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Old 06-03-2020, 09:00 AM   #1
Mini-Skoolie
 
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Air Conditioning Choices

What have you installed for air conditioning in your bus? RV Roof Mount? Portable A/C? Air Curtain? Advantages and disadvantages? Trying to decide for best layout options.
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Old 06-03-2020, 09:32 AM   #2
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I have an old 15k btu RV roof mount.

Advantages:
Can be bought used cheap(mine was 100 bucks off craigslist)
takes very little room in the bus
Can be wired up easily
Cools the back half of the bus very well. (It's completely enclosed with curtains which is important)

Cons:
Not very efficient power consumption wise.
Noisy(newer models aren't as bad, but aren't as cheap)
You have to cut a hole in the roof and do the required fab work to mount it correctly.

If I would do it again, I'd look at installing a mini-split. I'd mount the interior unit in the rear header, and mount the exterior unit in the skirting under the bus.

If you're looking for the quickest/easiest solution, I ran 2 window units in place of the bus windows for a while. But pulling window units and reinstalling the windows so you can travel got old after awhile. The window units were framed with 3/4" osb which fit right into the hole from the old windows. The units were given to me, and I had the osb laying around, so it was essentially a free solution.

You can buy one of the portable ac units they have now and plumb that to a hole cut into the side of your bus. But those units can be expensive.
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Old 06-03-2020, 11:56 AM   #3
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9K BTU Mini Split / Heat Pump.


Advantages

  • Crazy efficient. Low power usage is great for solar.
  • Does the job well in a well insulated bus.
  • Quiet.
  • Can heat, cool, or dehumidify.
  • Can install multiple interior units with a single exterior unit
Disadvantages
  • Will not cool/heat whole cabin at speed.
  • Have to incorporate coolant lines into your build.
  • If you install only one interior unit, circulation to distribute hot/cool air could be a challenge.
  • Not a DIY type thing. At least I don't think so. Positioning, mounting, drilling holes, OK. Dealing with coolant lines, I'd seek a pro.


One 9K BTU unit makes my build ice cold up front (where the interior unit is). The rear takes additional circulation (fans). I'll probably install a second interior unit.
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Old 06-03-2020, 12:10 PM   #4
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I was going to go mini split for the reasons listed in this thread already BUT I got a heck of a deal on a pair of Dometic 13.5k btu roof units. $215 for the pair (still had to spend another $100 on the interior roof boxes) but it's still way cheaper than $650 for a single unit online.
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Old 06-03-2020, 12:35 PM   #5
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Originally Posted by WIbluebird View Post
I was going to go mini split for the reasons listed in this thread already BUT I got a heck of a deal on a pair of Dometic 13.5k btu roof units. $215 for the pair (still had to spend another $100 on the interior roof boxes) but it's still way cheaper than $650 for a single unit online.
Do you use your roof top units for cooling while driving? I'm contemplating 2 mini splits, but I have 2 roof top units I can install. I was not fortunate enough to have factory A/C.
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Old 06-03-2020, 01:19 PM   #6
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I have two rooftops. With a curtain behind the front one and I modified the air delivery so it will cool the front enough while driving. This with running the genny while driving. Not the best solution but it does work. Less clothing helps too....
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Old 06-03-2020, 02:19 PM   #7
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Quote:
Originally Posted by Ronnie View Post
I have two rooftops. With a curtain behind the front one and I modified the air delivery so it will cool the front enough while driving. This with running the genny while driving. Not the best solution but it does work. Less clothing helps too....
I like the less clothing idea, especially where the wifey is concerned! Although I don't think she'll buy into that with those giant front windows!!

One thing I love about this site is how simple discussion feeds the idea generator! Thanks Ronnie, your comment and something I saw in Vlad's build thread has given me an idea to roll around.

I am doing a 21" roof raise. 21" simply because that's how high I need to go to fit 4'x8-10' sheets to skin the sides. I have been thinking on what to do for the curve in the ceiling when I saw that Vlad made trusses and went with a flat ceiling. This gave him room for utilities and ducting in the ceiling. When I pulled the A/C off the donor RV, I realized I can relocate the controls anywhere I want just by adding wire. By taking your idea of redirecting the air flow, I think I will make ductwork to direct that flow to the header panel above the driver blowing back, and down on the driver. I can do the same for the rear unit, and even add a third for the living space. I can easily mount controls in the walls or one at the driver panel for the front unit. I believe on shore power I should be able to run all 3 units, my current generator will run at least 2 at a time. Closing off the back of the bus and running the two front units should keep me sufficiently cool while driving, especially if one unit is specifically directed to the drivers seat. And like previously mentioned, those older RV A/C units are a dime a dozen and only take about 20 minutes to change out if they die, although the ones I have are 33 years old and still blowing strong.
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Old 06-03-2020, 04:59 PM   #8
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If you look at how the rooftop a/c is made the blower in them blows straight down. Either connect ductwork right to it, or as I did mine I cut with a 4 inch hole saw in the plastic shroud and used a 4" pvc elbow to direct the flow. It blows pretty directly on me while driving. I can turn it to the rear for bedroom cooling at night. So far I have not needed to run both units.

With your roof raise ducting would be best
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Old 06-04-2020, 07:33 AM   #9
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Question Split-mini Success With Automotive Plastic Tubing?

I've read a very few posts where the mini-split was installed with the plastic tubing instead of the copper. My bus came with grey plastic tubing going to the air conditioners and I was considering buying some of that somewhere instead of the copper.
I plan on mounting my two mini-splits on a 4 foot extension on the back of the bus, making a porch out of it with a roof and railings, somewhat hiding the mini-split units.
My current plans are only to use these mini-splits when I'm stopped; I do not plan on using them while driving down the road.
Some people don't realize the chassis of the bus does move compared to the cabin bolted to it which will flex the copper some, likely eventually breaking it.
The comment I saw said the pressure is higher on a mini-split and I've yet to verify that and know what those pressures are.
What I'm trying to find out is 1. where to get some good automotive, plastic pipe, and 2. if anyone has had success that way?
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Old 06-04-2020, 07:47 AM   #10
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Originally Posted by GaryTheRock View Post
I've read a very few posts where the mini-split was installed with the plastic tubing instead of the copper. My bus came with grey plastic tubing going to the air conditioners and I was considering buying some of that somewhere instead of the copper.
I plan on mounting my two mini-splits on a 4 foot extension on the back of the bus, making a porch out of it with a roof and railings, somewhat hiding the mini-split units.
My current plans are only to use these mini-splits when I'm stopped; I do not plan on using them while driving down the road.
Some people don't realize the chassis of the bus does move compared to the cabin bolted to it which will flex the copper some, likely eventually breaking it.
The comment I saw said the pressure is higher on a mini-split and I've yet to verify that and know what those pressures are.
What I'm trying to find out is 1. where to get some good automotive, plastic pipe, and 2. if anyone has had success that way?
The reason copper is an issue is because it works hardens, creating brittle spots at every mounting point and connection because of the flexing. Couple that with the higher operating pressures of 410a and you have the recipe for issues.

I don't think plastic will handle refrigerant duty well. You'd best look into another material then plastic or copper. We use a copper nickel alloy for brake lines on cars, and it resists work hardening, maybe look into using that.
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Old 06-04-2020, 07:59 AM   #11
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Most automotive a/c lines are reinforced rubber hose with crimp on fittings like hydraulic lines. That would be another possibility instead of the copper lines
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Old 06-04-2020, 08:06 AM   #12
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Thanks. Do you know what that pressure is for 410A? The reason I was considering the plastic tubing is that's what is already in the bus but the difference in pressure sure could be a problem unless there is a different plastic tubing that is rated for 410A pressure. I have no idea if copper nickel would be available in air conditioning sizes. I really have not looked for any tubing yet because I'm still completing the back platform.
What I guess would be perfect is having an automotive-air conditioning engineer who knows what the right solution is. I kind of had a thought part of the solution may be in how the copper is routed, making sure it isn't placed so it severely flexes in places. I'm a technical person but way too shy of an expert in air conditioning, which I claim not to repair despite having repaired several air conditioners because of the expense and the repairs did not involve the refrigerant (one exception was my farm tractor air where I replaced the compressor.)
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Old 06-04-2020, 08:06 AM   #13
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That's a good option too.

I think my local napa store could do it as long as they have the hose/fittings in stock. If not, they can likely order it in.

I've never done it though. The hose has to be refrigerant grade, so make sure they know what they're doing or you'll have issues.
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Old 06-04-2020, 08:48 AM   #14
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410A pressure

Shoot! I did a quick query on Google of the 410A pressures and here's what it says:
System Pressures
A normally operating R-410A system with the same condensing temperature of 120 degrees and a 45 degree evaporator saturation temperature will have a high side pressure of 418 psig and a low side pressure of 130 psig.Nov 2, 2003.
As a comparison, for r134A:
At Ambient Temperature 80 (F), Low Side 45-50 psi, High Side 175-220 psi
I was not expecting quite so high a difference!
Long ago and far, far away, I used to work with high pressure hydraulic tubing up to 10,000 psi which was very dangerous, could cut things if it leaked.
Searching onward. The thought came to me to ask the air conditioning company of my mini-split the question and see if they give me a good answer.
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Old 06-04-2020, 10:58 AM   #15
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Quote:
Originally Posted by Ronnie View Post
I have two rooftops. With a curtain behind the front one and I modified the air delivery so it will cool the front enough while driving. This with running the genny while driving. Not the best solution but it does work. Less clothing helps too....
Be careful with that one..... Less clothing works great. Right up to getting arrested.......

I remember well, trips across the Southwest on I-10 and I-40 in the summertime. Both roof airs blasting away and me driving in just a pair of shorts. It was miserable.

I am installing two mini-splits on my new bus. One will be mounted above the service door and pointed at the drivers seat. I will probably put a curtain behind the front seats to help keep cool while driving.

And no more Arizona visits in August! I am going to go "where the weather suits my clothes"
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Old 06-04-2020, 02:05 PM   #16
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I am using two mini splits. 12k in front. 9k in the back.

When I got home yesterday it was 104f on the bus.
One hour later it was 76.

All of this @ about 1k -1.1k watts.

Roof top air is super inefficient. Btw. With solar, avoid.

Also running the lines is a non issue.
I simply cut a hole in the side skirt and screwed the mini split chassis directly to the bus. Lots of room down there and meets all space requirements outlined in installation manual. Super easy diy by the way.
(You will need a/c manifold gauges though)

Then I ran the lines through the floor. Super sano and k.i.s.s. principle in effect.

Cheers!
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Old 06-06-2020, 03:40 PM   #17
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Quote:
Originally Posted by shaymcquaid View Post
I am using two mini splits. 12k in front. 9k in the back.

When I got home yesterday it was 104f on the bus.
One hour later it was 76.

All of this @ about 1k -1.1k watts.

Roof top air is super inefficient. Btw. With solar, avoid.

Also running the lines is a non issue.
I simply cut a hole in the side skirt and screwed the mini split chassis directly to the bus. Lots of room down there and meets all space requirements outlined in installation manual. Super easy diy by the way.
(You will need a/c manifold gauges though)

Then I ran the lines through the floor. Super sano and k.i.s.s. principle in effect.

Cheers!
How is the unit holding up to the over the road vibrations from the skirt?
How did you pad/insulate around the lines where they came through the floor?
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Old 06-09-2020, 02:07 PM   #18
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Where did you install the outside unit of the mini-splt? Under the bus? What orientation does it have to be, flat or stand up?
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Old 06-09-2020, 03:26 PM   #19
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Where did you install the outside unit of the mini-splt? Under the bus? What orientation does it have to be, flat or stand up?
The outside unit needs to be standing upright. They also need adequate air flow into and out of the unit. I have seen a few mounted under the skirting with success. I was going to put one front and one back. The rear unit I have room in the engine bay, with a lot of additional routing for fresh cool air to it, but I didn't have much room anywhere in the front for a second unit. I could, but don't want to have to redesign the whole front end of the bus to accommodate it.

What I have decided to do is go with 3 roof top units. I am planning on having a small attic space above my ceiling to run ductwork through. The front unit will be specifically for the driver area, the second one back will be for the living area. Both of those will be able to run at the same time. The third unit will be in the back bedroom area. It will run on the same circuit as the front. That way I will still be able to run the bedroom and living area, or living and driver area at the same time while on generator power, but not the front and rear units together. If I keep that circuit loaded lighter than the other one, I may be able to run all 3 when on 50 amp shore power. We have a good deal of family in Arizona that we actually enjoy visiting, so we will likely end up there in the heat of summer often. I am quite hopeful we will be able to run all 3 together on those hot days.
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Old 06-10-2020, 03:53 PM   #20
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Quote:
Originally Posted by Stoshtan View Post
What have you installed for air conditioning in your bus? RV Roof Mount? Portable A/C? Air Curtain? Advantages and disadvantages? Trying to decide for best layout options.
We've got a 40' re Amtrans. We did the window unit, then a 15kBTU portable.. Both used a lot of juice and cooled poorly. Waitng for our mini split delivery. Going to DIY it. Let y'all know how it goes.
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