Two fans or a roof-top AC - Ram Promaster Forum
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post #1 of 17 Old 01-01-2017, 09:49 PM Thread Starter
medicineman4040
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Two fans or a roof-top AC

Rare we are ever where it is seriously really hot and the She and I are fairly heat tolerant.
I've noticed some builds use two Maxxairs or two Fantastic fans; where one fan sucks in and the other blows out.
Personally I'd rather not ADVERTISE RV with a rooftop airconditioner and get by with two Maxxairs.

I've also noted some are putting in 'normal' or portable airconditioners inside the PM.

It's another puzzle to figure out eh? But I'm leaning toward two fans.
If I go that route I see just behind the drivers/passenger seat a logical place BUT what about the aft install ???

Thanks as always.
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post #2 of 17 Old 01-01-2017, 10:47 PM
GaryBIS
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Hi,
Not sure what the right answer is for you, but here are some thoughts...

Its tough to run a full size RV AC unit without having a generator. It would take a very large battery pack to run it for any significant time. It gets to the point where you would need to consider Lithium batteries for there energy storage density.
If you want to have a look at whats involved in running an RV AC off batteries, go to FitRV.com and search it for their post on running AC off batteries -- be prepared for some sticker shock.

Generators are also tough to install in a PM -- it seems like about the only practical place to put them is where the spare tire goes, and that means mounting the spare on the rear doors or something like that. Generators are also disliked (and that's a mild word) by other campers. In a lot of places people with generators are exiled to a special place where they can share the noise with others with generators. I actually saw a minor fist fight break out between a generator owner and his next door neighbor in the campground at the Aspen Bells in CO.

If you insulate the PM well, you can get the heat gain down considerably from what it would be in a regular RV, and you might be able to use a smaller AC that would not require a generator to run -- although it would still require increasing battery bank size.

Some places you might look at for a smaller AC:

Climate Right http://www.climaterightair.com/ (they sell ACs for Tear Drop Trailers)

Small room AC: https://www.amazon.com/Frigidaire-FF...=small+room+ac
This is a 5000 BTU/hr small room AC -- its pretty efficient as small ACs go, and dirt cheap.
But, you have to figure out how to mount it. I have seen articles on people using this AC in RV's -- google around for it.

To give the two fan approach a good chance of working, important to insulate well, and to have good reflective shades on the windows -- making them with Reflectex works well and is cheap and easy. This is what we did:
http://www.buildagreenrv.com/our-con...s-for-windows/

The heat gain through a window in the sun can be over 200 BTU/hr per sqft of window -- has to be controlled or you will never get there with fans only.

We use one MaxxFan coupled with open windows, and this works well for moderate temps -- some tests on my van here: http://www.buildagreenrv.com/keeping...n-cool-a-test/

Of course, parking the the shade makes a huge difference.

If you are traveling in a dry area (low relative humidity), then an evaporative cooler can work well and is MUCH more energy efficient than a conventional AC.
RD has a post on one he did that is really clever and simple, and works in conjunction with a roof fan.
Scroll down this page a little for plans for several more DIY evap coolers -- one is for a small trailer: http://www.builditsolar.com/Projects...htm#ActiveVent

edit: should have mentioned that if you camp at places that offer shore power, the AC is, of course, a lot easier. If you go that way, you might look into a hybrid inverter, which will let your batteries help a not so good source of shore power.

Gary

Last edited by GaryBIS; 01-02-2017 at 10:22 AM.
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post #3 of 17 Old 01-01-2017, 11:34 PM
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I am rethinking the idea we didn't need or want an AC unit and it is a dilemma. Traveling across the south last May we experienced some uncomfortable nights. EVERY campground we stayed at had and included in the price access to plug in AC even the state parks, no matter how far off the beaten path they were. A low profile unit like the Coleman Mach 8 or the Dometic Penguin weigh about 100 lbs, cost about $700 with interior fan and come in the smaller 13,500 btu size. They run on 110V and are easily installed in a 14” square opening like the Fantastic Vent, and are simply wired to the shore power. I know I am not fooling anyone when I park to camp despite the desire to be stealth (ha) so it really comes down to is the thing going to get used enough to justify the cost? A couple of nights we ran the evaporative cooler and it did help a bit (about 4 or 5 degrees) but as we got to Florida the humidity made it ineffective so we started the van and ran the AC for about 20 minutes after dark to get the residual heat of the sun out. Then we sweat for a couple of hours until it cooled down.

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post #4 of 17 Old 01-02-2017, 12:11 AM
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Where do you plan to camp? A coworker has a Sprinter conversion by Sportsmobile originally with no Air conditioning. When they were in Albuquerque there was no need. They did however use the heck out of the heater. Once they moved to E. TN they made one camping trip here and scheduled to have the A/C installed. It was miserable!! They hardly ever use the heater now and would quit traveling/camping if they didn't have the A/C. Humidity levels here border on rain forest. People in the south talk and act slow not because they are ignorant, but because they would die from heat exhaustion if they acted quickly.

As for me, the girlfriend has said " Phat girl gotta have A/C. if you want me to go with you, it WILL have A/C" no question if my rig will have extra A/C.

My short list of A/C is Coleman Mach 8, Dometic Penguin II, and Coleman Mach 10. Mach 8 and Penguin II are available with heat pump, but the mach 10 has less starting amps and less wattage draw, altho it is slightly less aero with a slightly larger height and frontal area. I would consider an under floor stealth option if it was efficient and effective. Decisions and compromises.. hmmm

I saw 104 degree F riding motorcycle and camping in PA once. That really sucked.

2015 3500 gas. High roof extended, RV-ish package. They do exist!
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post #5 of 17 Old 01-02-2017, 12:54 AM
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Some of my travels include a week to 10 days at urban rv parks for sport events.I fully agree on importance of sleeping comfort when hot and humid. I experimented with an 8K btu single hose portable AC unit. Midwest campground with 95F and high humidity only 8 degrees of cooling and no noticeable decrease in humidity. Learned this unit can't work (despite many positive reviews) because of constant air replacement of inside air with outside air. Plus the exhaust hose radiates LOTS of heat inside the van. Two-hose portable system may work but a real space hog. See 2 posts by MarkEVOL (sep '15) on the Onan generator thread for a window-type install. Still considering options.
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post #6 of 17 Old 01-02-2017, 09:50 AM
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I do much stealth camping with no electric power so I have no A/C. I do have 2 MaxxAir fans, one in and one out. They are variable speed and the 30% speed works well using very little battery power and they are virtually silent. I made this choice after owning 2 camper vans with roof A/C. Also I am in love with my Espar heater!
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post #7 of 17 Old 01-02-2017, 10:34 AM
RDinNHandAZ
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There are 12 volt AC units and perhaps some one here with a big honking lithium battery set might find them perfect. I calculated the usage and my 200+AH golf cart batteries would be down to 50% in less than 2 hours. It looks like a cool(!) unit with little above roof protrusion and simple instal. My question is would a 950Watt AC unit be enough? I think the Dometic and Coleman units are 13,500 watts.

http://www.indelb.com/products/parki...g_well/sw_oblo
In fact IndelB has a great line of Products!
http://www.indelb.com/media/files/51...%2009-2015.pdf
Also another 12 volt unit from Autoclima:
http://impianti.autoclima.com/img/sr..._autoclima.pdf

2015 136" HT Diesel Sandstone Metallic Born on 6/12/2015 Campervan build see: http://www.promasterforum.com/forum/...ad.php?t=37177
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Last edited by RDinNHandAZ; 01-02-2017 at 11:20 AM.
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post #8 of 17 Old 01-02-2017, 10:35 AM
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Quote:
Originally Posted by RDinNHandAZ View Post
I... A low profile unit like the Coleman Mach 8 or the Dometic Penguin weigh about 100 lbs, cost about $700 with interior fan and come in the smaller 13,500 btu size. They run on 110V and are easily installed in a 14” square opening like the Fantastic Vent, and are simply wired to the shore power. ...
Looks like Coleman also makes a 9200 BTU/hr model: http://www.pplmotorhomes.com/parts/r...onditioner.htm

Gary
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post #9 of 17 Old 01-02-2017, 03:37 PM
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I've been using a 5,000 BTU/hr window AC mounted inside my Ford E-350 extended window van (so it's not visible from outside -- custom vented through floor) for just over 10 years and wouldn't want to be without an AC. There are too many hot and humid nights along the Gulf Coast.

During the day it struggles to keep us cool unless parked in shade and day is not too hot, but at night it can freeze us out if we wanted; and that's with a window van with lots of glass and practically no insulation. At night it cycles on and off frequently, indicating excess capacity. The AC is primarily for sleeping at night because during the day we are either driving with engine AC on, or are busy with activities outside the van when parked.

My AC (older model) pulls close to 600 watts during the day, but at night that drops to around 500 watts (which is below its standard rating). Newer 5,000 BTU/hr energy efficient window units can have 12.2 EER and pull only 410 watts (rated). At night it should pull less power, although I'd want to test it myself.

As to rooftop ACs, check out the 11,000 BTU/hr Energy Efficient Power Saver model that only pulls 1,000 watts at rated conditions. That's less than the 9,200 BTU/hr model. I believe these are the ACs used on Roadtrek and Hymer camper vans that run AC from batteries and inverter.

If my van wasn't so old, I'd replace my AC with newer efficient 5,000 BTU/hr model and add batteries for 8 hours of operation at night.

Having an air conditioner obviously doesn't preclude having a roof-mounted fan. With screen windows I'm not sure I understand the benefits of having two fans, unless owner is worried about someone getting in through window screen or to have greater privacy.


By the way, if installed correctly, a window AC can be used on "FAN" to exhaust air out of van, and at same time to help recirculate air inside (both fans are on one motor). That uses a lot less power than when running as an air conditioner.
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post #10 of 17 Old 01-02-2017, 03:54 PM
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I agree two roof fans is just a waste unless you have no opening windows. I always keep my awning window in the back side of the van open (other than when it's below freezing out) and the roof fan just behind the front seats will easily and efficiently move the air in or out depending on the setting. No opening window in the back? then mount the roof fan there and crack open both front windows - cheap, easy and simple and best of all it just works!

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