Performance

StoryID
704486
ToolNumber
3
ComponentId
tcm:78-1628141
Image

The second-place Senco is a popular model, also available under the Grip-Rite and Rolair brands. Its slender hot-dog configuration balances well for carrying, but can tip easily in the truck.

Credit: Photo: By dotfordot.com

Current Draw. One thing I like about small compressors is that they generally don't pop circuit breakers. Nearly every manufacturer recommends plugging into time-delay breakers or fuses, but I can't count on my jobsites to have them. I frequently plug into exterior receptacles for doing siding, roofing, and exterior trim work, and the last thing I want is a tripped breaker when the owner is out for the day, and I have no access to reset it.

It's best to minimize the length of extension cord powering a compressor for the health of the motor and to reduce the chance of popping a breaker. Most of the compressors we tested have specific limits on cord length and gauge. The most common limit is a 50-foot, 12-gauge cord, but we all know what happens: one 50-foot cord gets plugged into a gang box and another 50-foot lead connects the compressor, even if it's only 10 feet away.

To see how the compressors would work under realistic conditions, we ran them from two linked, 50-foot, 12-gauge cords plugged into a 15-amp GFCI circuit that was about 50 feet downline from the breaker panel. We made sure they cycled regularly, and listened for any sound of motor laboring. I hooked a utility light to the splitter at the end of the same cord to get a crude sense of current draw by watching the light dim.

StoryID
704486
ToolNumber
4
ComponentId
tcm:78-1628141
Image

Portability is important and isn't just about weight. Carrying balance makes a big difference, as illustrated by the Porter-Cable (left) and Rolair units.

Credit: Photo: By dotfordot.com

Except for the first instant, five of the oil-free models showed no dimming. The oil splash models all dimmed the light slightly longer, but for less than a second before returning to full brightness. The Jenny seemed to draw the most juice and dimmed the light the most and the longest.

Only the diminutive Thomas compressor wouldn't operate–it just hummed, even when we shortened the cord to 50 feet, which its manual said is OK to do. It only started when we plugged it directly into the receptacle, despite the fact that it has a 6 amp motor and only requires 10 amp circuit protection. After using it for a couple days, we tried the same test, and got the same results. A replacement Thomas fared a little better but would only run on 12-gauge cords shorter than 20 feet.

Output. All the units worked fine in the field for the light- to medium-duty demand we placed on them. For paced work, like nailing off window trim or roof shingles where there are breaks between rapid firings, we had no trouble. That said, none of them could keep up with two roofing nailers on high-production straight runs or rapid-fire shop assembly work.

Our output test was pretty simple. With the regulators set to 100 psi, we dry fired a roofing nailer at a pace to maintain a tank pressure of 100 psi. Then we repeated the test with a finish nailer. Essentially, what we were checking was how fast the pump would let a tool work.

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The J-Air has many features we like, including low-slung stability, a heavy-duty air line and power cord, large vibration-dampening feet, and a well protected air filter. The vulnerable outboard gauge at right could be placed better, though.

Credit: Photo: By dotfordot.com

StoryID
704486
ToolNumber
5
ComponentId
tcm:78-1628141

We expressed the results in shots per minute for each tool. The Jenny outperformed all the other compressors and rivaled a much larger 4-gallon model weighing 50% more. The Senco and Rolair tools did extremely well, and the Makita was not far behind.

Noise Levels. I've always felt that oil-free compressors are noisier than the oil splash versions. I had a helper plug in each compressor in a room 18 x 18 x 7 feet high while I was blindfolded, so I could subjectively rate the noise level. This was not the same as rating the actual sound pressure in decibels; rather, it determined the annoyance factor of the different sounds.

It was next to impossible to tell a difference between most of the oil splash and oil-free models. The Makita was the only oil splash model that I could say sounded quiet; it has a low speed, 1,720 rpm motor compared to others that spin at 3,400 rpm and higher.

Some of the oil-free compressors made hissing noises, others whined, and all but one were annoying when we worked in the same room with them. Only the Bostitch sounded quiet to me. It's hard to tell if that's because of the design of the motor and pump or the fully housed design, but it had a mid to deep hum that wasn't bad.