Low Cost Dust Collectors vs Shop-Vac

I was using a shop vacuum for my 6040 CNC router dust collection, but it was loud, and my almost new Craftsman XSP blew it’s guts out from running all night. I changed to a small Shop Vac brand one, but I knew it was only a matter of time because these motors are just not meant for long-running use. I decided to get something more purpose-built.

Harbor Freight had two Dust collectors. One was listed as “1 HP” and $169.99. The other was “2 HP” and $299.99 – but I was tempted to get the larger one. Still, I got the smaller one for two reasons. One was that the larger one said “20 amps” and I didn’t have that much spare power in this room (though in hindsight, it it might only be 10 amps). The other is that it was a massive floor-standing unit and this room was already fairly crowded. It thought the smaller one would be powerful enough because it said: “The 1 HP portable dust collector produces 10 times more suction than ordinary shop vacuums.” 10x is a lot, so that would be great.

When I got home and unboxed it, I thought it looked very nice. I turned it on, and it was for sure quieter than my shop vac. The suction though was not much at all. It subjectively felt about 1x the suction of a shop vac. So, to see if it was really a 1 HP motor, I used a watt meter. It drew only about 400 watts. There are 746 watts in a HP, and motors are 50-90 percent efficient, so assuming it was 80% efficient (which is generous), it was about 0.43 HP. I could forgive them if they called it 1/2 HP, but a motor that is just over 1/3 HP is too far from 1 HP to be sold as such. Between the false HP marketing and the “10x” the suction, I felt mislead and decided to return it.

I then searched Amazon for what else was available. I found two WEN units. Having just purchased their electric planer and being happy with the quality and the very low price, I knew I had to try one. But which one? One of them was listed as “WEN DC3401 5.7-Amp 660 CFM Rolling Dust Collector with 12-Gallon Bag and Optional Wall Mount , Black” and was $141.66. The other was described as “WEN DC3474 7.4-Amp Rolling Dust Collector with Induction Motor, 15-Gallon Bag and Optional Wall Mount , Black” and was $197.32.

The cheaper one had a brushed motor. The brushes are rated for 250 hours of use, which is only 10 days if you leave it running. I read up on what an “AC Induction motor” was, and it was inconclusive if it was a desirable motor because single phase ones are not as good as 3-phase units. To add more to my confusion, the cheaper one was listed as 660 CFM, and the more expensive one was called 600 CFM. I know that CFM ratings are unrelible even more than HP ratings, so there was no way to know without testing them both.

Here are my results with them working through about 10 feet of 4″ dust-collector hose:

Note how the Harbor Freight (with the filter bag) is not 10x the suction of a Shop Vac with it’s own filter. In fact, it is only about 91% of the suction of one of the smallest and lowest-cost models that Lowes sells – one that is on sale for just $62 now.

One very interesting thing is that the “7.4 amp” WEN lost very little performance when the bag was installed. It went from 495 to 489 CFM – almost 99% of the unrestricted performance. The Harbor Freight went from 441 to 252 – a much greater drop. Is this because the Harbor Freight bag is very restrictive, or is the blower motor so low on torque that it reduces performance dramatically when there is even a small amount of resistance? The answer is some of each, but mostly the bag. The Harbor Freight bag would not fit on the WEN outlet, but the WEN bag on the Harbor Freight did raise the performance a lot – indicating that the Harbor Freight bag is most of the problem. Whether that is due to it filtering to a smaller micron level, or due to it being less efficient – I don’t have the means to test. It is entirely likely it simply filters smaller particles.

These impellers all looked like they would clog and so a dust-separator seemed important. I have the Home Depot kind with 2.5 inch fittings, but much to my horror it wiped out the performance of all of these units, except for the Shop Vac! Turns out that these centripetal blowers are all very sensitive to flow restriction whereas a Shop Vac is not! I thought about building a separator with 4 inch fittings, but this was becoming a project, and I could just buy the Harbor Freight “2 HP” model for $50 more than the larger WEN, since the local store had one with a damaged box at a discount. I had avoided this unit earlier because it claimed to need 20 amps, but by now I was pretty sure that all of these specs were exaggerated, so I got it and tested it. Turns out it did draw a bunch of power when starting up, but once it was spinning, it only drew about 7 amps / 760 watts. Now this is interesting, as this unit actually does draw a full 1 HP (but they call it 2 HP). The suction was a bunch better than the others ones – 3x my Shop Vac, all while using less power. Yes, it was louder, and it did take about an hour to assemble – but it’s the only unit that fully satisfied me and the one that I will be keeping.

To summarize, the “1 HP” Harbor Freight had about 10% more performance than the lower cost WEN – at least when no bag was on either. The smaller Harbor Freight cost about 20% more than the cheaper WEN, but it has an induction motor, and the brushed motor of the lower-cost WEN is only rated for 250 hours of use before needing the brushes replaced. A “2 HP” Harbor Freight averages about 1 HP of power consumption, and likely makes about 4/5 of 1 HP of actual mechanical motion – and I sure wish they would just rate them truthfully. I felt like the suction of the larger Harbor Freight was the only one that was truly good enough, and that is my favorite – but it is massive and louder. Still, if I need something for portable use such as drywall sanding, I would just use the Shop Vac, so I think the larger one is the only one that makes sense for a workshop.