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I have a Master-Cool evaporative unit on my home in AZ. It can make that 1600 sq ft house so cold you cannot stand it. We have it on a thermostat because if it runs on low all the time (which is normal for them) we have to put on a sweater even at near 100 outside. Dry is the secret. 4% humidity is not unusual there. If you want to try evaporative cooling in your van expect 10º delta and it does work well at even 50% humidity. See:
http://www.promasterforum.com/forum/showthread.php?t=50722
 

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Nice job making those fit tightly. Will you share more info? Like size of your van, number of windows, type of insulation, A/C capacity, where you store it while traveling, how it's powered (generator or campground?), etc. Mostly I'd love to hear how well it cools during the day if parked in sun.
I have a 159" high roof. I have a factory window in the slider and a CR Laurence on the other side. All but the roof is insulated with thinsulate and EZ-Cool. The roof only has 1/8" closed cell foam.

The a/c unit is a Whynter.

https://www.amazon.com/Whynter-ARC-14SH-Portable-Conditioner-Storage/dp/B002W87P9C/ref=sr_1_5?s=home-garden&ie=UTF8&qid=1498700212&sr=1-5&keywords=whynter+portable+air+conditioner

This weekend will be the real test. I have a track day in South Carolina and it will be in the 90's during the day and low 70's at night. The humidity will probably be high too. I will report back with how it does. Weekend before last I used it to cool a very small farmhouse. We put it in the kitchen and it did a very good job of keeping us comfortable. I usually have it plugged in to shore power. I'm not really sure how it would do in the sun. If possible I will test it this weekend. I usually strap it to the wall in the back of the van.
 

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Nice job making those fit tightly. Will you share more info? Like size of your van, number of windows, type of insulation, A/C capacity, where you store it while traveling, how it's powered (generator or campground?), etc. Mostly I'd love to hear how well it cools during the day if parked in sun.
I have a 159" high roof. I have a factory window in the slider and a CR Laurence on the other side. All but the roof is insulated with thinsulate and EZ-Cool. The roof only has 1/8" closed cell foam.

The a/c unit is a Whynter.

https://www.amazon.com/Whynter-ARC-1...ir+conditioner

This weekend will be the real test. I have a track day in South Carolina and it will be in the 90's during the day and low 70's at night. The humidity will probably be high too. I will report back with how it does. Weekend before last I used it to cool a very small farmhouse. We put it in the kitchen and it did a very good job of keeping us comfortable. I usually have it plugged in to shore power. I'm not really sure how it would do in the sun. If possible I will test it this weekend. I usually strap it to the wall in the back of the van.
 

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Roblee
Subjectively I would say that the unit cools effectively but I'll get come temperature drop data (delta air return to output) when I have the opportunity to operate it for a longer period of time. It was somewhat challenging to find appropriate locations for having the 4" elbows go through the floor in the rear location I used. A side installation would give greater freedom but I ruled it out from an aesthetics standpoint. I think the most important issue is adequate airflow through the condenser and my Sythe DFS123812H-3000 case fan booster is quite effective yet uses about 8 watts. Even more powerful 120mm fans are available but noise db increase rapidly. The fan is barely audible in my installation.

With my 654 watt PV panels the 450 watt AC will run on a sunny day without taking energy from the battery pack (four 230 amp GCB's). At night I calculate about four hours of AC without going below 50% of pack capacity and allowing for my compressor frig and other minor draws. My guess is that a 5kbtu unit is not going to be adequate for most Promaster conversions. I have only rear windows and 3" of Polyiso foam in the walls, 1" in the floor, and 1.5" in the ceiling. Solar panels shade much of my roof. It may be feasible to build in a compact 8kbtu unit in a similar fashion.

So far we are quite happy with the performance of the AC installation. In our two previous RV's the roof AC was so loud we often used ear plugs. This installation is a significant improvement.
This week I had an opportunity to test the performance of my AC unit. It was 75F outside and 80F in the van. Sunny but with scattered clouds. Running on my inverter the battery monitor showed 100% charge until clouds rolled by and it dropped to 97% after several hours. The delta for output versus air return stayed steady at 22F. I used the probe for my digital thermometer in both grills to keep the measurement accurate. To my surprise using the 130 cfm booster fan did not increase the differential. For my installation this says that concerns about screen on the input and gap behind the condenser are not significant issues because if they were the much higher air flow with my booster fan would have increased the delta.
 

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It does not mean that to me at all. That's not the way refrigeration works. I designed and installed a few custom 300- to 500-ton blast freezers so I know a thing or two about this subject.

Anyway, I apologize if I was critical of your design, but I was just trying to help you by pointing out weak areas in the design. More importantly, I was pointing these out so someone else without experience doesn't copy it too closely and create themselves a serious problem.

I get you and others may not want or appreciate my help so I'll stay out of your design entirely. Sometimes it appears there is no way to critique a design without hurting people's feelings because they take it personal.

Good luck. :)
 

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This week I had an opportunity to test the performance of my AC unit. It was 75F outside and 80F in the van. Sunny but with scattered clouds. Running on my inverter the battery monitor showed 100% charge until clouds rolled by and it dropped to 97% after several hours. The delta for output versus air return stayed steady at 22F. I used the probe for my digital thermometer in both grills to keep the measurement accurate. To my surprise using the 130 cfm booster fan did not increase the differential. For my installation this says that concerns about screen on the input and gap behind the condenser are not significant issues because if they were the much higher air flow with my booster fan would have increased the delta.
Hi,
Thanks for the test results.

Hope you can repeat the test when its hotter outside both to understand if the 5K BTU unit is up to cooling the van, and to see if more circulation from the booster fan improves performance when the AC unit has to work harder.

You have probably mentioned this before, but how well are your van and windows insulated, and is it a 136 or 159?

I did see a YouTube video in which they mounted the AC unit down low (similar to yours), and said that there was quite a bit of stratification and that when you got more than 3 or 4 ft off the floor it was pretty warm. Have you seen this? I wonder is some sort of diverter or fan would solve this problem (if it exists)?

Thanks -- Gary
 

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A quick thought

It appears that to use a hose - equipped stand alone unit you need a good place to route the heat output hose so that the system works best.

Has anyone tried a square adapter plate over the Fantastic/Maxxair vent unit to suck the hot air out of the AC unit. Seems to me that if the fan speed was "synced" to the AC output fan speed, you wouldn't need to vent out a window, but could use the vent to remove the hot air.

Just wondering if it would work or if it's been tried...:nerd:
 

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It does not mean that to me at all. That's not the way refrigeration works. I designed and installed a few custom 300- to 500-ton blast freezers so I know a thing or two about this subject.

Anyway, I apologize if I was critical of your design, but I was just trying to help you by pointing out weak areas in the design. More importantly, I was pointing these out so someone else without experience doesn't copy it too closely and create themselves a serious problem.

I get you and others may not want or appreciate my help so I'll stay out of your design entirely. Sometimes it appears there is no way to critique a design without hurting people's feelings because they take it personal.

Good luck. :)
Chance
I assure you no offense was intended. I related my experience my experience in operating the unit and gave my conclusions about use of the booster fan. I would appreciate hearing your conclusions and the logic behind them. Bill
 

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Any more on this sort of an instal is good to get here and since you two are doing it in a similar way by venting through the floor I would appreciate whatever more you know or have learned. I looked for conflict in rereading and I thought you both presented respectful details and no criticism. That is great in my mind. I tend to think the forced ventilation is a good thing and both cheap and low energy so it might be preferred.

proeddie,
Interesting. Moving the cooler air around the van is one issue and exhausting the hot air off the condenser is another. which are you thinking.
 

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Dumb question: why draw outside air for the A/C intake? Wouldn't it be more efficient to draw air from in the cabin, like putting your car A/C on recycle (recirculate)? It seems counterintuitive to draw hot, humid air, but I bet you have a darn good reason, don't you?
 

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Hi,
This has been a really interesting thread to me because I'm trying to decide on some sort of AC for the van. But, I don't want to get into needing shore power whenever I need the AC.

Our traveling is nearly always in the west, and if we did go down to the gulf or Florida it would be in the winter when no AC is probably needed. So, mostly dry conditions.


I'm still on the fence about using some type of evaporative cooler or something like a 5K BTU/hr window AC adapted to the van.

I've got a roll around evaporative cooler that we use for the house that does a good job for the few days of hot weather we get in Bozeman each summer. We have a couple days of 90F coming up, and I'm going to put it in the van in full sun and see what it does. The plan would be to put this between the driver and passenger seats with the cab windows and back windows all open some (as evap coolers like).

The evap cooler takes up some space and we would only take it along on hot trips, which would not be common for us. Its this one: https://www.amazon.com/Honeywell-CO25AE-Outdoor-Portable-Evaporative/dp/B008UHXXBI/ref=sr_1_7?ie=UTF8&qid=1498878055&sr=8-7&keywords=honeywell+evaporative+cooler

The one we have in hand runs on 175 watts, and with 95% inverter efic, this would be 16 amps, and adding 4 amps for other stuff would put us at 20 amps with AC running. So, going down to 20% SOC on our 220 AH batteries, we could get 9 hrs of night use. During the day the solar would keep with the load, and normally we would be driving and not even running the evap AC. So, that seems workable?

There are other evap coolers with less capacity that use much less than 175 watts (eg 50 watts), and this would also be a possibility if our large cooler seems like too much capacity. With a 50 watt cooler, we could go forever on batteries and solar.
https://www.sylvane.com/honeywell-cs071ae-evaporative-cooler.html

I'll report on how the test comes out.

Other possibility is to uses a 5 or 6K BTU/hr window AC unit. I've looked at some of the ways people have done this (Wbullvent, Chance, and Sonicsix plus some others on YouTube etc). The ones that actually replace (say) a back window seem likely to give the best performance, but I don't like the idea of the window mount. SonicSix's setup http://rvroadtrip.us/library/van_airconditioner.php seems like the most likely to give the full cooling performance of the window AC as it has a decent condenser cooling air input area, and a large condenser cooling exhaust area?? But he says that is did not cool well enough for him and he went to a larger portable unit -- I think he is in Alabama, so tough area for cooling.

Chance, sounds like yours is working well -- would you say its good or 90 or 95F dry conditions?

My rough calcs say that in the shade, my insulated van with the Reflectex plugs in the windows, and 95F ambient, the heat loss is 1600 BTU/hr plus 1500 BTU/hr gain from two people, dog, ... -- so, about 3000 BTU/hr. So, looks like a 5 or 6K unit would do it, but not with a lot of margin??
With my current battery setup, I'd only be able to get about 5 hrs, but that might be enough, or I could go to 4 golf cart batteries.

I'd appreciate any thoughts, advice, suggestions on which way we should go?

Thanks -- Gary
 

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Just my random comments on using a 5k btu window units. I think people are under sizing the condenser air flow requirements. The condenser fan is about 9" and people are trying to get that air flow thru a 3 or 4 inch hole, you will need a leaf blower to get enough air flow. As the air temperature around the condenser increases the efficiency drops. If you measure the condenser intake area and exhaust area they are pretty close in size. It takes 4.25 - 4" holes to equal an 8 inch hole. Putting bug screen on the outlet reduces the "net free area" of the hole and increases back pressure. An a/c mounted on the floor will stratify the air in the van, a fan is needed.

I use a 5k unit spliced into the duct work of 2500 sqft home to avoid running my "about to fail at any moment" 2.5 ton a/c system.

Yes it runs continuously, but it's cheap and only uses 5 amps.
 

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Chance
I assure you no offense was intended. I related my experience my experience in operating the unit and gave my conclusions about use of the booster fan. I would appreciate hearing your conclusions and the logic behind them. Bill

Bill, I'll share my thoughts if you really want to know because I'd like you to be as successful as possible. I'm still thinking I may do a window unit again on my next van because it has advantages I really like (it's not about the lower cost), like not increasing height so much so I can park in garage, better aerodynamics, and doesn't look quite as much as a camper to my HOA. I like that it's so quiet from outside of van that it can't be heard, that water doesn't run off roof, etc.


Anyway, the reason I stated I would not come to the same conclusions you did based on data you shared is because it's not definitive. In my engineering opinion you are assuming facts that may or may not be correct (and chances are they are not based on my experience with industrial refrigeration). And also based on extensive testing I did on my A/C before and after installation. I wrote all data down but don't have access to my files at present.

On an A/C, limiting the cooling air to condenser, even if significantly, may not reduce the inside cooling capacity enough for you to measure. Hard to believe but it's true. You'll still feel or measure the cooling essentially the same. What will happen is that as less air flows across the condenser, the temperature differential will go up, increasing the condensing pressure. This will make your A/C work harder, run warmer, use more power, and fail early. If sitting inside the van a person wouldn't notice any of this that should/must be avoided.

You tested on a very cool day, so even if your air flow was cut in half, the condenser's discharge was still likely under acceptable temperature limits. In my opinion you need to test on much warmer days, but more importantly, you need to measure air temperature going in and out of condenser through your floor vents. I also measured air flow but that's not necessary as long as discharge air temperature doesn't get too high. Measuring power draw will also help determine how hard the A/C is working as temperatures vary.

I would try to determine if the "booster" fan is helping at all. It's actually possible it's not. It's even possible that it's restricting air flow. The size and power rating is so low compared to the A/C's fan that it "could" be limiting air flow. I looked at fans and was going to install a blower with about 1/4 HP based on measured air flow. Instead I added a second discharge port and took a chance (which has worked).

Screens do restrict air flow a lot. Partly it is the reduction in free air, but mostly it's the aerodynamics of the fine mesh. Think about how in Florida every time there is a hurricane, one of the first things to go are screens in open rooms.


Sorry for length. Bottom line is I'd do more testing focusing on condenser air flow and temperatures. Inside temperatures, sadly, don't mean as much on whether the system is engineered correctly or not. Getting the A/C to cool is easy. Keeping it working long term and or not starting a fire because it overheats is the real challenge.



By the way: Love the way your A/C looks. It's 100 times better than mine. I really like the flush mount. Will borrow that next time if I have more cabinet depth. :)
 

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Just my random comments on using a 5k btu window units. I think people are under sizing the condenser air flow requirements. The condenser fan is about 9" and people are trying to get that air flow thru a 3 or 4 inch hole, you will need a leaf blower to get enough air flow. As the air temperature around the condenser increases the efficiency drops. If you measure the condenser intake area and exhaust area they are pretty close in size. It takes 4.25 - 4" holes to equal an 8 inch hole. Putting bug screen on the outlet reduces the "net free area" of the hole and increases back pressure. An a/c mounted on the floor will stratify the air in the van, a fan is needed.

I use a 5k unit spliced into the duct work of 2500 sqft home to avoid running my "about to fail at any moment" 2.5 ton a/c system.

Yes it runs continuously, but it's cheap and only uses 5 amps.


And yet mine has worked flawlessly for over 10 years. Go figure. :)


Agree it's not ideal to limit air flow but keep in mind portable units over twice as large in capacity often vent through a single long hose with much more restriction. It's obviously possible to make it work "good enough". Doesn't have to be perfect.
 

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Chance,

I agree, i'm trying to narrow down the intake and output sizes.

I know the window unit condenser airflow is designed for the worst case scenario.

You have 25 sqin for the exhaust, what is the intake size?

I'm thinking 2 - 4" holes or a 6" hole maybe all that is necessary for the exhaust. Also pondering if a single 4" intake hole would work, since the cool intake can be less than the heated output.
 

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Bill, I'll share my thoughts if you really want to know because I'd like you to be as successful as possible. I'm still thinking I may do a window unit again on my next van because it has advantages I really like (it's not about the lower cost), like not increasing height so much so I can park in garage, better aerodynamics, and doesn't look quite as much as a camper to my HOA. I like that it's so quiet from outside of van that it can't be heard, that water doesn't run off roof, etc.


Anyway, the reason I stated I would not come to the same conclusions you did based on data you shared is because it's not definitive. In my engineering opinion you are assuming facts that may or may not be correct (and chances are they are not based on my experience with industrial refrigeration). And also based on extensive testing I did on my A/C before and after installation. I wrote all data down but don't have access to my files at present.

On an A/C, limiting the cooling air to condenser, even if significantly, may not reduce the inside cooling capacity enough for you to measure. Hard to believe but it's true. You'll still feel or measure the cooling essentially the same. What will happen is that as less air flows across the condenser, the temperature differential will go up, increasing the condensing pressure. This will make your A/C work harder, run warmer, use more power, and fail early. If sitting inside the van a person wouldn't notice any of this that should/must be avoided.

You tested on a very cool day, so even if your air flow was cut in half, the condenser's discharge was still likely under acceptable temperature limits. In my opinion you need to test on much warmer days, but more importantly, you need to measure air temperature going in and out of condenser through your floor vents. I also measured air flow but that's not necessary as long as discharge air temperature doesn't get too high. Measuring power draw will also help determine how hard the A/C is working as temperatures vary.

I would try to determine if the "booster" fan is helping at all. It's actually possible it's not. It's even possible that it's restricting air flow. The size and power rating is so low compared to the A/C's fan that it "could" be limiting air flow. I looked at fans and was going to install a blower with about 1/4 HP based on measured air flow. Instead I added a second discharge port and took a chance (which has worked).

Screens do restrict air flow a lot. Partly it is the reduction in free air, but mostly it's the aerodynamics of the fine mesh. Think about how in Florida every time there is a hurricane, one of the first things to go are screens in open rooms.


Sorry for length. Bottom line is I'd do more testing focusing on condenser air flow and temperatures. Inside temperatures, sadly, don't mean as much on whether the system is engineered correctly or not. Getting the A/C to cool is easy. Keeping it working long term and or not starting a fire because it overheats is the real challenge.


By the way: Love the way your A/C looks. It's 100 times better than mine. I really like the flush mount. Will borrow that next time if I have more cabinet depth. :)
Chance
Thanks for your ideas. I'm going to do more testing at higher temps taking your comments (& Phil's) into account. My screens can be easily removed and I'll see if that makes a difference. Do you have any idea what kind of delta I should be seeing both inside and at the outside vents?
Bill
 
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