Devils Tower

Devils Tower

Friday, July 11, 2014


It didn't take long to figure out I had miscalculated the design of the air conditioning on the trailer. This guy showed up and taunted us.
 I had tested it out in the shop, out of direct sunlight.  Well, on our trip the first stop we had was 112* with about 45% humidity, in direct sun, no trees anywhere to be found.  No way, would the a/c keep up.  Something I had not taken into consideration, was the lack of a manual temp control on the window unit.  It was all fancy and digital, with a remote control.  What else could you need?
OK, look in the corner of the picture where the a/c is.  This little compartment that was created made sense at the time.  Here's the sees that small space as the room.  So when the temp in the little room gets down to say 65* it shuts off the compressor, because mission is accomplished. Hardly.

I have 2 problems.
1.The first is the register I installed was a return vent register and it is way too small and restrictive. This has had me experimenting
with several options.  At first, I had gone down the path of expanding the size of the outlet register. 
After, playing around with it, I decided to go another route.  What I need is velocity. I need the air to jetison out into the room.  I think what I may do is I am going to build a sheetmetal plate that envelopes the outlet grate and force it down into a 4 inch flexible duct.
By reducing the size of a duct, the air traveling within it will begin to speed up exactly like water does when a person puts a finger over the nozzle of a hose.
The result is that more air will flow through the system in a shorter period of time, and the air that comes out of the vents will travel further across the room it is cooling.

2. The next thing is that I need to add a return air route and some sort of fan to draw it through the length of the bed to mix with the cold air in the little cavity where the a/c is located.  I have been reading a lot lately and the thing that comes to mind is a bathroom fan.  I wanted something that moves a lot of air, that is moisture resistant and quiet.

  The one that always comes up with awesome reviews is the Panasonic Whisper series. The amount of noise this thing creates will be key.  I don't want this thing humming all night, keeping me awake.  The one that looks like it might work is the FV-10NLF1 WhisperLine 120 CFM In-Line Fan.  It's fairly small and I think it will fit in one of the areas under the bed, that is kind of wasted space anyway.

Now for the math.  This thing moves 120 cubic feet per minute.  I need to see how many cubic feet are in my trailer.  The dimensions are 17' L x  7' W x 6.5'H = 773.5 Cubic feet.
Now , we need to divide that by the amount of circulation the fan provides.  It is 120 CFM.   773.5 /120 = 6.44 minutes to circulate all of the air in the trailer one time. So, in a perfect world the air would completely circulate 9.3 times per hour. 

That has to help, or at least I think it should.  I will add a return vent on the opposite end of the bed, as far away from the outlet as possible. 

Below is a pic of the return air inlet. I just used a floor register and modified it to fit in the space.
 Here is a pic of the cover panel I made to utilize the hole that was previously made in the original version.  It has 2 outlets and a power switch for the return fan.

  Here is a picture of the return fan installed.  I just blocked it in with a couple of 2x2 's.
I just drilled a hole big enough for the air return to fit through. This  forces the hot air into this cavity, fooling the air conditioner into thinking this air is the ambient air temp in the room.  It does away with the compressor cycling off, because the space under the bed is now the same temp as the cabin air… it should be.

We recently tried out this mod and it word way better than before. I will give the Panasonic Whisper fan an A++.  It is the quietest fan I have ever seen.  I'll be putting them in my house as soon as I have a little extra $$.

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