Need help with vent fan position

It seems like everyone centers a fan on the factory fan circle in the second roof section from the front (where the factory optional fan is mounted).

I am planning to put two maxfans in. One in the front between roof ribs 2 and 3 and a second fan over my raised bed. I also want to maximize roof space between the fans for solar panels. I am using maxfans which use a standard 14" hole, but in addition to all their advantages, they have a long "tail" that extends back an extra 7" farther than a standard square fan. To meet my goal I will put the second fan as far back as I can over the bed. The bed will be similar to the OutsideVan layout like a loft over the front of the motorcycles in the garage.

I might also put one solar panel behind the second fan, but I digress.

I assume it would be a bad idea to mount a maxfan in the first section as:
1. it would look bad
2. it would be right in the air flow coming up off the windshield
I would be curious to see a photo of a maxfan mounted between roof bow 1 and 2 as far to the rear as possible. I'm sure the factory position is based on 1 fan for the entire van. It is also likely the best place to put an A/C for most conversions.

Has anyone moved the front fan as far forward as possible in the second section of the roof, between bows 2 and 3 so the cutout is just is behind the edge of the second roof bow? Instead of centered on the circle it would be offset to the front. (The cut would be just behind the edge of the flange for the roof bow.) This might give a couple more inches behind the fan.

Just to give you a rough idea, the red line would be the change from the typical blue.



Any thoughts on whether this would cause any problems?

I haven't had a chance to get up on the roof and check the ridges and how that might be affected with positioning the adapter I already have from Hein, but if necessary I can modify it or have him make another.

Thanks in advance.

I have a fan mounted in the first position. I've had no problems. I would have moved the rear fan all the way back, I put it in the factory location. I saw an install with it all the way in the rear and I would have appreciated the 400 watts of solar over 200.

I don't see any problem with shifting forward. Let me know what you decide and we'll ship out a new adapter. Then just send the one back that you don't use. Easier for us to machine a new one than for you to have to rework it. Just let Kim know and we'll get it done for you.

All the best,
Hein
DIYvan.com

I used hein's adapters to mount two fans, one in the factory spot and one in his "most rear 170" spot. I highly recommend his adapters, especially the rear one. I have plenty of room between the fans for my Silfab 360 watt/72cell solar panel which is 78 inches long. I think I would be able to fit even more solar using multiple smaller panels but wanted to keep things simple.

vantastic adventure said:

I have a fan mounted in the first position. I've had no problems. I would have moved the rear fan all the way back, I put it in the factory location. I saw an install with it all the way in the rear and I would have appreciated the 400 watts of solar over 200.

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Any chance you could post a photo?
Which type of fan do you have?
Do you have a problem with wind noise?

I set my maxx air in the spot today to see what it would look like and it didn't look bad when shut. when open it looks like it will be right in the turbulence of the air stream coming up the windshield and over the curve part above it. (like the curve will help the air stream come down so it smacks right into the fan.

I realize that a fan mounted back on the flat part of the roof is going to have the air stream hitting it head on, but it wont be almost directly over the driver's head. I'm sure the sprinter is going to be better now that I insulated above the cab headliner, but the are always so noisy with the large windshield and around the b pillars. At least it won't be as bad as a class C with the body jutting out making a square corner and flat wall right at the B pillar to make all that noise in my ear.

I am really hoping, and working pretty hard, to be able to have a conversation between the front seat passengers without yelling.

How often do you really drive with the vent open?

Keep in mind that I am originally from Texas so the fact that I am building a conversion without roof air is a huge leap of faith. Two maxx fans, probably the orton floor vent and try to stay out of the south in the summer. I prefer the mountains. If you are too hot they just go higher.

Windows went in in the last three days. That was quite an accomplishment. The vent should be easy in comparison.

On a related note, has anyone actually compared the output of their solar panel when they open the max fan and it shades part of the panel? How bad does it drop.

I am thinking that I might be able to put 2 renology panels between the fans if I let the shade happen. I am thinking that maybe some is better than none. Here is my logic, ignoring cost, and all not shading effects.
If a 100W panel can produce 50W x 4hrs per day on a part of the roof where it is never shaded.
What if I put 2 100W panels where the front of one panel is just behind the front fan and the second panel ends just before the second fan (covers when shut looking down from above). That would cause zero shade at noon if parked east west, and the front fan would throw a decent shadow before noon and the back fan would throw some shadow after noon. I have no idea how much partial shade affects the output of the renology panels, but even if the the shaded panel still could produce half then I would end up with essentially a 150W array and just accept that I am going to live with the shade.

Thoughts?

julie777 said:

Keep in mind that I am originally from Texas so the fact that I am building a conversion without roof air is a huge leap of faith. Two maxx fans, probably the orton floor vent and try to stay out of the south in the summer. I prefer the mountains. If you are too hot they just go higher.

Windows went in in the last three days. That was quite an accomplishment. The vent should be easy in comparison.

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Fans are great for the Pacific NW area.

I have real doubts that they will make you happy in UT or TX. It is a completely different solar energy experience.

A possible alternative for you is to just cover the entire roof with solar, and use a bathroom exhaust fan (blower) to vent the air down through the floor for those occasions when that is enough.

There are some dual hose portable air conditioners on the market (one hose each for the inlet / outlet air that flows across the condenser coils) It looks like they pull about 1 kW, so potentially could take the edge off on a hot day.

julie777 said:

I have no idea how much partial shade affects the output of the renology panels, but even if the the shaded panel still could produce half then I would end up with essentially a 150W array and just accept that I am going to live with the shade.

Thoughts?

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For some guidance, you might take a look around the 'net for people with solar panels on sailboats. They have to deal with shading from masts, spars, and such. Depending on how the panels are constructed/wired, even a little shade can significantly drop panel output according to what I've read. If multiple panels are wired in series, one partially-shaded panel can significantly reduce the output of the entire system.

I'm going with a 100W roof mount and a 160W portable panel. Park in the shade--move portable panel into the sun---hopefully.

I put my fan all the way back, and off to the side so that it is over my head when sleeping. In warmer weather I have reversed the flow to make it more of a ceiling fan. The hood then opens away from the panels, so shading is not an option. I thought I had a better picture, but can’t seem to find it...




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Here’s the fan position from the inside -

GSWatson said:

I put my fan all the way back, and off to the side so that it is over my head when sleeping. In warmer weather I have reversed the flow to make it more of a ceiling fan. The hood then opens away from the panels, so shading is not an option. I thought I had a better picture, but can’t seem to find it...

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Click to expand...

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Thanks for the reply.
I am very curious about your solar mounts. The way you have the 80/20 sticking out with a living hinge/structural angle on the end make me wonder what you have in mind. Do you have something planned that isn't shown?

Instead of two fans why not one with a hole in the floor to provide circulation? I have a 4" square hole in front of the left rear wheel that I can open/close. Hole plus open Maxxair provides enough air flow without powering the fan most of the time in my climate. Cooler air from under van flowing up through the van I would think is better than moving warm air just under the roof from front to back.

One fan provides additional space for solar. I had a 135 watt panel on the Sprinter that almost kept up with the refrigerator power needs in my climate. Changed that to a 205 watt panel that did keep up. Transit has the same physical size single 300 watt high voltage panel that easily covers my electrical power requirements.

Maxxair is located over the bed in back so it can be manually operated either from bed or while standing in the aisle. Did not want a remote.

Warning on Maxxair: Do not drive with it partially open. That will destroy the lid opening gearbox. Either full open or fully closed.

http://www.ortontransit.info/solar.php

Thanks Dave. I am planning to put in floor vent you pioneered.

I am pondering the single vent and will probably start with just one. I really like the idea of the single 300 watt solar panel too. Using a single vent over the bed, which is in the middle of the van, I could put the solar in front of that if I didn't have a front vent.

julie777 said:

Thanks for the reply.

I am very curious about your solar mounts. The way you have the 80/20 sticking out with a living hinge/structural angle on the end make me wonder what you have in mind. Do you have something planned that isn't shown?

Click to expand...

Yeah, I have a design for a fox wing awning kicking around in my head. I’m not sure how it will mount, so I left everything long and then put the curved end pieces on for the clean look...


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Did you mount it in the forward position in the end? I'm thinking of doing the same in our van but im also concerned about added wind noise.

Any updates on locating this at the forward most position? I am thinking about that option to maximize the number of panels on my roof.

I mounted maxfan in last position hoping that would draw more air passively while in motion - BZZT - seems to be a dead air space, at least in the forward position a low-pressure zone from the windshield heaving slipstream above/away from roof would draw a better draft... may be time for second vent fan install, tobacco smoke hangs blue in the air in the wayback for 20+ minutes while doing 65mph...

Has anyone experimented with aviation NACA ducts or vents?
Seems like thats exactly what yall are looking for.
I am an aviator and building an RV10. My plane will have two in the rear on the fuse to power all of the interior overhead ventilation.