Air Compressor Mobile Cart

This was debatable as a “mod” or a “build.” I’d like to think of “builds” as constructing a piece of equipment from parts and scratch. “Mods” are more modifying an existing tool to suit a better need, such as a large drill press table, reinforcing cheap tool cabinets. Whereas “builds” are complete projects that do not necessarily modify a tool or a piece of equipment directly, such as this case, where I built a mobile chassis for a large industrial air compressor unit.

I managed to score an Atlas Copco SF2 from my buddy, GL. His company was literally about to throw a brand new air compressor, for the sake of getting rid of equipment! The downside, for most folks, is that this specific air compressor was a 3-phase compressor. Residential homes use single-phase. You rarely see a 3-phase home, since those are used commonly in commercial and industrial complexes.


Now, mind you, when I got this off of GL, there were no cables, hoses, gauges, or regulators of any sort. No manuals or paperwork, except for an electrical schematic that I didn’t find until much later in the process. All that I got packed on the back of the truck was the compressor unit (the gray rectangular box), the tank, and the condensate pump (little unit on the bottom of the tank, in the image above). Fortunately, this is 2016. After looking up the appropriate support centers, calling a few numbers, and a couple of e-mails letter, I got a very detailed instruction manual on how to use this thing. In situations like this, when you’re offered very little information with unfamiliar equipment, it’s always good to do your due diligence in properly doing the research. And in this case, the proper thing to do is to RTFM (hint to what RTFM stands for…the R is for read and the M is for manual).

The electrical disappointment.

Since I was already aware that the equipment uses a 3-phase power source, the question was what voltages are being supplied? There are 2 varieties of 3-phase power: wye (or “y”) and delta configurations (you can read up on all the goodies on the 2 types of configurations here). Since I’m located in North America (if you’re from other reaches of the world, it’s best to check your local standards), wye configurations are 120/208VAC. The 120/208VAC usually means that if you measure the AC voltage between two hot lines, they will measure at 208VAC; similarly, if you measured the voltage across a hot line and neutral, you would 120VAC.

Delta configurations are pretty simple. They either come in a 208VAC or 240VAC flavors. There is a “high-leg” delta configuration, which is not your typical configuration, where you get 3 different voltages. At the end of the day, it doesn’t exactly matter which type of configuration your 3-phase is set up for, but it does help identify how an electrician installed it. Knowing if you have a shared neutral and ground/earth connection will indicate a wye configuration, is definitely great for pulling any additional 120VAC lines.

IMG_1064So once I checked the circuit breaker, I determined it was a wye configuration (120/208VAC). The problem was that I needed 3-phase 240VAC (delta configuration), per instruction manual. This was not good. Technically, you can run a compressor under-powered, but this wears out the life of the compressor motor, as the power demands require a higher current draw. This in turn means the motor runs hotter and eventually wear out.

Enter the step-up converters.

I found a transformer that would step-up the voltage appropriately. I snagged one used and one refurbed Federal Pacific transformers. I wanted something cheap, and didn’t result in putting a lot of unnecessary costs on boosting the voltage for the air compressor.

Turns out I need two of these small transformers (the two totaled approximately $140 together) to boost the voltage from 208VAC to a nominal 230VAC, for the proper voltage to power the compressor. I got 230VAC from the good ol’ instruction manual.

IMG_1057After solving the voltage supply issue, I looked into fuses and an isolating switch. The instruction manual specifically stated that fuses on each phase (hot wires) was required, as well as an isolating switch. I could have killed two birds with one stone by using the fused safety switch box (that large, gray rectangular box with a red knobbed lever that you see below), but I decided to add an extra isolating switch for the heck of it (the white/gray box to the right of the fused safety switch box with two sets of cables going into it).

Again, I managed to snag some 15A fuses, fused safety switch box, and isolating switch off of good ol’ eBay, per usual. I’m not to worried with used parts when it comes to these types of electrical boxes and switches, with the exception of fuses (used, blown fuses are…well they defeat the purpose of what they’re used for, obviously).


IMG_1058Air pressure regulator and air filter supply.

After getting the majority of the bulk electrical hooked up, as well as hooking up the wiring connections for the 3 phase within the compressor unit, I decided to tackle the air supply out of the tank. I knew I wanted a pressure regulator and air filter supply. I did contemplate installing an oil reservoir, but I decided against it, since I had plans of using HVLP paint spray guns. It would be a bad idea to feed oil to the paint spray guns, as that would promote orange peel and surface paint quality issues on the final product that would receive the paint. However, it’s crucial to apply oil to all your air tools that are not HVLP spray guns!

Ideally, for the air hosing, you would want to use the largest allowable hosing. I went with a 1/2″ diameter hosing, as this was the largest allowable size for the air tank. I snagged a couple of 3′ hosing, a 6′ hosing, and a 100′ length hose. I would later use a step-down hose, to a 1/4″ diameter, at the end of the 100-foot 1/2″ hosing, for flexibility. The reasoning behind this was that I wanted to maximize the length of hosing, in case I need to run long lines, due to the awkward location of the air compressor. A larger hose diameter would maximize this.

The hose reel.

IMG_1061This massive hose reel was a pretty sweet build. It took a bit of time to acquire some of the parts, since I couldn’t regularly find some of the parts at the local hardware store. These “specialty” parts include a 1/2″ swivel, a 1/2″ tee, and 1/2″ quick connect fittings. Most hardware stores carry a 1/4″ fitting instead, which is no es bueno. Ideally, you want to max out the hose diameter size, to maximize the distance that you can effectively provide the same from your pressure regulator to the output (i.e. HVLP paint gun or air nailer). That’s why you see a ton of thick 1/2″ yellow hosing.

The concept behind the hose reel is pretty simple. The swivel fitting goes from the yellow hosing, coming from the pressure regulator, to the piping in the hose reel. The special swivel fitting helps prevent the hosing from twisting on itself, or twisting off the galvanized pipe threads.

IMG_1060Within the hose reel, the line is split by the tee, and the handle is simply a set of straight pipe fittings mated with angle fittings, and capped at the end. Yes, the handle itself is pressurized. To avoid accidentally twisting the pipe off, I used a 1″ PVC pipe to act as a free-rotating sleeve over the 1/2″ galvanized pipe.


All-in-all, this was a great build and having this brand new industrial compressor for free, and getting all the accessories and whatnot was pretty awesome. I figure if I ever did sell this in the future, the new owner can use my rig, and the ability to bypass my step-up conversion to their own delta 240VAC configuration.