Rooftop, Portable, Window Air conditioning

[jimindenver]

Debit

Think of it this way. You have a fridge or freezer with one hot wall. The more you try to cool it down, the hotter the wall gets. It's a never ending battle that eventually the heat will win. Why? Because you create more heat cooling the air than you remove from it, you can not win.

It would help if you could butt the unit up to a window or wall and vent it directly outside. All that would be left then is the heat from the case and there is nothing to be done about it.

So power wise window units are more efficient.

Since they are not fighting themselves a window unit requires less BTU to do the job.

Window units are much less expensive too but they do have the drawback of needing to be mounted.

 

[freeskiier13]

In regards to suffocating from dry ice...yes that is a very good point.

 

[billybob200138]

Speaking of cooling. Right now you can get a can ,gallon, of the cooling roof paint for $20 Amazon was talk twice that. Have a dark blue van, now it's getting a white top... . HOBOJOE

 

[debit.servus]

Just look at the comments on the portable units (and RV units) on Amazon.  While a dual-hose unit may not be 2x less powerful, it will radiate heat from the body and hose.  But cooling effectiveness is only one metric: you have to also look at acquisition cost and efficiency.  Window units are far cheaper and have much better energy efficiency.

In general, "COTS" (commercial, off-the-shelf) equipment provides far better value than specialty stuff.  While everything we are discussing meets the military's definition of COTS, my point is that window units are a very competitive and mature industry, while portable and roof-mounted units are specialty items and, relatively, garbage.

Still don't see how a portable A/C is half as efficient as a same-BTU rating window A/C. When I feel the back of the DELONGHI 12,500 BTU single hose portable A/C, I don't feel any radiant heat. The hoses do bring a little heat back into the space, and there is also the suction that a single hose portable has, which could be overcame with an intentionally leaky window.
The good thing about portable A/Cs is well, they're portable. They do cost more than window A/Cs and are less efficient due to their fundamental design. Window A/Cs are the best value if one has a hole in their rig to put it through, or can remove a glass window. Portables are great for those changing rigs every year and desire/need stealth A/C. COTS does provides far better value than specialty stuff.

Debit

Think of it this way. You have a fridge or freezer with one hot wall. The more you try to cool it down, the hotter the wall gets. It's a never ending battle that eventually the heat will win. Why? Because you create more heat cooling the air than you remove from it, you can not win.

It would help if you could butt the unit up to a window or wall and vent it directly outside. All that would be left then is the heat from the case and there is nothing to be done about it.

So power wise window units are more efficient.

Since they are not fighting themselves a window unit requires less BTU to do the job.

Window units are much less expensive too but they do have the drawback of needing to be mounted.

I don't understand, the heat is exhausted through a hose and out of the space. It's not like the hose is removed from the portable, and the heat can't be exhausted out of the room. Some portable A/C models probably radiate heat from the back of them; but the DELONGHI I have doesn't, at least noticably. Even with the lesser efficiency, it's still going into the van this summer and might serve as cab A/C if the vans refridgerant can't be recharged.

...
I only used dry ice in my 12v AC unit once in Phoenix, and it was way too cold for me, even though it was about 120° in the shade there.  After only  a couple of hours, I switched back to just plain ice, which kept my van plenty cool enough.

Dry ice does work great for turning a regular ice chest into a freezer though.  Starting out with two ice chests, one block of regular ice, and one block of dry ice, I can boondock for up to a month, with one cooler for a fridge, and the other a freezer.  The freezer can make more ice for the fridge as you go.

Off Grid 24/7, I am skeptical how the Non-Evaporative Swamp Cooler/Heater Core/Recirculating Ice Box A/C (what is the best term for this) can substitute A/C in 120+ degree heat for more than an hour, even with dry ice. What temperature is/was "plenty cool enough"? A comfortable temperature with strong radiant heat and 100+ outdoor air temperature is the upper 70s inside, which is where the back of the van got to in Hitchin' Post RV Park with 11,000 BTUs of A/C running at max cool; with daytime highs at 97-116 degrees (116 degrees F on Saturday, June 20th, 2015 in North Las Vegas, NV). The van was in direct sunlight, with back blacked out, and cab glass un-reflectixed.

Keep in mind that Dry Ice is expensive cooling, only cost effective in the short term. Bought 80 pounds of dry ice to keep food cold for BM 2015, and don't plan to again. Desire a 12v compressor-based chest freezer so bad... WAY cheaper than dry ice in the long term.

It occured to me one could recirculate water with copper tubing coils at each heat transfer point between a operational 12v compressor chest freezer and a couple ice chests instead of forming ice or swapping ice bottles between freezer and ice chest. It could make a great heatsink for the Non-Evaporative Swamp Cooler/Heater Core/Recirculating Ice Box A/C, with the 12v compressor chest freezer in a seperate "room" with ventalation away from the one to be cooled. For vandwellers, the 12v compressor chest freezer is in the cab with windows down while the fan with coils/heat exchanger is in the back of the van.

 

[ascii_man]

Still don't see how a portable A/C is half as efficient as a same-BTU rating window A/C. When I feel the back of the DELONGHI 12,500 BTU single hose portable A/C, I don't feel any radiant heat. The hoses do bring a little heat back into the space, and there is also the suction that a single hose portable has, which could be overcame with an intentionally leaky window.
The good thing about portable A/Cs is well, they're portable. They do cost more than window A/Cs and are less efficient due to their fundamental design. Window A/Cs are the best value if one has a hole in their rig to put it through, or can remove a glass window. Portables are great for those changing rigs every year and desire/need stealth A/C. COTS does provides far better value than specialty stuff.

I don't understand, the heat is exhausted through a hose and out of the space. It's not like the hose is removed from the portable, and the heat can't be exhausted out of the room. Some portable A/C models probably radiate heat from the back of them; but the DELONGHI I have doesn't, at least noticably. Even with the lesser efficiency, it's still going into the van this summer and might serve as cab A/C if the vans refridgerant can't be recharged.

A dual-hose unit might not be half as efficient as a window unit, but I think they had much lower EER ratings. But even at 100% efficiency, 12,500 BTU/h requires a lot more power (that's "power", not "energy") than a 5000 or 5200 BTU/h window unit, which are difficult enough to run off batteries. And they cost far more to purchase than window units.

 

[highdesertranger]

ok let me take a shot at this. on the portable unit both the condenser(hot radiator) and the evaporator(cold radiator) are inside the room. the exhaust fan cannot remove all the heat from the hot side. simple physics, nothing is 100% efficient it's impossible. so part of the cooling is taken up by the heating. this is why the portables are less efficient. hope this clears it up. highdesertranger

 

[freeskiier13]

Has anyone researched/experimented with retrofitting a larger startup capacitor into a window a/c unit to alleviate the highest of peak loads to potentially run one off of a smaller generator?

 

[jimindenver]

There is a you tube on someone doing that so they could run it off of their Honda EU 1000.

 

[debit.servus]

ok let me take a shot at this.  on the portable unit both the condenser(hot radiator) and the evaporator(cold radiator)  are inside the room.  the exhaust fan cannot remove all the heat from the hot side.  simple physics,  nothing is 100% efficient it's impossible.  so part of the cooling is taken up by the heating.  this is why the portables are less efficient.  hope this clears it up.  highdesertranger

So the hot side exhaust isn't getting all the heat from the condenser to blow out of the room? Plus the radiant heat from the condensor plate interacts with the housing on the portable A/C? While the window A/C radiates the heat on the hot side to the outside world?

Has anyone researched/experimented with retrofitting a larger startup capacitor into a window a/c unit to alleviate the highest of peak loads to potentially run one off of a smaller generator?

People have configured window A/Cs with startup capacitors. Somebody needs to manufacture an affordable plug in solution because most people can't or won't modify the electrical on their window A/Cs. Would be nice to run an A/C from a little 800 watt generator.

 

[highdesertranger]

by George I think you have got it. highdesertranger

 

[jimindenver]

There isn't much reason for manufactures to add a start capacitor to a unit designed for use on a 15a grid tied line. Plus they charge twice as much for one that uses 50w less. add a start capacitor and it will be 3x.

 

[IGBT]

We run a little 6000 BTU window unit in our homebuilt RV and it runs just fine on a Honda EU2000i generator.

I can actually run the Honda in Eco mode if I turn on the Magnum inverter.  The Magnum has generator sharing, where it provides power from the batteries if the external power (shore or generator) is not up to snuff.   When the compressor in the window unit cycles on and draws more power than the EU2000i can deliver in Eco mode, the Magnum instantly makes up the difference for the few seconds until the compressor in the A/C is running.   Very minor hit to the batteries since the inverter is only pulling 20 or 30 amps for few seconds to give you that extra 500 watts or so (24V battery feed to the inverter).

Also can run the window unit directly off of solar for about 6 hours out of the day.   You have to love these $99 window units...pretty amazing what you get for that little bit of money.

 

[jimindenver]

One thing I will try this summer IF I get the temperatures to do it is starting the A/C before the sun gets high enough to have the solar run it on it's own. Turn it on early when the trailer is cool still and it will easily keep it there and cycle on and off all day.

Why might this be better? Because having everything inside stay cooler means the A/C cycles off longer all day. Waiting until the sun is high enough might mean allowing the trailer to get hot. When that happens the A/C cools the air and cycles. Since everything else has warmed up, it warms the air back up and the A/C cycles again.

So the trailer should stay cooler, the A/C use less power and the system will have no issue catching up while the A/C does cycle.

Personally if I were to run a small window or even a portable off of a small inverter generator, I would go with a 2000w model. You can put a soft start on and run it off of a 1000w or even a HF 800w but it puts more strain and makes much more noise than the bigger generator.

Believe me the start surge can be formidable. Starting the A/C took out a cheap 3000w PSW inverter and was the last straw for my original 8-D.

 

[amwbox]

The problem with the portable units on wheels is that they radiate heat from the cabinet since the whole thing is inside. That hot air exhaust hose that you are supposed to stick out a window does not remove all the heat. You are basically sitting next to a little radiator that is trying to remove heat from the space it is radiatively heating. These things are only good if you are sitting with your face in front of the vent...

Cut the BTU output number in half on these, and you probably are getting about that.

5K BTU window units work pretty well cooling small spaces, and can sometimes run on a 1000W genny, depending on the startup surge and the capability of the genny to handle it.

Its always seemed to me that if someone really wanted to use a window AC in a van, the best bet would be to have a fairly decent bulkhead between the living area and the driving area. One could cut a hole to hang the AC through as if it were a window, and just let the hot air exhaust itself through the cracked windows in the cab. Would probably need to be either high, to clear the seats, or low, to clear a seat slid forward as far as it would go. 

Considering how small a volume a van really is, even the inefficiency of portable units might be acceptable considering you'd instead just be running an exhaust hose, as opposed to the heavy duty mounting needed for a window unit in this configuration.  If one of these portable AC's is capable of cooling a room sized airspace, surely a van that is 70% smaller should be doable, even if less efficient.

 

[debit.servus]

There isn't much reason for manufactures to add a start capacitor to a unit designed for use on a 15a grid tied line. Plus they charge twice as much for one that uses 50w less. add a start capacitor and it will be 3x.

What I mean is a UPS like thing to plug in inline to handle the startup surge of an A/C so one can run an 5000 BTU window A/C from a 1000 watt genset. Shouldn't cost the consumer more than $100 to buy such a surge handler.

We run a little 6000 BTU window unit in our homebuilt RV and it runs just fine on a Honda EU2000i generator.

I can actually run the Honda in Eco mode if I turn on the Magnum inverter.  The Magnum has generator sharing, where it provides power from the batteries if the external power (shore or generator) is not up to snuff.   When the compressor in the window unit cycles on and draws more power than the EU2000i can deliver in Eco mode, the Magnum instantly makes up the difference for the few seconds until the compressor in the A/C is running.   Very minor hit to the batteries since the inverter is only pulling 20 or 30 amps for few seconds to give you that extra 500 watts or so (24V battery feed to the inverter).

Also can run the window unit directly off of solar for about 6 hours out of the day.   You have to love these $99 window units...pretty amazing what you get for that little bit of money.

So one can buy a NEW 5000 BTU window A/C for $100 at an everyday low price, which store was this? In WALMART here in San Jose, CA I saw the HAIER 5000 BTU window A/C in two variants, digital display with remote (like the 10,000 BTU HAIER window A/C I have) and the low-tech mechanical dial model. The dial model was $115 and the digital display model was $130, which is what the mechanical dial version retailed for last year.

They had to have cheapened the inner workings some more to get to that $115 price point, as the cost to manufacture it without cheapening it will have gone up. Which means the new model HAIER window A/Cs will have a shorter lifespan than the one I bought last year. Which means people who sell their high-end window A/Cs on Craigslist will get less for them as people see a cheaply made HAIER 5000 BTU window shaker go for $115, due to price perception.

 

[surfer]

Even though my entire system is 12v only, I still have a microwave, bug zappers, electric blankets, Peltier thermo-electric heating/cooling/massage seat cushions, fully dimmable LED lighting, fans, Air Conditioning, TV, Laptop, etc.  Plus I have lots of toys to keep me entertained, a solar Sun Oven, a solar magnifier type stove and grill (two separate units, made by an outfit out of Eugene, Oregon.), and a solar umbrella cooker.

I am currently playing with the idea of running a Stirling Engine, and a Steam Engine via either magnified solar power, or umbrella solar.  My goal is to be able to fully charge an electrical system with under a half an hour of sunlight per week, using no fossil fuels.  The challenge is in converting solar power into strong  mechanical power, and keeping the system portable, no bigger than 1' x 2'.

When I started reading this thread  I anxiously awaited for Peltier Air Conditioning to come up. I've been looking for a year. I thought it would after your mentioning "Peltier thermo-electric heating/cooling/massage seat cushions" but it didn't.  Therefore I'm guessing no one is using it. All I know about it is from videos I have seen: Peltier Air Conditioning 1/5 video & forum: http://offthegrid.forumsmotion.com/t4-tec-peltier-effect.  Since it was used on a boat I was hoping that the application had been replicated to van (& other tiny home) dwelling. I'm hoping others better suited to it will figure out if & how to apply it to van life since he seems to have dropped the topic on the forum. His last entry said " This seems to be a very popular device that interests many... I will need to get them installed on the teak boat soon, so I can make a few video's showing others how to make them as well!"  on Dec 20, 2014. He has responded to his 5/5 video a week ago though. 8 months ago he responded "We made this one, but someone must commercially make something similar." but I have not found any. If anyone could give me build instructions or where to buy,  I'd be greatful!

Another interesting rv solution: 12 Volt DC Air Conditioner for Semi-truck, RV, Lim 
.

I hope you will share your solar engine results. Best of luck!

 

[blars]

Pelter devices are inefficient and need someplace to put the excess heat. See the many threads on how useless the "coolers" that use them are.

 

[florida454]

Hello all, I have lurked and this is my first post.

To help your AC start consider a Hard Start kit, which adds a starting cap and relay as one unit and is very easy to install.
This will add to the units capacitor mfd's, advancing the sine wave a little more on start up to further unbalance the motor and let it turn over easier, then it promptly drops itself out of the circuit.
Example below: read reviews
http://www.amazon.com/SPP6-Capacitor-Combination-Operating-Voltage/dp/B000LDPI26

Here is a video: 5000 BTU air conditioner running on a 1000 watt generator


Please note in my experience this style of hard start kit may last only a year, maybe three. For $9-12 and 2 minute install that's not too bad. Just a heads up to recall this when it goes bad and you don't know whats wrong.

Also about the portable AC units...they are less efficient.
You have to add a volume of fresh air equal to the warm air you exhaust. So if you are adding hot air you now have to cool that added air, this increases your total heat load on the AC unit. So a 5k BTU portable unit will have run longer than a 5k BTU window unit to cool that same square footage.

That said a portable unit will cool your your van just fine. A really good solution if you do not want to remove a window or cut door panel to install a window AC.
A perfect solution if my work van needed to be a camper van for the weekend.

 

[amwbox]

Hello all, I have lurked and this is my first post.

To help your AC start consider a Hard Start kit, which adds a starting cap and relay as one unit and is very easy to install.
This will add to the units capacitor mfd's, advancing the sine wave a little more on start up to further unbalance the motor and let it turn over easier, then it promptly drops itself out of the circuit.
Example below: read reviews
http://www.amazon.com/SPP6-Capacitor-Combination-Operating-Voltage/dp/B000LDPI26

Here is a video: 5000 BTU air conditioner running on a 1000 watt generator


Please note in my experience this style of hard start kit may last only a year, maybe three. For $9-12 and 2 minute install that's not too bad. Just a heads up to recall this when it goes bad and you don't know whats wrong.

Still...that guy reduced his startup surge by something like 70%. That is huge when considering wear and tear on expensive inverters and generators. A 2000+ watt surge every time the compressor kicks on throughout the day...eek. Who would want to beat up their power system like that if they could avoid it?

 

[Moonbeamsandukuleles]

I have a 12 ft TT, a 1980 Sunline.
After looking at AC options so that I can stay in Florida,  i decided on a small window unit.
We had to cut a hole in the front,  since it wouldn't fit in the window. A friend reinforced the wall and i think it looks great. We added a shelf outside for support. 
It cools the whole little space in a couple  in minutes and is super quiet. It was around d $150 from HD
I posted a picture of the inside.