Member
I have a CV1800 with 16" impeller. It's a beast and works great. I use 6" PVC runs, minimal or no flex, vent outside and have 6" ports on my machines (3x4" on the bandsaw). It pulls about 4500w or 6HP from the wall and I get between 850 and 1000cfm at each machine. People who are able to get 800 or more CFM with a 2HP or smaller dust collector are doing very very well. My old 2hp dusty with 3 feet of flex pulled about 350cfm from memory.
Cheers, Dom
Lots of good info so far. In short, you are doing the right thing in making dust collection a priority. Since you are currently looking closer at it you are finding why folks say get the best you can afford. For me this makes sense as the cost of waiting till you can afford your dream system just means more time in the shop in unhealthy conditions. I run a 2HP cyclone and it does well but, I wouldn't turn down better. I run a separate 1HP unit with an after-market filter bag for the jointer as this worked better than a duct run to that position. We don't all need perfect but, we all need something. Keep looking and be ready to strike when the opportunity come along.
"A hen is only an egg's way of making another egg".
– Samuel Butler
[OP]
Member
Scott, I know that large diameter, slower-moving ducts are not optimal for small hand tools. Are you saying that a larger impeller helps overcome this issue? I don't quite understand this, but I would LOVE to be able to use my main dust system for smaller tools like sanders & tracksaws.Originally Posted by Scott Bernstein
I was going to buy a second (expensive) shop vac, but I could put that money towards a better cyclone.
Can anyone explain this, if it's true?
Member
A bigger impeller and more HP can compensate somewhat for it but I can't quantify that... opening an upwind blast gate for makeup air to keep the dust moving is probably the easiest option to keep enough air moving through the main.
Contributor
Download the Cincinnati Fan PBS tables. You get a pretty good idea of the cfm various diameter BC impellers pull at various inches of SP. There will be some variation due to inlet size and housing design, and a huge difference between curved and straight blades, but the numbers are quite accurate in predicting what a CV or Oneida impeller of the same diameter can pull and the amperage needed. Dave
Moderator
I don't have experience with a 1.5 hp dust collector, but I know someone with one and based on that I'd consider it between poor and marginal. They used it a while then started saving for a better system.
I used shop vacs before I put in my DC and they did collect a little dust but nothing like I have today. I installed a 5hp ClearVue and ran 6" ducts through the shop, split at the bottom of the drops into 4" flex as needed for specific tools. My longest run is probably 40-50'. This system is astounding, both in the dust pickup and the separation. It drops powder-fine dust into the bin and almost nothing goes into the filters. After using this, I would not be happy with a smaller system. It is loud, though. I built a sound-insulated closet for it and the big air compressor.
JKJ
Member
I can just tell you based on my experience. Right now I have 25' of 6" flex line going into a splitter to two 10' lengths of 4" flex line. I tried measuring the CFM today on my CV1800 (5hp, 16" impeller) with an anemometer and didn't have much luck at the 6" line...the windspeed topped out at 144 kilometers-per-hour and then registered "overload" so who knows what the windspeed actually was...suffice it to say it was at least 150kph and probably more than that. So I was getting at least 1600CFM through 25' of flex line...and probably way more than that. The wind speed also maxed out when I measured at the end of some 4" flex line (10 feet, after the splitter). So who knows, maybe 800-1000CFM through both 4" flex lines open at the same time? I then put a 4"-to-2.25" adapter on one of the four inch flex lines. Based on qualitative feel of the suction it certainly felt stronger than my shop vac, so I don't see why I couldn't use this with hand sanders, etc... It's got to be moving at least as much air as my shop vac, and it feels like more. I think this ought to work especially if an extra, larger, line is kept open to keep the air moving inside the large main line. I think the motor works HARDER when it's wide open - say, with no collection bin, filters, or intake tubing. When the airflow is clamped down the motor has an easier time since less air is being moved - at least that's what ClearVue says.
As far as the larger impeller, I told Clearvue I'd probably use this machine with tools that have smaller ports (less than 4") and probably some hand-held power tools. They suggested that the larger impeller can help push air against this higher static pressure load.
I'm pretty sure no one ever sold their dust collector on the basis of it being too powerful...
Scott
Contributor
Just a comment about a hand held anemometer. There are very inaccurate for measuring airflow at the end of a duct or hose. They typically way over estimate air flow
Contributor
Recommendation for a better tool then?
Contributor
What you want to look for is a hot wire anemometer. This one is supposed to be decent. https://www.testo-direct.ca/product/...SAAEgJxwfD_BwE You should be able to find a US source so the price to you would be closer to $112US.
Contributor
I have the 1.5HP Oneida with the external filter in a small shop with very short runs.
It works fine in my installation...Rod
Contributor
Sorry, what's better about a hot wire anemometer? Oddly enough I borrowed a probe from the same company. Buddy of mine does HVAC for a living, so he has all the (somewhat) expensive toys.
https://www.testo-direct.ca/product/...ane-anemometer
Contributor
The cross section of a hot wire probe has the least disruption to the airstream. A fan type has a large area that creates a disruption to the airflow speeding it up to get past the fan and housing thus giving erroneous readings (higher). Used properly the hot wire should be used to take a number of reading across a duct and then averaged. A pitot tube type, also available from the same company, can give good readings when averaged across a duct but the alignment of the pitot tube is critical to getting good readings making it more difficult to use. Test readings from either the hot wire or pitot tube should be taken in a test duct which if my memory is correct should be ten diameters long in front of the probe in order to ensure the airstream isn’t turbulent. On the desktop I have a link to a mining paper on correction factors for fan type anemometers that I’ve linked before and can again. Keep in mind they are dealing with big ventilation shafts and not small high speed ducts.
Member
Hi Allan -
I think I have the same Oneida unit with internal filter. I'm in the process of installing/ commissioning it, so can't yet comment on performance. I'm using 6" PVC drain/waste/vent pipe, which I will try to maintain all the way to each tool.
I was planning on keeping the internal filter, until and unless that becomes a problem. I'm not sure how good the original HEPA filter is in that unit. In your investigations, did you determine if there is a suitable replacement filter for this unit?
- Phil
[OP]
Member
Phil, you can use any external filter, of course. The only trick is connecting it, but that's not really such a big deal, esp since the Onieda has a rectangular flange. You can even buy a kit from Onieda, but I think making a plenum out of MDF actually makes more sense. It looks better and has some mild sound-deadening qualities. I was even going to make an entire cover for the filter out of MDF, maybe with carpet or mineral wool on the inside.
The cheapest way to add a good filter is to buy from Wynn. Onieda is way overpriced. Buy the one with the flanged top, it's specifically made to attach to a home-made plenum.
Make your own bottom dust pan as well, as the commercially made ones are insanely expensive. - Or just use a small bag.
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FWIW, I'm 99% sure I will pass on this unit. Jim Becker wrote (above) that these had smaller impellers, and that makes sense given that a lot of internal area is taken up by the filter. If you remove that internal filter, that area is not likely designed specifically to swirl dust & chips. - So I doubt you have the same physical system as a modern 1.5 HP Onieda, and those are still marginal.
- But please report here on how it goes. There seem to be a LOT of these units for sale, for pretty cheap. If they can be made to work well, it would be worth knowing.
Last edited by Allan Speers; 04-14-2019 at 2:26 AM.
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