Dust Collection Trunkline

Re: Dust Collection Trunkline

Felix B

>I know exactly what you are talking about. I have similar DC, it's 580 model. When I first got it, I expected to see 6" opening under the plastic 2x4" splitter... Well, not quite. The plastic thing was installed on 6" dia. outlet, but the actual opening into the impeller was 5".

To make a long story short, I took plastic adapter off, I cut 6" opening where it was 5" and installed my 6" main duct line :)

Let me know if you want to see it in pictures.

To answer your original question - using 6" pipes with 5" dia intake won't make it worse. It comes down to the volume of air that passes through the pipe. Smaller pipe will have higher velocity then larger pipe, but the amount of air (volume) that passes will remain constant.

Cheers,

Felix

Re: Dust Collection Trunkline

Mark McC

>I think it's minimal and the difference which is possible I suppose for some here to calculate isn't worth the effort IMHO. I have a basement shop with a 2hp General and two main trunks,I focused on trying to keep the trunk run's as straight as possible and minimized the use of Y joints, corners and flex pipe to connect machines. I think those factors kill a system's efficiency more then one reducer will, right at the machine hook up where the CFM is the strongest.

Re: Dust Collection Trunkline

Mark Kauder, Phenix City, AL

>One minor correction to what Felix said:

The while the velocity of the air will increase with the smaller ducting, there is a limit - the impeller/fan can only pull so much air based on it's size and speed.

The CFM will NOT remain the same regardless of the ducting size. Basically, with a relatively short run of 4" ducting, and a normal 1.5 to 2hp DC, you will only pull about 850CFM. Though air is compressable (more cfm through a smaller hole, at a higher speed), that compression is limited by the power of the motor, and the size of the impeller.

The ducting itself has an effect. The interior smoothness, twists and turns, all effect the compressed air, and thus the velocity and volume.

The trick with DCs is that you have to have enough speed to keep the larger debris suspended in the airflow all the way to the impeller, and pull enough CFM at the far end to pull the debris from the large volume area of a machine like a table saw.

It is all very confusing.

Mark

Re: Make sure you don't overload the motor

Grant Smith(remove 1 for email)

>The manufacturer placed the 5" opening to the blower likely for their own best interests. It prevents too much air from entering the blower, and thereby pulling more current than the motor is rated for continuously. Depending on how conservative they were (or how cheap the motor was they used), you might eek out more CFM by changing things around...BUT:

I suggest you take the following precautions:

1. Measure the amperage draw with an ammeter of the collector drawing air through the existing 5" hole. Compare this figure to the current ratings on the motors plate. If the measured amount is close to the motors continuous rating, then I'd leave the 5" hole alone.

2. If you just can't stand it and are compelled to cut the opening larger, then monitor the result with the ammeter to ensure that the motor doesn't draw more than its rated current capacity. Otherwise, be prepared to replace the motor prematurely.

3. Note that the current draw on the motor increases as it draws more air. A blocked inlet causes the motor to speed up, but current drawn to decrease dramatically. Note also the vast difference in surface area of a 5" circle versus a 6" circle. (If my calcs are correct, a 5" circle has an area of 19.6 square inches versus a 6" circle having an area of 28.26 square inches or almost a third more). The manufacturer saw fit to limit warranty repairs by using a restrictor (5" hole) on the inlet side of the blower. If you decide to "hop it up", be prepared for motor replacement sooner.

FWIW, I recommend you find some 5" ducting for max cfm and velocity since you need both to carry chips and dust effectively.

Addy protocol: NOT a fluid engineer, but have studied and played with these things quite a bit and am a student of Bill Pentz's teachings. I also know motors and their limitations.

Regards,

Grant in iowa

Re: Make sure you don't overload the motor

Mark Kauder, Phenix City, AL

>Great Grant - I was stepping all around that fact, but don't really know enough technically to comment. Bill Pentz's site is the real mecca for this subject - especially for the Hobbyist.

When I was exchanging emails with either Bill or the guys at clearvuecyclones.com, I was telling them that I would like to slowly upgrade my shop ducting, in preparation for getting a ClearVue Cyclone DC a little while down the road. I was wondering if I could go ahead and put in 6" ducting now, but have it still work OK with my 1.5hp Grizzly DC. If memory servers, whoever responded said that putting in 5" ducting now would improve the performance over my current setup (4" PVC), and not significantly hinder the new DC when I put it in. I could be wrong, and intend to check on that again.

Mark

Re: Dust Collection Trunkline

Ells in Boulder

>Jim,

If I understand correctly, you are not asking about opening the inlet at the collector to 6" but rather stepping up from the 5" inlet to your 6" ducting. In that case you should lose only velocity, not volume flow, until you have to step down again, probably to 4", at the machines. So, you don't have to worry about over stressing the motor with excess flow but perhaps the velocity drop of 4" to 6" could leave debris in the ducts, certainly at any rough edges, joints, bends etc. However, with the 6" duct already acquired, if you install it you'll be ready for next upgrade to a 6" inlet system if clogging becomes an issue.

Ells

Thanks for the input!

Jim in Lakewood, OH

>You've all given me some great input to consider, as I knew you would. I'm leaning towards using 5" ducting at this point. It sounds like the safest way to go, & I suspect that by using 6" duct, I wouldn't gain anything without opening up the manufacturer's 5" opening - something I'd rather not do.

Jim

Re: Dust Collection Trunkline

Bob Dodge

>Jim,

Just use a 6"-5" reducer, and you'll be fine. If you have a choice, go with a "long-taper" reducer. According to the tests in the Fine Woodworking Magazine review published last spring, your dc can easily feed a 6" main, but there are limitations.

You can run a 6" main to any of your machines with twin 4" ports, such as a table-saw equipped with an overarm blade-cover. A 6" drop and a 6x4x4 wye should perform quite well as long as you're reasonable regarding placement of the dc relative to your saw.

If your other machines have single 4" ports, you'd want to reduce that 6" main, to 5" after the saw's 6" drop. You don't want that 6" main to be too long, since the single 4" port machines won't be able to feed the 6" main adequately. You'd need a minimum of 685 CFM feeding the 6" main, to get 3500 FPM waste-support velocity. With a 5" hose connected to that single 4" port, you'll probably be close, depending on hood design, but, if you use 4" hose (or pipe) to that single 4" port, you definitely won't get there. You'll have roughly 4"SP resistance at the hood alone.

Some commented on the air "compressing" as the air passes through restrictions, well, that's incorrect. The air either speeds up, or slows down depending on the diameters involved. Resistance will rise or fall according to that velocity.

Amp-draw, will also be a non-issue with a ducted system. Your amp-draw will be highest when you have no ducting connected, because that's when you're moving the most air. By adding pipe (and resistance), you'll lower the amp-draw.

Bob

Good Info ...

Jim in Lakewood, OH

>Thanks Bob. I let my subscription go for a few months & missed that issue. I'll have to track it down. It sounds like my DC was one of the ones reviewed, & I suspect the rest of the article will be helpful too. Your highlighting the info gives me a lot to work with. Guess I'm back to the 6" main duct.

Jim

Re: Good Info ...

Bob Dodge

>Jim,

I think it was the April issue, 2006. Ten 1.5 HP dc's tested, and the Delta 50-760 was in a class by itself. Published figures for the Delta showed roughly 925 [email protected]" SP.

I spoke to Michael Standish (author), several months after the article appeared, and he verified that AMCA test procedures were not followed, but rather, a single-point center-line velocity-pressure reading taken. All dc's were fitted with bell-mouth entries on the test-pipe. Stated CFM would be rather optimistic, and especially so at higher static-pressure points.

None-the-less, since all dc's were tested in the same fashion, the Delta was far-and-away the best performer. Furthermore, the Delta was fitted with a 5" pipe, while those dc's with 6" ports, were tested with 6" pipe. The Delta still managed to pull more air than the 6" intake dc's.

Bob