Ventilation - My Way - Ford Transit USA Forum
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post #1 of 13 (permalink) Old 08-16-2019, 11:51:AM Thread Starter
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Ventilation - My Way

The typical approach to ventilation is cutting a big hole in the roof. For those of you that want this, more power to you. I did not (and still do not) want this, so have had other ideas ever since beginning my conversion. If you want to argue that a roof vent is better, please start your own thread. My intended goal with this thread is to share my experience so far with products and ideas - what's worked and what hasn't.


My concept for ventilation is to eventually have the ability to change the air flow intake/exhaust direction from the ceiling and the floor. This should help maximize heat retention in the winter and maximize heat expulsion in the summer. The system is still in it's infancy, but I've made some progress with the selection of components and control methods. I have a 4-1/8" hole cut (finally) very near to where many people seem to put their floor vent, not far behind the driver's seat and on the left side of the van. From there I intend to have ducting that extends up to the ceiling of the van where air will be sucked out in the summer and blown in (at a reduced rate) during the winter. I have yet to build the cabinetry and ducting to support this, but have purchased and experimented with the following products and how they can be used:


SEAFLO 12V 320 CFM 11A Air Flow Bilge Blowers for Boats Bilge Ventilation
https://www.amazon.ca/gp/product/B01GDMFZVW/


D DOLITY Marine Boat 12v Quiet Electric in Line Bilge Blower High Air Flow - 4 inch 10.3cm Diameter
https://www.amazon.ca/gp/product/B076P6XBS9/


3.3V 5V 12V 19V 24V 5A Adjust DC-DC Buck Step Down Voltage Regulator Module 1Pcs
https://www.ebay.ca/itm/3-3V-5V-12V-...s/173672756205


Initially I wanted to control the fans with a PWM switched MOSFET through software (Arduino-based), but quickly discovered that neither of the fans appreciated that approach. I tried varying the PWM frequency and duty cycle but in every iteration the noise was intolerable or the frequency not a good match for the motor's inductance. The step-down regulator boards I purchased weren't originally for this part of the project. They were intended for powering small electronics directly from 12V DC instead of their 120V AC "wall warts". But after I determined that PWM wasn't working, I looked at the actual current requirements for the fan I was experimenting with at the time (Dolity) and decided it was well within the limits and to try it out.


I was happy to discover that it ran the fan without introducing additional noise and control throughout the voltage range was continuous and fluid. I could go from moving a slight breeze to full on typhoon. Unfortunately the Dolity fans (both direct to DC and with voltage control) are VERY CHEAP and VERY NOISY. The best way I can describe the sound is something like "clattery" No big surprise given the price.


But the concept was sound, so I decided to try connecting the SeaFlo fan for some low range trials. The regulator board probably won't support full voltage/speed of the fan but that's a future experiment. I ran the fan just placed in my floor vent hole overnight at about 3V, which provided reasonable air movement and was very quiet. I was a little surprised that even down to the minimum voltage available from the regulator (~1.2V) the fan reliably turned slowly. In the morning I noticed that the main chip and capacitors on the board were slightly warm but nothing to be concerned about.


My next steps related to this will be to build the ducting and do some modifications to the regulator that will hopefully allow digital control through software. If I find that the regulators aren't adequate for full power to the SeaFlo fan I've thought of two potential solutions: 1) Find a supply that's properly rated, or 2) use a relay (or MOSFET) to switch between power from the regulator and direct full power when I want to use it for high volume air exchanges (like when cooking).


I'm pleased that this has turned out better than the direction it was going at the start. I hope this may give others some ideas for non-traditional ventilation options as well.
ultane, Travlin, elia1222 and 1 others like this.

2018 148" WB High Roof, 3.7L
2x 6V 232Ah GC2 Batt + UGP-80L1 DZ Fridge.
Propex HS2000 Furnace (to be installed)

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post #2 of 13 (permalink) Old 08-16-2019, 11:59:AM
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Where is the intake air coming from?
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post #3 of 13 (permalink) Old 08-16-2019, 12:06:PM
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Something not mentioned above, but worth consideration ...

Most venting systems work best with two holes to the outside so the air may flow from one to the other.

These are often designed with one low and one high to get the best mix of cabin air and utilize natural convection currents to supplement any powered airflow.

Have you planned for another inlet/outlet (depending upon the direction of flow selected in the above system)?

Are you planning to use dash venting for the other end of the flow path?

Will there be any stagnant air zones where the flow path does not carry air through them as it enters and leaves the van?

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post #4 of 13 (permalink) Old 08-16-2019, 12:10:PM Thread Starter
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There will be another intake hole at some point. In the meantime it comes in through the cab windows and openings around the partition.
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post #5 of 13 (permalink) Old 08-16-2019, 02:33:PM Thread Starter
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Quote:
Originally Posted by Travlin View Post
Will there be any stagnant air zones where the flow path does not carry air through them as it enters and leaves the van?
I intend on having one high (front), one low (back, possibility opposite side) as you've mentioned. Other than closed cabinets, I hadn't given more thought to "stagnant air". Can you elaborate on the considerations here?
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post #6 of 13 (permalink) Old 08-16-2019, 02:55:PM
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Quote:
Originally Posted by Sparky961 View Post
I intend on having one high (front), one low (back, possibility opposite side) as you've mentioned. Other than closed cabinets, I hadn't given more thought to "stagnant air". Can you elaborate on the considerations here?
I like to think that the air will tend to move most of the airflow across the shortest path, so, if it isn't being drawn through the van there could be areas where the air can continue to accumulate heat even though there is moving air somewhere else. This is probably not a significant concern, as convection will help mix things up too. But, it is something that can be considered during the planning stages easier than it might be addressed later.

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post #7 of 13 (permalink) Old 08-16-2019, 04:26:PM
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Ventilation - My Way

There is already a large (~4”?)square flapper hole in the driver side D pillar underneath the floor level that may assist you.

3.5, 3.31, 148", Ext, HR,
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post #8 of 13 (permalink) Old 08-16-2019, 05:36:PM
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Sparky, I am definitely interested in seeing your results with this! Great work so far!

I am also trying to see what I can come up with for ventilation without the ubiquitous MaxxFan hump on my roof. I have the rear AC and am trying to utilize its blower for ventilation by ducting outside air in from the flapper hole when the ignition is off. If this doesn't end up working an inline fan like yours was next on the list for the outside air portion. I hadn't thought about the exhausting hot air scenario but with the A/C vents up high and a directional fan could make it possible.
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post #9 of 13 (permalink) Old 08-16-2019, 11:20:PM
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The underside of the D pillars have the 4" plugs that can be removed to allow air to enter the cabin. To me, that's not enough space to promote adequate air flow.
We use the metal grate window inserts purchased from Eurocampers. They allow a great airflow into the van with a rear mounted Maxxfan.
We found that without adequate air flow, the inside of the van can become uncomfortable when sleeping. Also, it seems to trap more moisture when the ventilation isn't adequate.
Good luck on your build.
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post #10 of 13 (permalink) Old 08-17-2019, 11:59:AM Thread Starter
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Some quick numbers for those of you who are interested/curious. This is running the SeaFlo fan through the SMPS, recording a series of data points...


I noticed during the test that sticking the fan in and out of the hole caused noticeable audible and current differences. This had me puzzled until after I was done and I realized that I had the front windows closed due to running the A/C earlier. Later on I still had the fan running stuck in the hole and I opened the window. There was an obvious change in sound. This confirms that the fan is pulling air in through the window(s)! It also means that my current numbers aren't absolutely ideal, as there was some obstruction in the intake air path.



[SEE ATTACHED]

Horizontal = Output volts, Vertical = Input Amps



Conclusions:
- The voltage indicated on the display is off by up to 0.15V, which is only slightly worse than the listed +/- 0.1V but not bad for the price and intended application
- The current and/or voltage was limited when I increased it to 9.8V out, at which point it wouldn't adjust any higher. I verified this by unplugging and re-plugging the motor and when connected it would drop down the output accordingly. Handy. Oddly enough, it's limited to about 75W - which is what the eBay listing specified! Go figure, an inexpensive "made in China" electronic device that appears to live up to it's specifications!
- Re-reading the eBay listing, I also see that there is thermal limiting, so one might assume the device will shut down or reduce its output automatically. Difficult to test this one without knowing the actual trip point though. The components absolutely DO get hot when running higher power levels but no smoke was released so far. But really, 75W _is_ hot. Think incandescent light bulbs folks... how long are you holding onto that 60W light bulb for after it's been on for a while?
- Below 1A (~5V), the fan noise can easily be slept through. Lulling, even. Without obstruction at the input or output it moves an impressive amount of air down in this range too. I anticipate that ducting will require more current to move an equivalent amount of air, though I'll be trying to keep it as large as possible to minimize this.
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2018 148" WB High Roof, 3.7L
2x 6V 232Ah GC2 Batt + UGP-80L1 DZ Fridge.
Propex HS2000 Furnace (to be installed)

Last edited by Sparky961; 08-17-2019 at 12:06:PM. Reason: Table and graphic didn't show properly... changed to attached screen capture
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