Helium results!!! Window air con chill box build. - Page 3

Thanks for that Drew.....although the normal current draw is 1.14A the start up draw on those fans is 2.69A so I'd be looking at one of 100watts.....I was thinking I may be able to do it cheaper with a simple rheostat but tbh the only ones I could find were expensive....even 50watt ones were £50+.... I've found this fan controller that should be man enough with 45watts per channel and only £25.

http://www.overclockers.co.uk/showproduct.php?prodid=BB-000-LP&groupid=701&catid=57&subcat=189

So Acrylic should be okay for the build then...I've had temps below -20 deg C even will a heat load of 150watt.....my temp probe has still not arrived so I can't give accurate temps yet as my bulb thermometer is off scale below -20 deg C.

Don't seem to have seal string in the UK.....is it like plumbers PTFE tape?


I've bought some more insulation board.....its coated with heavy foil and has much denser insulation filling/foam than polystyrene, I've taken some pics but it doesn't show up so good.



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Edited by technogiant - 6/9/12 at 11:16am

Well my rebuilt is progressing slowly, I've made the insulation box from the above insulation board, it doesn't seem to absorb moisture, I place a quantity of water on a cut section and it just sat there for an hour in a proud blob, seems the foam is quite hydrophobic which is a good thing.

No pictures yet...it's just a box....but I've ordered all the other things I need so hopefully I'll have some more progress to log shortly.

Hey guys, I've built the internal insulation box.
I'm going for the same layout as before in that the evap will divide the chamber into two parts with the fans to the side to get a circular air flow. I'm going to have the fans pulling this time as you suggested Drew.

A slight modification is that instead of having a cap over the rad and fan stack I've lowered the chamber walls so they are the same height as the evap so that the lid will simultaneously seal the airflow chamber when put on. That way I will have access to the rear chamber as I want to put desiccant in there which will need drying out from time to time.

I'm also going for a belt and braces approach in that I'm going to try and make both the internal insulation box and the external acrylic box sealed and air tight.

Also bought some ratchet ties/webbing to clamp the lid on with and a couple of large sachets of desiccant each one meant for a caravan sized space so two of them should be more than adequate for my little chamber.

Also been working on methods to seal the atx cable and other cables that need to pass through the chamber wall.

I got some of this self amalgamating tape, seems to be just the job, just stretch it out so its width decreases by about 1/3 then wrap the individual cables in the bundle under tension (little awkward). Then just squeeze and massage them all together and it all just bonds.

http://www.diy.com/nav/fix/electrica...Metre-11348108

I've tried other methods but with the amalgamating tape you know each wire is individually covered and they will just bond when you press several together, it is soft enough to be squashed when you squeeze it so that gaps between the individual cables will become sealed together, could even use cable ties to give higher squashing pressure.

You have to be careful as regards what sealant you use.....the tape seems to be bitumen based....some silicone can't be used with it.
I tried it with "evostick sticks like" sticks to anything and is good down to -40deg C....seemed okay with that, but another general purpose silicone dissolved it!!

I've ordered a load of cable extenders and everything is starting to come through now.....My acrylic has just been delivered... so the build will be starting shortly.

............

So I've started cutting the acrylic panels today, never worked with acrylic before.....it's truly horrible.

I have some kind of aversion to the smell of acrylic....my daughter is doing a nail beautician course and when she gets the nail acrylic solution out I have to leave the house....this stuff smells just the same when you're cutting it as it melts a little.



The other thing is that as you cut it with a jig saw the stuff melts a bit then resets behind the blade....so you get to the end and have to run the saw through it again so it weakens enough to break off.....hard work or what, I must be doing something wrong.

Also with the edge melting it doesn't cut as accurately as I'd like ...still I'll make it work.

Made quite some progress, I've completed the acrylic box and the insulation box is fitted inside it with the cut out made to accept the evap pipes.

I still have to make the lid and fit the gaskets...that will be tomorrow.

Also haven't run the cabling through yet. My cabling/extenders have all arrived but overclockers.co.uk messed up my fan controller order so I won't get that till next week.

No pics atm as tbh I'm embarrassed...It's very messy...I built the acrylic box around the insulation box to ensure it would fit, then when finished tried to take it out before it got stuck in there with any extraneous adhesive.
Of course when I tried to pull it out the acrylic box all came apart and I, the acrylic and the insulation box all got covered with goopp adhesive.

I'm full of ideas but my diy skills always let me down...still it's back together now even if I did have to jam the insulation box in there before I wanted to.

I't all sealed up even if messy.....I'll have to try and clean it off when its all solid, perhaps even paint the exterior.

It's very close to being done now........I'm hoping to be able to show test results together with some pics.......sort of hoping that good temps will divert attention from my messy build...lol

Okay you've asked for it, I'll upload pics...but please excuse the messy build.....it may be messy but I've put a lot of thought into this and I'm sure its going to be as tight as a drum.

Here's an overview of what it looks like just so you can picture what I'm talking about. The outer shell is made of 6mm acrylic, all the joints a triple sealed in that they are not only edge sealed but also are sealed to internal 90 deg plastic angle and externally again plastic angle has been sealed over all the joints.

The insulation box is made of 50mm insulation panel and sealed along the joining edge and on all the joins internally and externally.

A bead of seal is also going to be run along the top edge of the insulation box sealing it to the acrylic outer layer.

I've lowered the height of the insulation box to the same height as the evap/rad and fan stack so that the lid will seal to them and so divide the box into two chambers for a circular air flow. That allows me to have access to the back chamber as I've got sachets of desiccant to go in there which will need drying out from time to time.



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The lid is made of an acrylic outer and insulation board inner. You can see I've put a viewing panel in there, also see that I've got an overlap on the acrylic. That will seal via a gasket to the acrylic box, also the insulation layer will seal again via a gasket to the insulation box, both boxes are independently air tight.

I'm going to put a section of mdf over the top of the lid for extra rigidity (although the acrylic is quite strong) as I will be clamping the lid on with ratchet webbing ties.



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Here's a picture of the top edge of the acrylic box, you can see I've put an extra layer of acrylic around the top, this doubles the sealing area for the gasket/lid to 12 mm for a better seal. (got to tidy that up a bit yet)



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A big problem is running cables from components that can't be in there like the psu and hard drives through the box wall and still keeping it air tight, particularly those bundled cables such as psu cables where air can channel between the cables.

I've used cable extenders to enable me to change my psu if required without having to break the box. I stripped off all the braiding/mesh and then wrapped each individual cable in self amalgamating tape. This stuff just melds together when you squash and squeeze it. So I was able to turn the individual cables into a solid block of amalgam as pictured below. This really was a hard and time consuming part of the build, particularly the 6X pcie 8 pin cable extenders.



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Once passed through the box the cables were sealed to both the insulation box and acrylic box. I also put two further layers of acrylic around the outside of the cables to increase the joins depth and strength....so they are passing through 18mm of acrylic all sealed with copious amounts of gooop. On that note I should point out that I've used evostick "sticks like" its a very strong gap filling sealant/adhesive that is good down to -40 deg C.

Below top right are the pcie power cables, the red ones underneath are the sata data cables, below that the main atx power bundle and on the left the atx additional power cable.

I'm still waiting on a dual link dvi cable to complete running the cables from the left hand side of the box.



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On the right hand side I've installed my fan controller, had to use a beefy 45 watt per channel unit as my 3X scythe gentle typhoons 5400rpm 150cfm fans each draw 1.14A and 2.69A on start up. Also I've run my temp probe through here and attached it to to the fan controller. The other cable you can see is for a light so I can see whats going on in there, and the small switches to the right are the power on, reset and cmos reset buttons.



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Finally for the "piece de resistance" I've included an idea that I think will greatly assist in leak prevention. Obviously when you are drastically reducing the air temp in a sealed space the air will contract and the pressure in the box will drop. We all are aware of this when you briefly close a fridge door and try to reopen it....there is a suction effect.
This suction will find the smallest of faults in your seals and suck in air, carrying with it water vapor that will condense out in the box. I've worked out that at the air temps I'll be using the drop in air volume will be about 15% or 9 liters in my case.

To over come this I will be using an expansion chamber...or more correctly in this case a contraction chamber. I've run a 19mm breather tube from inside the chamber to the outside. This is sealed to a rubber sac that will expand and contract like a lung and so equalize any pressure changes and eliminate any external air being sucked into the unit.

I had great difficulty in finding anything suitable for the rubber sac so finally settled for this.



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Okay I know it's a child's toy....lol...not many of you would have that in your pc build I'm sure....but it's actually ideal....it has a pumping point on it too so I can put some pressure in there and leak test my chamber.

So that's it so far I still have to run my gaskets properly and seal the cables on the left hand side.....but should be ready for some testing in the next few days....I'll keep you all posted ;-)
Edited by technogiant - 6/27/12 at 1:41am