Often they outclass the stuff designed for RV's.

 

[SoulRaven]

While I'm certainly in favor of good ventilation, by your description of the heat, it sounds like you need a good 12v A/C unit.

Simpler solutions often produce superior results.

 

[loess]

Assumptions:
You have very limited solar/battery capacity

I have a 230 watt Astronergy solar panel. Have yet to buy a battery (I have intentionally left it as the last component to purchase so as to buy one as "new" as possible). Am thinking a single AGM 225 amp-hour battery or two 6V golf cart AGMs. I have calculated it with a Kill-A-Watt and that should more than cover my daily power needs but I figure it's better to have plenty to spare just in case I discover that I need more as I adapt to life in the van.

You wish to use this ventilation system in all weather conditions
You wish to maintain stealth

Yes I'd like to have an option for fans/venting in wet weather. And stealth is indeed a fairly important priority for me. Though of course I am willing to concede there when it comes to the solar panel which is going to be visible no matter what.

But if fan diameter is not limited, and it will not be in that moonroof, the larger the fan, the more air it can move for less noise, and if it has a speed control like the FM181 then you can dial it in for every temp you come across.

Yep, plenty of room for a 250mm fan or even a bit larger in that opening. Will have to hunt around for a large fan that has a high CHM rating but is still fairly quiet and I like the idea of having speed control for versatility.

One other thing I must mention is the possibility of airflow when driving causing the fans to move. Not an issue with fans with no speed control, But I had one Silverstone in my roof vent, but with the mushroom vent removed.

Hmm, I don't yet know enough about how shrouds work but I wonder if I could build a shroud that would somehow clamp/screw/affix to the inner frame of the moonroof, but still let the moonroof glass tilt open and closed as it currently does. Then I could simply close it shut while driving. I would have to make a pattern and cut the shroud so that it that goes around the two hinges and lever, but figuring out how to maintain a good seal around the lever could be tricky since it swivels out and up when you open it.

Perhaps doing a mock-up with a fan or two and some cardboard will shed some light on the possibility of using your existing windows. Are there any aftermarket replacements for your van, something more like SternWake's windows? Just a thought...

That's a great idea, I will do some experimenting. As for aftermarket replacements I have not come across anything and paying a shop to have them modified would require more $ than I care to put into it at this time.

While I'm certainly in favor of good ventilation, by your description of the heat, it sounds like you need a good 12v A/C unit.

Could be, but certainly insulation, window/windshield coverings and these fans can't hurt. I actually don't know a whole lot about 12v A/C options, will have to search the forums and such for info...

Thanks for your thoughts and ideas y'all!

 

[stude53]

This has been mentioned (and implemented by some here already), but a great solution would be to add ladder racks to the top, paint a sheet of plywood with a good grade of outdoor white, and put it across the racks to form a platform for mounting your solar panel (also gives shade to the roof and airflow above the roof).
For more concealment of the solar panel, two lengths of 3" PVC placed along the outside edge of the plywood would shield it from side view (and could be used with end caps to store fishing rods, etc. Some even suggest using the PVC for passive heated solar shower water.
Just some food for thought.

Bob

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OOPS!
This comment above should have been directed to Loess ( sorry for my confusion.

Bob