So I swallowed a bird to catch the spider...

[BradKW]

I haven't posted an update in a few weeks, and I'm not going to add this to the build thread until it's done. Plus, I wanted to use this thread title, as it's been bouncing around in my head for a awhile now. I decided that I not only wanted stealthy AC from a window unit that runs off battery/solar, but then I moved the original placement of back wall to middle of box, on tyop of the refrigerator. Being able to work the larger 'fridge into the build was actually the initial "fly" I swallowed, to keep with the analogy.

I knew when I did that, and I mean "knew" as in "yeah yeah, it'll work itself out" sorta way, that it would be more difficult. And wow, it has turn production into puzzle solving exercises. 

AC unit needs: 1) Three separate, sealed off air zones...fresh intake, exhaust, and cooling (into room). 2) Secure mounting, but can't be too permanent for maintenance/replacement. 3) Condensate drain to keep inside cabinet dry. 4) 110v wiring.

Refrigerator needs: 1) intake/exhaust for compressor, 2) insulated, 3) 110/24v/12v wiring.

I'd feel a lot better about making this contraption if I knew it would work well...as it is, I'm guesstimating some stuff like CFM requirements and intake/exhaust specs. I think it'll work fine, but I've never seen it done before so there's no helping that niggling doubt that makes me wonder if all this work will be for naught. Even had an HVAC guy tell me it couldn't work due to overhead pressures, and had to spend a night Googling and convincing myself he doesn't know what he's talking about  

Anyway, here's some progress pics...seems I lost some of them too...
Insulated wheel well with soundproofing mat and then 2" foam

[img=400x400]http://i465.photobucket.com/albums/...ads/IMG_20160910_150836_zpswcjt7lzp.jpg[/img]

Bottom shelf for 'fridge, cutouts are for rear airflow upward over compressor and to AC unit. Adhered 3/4" foam to underside:

[img=500x400]http://i465.photobucket.com/albums/...ads/IMG_20160918_140528_zpsxvo3dd30.jpg[/img]

Unit temporarily assembled...can't see it, but air intake will be in floor in front of wheel well. I calculated the AC needs about 130 CFM supply...by using a 50 gal garbage bag placed over back of AC and a stop watch    

[img=400x500]http://i465.photobucket.com/albums/...ads/IMG_20160918_150422_zpsvk6ox9wy.jpg[/img]


  Rear exhaust zone, metal redirecting air to side:

[img=400x500]http://i465.photobucket.com/albums/...ads/IMG_20160924_113823_zps8sbkxyfh.jpg[/img]
[img=300x400]http://i465.photobucket.com/albums/...ads/IMG_20160924_113833_zpsalhcjtah.jpg[/img]

 

[BradKW]

AC drain...drilled two holes in bottom of AC unit, sliced 1.5" PVC, tap/threaded 3/8" barbs into end caps:

[img=400x400]http://i465.photobucket.com/albums/...ads/IMG_20160925_140439_zpslwdjckpe.jpg[/img]

Liberal use of 3M 5200 to secure drain to underside of AC:

[img=400x400]http://i465.photobucket.com/albums/...ads/IMG_20160925_173055_zpsbgyvkgqm.jpg[/img]

Have gotten a bit past this, but some pics vanished. If it all works as I hope it will, it'll have definitely been worth the trouble. If it doesn't...well...   :/

 

[rvpopeye]

Certainly a bunch of work there,,,,,,,if it doesn't work (and I'm not saying it won't) , no one can say you didn't try ! And if it does , this thread will get lots of readers..........

 

[LeeRevell]

Will you use a louvered grill to vent hot exhaust air outside the van, or direct it underfloor?

 

[jimindenver]

don't you mean outside?

 

[BradKW]

Will you use a louvered grill to vent hot exhaust air outside the van, or direct it underfloor?

That's a good question, and one I'm still trying to decide. Here are the 3 options:

1) Stay high and duct it out top of rear wall. Least desirable.

2) Drop duct down, still out back wall, but low enough that vent is hidden by lift gate...so about 3' high on wall.

3) Duct it out floor. Most desirable.

So. Heat rises, and AC exhaust is pretty warm...lower I go with vent, more I'm fighting physics? I don't have any knowledge to base this decision on unfortunately. I did buy two Noctua Industrial 12v fans, think each is rated at 130 CFM, along with a PWM controller...thinking being I can run them at low speeds for quietness.

NF-A14

[img=300x300]https://images-na.ssl-images-amazon.com/images/I/71A3MVyQw-L._SL1302_.jpg[/img]

Will they overcome physics of hot air rising? I'd think so...but just more guesses on top of guesses...

 

[SternWake]

Sweet method. Out the floor can certainly work, and the 140 Noctua fans are efficient, but perhaps not ideal.

if you have the room for 180MM fans the silverstone fm 181 comes with a speed controller, claims to move 165CFM or som does so very quietly, for 0.27 amps.

Have you tried the PWM conttroller on the Noctua's? I waqnt to control Industrial Noctuas Via the 4th wire, rather than run the red and black power leads through a pwm controller. "They" say that this is better for the PWMfan, and if the PWM controller you bought is not in the 21KHZ range, it 'might' make the fans whine audibly.

I have many fans on a 13KHZ LED Dimmer/controller, and their speed is nicely controlled but they make twice as much noise as they otherwise would when slowed.

I have not yet explored the full potential using the 4th PWM wire on the Noctua industrials for full sped control, but do have a few bookmarks for products which should fit the bill, But funds and being a surfbum and other projects, have not allowed me to pursue it further.

If you feed the window shaker with another fan, AND exhaust the condenser with another fan, in theory it should make it more efficient.
And of course if the fridge is sucking cooled air through its condenser it will use much less electricity as well as not having as high as ambient temperatures to fight.

I also must bring up the silverstone AP182, which has 2000 rpm as opposed to the 1200rpm of the fm181. I've owned both, the AP182 can move seriously more air and at higher pressures, but can also draw 1.3 amps @2000 rpm and does not like battery charging voltages. Mine failed due to initial overheating of hub motor and likely mostly because of corrosion on the circuit board.

The static pressure ratings are more important than CFM ratings when there is any resistance to flow. I am not sure how they even test cfm ratings or if there is a standard procedure by which all fans must be tested.

Did you get the 2000 or 3000 rpm Noctua industrial models?
Test the Noctuas, See if they whine when slowed to 90% speed and slower on the PWM controller. See if the hub gets hotter at 90% than it does when fed direct battery voltage at full speed. If it does then 4th wire PWM manipulation of the Speed might be the more reliable long term choice.



I'd love to know the results of the above paragraph if you care to perform the test. I wish I could tell you for sure one way or the other. The Industrial Noctuas are the only ventilation upgrades I could easily perform, but I do not really need them, so they are on the backburner till I get some steady work.

 

[jimindenver]

Since you are venting the A/C through the floor, leave it down there and duct the cold air up.

 

[BradKW]

Did you get the 2000 or 3000 rpm Noctua industrial models?
Test the Noctuas, See if they whine when slowed to 90% speed and slower on the PWM controller.  See if the hub gets hotter at 90% than it does when fed direct battery voltage at full speed.  If it does then 4th wire PWM manipulation of the Speed might be the more reliable long term choice.

Not sure if you saw my link above...Here's what I got:

Noctua SSO2 Bearing Fan Retail Cooling NF-A14 iPPC-3000 PWM

And here's the controller I bought:

NZXT Technologies Sentry Mix 2 Fan Controller

[img=300x200]https://images-na.ssl-images-amazon.com/images/I/71avB1ThHQL._SL1500_.jpg[/img]

I haven't had a chance to unbox it yet, but my understanding of what I got is 4-pin PWM fans and a 3-pin controller that will accept 4-pin fans. I believe this controller actually varies the voltage, as opposed to PWM. Honestly, now than I'm looking again, perhaps I have a mismatched set? It gets confusing...I've re-learned fan science every time I build a new PC, and it never sticks. Going to paste something below:

3-pin fans only operate in Voltage Control Mode. The signals to them are Ground on Pin #1 (Black), varying +DCV on Pin #2 (Red), and Speed pulse signal on Pin #3 (Yellow). The voltage supplied on Pin #2 can range from 0 to 12 VDC, although fan headers rarely reduce this voltage below 5 VDC because there is a real possibility the fan could stall and fail to re-start until voltage is increased significantly. This varying voltage supplied to the fan is the means of changing the fan's speed. The fan motor itself generates a speed signal as a series of pulses (2 per revolution) That is sent out on Pin #3 to the mobo header. The mobo counts those pulses to generate a speed readout for information. Most mobos also monitor that signal for fan failure - a missing signal will trigger an alarm of failure. In the special case of CPU_FAN headers, some mobos go further and will shut down the system after a very brief alarm warning to prevent possible CPU overheating, without even waiting for the CPU's internal temperature sensor to report such a major problem.

4-Pin fans work differently using PWM Mode. For computer fans this is not done the same way as PWM speed control of common DC motors in industry. A computer PWM fan is supplied with these signals: Ground on Pin #1, +12 VDC fixed on Pin #2, Speed pulses on Pin #3, and the PWM signal on Pin #4. Note two differences here: Pin #2 always has +12 VDC, not varying; and Pin #4 has the new PWM signal. The PWM signal is something like a "square wave" in that it is either full on or full off. BUT it is not fixed at 50% On as a square wave is - the PWM signal's "% ON" value varies. The signal frequency is 20 to 25 kHz. Inside the fan motor case there is a small printed circuit board with a few components, and some of these modify the current flowing through the motor windings from the +12 VDC supply from Pin #2. The current flow is turned on and off by the PWM signal, so that the average torque produced in the motor rotor, and thus the fan's speed, is altered.

The signals on the first 3 pins of each fan type are similar for compatibility. For example, the Speed pulse signal on Pin #3 is the same in both. This similarity and the mechanical design allows both 3- and 4-pin fans to plug into both 3- and 4-pin mobo headers. BUT there are limits on compatibility.

If you plug a 3-pin fan into a 4-pin header using PWM Mode, the fan gets a fixed +12 VDC on Pin #2 and never receives the PWM signal from Pin #4. It has no circuitry to use that signal anyway. So, that fan always operates at full speed with its fixed voltage supply.

If you plug a 4-pin fan into a 3-pin header operating in Voltage Control Mode, the fan receives no PWM signal, so its modulation circuitry cannot do that job - it merely feeds the power supplied on Pin #2 to the motor windings. However, the power supplied to the fan on Pin #2 is NOT fixed at +12 VDC - it varies, so the motor speed varies according to that voltage, just as a 3-pin fan would do. This arrangement eliminates two small advantages of 4-pin (PWM Mode) fans over 3-pin: PWM fans can be started from a stopped state with less than 100% "On" of the PWM signal, and they can be operated at lower minimum speeds than can 3-pin fans without stalling.

Computer PWM fans are not the same as common DC motors used with PWM speed control systems. They do require 4 wires because they must have a smooth clean 12 VDC supply and a separate PWM signal. Their makers specifically tell you NOT to try to use them with the types of PWM speed control systems normally used with common DC motors, because a PWM-modulated DC supply can damage the computer fan's internal circuitry.

If you connect a 2-wire fan such as those supplied for connection to a PSU Molex output to a mobo fan header's Pins 1 and 2, it will act exactly like a 3-pin fan but without feeding any speed pulse signal back to the header. On a Voltage Control Mode header its speed will be under mobo control; on a PWM Mode header it will run at full speed all the time. In either case the mobo may warn of fan failure since it will receive no speed signal.

 

[BobBski]

I'll be tracking your trials and tribulations, I'm working with the same concept.  Box/shelf was built into the build and AC bought.  Working out the venting plan to have completed by next AC season.  Have a few ideas but want to check with some custom guys in California after the RTR...primarily custom windows in back doors.

 

[SternWake]

Thanks for the extra info Brad. Missed the link.

I had assumed you were using a PWM motor speed controller like this:

https://www.amazon.com/uniquegoods-...ontroller&qid=1465288955&ref_=sr_1_73&sr=8-73

http://noctua.at/en/products/product-line-industrial/nf-a14-industrialppc-3000-pwm/specification

158.5cfm at 3000 rpm. Will be loud, but a huge static pressure rating at 10.52mm
150cfm at 1200 rpm for silverstonefm181 and a much lower SP rating of 2.38mm, but very quiet. I can sleep with this thing at full speed inches from my head. The built in speed controller is sweet.

That Noctua is a PWM fan so unless your controller is using that light blue wire to control fan speed it is likely not the best for the motor or circuit board, but am not sure.

http://www.ebay.com/itm/PWM-0-90-Fr...nal-Generator-Duty-Cycle-Adjust-/131773432474

http://www.ebay.com/itm/NE555-Duty-...-Module-DIY-Kit-Pulse-Generator-/331832105593

https://www.amazon.com/uxcell-Squar..._UL160_SR160,160_&refRID=GQHT83M0D5W0NV88GQ8R

http://www.ebay.com/itm/Adjustable-...utput-adjustable-based-on-NE555-/281689387718

https://www.amazon.com/uxcell-Squar..._UL160_SR160,160_&refRID=GQHT83M0D5W0NV88GQ8R

Those are all the links I have in my pwm driver folder, but I never followed through, but I hope to one day, as The industrial Noctua's are just so impressive.

I think one must consider air pressures when moving too, The fans might not be able to fight under vehicle air turbulence. perhaps not an issue for the AC, but would be for the fridge if you share the vents for exhaust flow.

 

[BradKW]

Looking back over it...again...I see what I based my choices on, these two paragraphs:

"If you plug a 4-pin fan into a 3-pin header operating in Voltage Control Mode, the fan receives no PWM signal, so its modulation circuitry cannot do that job - it merely feeds the power supplied on Pin #2 to the motor windings. However, the power supplied to the fan on Pin #2 is NOT fixed at +12 VDC - it varies, so the motor speed varies according to that voltage, just as a 3-pin fan would do. This arrangement eliminates two small advantages of 4-pin (PWM Mode) fans over 3-pin: PWM fans can be started from a stopped state with less than 100% "On" of the PWM signal, and they can be operated at lower minimum speeds than can 3-pin fans without stalling.

Computer PWM fans are not the same as common DC motors used with PWM speed control systems. They do require 4 wires because they must have a smooth clean 12 VDC supply and a separate PWM signal. Their makers specifically tell you NOT to try to use them with the types of PWM speed control systems normally used with common DC motors, because a PWM-modulated DC supply can damage the computer fan's internal circuitry."

My logic was/is that the 4th pin really does nothing for me in my usage scenario...i.e. not in a PC and not caring about bottom end speeds. And the basic PWM DC controllers you've linked seem to fall under the catagory cautioned against in second paragraph. I make no claim to the veracity of any of these claims

edit: oh, and the notua fans are 160 CFM @ 3000 RPM, I need 130 CFM, figured two Noctuas dialed back to 1500-2000 RPM via controller should give me in excess of 130 CFM at a quiet db level...

 

[SternWake]

Well the first motor speed controller link falls into that second paragraph, but the other PWM driver links send out a pwm pulse only to the blue wire, not a PWM modulated DC supply( red and black wires fed the PWM)

Voltage control should be fine too, as long as the fan slows enough via voltage for you.

Noctua answered my Email quickly as they did not use red and black wires, and I missed the info on the data sheet and felt like a fool who did not look. I put a 1500rpm NF-f12 on my fridge condenser in October 2012.

Anyway don't want to derail your thread, thanks for the info, Love to hear how voltage control modulates the speed of these Noctua's. I am not really keen on the PWM drivers I would have to wire up and protect.

 

[ArtW]

Sounds complicated
When i was planning on putting AC into a cargo trailer, I looked at the small Casita, as I uses a residential AC (window unit)
they put it at the bottom of the front closet and use a grill on the outside to vent the hot air out the side

 

[AngryVanMan]

The squirrel cage blower in the AC should deal better with static pressure than axial fans, so you may not need to add any sort of supplemental fans to achieve proper cooling of the condenser. Just size your ductwork based on any standard duct chart, and if you have more than one 90 degree bend in the circuit, up size to the next bigger one.

Stack effect (air moving by differential temperature) is not usually a consideration for duct work with powered fans or blowers. Likewise, height differential (gravity) is not a major concern in pumping air like it is with pumping water.

You can install a few test ports on the side of your duct to see if you are developing any significant static pressure or vacuum in your ducts, you would hook this small port to a homemade manometer (u-shaped clear tube with water in it) and test the inches of water column that are developed at the output/input of the condenser. One side of the manometer tube would be in open air and the other side hooked to the duct, so the pressure can be indicated.

 

[BradKW]

Really having to fight the "git-r-done" temptation on this...keep having to redo things to correct tolerances for air seals and make it so everything survives bouncing on a regular basis. And modular enough that it can come apart for maintenance. I had the seal for between zone 1 and 2 (interior cool air and intake vents) pretty much done with vinyl door sweep before deciding it wouldn't hold the unit securely enough and maintain a seal...so scrapped this plan:  

[img=400x300]http://i465.photobucket.com/albums/...ads/IMG_20161001_110748_zpsqibehke9.jpg[/img]

Instead made a full cutout, trimmed with auto gasket, cut in half (kinda) and used two hold-down clamp latches to tighten seal:

[img=400x300]http://i465.photobucket.com/albums/...ads/IMG_20161002_151459_zps0j7lrehe.jpg[/img]

Re-did the rear seal between zone 2 and 3 (intake and exhaust) using vinyl door stop. once you get the fit right, it not only provides a nice seal, it also makes a solid rear stop:

[img=300x400]http://i465.photobucket.com/albums/...ads/IMG_20161001_143214_zps1xiucs3j.jpg[/img]

Working now on exhaust zone...hoping next weekend puts this component to rest.

[img=400x400]http://i465.photobucket.com/albums/...ads/IMG_20161002_160620_zpsy8thavbk.jpg[/img]

 

[BradKW]

I have decided to exhaust the ventilation system through the floor...actually the wheel well, but same difference. Thanks for the feedback that helped me reach this decision.

I also decided to incorporate two 140mm fans to assist exhaust. They will be able to be controlled independently and variable speed. Maybe they're not necessary, but I already bought'em and it's one of those things that by the time I learn if needed, it'd be a huge hassle to add them back in. Plus, this vent system will also vent the shower/bathroom, electronics cabinet, and two 12v batteries, provided I feel comfortable keeping battery gas going backwards into electronics...will see.

Picked up a cheap insulated register vent box at HD, removed the bottom and affixed a wood frame inside:

[img=300x400]http://i465.photobucket.com/albums/...ads/IMG_20161008_164052_zps8z4gatvj.jpg[/img]

Added a top plate...
[img=300x400]http://i465.photobucket.com/albums/...ads/IMG_20161008_164102_zpsbugdpvkj.jpg[/img]

Mounted fans temp installed it...the box will be enclosed in 3/4 polyIso which will form the duct to the floor:

[img=300x450]http://i465.photobucket.com/albums/...ads/IMG_20161008_165122_zpsbk1bogkm.jpg[/img]

 

[BradKW]

Also made the entry and exit boxes. The brake was out on a job, so I improvised with a could pieces of granite that were laying around:

[img=400x300]http://i465.photobucket.com/albums/...ads/IMG_20161009_121237_zps6nv1zzkp.jpg[/img]

Used butyl tape to prevent any vibration issues, and riveted together:

[img=300x250]http://i465.photobucket.com/albums/...ads/IMG_20161009_130144_zpsncpr3gkp.jpg[/img]

 The one above has a bottom flange and it'll be riveted flush onto wheel well. The other one is the intake, and I framed it and dropped through floor:

[img=300x250]http://i465.photobucket.com/albums/...ads/IMG_20161009_141233_zpsouszyyzl.jpg[/img]

It will have screening and an accessible filter when done...

 

[SternWake]

I think the Industrial Noctuas mounted on a shroud caused me some slight arousal.

 

[speedhighway46]

Brad: VERY nice work . . .