HVAC questions

Now that I have decided on definitely getting a van, I need to figure out a way to rig up some grassroots A/C in the back for camping when I plug into 120v.

I thought about getting a small window A/C unit, cutting a hole in the back door and be done with it, but I can't be sure of properly supporting it, especially considering the bouncing it will endure. I thought about getting a rooftop RV unit, but I don't like the added height, wind resistance OR THE PRICETAG. They ain't cheap.

So, I'm thinking about getting the individual components (either new or salvaged) and building a small A/C setup for it. That way I can mount the evap/blower inside somewhere and the condenser/compressor on the frame or something. Maybe get a window A/C off CL, disassemble and install it, then connect the lines and recharge it?

Anyone done something like that? How do I go about figuring out how many BTUs I need for the volume and insulation?

How about something like this portable a/c unit: http://www.google.com/products/catalog?q=portable+air+conditioner&hl=en&biw=1677&bih=957&prmd=ivnsr&bav=on.2,or.r_gc.r_pw.&um=1&ie=UTF-8&cid=465380801234618276&sa=X&ei=Bl60Tb2TF4Hc0QGE15DsDQ&ved=0CK4BEPMCMAk#ps-sellers When you're camping you could put it outside the van and run the duct in through a window or a fabricated hatch. It costs $200, but you'd probably spend that much fabricating something yourself.

Another thought is getting a regular old window shaker air conditioner, and coming up with a way of quickly installing it in a window when you get to the camp site instead of trying to permanently attach it. You can pick those up cheap, new or used, all day long.

Buy a window shaker, some copper tube and a recharge, and you've got all the components you need. Evacuate, dissassemble, fabricate and install as needed, solder, recharge.

I recall a guy who built a tear drop... he had a setup with a/c in it... he used a small window unit... he removed the front pannel and made it so he could hook up a hose for the vent and return... he'd had it sitting in the front of his trailer early on but he said it made to much noise so later he ran the ducting hose and set it under the trailer...

oh ya he mounted a wire to the thermostat inside the thing also

curtis73 wrote: Now that I have decided on definitely getting a van, I need to figure out a way to rig up some grassroots A/C in the back for camping when I plug into 120v.

I've seen this set-up, although it was installed in a truck-style camper. The trick will be finding one small enough so it won't freeze you given the small area of a van.

Curious to see what you can come up with...

what type of refrigerant do window units use? I have a manifold for R134. I'd have to do a custom charge, right? Since I'm adding volume with the extra tubing?

If I remember, window units don't have charge fittings. Just something to look for.

mount the window unit on a roof rack, with ducting through the roof.

AngryCorvair wrote: mount the window unit on a roof rack, with ducting through the roof.

One problem with this is that while the 'outside' part of the window unit is designed to be outside, the 'inside' part is not.

I wouldn't worry too much about BTU's. Even the smallest window unit will be more than enough to cool the interior of a standard van (roughly 70 sqr ft).

What I would do (and as I've mentioned before, I've spent a lot of time thinking about this sort of thing) is find a small window unit and mount it in one of the rear doors. Support could come from one of two ways. Either weld/bolt additional support brackets, or get a rear spare carrier and add supports from that - with the added benefit of the rear spare will sort of "hide" the added length of a box hanging out of the back of the van as well as freeing up under-carraige space for things like water tanks.

how about mounting it on the lower half of one of the rear doors? A few pics here of one done that way.

http://www.expeditionportal.com/forum/showthread.php?t=51250

Ian F wrote:

AngryCorvair wrote: mount the window unit on a roof rack, with ducting through the roof.

One problem with this is that while the 'outside' part of the window unit is designed to be outside, the 'inside' part is not. I wouldn't worry too much about BTU's. Even the smallest window unit will be more than enough to cool the interior of a standard van (roughly 70 sqr ft). What I would do (and as I've mentioned before, I've spent a lot of time thinking about this sort of thing) is find a small window unit and mount it in one of the rear doors. Support could come from one of two ways. Either weld/bolt additional support brackets, or get a rear spare carrier and add supports from that - with the added benefit of the rear spare will sort of "hide" the added length of a box hanging out of the back of the van as well as freeing up under-carraige space for things like water tanks.

I'll look into that, Ian. It will leave less space for me to spray paint "free candy" on the back, but its a trade-off.

I'm not too concerned about getting enough BTUs, but I am concerned about getting too many. If the cooling doesn't cycle on/off enough, you get mold/condensation issues. I really think I need 2000 BTUs. It would need 1500 based on size, but poor insulation and often times direct exposure to sun in 100+ degree heat I think 2000-2500 would be perfect.

I wonder how many BTUs a typical fridge does? If I had a fridge compressor and then put a different evap and condenser on it, maybe that would do the trick?

Window units USED to be R12 years ago. I would suspect they were R134a today. There's probably a sticker in them somewhere. If it doesn't have an access port, you can buy a thing that clamps onto the copper line, pierces it and provides you with an access port.

A total home brew system would be way cool. Like, pick up a condenser at the junk yard, maybe get an evaporator too. Put an expansion valve on it, run some lines, a 12v compressor or maybe one from a refrigerator or freezer, muffin fans on both coils. That would be neat. Or just get a window unit and make a strong mount for it and don't worry about it.

I just replaced the freon lines on the Esprit. I still need to button it up. That's why I've got AC on my mind. What a PITA.

I'm not sure... I just looked at our office fridge and it doesn't say... I does use r134a... the other odd bit is fridge compressors are designed to run the fridge and the freezer. Could that idea work? Probably. But you would need a refrigeration engineer to size the coils and valves. Get either wrong and the system won't work correctly. I'd be very concerend about condensation with such a split-system as well. Possibly even frost issues on the evap coils.

Another semi-cheap split system idea is to use automotive components, powered with a 120V electric motor. That said, I'm not sure of the HP required to spin a common Sandon style compressor (although I understand it's not much). At least there the parts are all off-the-shelf and already pre-sized for the application.

Ian F wrote: ... the other odd bit is fridge compressors are designed to run the fridge and the freezer. Could that idea work?

Some cheap fridges only have evaporators in the freezer and then a vent hole into the fridge. They're just designed for the fridge to be X degrees warmer than the freezer. There is also the possibility of getting a salvaged commercial fridge that is just a fridge - no freezer.

I'm forging all kinds of ideas... don't know if any of them are good ones. A pre-designed setup like a window unit is nice, but (at this point anyway) I don't know how to size compressor volume with evap and expansion valve sizes. I know that you can't really go too big with condensers. Maybe I can buy a book on it or find something on the googly.

Dr. Hess wrote: If it doesn't have an access port, you can buy a thing that clamps onto the copper line, pierces it and provides you with an access port.

Best not use the piercing valves, they are a 2 pc.saddle valve w/ rubber gasket, they will leak eventually.

There are schrader valve fittings that can be soldered inline to the low and high side tubing (like cutting in a tee). There's also a single fitting w/ valve that can be soldered on the process tube of the compressor. I will look for linky.

If the system is cut apart, like it sounds like it will be, it's better to install at least one schrader valve on the low side tubing or compressor for charging and service.

In reply to fasted58:

Example of low/ high side in line access valve: http://www.cdvalve.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=33&category_id=7&option=com_virtuemart&Itemid=60

Process tube access valve: http://www.grainger.com/Grainger/14-In-Extension-Tube-4PDH2?Pid=search

Ok, did a little research. Fridge-type "canister" compressors that are rated in the 1/4 - 1/3 hp range are rated at or around 3000 BTU. From the link that Failboat posted (great thread over there) many of the guys are saying that 5000 BTU is a better ballpark, even with insulation.

So a small window unit is looking smarter all the time. I'm still strongly leaning toward taking that unit apart. I would much rather install the outside stuff under the van and then only have to drill a couple holes in the floor for installation instead of cutting a 13" x 20" hole in the van.

Well, I haven't even bought the van yet, but I'm already looking for goodies for it

just a guess but how bout somethin like this:

http://kingersons.net/portable_ac_7500m.htm

only takes a smallish hole to vent the condenser outside

had another thought.... if I cut a big hole for a window unit, won't I have trouble finding another one that fits when the first one dies? The smaller window units are kinda disposable. When they die, you toss them in the trash and buy another one for $100.

But then again, buying each part individually from somewhere like Grainger is way too expensive.

I'm just thinking of servicability. Its not like I will be using this every weekend and putting a lot of stress on the A/C, but I guess I was just trying to think ahead. If something fails I want to be able to replace a part, not necessarily re-engineer the whole installation.

I would definately insulate the van as much as possible as shown in the link I posted yesterday. It makes a huge difference if you can improve on it at all. Makes good sound deadening too, the doors close with a nice thud instead of a metallic clang.

The problem with conversions is, once you start taking them apart you see how shoddily they were put together. If I ever get another van that I want to outfit for camping, I will start with a stripped out cargo or some other OEM model.

I camped in and drove my van with NO insulation for a few years, it was literally an oven in the summer as you can imagine, and an icebox in the winter once the heater core blew out and I had to limit my use of the heater.

The 79-95 chevy's had a little adjustable vent above the drivers front wheel under the dash that allowed outside air into the van, was nice in the summer time for air circulation, but oh my god was it cold in the winter when it wouldnt properly seal anymore.

curtis73 wrote: I'm just thinking of servicability. Its not like I will be using this every weekend and putting a lot of stress on the A/C, but I guess I was just trying to think ahead. If something fails I want to be able to replace a part, not necessarily re-engineer the whole installation.

This is why I lean towards automotive-based system: easy to find parts (can probably source most bits at a local junk yard); anyone with an auto guage set can service it; engineering is more or less already done.

failboat wrote: I would definately insulate the van as much as possible as shown in the link I posted yesterday. It makes a huge difference if you can improve on it at all. Makes good sound deadening too, the doors close with a nice thud instead of a metallic clang.

I'll have to wait until I actually get my hands on a van (I'm buying a cargo) but from the pictures it looks like insulating and siding it will be dirt simple. Like that thread indicates I will have to be cautious about sweating and condensation, but I think the ideas I have in mind will be enough insulation but still let it breathe just a bit.

I lean towards automotive-based system: easy to find parts (can probably source most bits at a local junk yard); anyone with an auto guage set can service it; engineering is more or less already done.

Agreed. I'm going to do some more research on it. What I'd like to do is take a complete automotive system and then drive it with a 120v compressor. I like the idea of running an automotive compressor with a 120v motor, but I'm also finding that it might take a pretty hefty motor to spin it... like on the order of 3-5 hp. The whole thing might be pretty noisy and require excessive amperage to run.

By the way, according to Grainger, most of the refrigeration compressors are R134. Most of the residential ones are R22.

I have heard if you use rolls of insulation similar to whats pictured, stop them about 6 inches short of touching the floor of the van. That way if you ever have any sort of condensation/water accumlation at the bottom of the wall, the insulation will not sop it up every time.

But yes it is super simple to insulate like shown. Just add paneling over it when you are done, which you can wrap with foam and upholstery as desired before final installation. One thing to be careful of, make sure the screws you use are short enough to not push up into the roof of your van.

I had a few screws on my conversion van (no raised roof) that pushed up on the roof, cracked the paint, started to rust and there were at least 5+ pinholes leaking water into the van every time it rained. I had no idea until I dropped the paneling on the roof and the support boards were all rotted out from being soaked for years.

curtis73 wrote: Agreed. I'm going to do some more research on it. What I'd like to do is take a complete automotive system and then drive it with a 120v compressor. I like the idea of running an automotive compressor with a 120v motor, but I'm also finding that it might take a pretty hefty motor to spin it... like on the order of 3-5 hp. The whole thing might be pretty noisy and require excessive amperage to run. By the way, according to Grainger, most of the refrigeration compressors are R134. Most of the residential ones are R22.

True... a 'real' 3 HP motor will draw about 34 amps at 115v and require a 70A breaker to handle the in-rush load. About 1/2 that for 230v.

The tricky part will be figuring out the compressor and condenser requirements... Not sure what to tell you there... my last company had a refrigeration dept (we did a lot of supermarkets), but it's something of a specialized field since most commercial split-systems are factory-engineered. And to size the compressor you will need to find the specific load data for the evap unit you end up using.