Homemade R290 unit, up and running!!

I have finally finnished brazing up my phase change unit. There is still tonnes of work to do on the powersupply, fans, wiring, case, chilled water loop etc, but the actual phase loop is up and running. I vacumed it and charged it up with crappy camping bottle propane just to see what it could do. I managed to get down to -47.6c.. not to shabby for a first build, but this is no load of course.

The system was running at 15" HG and 135psi. One thing I'm a bit confused about though, at 15" HG, the evap temperature of R290 is around -57, so where did my 10 degrees go? I had the temperature probe pressed on the bottom of the evap with some insulation over it, so it should have been pretty accurate.

The system uses a 1/2 hp rotary compressor, large AC unit condensor, 93" of 0.028 cap tube, home made evap and a SS flex line. Any of you propane guys have any advice? What sort of pressures do you run your systems at when they are on a cpu?

Anyway, here are some picks of the thing running.

Good job on getting your build up and running finally. What is this I am reading about a chilled water loop? I dont understand what thats all about...

Fill me in man.

Is this current phase change system on your 2600M? Anyways, congrats, everything looks good!

Once I get this phase system up and running, it will be going on my 2600M. Right now that chip is just under water, as in my sig.

Ad Rock, the water loop is for my GPU. I have made a little heat exchanger that is on the suction line just before the compressor. The water loop consists of an NV-68 waterblock, a VIA aqua 1300 pump, a big all copper heatercore from an 80's subaru, 1/2" tubeing, and the heat exchanger on the suction line. Because there is a heatercore in the loop, it isn't really "chilled" in the common sence. When the CPU and GPU are loaded, the heatercore will take most of the heat from the GPU and Pump, and then the heatexchanger will give the water just a little chill. The water in the loop will probably be within a degree or two of abmiant all the time. The added bonus of the heatexchanger is that I don't have to worry about liquid refrigerant making it back to the compressor, even if the CPU shuts down. If there is no cpu load, the water in the loop will drop below ambiant and the heatercore will actually warm it up.

Here is a little diagram of how it will all be connected. The waterloop is drawn a little out of order, it will actually be GPU->Pump->radiator->heatexchanger->GPU.

oh, here is a picture of that heat exchanger on the suction line while the system is running. Those barbs at the top are where the water loop would be connected.

Cant wait to see the results, keep us posted.

That looks sweet matt, pretty inventive idea there too.

On a side note, r290 is a pretty nice gas to use hey? I mean if you can get over the fact that you could blow yourself up you can have some great temps with it and its cheap. My r290 phaser had my dothan down to -29c loaded (and that was without doing any tunning).

If you need any help getting more schrader valves or drier's or insulation let me know, I got hooked up at my local refrigeration supply store (they are selling me stuff at half of list price).

wow Matt, that heat exchange idea is really something, haven't seen anything like that before, may be u should make a thread for that in WCing or something.

Is that heat exchanger covered in frost or something?

petteyg359 said:

Is that heat exchanger covered in frost or something?

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Yep. I was testing the system a little bit and the whole suction line got rather frosty since there was no load. The way I have everything hooked up, the heat exchanger won't normally be much below ambient when the system is running. I have tuned the system to cool the CPU mainly and then just hold the GPU loop down to ambiant. I could change things a bit to actually make the GPU loop cooled to subambient though. I could shorten the cap tube to raise the capacity of the system, and remove the heatercore from the GPU loop. This would result in lower GPU temps, but higher CPU temps. I would also then have to insulate the entire water loop. I am more concerned with my cpu temps and don't want to insulate the gpu, so I haven't done this, bit it is an option for anyone looking to cool the CPU and GPU subambiant with one phase system, without makeing a dual evap.

Anyways, It now looks like I may have a pinhole somewhere in my system. It lost some of it's charge last night, and through the day today it has lost about 7psi in static charge. The leak is so small it shouldn't be any trouble to fix, but finding a leak that small may be next to impossable. Any one have any good ways to find a leak? soapy water and a lot of looking?

The best way to find it would be to take all the the electrical components off the unit and insulation off and stick it in a bathtub full of water. Then if you add a bit of soap to the water you can leave it and see if you actually have any bubbles when you come back (or just sit there and wait patienly).

hey question matt, how much did building your own phase change unit cost you? I'm just wondering how much it might cost me.

Ad Rock said:

The best way to find it would be to take all the the electrical components off the unit and insulation off and stick it in a bathtub full of water. Then if you add a bit of soap to the water you can leave it and see if you actually have any bubbles when you come back (or just sit there and wait patienly).

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I think the leak is too slow for that. The leak wouldn't appear as bubbles comming off the system, but as a small bubble slowly growing. Unfortunatly when you stick things like this in water for a long time, bubbles will form all over it naturally

hey question matt, how much did building your own phase change unit cost you? I'm just wondering how much it might cost me.

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It can cost anyware from a whole lot to nothing depending on the quality and what you already have. I would estimate that I have spent around $400 on parts and tools so far, maby more. If you just want a good phase change system for as cheap as possable, it is cheaper to get a unit from chilly1 or pc_ice or sandman than it is to buy tools and make your own. The homebuild units are more for the fun of actually makeing them and tinkering.

Well I just went and checked the gauges, and I'm not even sure it has a leak now. It looks about the same as it did 14 hours ago, maby a couple psi lower but that could come from temperature difference. I guess I will just have to keep an eye on it.

Here are a couple pictures of the water loop partially assembled. The barbs on the NV-68 point the wrong way so I hade to make a couple 180 degree pipe elbows.

Looks awesome man! I cant wait to see what the water loop does to overall system load. You should run it loaded without the water loop and then add the water loop loaded to see how it effects system performance. Then tune for best full load temps. You should also wrap that cap tube around the suction right at the evap head if possible. If you made a large enough suction HX, you may get better results by actually removing the radiator...It will be interesting to experiment with the rad and suction HX to figure out the best way to move the load; through the condenser, or through the rad. Sweet project!

stockhatch said:

Looks awesome man! I cant wait to see what the water loop does to overall system load. You should run it loaded without the water loop and then add the water loop loaded to see how it effects system performance. Then tune for best full load temps. You should also wrap that cap tube around the suction right at the evap head if possible. If you made a large enough suction HX, you may get better results by actually removing the radiator...It will be interesting to experiment with the rad and suction HX to figure out the best way to move the load; through the condenser, or through the rad. Sweet project!

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Thanks. I have set it up with a large radiator and cap tube tuned for mainly just the cpu mainly for stability for now. Should my CPU lock up when I'm not around, and the system stay running, the radiator would keep the evap temps from dropping way down and possably getting condensation or maby liquid refrigerant into the compressor.

I have the cap tube running inside the suction line, so it should be plenty cool when it exits.

As for my possable leak, I have no idea. I sat the evap head (place I would suspect was leaking) into a bucket of water and left it over night. In the morning, not a single bubble, nothing, nada, zip, the head was bare. The unit has lost about 10psi over the last 5 or 6 days. I'm starting to think the phase system is leak free and it is leaking from the manifold gauges or more likely the shrader valve connections. I'll charge it up and take the manifold gauges off and see if it hold pressure better that way.

hows the heat exchanger doing w/ that? Is it really working for the WC line?

I'm not far enough along to tell yet. I still have to modify/install the units powersupply, a bunch of fans, do a bunch of work on the case, etc.... I'll let you know when I get the whole thing working, but it will probably be a while.

As far as the leak, could be two things if not an actual leak.. Propane mixes with any OIL very very well.. Some of your r290 could be getting absorbed by the oil inside the compressor over time causing your pressure to slowely drop.. Also ambient temps will affect your pressure, how much depends on how much of a change in the ambient.. Looking good so far. Keep us updated on how things work out.. Also what evap are you using?

The system has been sitting in my basement at a fairly constant 18-20 degrees, so that shouldn't change the pressure any, but it could be the oil absorbtion. I was thinking it was most likely leaking from the shrader valves on the unit. I didn't clean them up all that well and the rubber ring on the gauge set probably didn't seal that well.

I made the evap myself. $30 drill press, cheap grinder, hack saw, mill file.... one home made block. Here are it's inards. It is designed to sit vertically, so you can put the mobo in a case. The refrigerant enters the small cup in the middle (sized for my Barton core). It's a bit hard to tell the dimmentions. It's 1" thick and about 1.5" wide.