Copper Air Dryer Design - Check my Math

I’ve been looking at the two main options for air dryers for the plasma table… the Harbor Freight Air Dryer system or a set of wall-mounted copper lines.

For pure simplicity, I am tempted to go with the wall mounted copper line setup. No moving parts, no electricity, and if properly designed… should cool air well enough to condense all water vapor.

The $64,000 question is: How much surface area is required to effectively cool with copper lines?

I did a quick 15-minute analysis of available materials and looked at the systems people have posted on YouTube for reference and came up with the following chart.

A lot of guys seem to use simple 1/2" pipe with around 6 passes which works out to around 2271 sq in of cooling surface area. I put larger diameter options in the table just to see how the overall surface area compares, but also to see if using fewer, large diameter copper tubes was actually more cost-effective, or if it all works out the same.

As it turns out: A 6-pass 1/2" system equals a 4-pass 3/4" system equals a 3-pass 1" system… each offers around ~2200 sq in of cooling surface area.

Didn’t bother to price out couplers, reducers or ball valves yet… this initial table is really just to figure out what sort of surface area target makes sense.

The larger diameter tube can definitely match the overall cooling effect (with fewer pipes) of a large 1/2 copper tube cooling system. The added benefits are slower air velocity which should aid in water removal effectiveness, and a bit of extra air volume to store air (though probably negligible). Downsides are certainly that the fittings will all be more expensive for large diameter pipe, but fewer will be needed to build an equivalent system.

Pricing is just today’s Home Depot price list applied for the various grades of copper pipe (L vs. M) and with different diameters.

Feel free to add commentary and opinions. I haven’t bought any materials yet… but was just doing some research before heading to the store later on this week.




Another option a trans cooler for less than 100 buck and a box fan. Cleaner look than copper piping all over the wall. Drops my air temp from around high 200s down to like 120. Two would bring you down even more.


Save yourself a lot of money and just put a transmission cooler with a water separator between the compressor pump and the tank.

I have a 60 ft run of 3/4" copper with 4 drops and ball valves and hardly get anything more than vapor out of the valves. Its not very effective at removing water from the air.

I installed one of these between the compressor pump and the tank with a water separator at the exit of the cooler and I get a lot of water in the separator. I probably get a 1/2 oz. of water for every compressor cycle. Its much more effective at removing water from the air and a lot cheaper than all of that copper pipe.

I go from the tank to a 1 quart dessicant dryer and then into a Motorguard before the plasma cutter.


Yeah… I’ve seen those too. I like the idea of cooling to compressor charge BEFORE it goes into the storage tank too… but I don’t really like the idea of a spinning fan making noise in my shop. Unfortunately, my compressor shares the workspace with me so I don’t have the luxury of an outbuilding or small exterior shed to hide a fan/radiator setup.


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Wire it up to come on with the compressor.


I don’t have a separate fan on my trans cooler. I have it zip tied to the cage next to the fan for the compressor pump.


That works I was wondering does you compressor run hotter? I was afraid of oveeheating. I did a remote with a 10 in fan works great.

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No problems with overheating so far. It runs quite a bit when I’m sandblasting and I haven’t noticed any problems. The water separator is usually at least half full of water by the time I get done blasting for about 10 minutes.

I’m sure it would be more effective if I had more air flow over it.


I do sandblast a lot too. I actually put a 20 in box fan on the cage to help the compressor cools it down faster between cycles…

It is a lot of personal preference. What works for a individual.

I liked the trans cooler best. I actually put another coming out of my tank before my air dryer. Works great for me .

I see a lot of copper pipe dryer that work. I didn’t have wall space either.

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It would be interesting to see how much more length of the 1/2" pipe you need to get the same contact time with the higher velocity in the 1/2" pipe.

Ill second @ds960 on the trans cooler. Mine gets here tomorrow.

I followed @brownfox thread on the topic for the most part. I think in the thread he mentioned that he was going to go with a copper manifold. Never saw if he did switch to… or add a manifold to his system. If so it would be interesting which one he found was most effective.

Sounds like DS960 has had better results with the trans cooler.

I went back and forth and decided to go with the trans cooler in the end.

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Keep in mind also either way will not remove all the moisture from your air. they will remove a lot.

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I think most people are wiring the fan so that it comes on with the compressor. I wonder if you would hear the fan over the sound of the compressor?

I have an extra 12v fan laying around that I am going to zip tie to the cooler. My compressor is also in the shop. Eventually I would like to move the compressor out of the shop into an adjacent storage shed that shares a wall with the shop.

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Yeah… for some reason I was imagining the fan running 24/7 with that radiator setup. Clearly that does not have to be the case which means I’m not likely to ever hear it. It seems like it would’nt be all that hard to run a mechanical fan off the existing upright compressor (Quincy 60Ga 5HP). Just extend the shaft on either the small or large pulley side and every time the compressor kicks on the fan spins with it. Hmmm… this has me thinking. :slight_smile:


Electric fan. My compressor only uses one side of the point. Wire it up so when points kick in to start compressor your fan starts up.

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I think where you live has something to with it. I am in Michigan and in the winter my shop goes to 50 at night and on the weekends. If the temp coming out of the trans cooler is 120 that is 70 degrees hotter then my copper air lines. I would think you would still see condensate at those temps but maybe not. After the shop is up to temp (65) it would better, but still much cooler.
Do you guys that run trans coolers use desiccant dryers too? Are you in warmer climates?

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That is on a hard pull. Compressor running constantly for 10 plus minutes.
I see it as most bang for the buck.

Even your copper tubing dryer isn’t going to get all the moisture out.

I have a fan cooled trans cooler with a separator, a fan cooled trans cooler with separator coming out of my tank, into a refrigerated air dryer. Then my bead dryer still catches moisture.

I am in the southwestern part of va.


Oh did not think you guys were running a refrigerated dryer. So did you ever run your system with just the refrigerated dryer? That what I use but nothing else. I do have motor guard filters on my powder coat equipment and plasma cutter but that’s it. I have never changed the filter on the motor guard as it looks like new.

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I have a bead dryer, I haven’t installed the after cooler yet.

I’ve only had to swap the beads out once this year. A big part of that is I usually turn the compressor on first then get everything if ready to let the air cool in the tank. I also have a second tank in-line before the bead dryer.

I live in a dry climate tho.


I hooked my dryer up straight for giggles. Just used quick couplings to see how it changes things. Yeah I it froze up so much moisture.

I can’t tell you how much my first one catches I leave the bottom drain loose. It looks like a water hose running…

Just a standard fill up my compressor runs for a few I use 140 gallon capacity worth of being a dry air tank. I can hold my hand on pipes not even warm. My example earlier was a extreme condition guess should have made that note.

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Anyone ever try is fan guard mounted radiators?

This one from Amazon looks like it’s good for 20 CFM. The M15 from the pdf would be equivalent to the Amazon link.

More money than the Derale 15300 but would make a slick installation. I also like the configuration of the ports better and it would likely have better pressure drop characteristics.