Fun custom A/C job in my van

Condensed version: 99 E350 diesel cargo van. Its empty except for the driver and passenger buckets. I'm turning it into a work van/weekend camper. I tossed around several ideas for 120v A/C for when I plug in. I've run the whole spectrum from hacking up an old fridge to cutting a hole and putting a window unit in the back door.

Then I saw a rear A/C unit in another Econoline. Its remarkably compact and nicely tucked away. Ya think I could find a 120v compressor to run it instead of the belt-driven one? How does one size a compressor and evaporator for the job?

A fridge compressor is barely enough to cool a computer processor. Think of how long it takes to cool one down. Mine takes about 2 hours to get the fridge side cool enough to even think about loading food into. Those compressors, for lack of a better term, don't move enough heat. If you're thinking 120AC, look at window units.

Sorry I'm not any more help than that. I used to be far better versed on phase change than I am now.

Agreed on the fridge compressor which is why I abandoned that idea. They are small BTU, but they work for fridges and freezers because of the insulation and the thermal load they generate in the airspace over long periods of time. No good for instant cold air.

I thought about hacking a small window A/C unit (condenser outside, evap inside, and just the refrigerant lines going through the floor) but have you seen those things? They are like a one-piece unit. Very hard to separate the components. Not to mention they are cheap plastic-y things that won't be easy to repair. I want to stay firmly in the realm of component parts that can be universally replaced.

I figure 5000 BTUs would be effective without being overkill.

Is a roof top AC out of the question? May not be totally DIY, but it may be more cost effective. At least in my area, a lot of RVs are found in non-running condition so they sell for scrap value, but often that roof AC runs just fine.

Buy dead RV, pull roof top AC, scrap the rest, profit?

From a $ standpoint you would be hard pressed to get cheaper than a window unit replacing one of the rear door windows and either an inverter to run it while down the road or just plug in when stopped. The newest $100 window units are so small they'd fit right in and not stick out much past a full-sized spare tire on the back.

Otherwise, if you don't want to be seen with the unit hanging off the back of the truck but are planning on plugging in anyway, get one of those units that sit inside with the duct hose to the window. Either open a window when you use it or duct to a dryer vent or chimney for getting the hot to the outside. Also chap and easy.

And lastly, for a real DIY experience, a dehumidifier might offer up a better sized unit for taking apart and replumbing into the van. They can be found all over the place for next to nothing and are pretty much just an AC unit that re-heats their own cold air.

I generally agree with the rear-window powered from a couple of batteries through an inverter idea. However, I've had a damned of time finding one that small (narrow). But it sounds easiest to install: pull out the window and replicate the window in metal, then cut out for the a/c unitand add bracing to stiffen the panel. Paint to match and reinstall in the OE window gasket with some additional bracing to transfer weight to the door.

Some window units use R134A refrigerant. You could get one sucked down by an a/c vendor then re-package it how you like with custom plumbing (soldering copper pipe is easy) and refill it yourself.

Really I would go for a rooftop unit intended for RV use but if you wanted to custom-make it, that seems like an option.

Roof top is tempting, but it's going to add aero drag and noise on the hwy. I vote window route out the back. Just make sure it drips clear of the body so you don't get rust streaks.

curtis73 wrote: Then I saw a rear A/C unit in another Econoline. Its remarkably compact and nicely tucked away. Ya think I could find a 120v compressor to run it instead of the belt-driven one? How does one size a compressor and evaporator for the job?

You could use an 120V electric motor to run the belt driven compressor, could even mount the compressor in the back as well along with the condenser and a cooling fan. Not sure how easy that would be but at least you know the compressor would work with the rear a/c unit. Just a thought.

Are you set up to work with R134a refrigerant at all? (ie, vacuum pump, manifold gauge set) If so, the more I think about it the more fun it would be to put something custom together. Either making it out of a window unit or whatever. In order to vacuum it down you install a braze-on refrigerant service valve. Here's a google shopping link for it:

https://www.google.com/search?q=refrigerant+service+valve&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#hl=en&safe=off&client=firefox-a&hs=l4k&rls=org.mozilla:en-US%3Aofficial&tbm=shop&sclient=psy-ab&q=refrigerant+service+saddle+valve&oq=refrigerant+service+saddle+valve&aq=f&aqi=&aql=&gs_l=serp.3...9848.10759.1.10950.7.7.0.0.0.2.189.793.5j2.7.0...0.0.S-80jYi1dsw&pbx=1&fp=1&biw=1280&bih=888&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&cad=b

Obviously pick based on your tubing size and refrigerant type. You could then plumb it how and where you'd like. It would be too much work obviously but it would be fun and could look a lot better than a window unit sticking out the back. Or it could look like crap and work terribly, but at least you made it yourself and spent too much money on it! (Isn't that what we all like doing, anyway?)

Make sure if you do do a window unit that it is level, otherwise it will drip in the van when its running or raining

Park with it on the down side too.

The roof top air is the only thing you don't hear in Mongo

In reply to dculberson:

Just do what he said, except pirate the entire A/C system from a small car and drive it with an electric motor?

ProDarwin wrote: In reply to dculberson: Just do what he said, except pirate the entire A/C system from a small car and drive it with an electric motor?

Yeah!! I wonder how big of a motor it would take to turn it? And how fast it would have to turn to be effective?

81cpcamaro wrote: You could use an 120V electric motor to run the belt driven compressor, could even mount the compressor in the back as well along with the condenser and a cooling fan. Not sure how easy that would be but at least you know the compressor would work with the rear a/c unit. Just a thought.

That's actually a great idea. No compatibility issues with the evaporator, and I have plenty of room under the body for a massive condenser.

dculberson wrote: Are you set up to work with R134a refrigerant at all? (ie, vacuum pump, manifold gauge set)

Manifold and guages - check. Vacuum pump - check. Brazing torch - check.

dculberson wrote:

ProDarwin wrote: In reply to dculberson: Just do what he said, except pirate the entire A/C system from a small car and drive it with an electric motor?

Yeah!! I wonder how big of a motor it would take to turn it? And how fast it would have to turn to be effective?

I like that idea. My only problem with the "small car" idea is that its designed to generate enough BTUs to cool a small car. My van will be fairly well insulated, but its a massive volume compared to a civic. Come to think of it, the rear A/C in a Ford Van is designed to supplement the front A/C, not replace it.

As far as the motor is concerned, that's pretty simple math. Vehicle A/C compressors are designed to be make peak efficiency at or around the vehicle's cruise RPM. Since the actual compressor speed is a function of vehicle cruise RPM altered by pulley ratio, its pretty straight forward. I did some quick guestimates on the compressor that is mounted on the van and it looks like the 2400-rpm cruise RPM translates to about 3600 rpms at the compressor pulley.

... which is pretty simple since most industrial 120v motors turn at 1850 or 3650 rpm.

Hmmm.... although, piston-driven vehicle A/C compressors are pretty inefficient. Lots of friction. Since power is in abundance from a crankshaft it makes sense. A person can lose 5hp from the crank and not notice it, but driving it with an electric motor? A 5hp electric motor is no small thing.

Perhaps a larger refrigeration compressor, like from a walk-in fridge? Or a central A/C from a house? I think they use a fridge-type diaphragm compressor and they have tons of BTUs in reserve.

More research.... :)

Rather than central A/C from a house you could go back to the tearing apart a window a/c unit concept. There are plenty of high efficiency and quiet window a/c units that could donate the evap, compressor, and condenser.

Oh, keep in mind window a/c units (and refrigerators) won't typically have a service port, it'll be a brazed closed system. That's why I linked to the braze-on saddle valve service port earlier.

An excellent link, by the way.

I've found that most of those cheapy window units use proprietary parts. I was thinking if I used a universal compressor brazed to a universal condenser, brazed to....

I'm afraid that if I used one of those $99 window units and hack it and it fails somewhere down the road I'll either have trouble replacing the part, or I'll end up buying another $99 unit and have to re-engineer the whole thing.

Every central AC unit I've repaired has been 220v.

You're going to run into proprietary parts in just about everything that's been named here. Don't worry about any of that stuff, seriously. If you're brazing everything up, you can simple redo what you did when you built the setup.

Have you thought about paying a trip to an appliance repair guy? You need to find the appliance junkyard in your area, if you have one. We had one, but the gentleman that ran it died and everything was scrapped. That place was an absolute GOLDMINE for what you're doing.

The other place I'd look is anywhere you can get used RV parts. I've seen RV junkyards here and there, so that might be a good option, at least for some of the parts you're looking for.