Two DC together?

[William C Rogers]

I have two DCs. Jet 1900 and Jet 1100. In my shop before I never put in overhead duct work. I just connected the tool to the closest DC. I have since moved and built a new shop. I have a 30 x 50 pole barn with 12 foot to the bottom of the rafters and was thinking about putting the DC above the rafters and running duct work. I have plenty of room overhead. Note the shop was built with load bearing rafters. I would leave the cyclone on the shop floor. Would I gain anything by using a wye from the cyclone with a branch to each collector or will this have a negative effect? I have Wynn filters on both DCs so I am not too worried about dust overhead and I will run a jet air filter and a homemade filter unit. As far as full bags I would just use a rope hoist to lower them down. Are there any other ins and outs to putting the DC overhead?

[Jim Neeley]

William,

I can't speak to your question but, if you find that infeasible or impractical, there's another potential good use for the second collector.

Once I get my shop electrical upgrade (waiting for spring) I'd get my Clearvue set up, which will free up my 1100. My intent is to repurpose the 1100's blower to the base of a sanding downdraft table whose exhaust feeds the inlet to the Clearvue.

I'd originally planned on skipping the 1100 and hooking the Clearvue directly but, knowing how high of a SP drop a <Bill Pentz style> sanding table has, I figure I can use the 1100's blower as a "supercharger" for the main cyclone. The Clearvue has more "swallowing capacity" than the 1100 so shold create a net suction on the blowers discharge rather than the pressure normally existing when you run it through filters and I expect the 1100, discharging into a suction, will be able to generate more suction than the Clearvue can do. I'll need to monitor the amperage on the 1100 to ensure it doesn't overshoot but don't expect that a velocity-based design like bills will permit enough air mass into the 1100 to let that happen.

When I get to that point I'll be looking to somehow quantify the effect on flow and suction since I'll be able to test it before committing to the design. I guess the simple way would be to measure the dP between the room and the plenum beneath the sanding grid. Not very quantitative but better than nothing!

Jim

[William C Rogers]

William,

I can't speak to your question but, if you find that infeasible or impractical, there's another potential good use for the second collector.

Once I get my shop electrical upgrade (waiting for spring) I'd get my Clearvue set up, which will free up my 1100. My intent is to repurpose the 1100's blower to the base of a sanding downdraft table whose exhaust feeds the inlet to the Clearvue.

I'd originally planned on skipping the 1100 and hooking the Clearvue directly but, knowing how high of a SP drop a <Bill Pentz style> sanding table has, I figure I can use the 1100's blower as a "supercharger" for the main cyclone. The Clearvue has more "swallowing capacity" than the 1100 so shold create a net suction on the blowers discharge rather than the pressure normally existing when you run it through filters and I expect the 1100, discharging into a suction, will be able to generate more suction than the Clearvue can do. I'll need to monitor the amperage on the 1100 to ensure it doesn't overshoot but don't expect that a velocity-based design like bills will permit enough air mass into the 1100 to let that happen.

When I get to that point I'll be looking to somehow quantify the effect on flow and suction since I'll be able to test it before committing to the design. I guess the simple way would be to measure the dP between the room and the plenum beneath the sanding grid. Not very quantitative but better than nothing!

Jim
Jim

I never thought of using the 1100 as a "turbo charger". I am wondering why not do it for the entire system. Bring everything into the 1100 and then to the input of the cyclone using the 1900 on the output of the cyclone? In a sense it is what happens when the Dewalt 735 is hooked up to a DC with it's blower. This might be the best solution. I don't have the commercial cyclone, mine is the one from eBay. I have never hooked it up yet, so I really don't know how this would work, however this idea seems like a better solution. I think it would depend on the amperage effect on the 1100.

Bill

[Rollie Kelly]

William,
Before you hook the 2 blowers in series do some research on this practice. A fan's load is determined by the amount of air it is moving. When you increase the load on the 1900 by "turbo charging" with the 1100, you will overload the motor on the 1900.This could result in burning up the motor on the 1900, worst case, probably just triggering a protection device. Either way not something you want.
I know this sounds screwy, but that's the way it works
Rollie kelly
Rockport,In.

[Jim Neeley]

William,

+1 on research, or at least testing. One mitigating factor: Jet doesn't currently show a 1900 (that I could find) but assuming the unit is rated for 1900 CFM, I don't know if the 1100 is capable of passing sufficient air to overload the 1900. I'd have to think more before commenting on the effect on the 1100 draw.

A DC's electrical draw is related to the mass of the air passing through it and if you force feed it too much it'll overload. This is the reason many DCs say not to run the DC without hose or ducting connected.

The difference with a BP style downdraft table is that you end up with a surface like a reamed-out pegboard. With a "relatively blocked path" there will be a relatively high SP drop across the face of the table (in order to get the high velocity you want to pick up the fines). The turbocharger would help to make up for this loss.

To protect from this, my intent is to start out with a pegboard-like surface with ammeters on both DCs and incrementally ream out holes until I get a good balance of air vs load. With a blast gate installed between the 1100 and the 1900 you could partially close it if necessary to bring down the motor draw, if it's overloading.

[William C Rogers]

Jim/Rollie

I will need to do some load checks to see what effect it has on amperage of each machine to see if either one is overloading. That I can do as I have a amp meter. The real test is seeing if it makes a significant impact. My ideal outcome would be I could leave all my gates open, not overload either DC, and have a 25% increase in performance. One can hope.
Jim, I am in a similar situation. I am building a house and right now I am running my shop off two 15 amp circuits and a generator for 220. I need to use the 220 from the saw post to heat the house during construction. So it is spring for me also to really do anything. I just keep plugging and unplugging when I am not tripping over something building my kitchen cabinets. The Jet 1900 is a 3hp collector (4 bagged) I bought for $300, so that is why I have two. I know Powermatic has a 1900 that I would expect to be similar.
Rollie, I am not all that far from you, Haubstadt, In (Evansville area).

Bill

[Jim Andrew]

William, I had my dust piping on top of the framing for the ceiling, and it was a pain. Climbing around in the attic when I had to change something. Took it all out of the attic and am hanging it below now. Did some rearranging, and looks to be an improvement.

[Alan Schaffter]

Ditto on the research.

There was a lengthy thread here several years ago that fully explored the concept of running two DC's in series. There was one poster (a real troll!) who claimed he had done/was doing it, but his understanding of and explanations were contrary to actual blower characteristics and physics. Despite being asked repeatedly, he never provided technical results or photographic evidence supporting his wild claims (he finally disappeared). The general consensus was the lower hp/lower current motor would be allowed to move too much air because of the boost provided by the bigger unit, draw too much current, and likely burn out. Those who tried it experienced quickly popping breakers and some almost burned out the smaller motor. Supposedly Jim Halbert an early pioneer of home cyclones, etc. was partially successful by carefully monitoring and (automatically?) controlling the current through both motors or limiting the air flow (counter productive). He found it difficult to balance the blowers and I believe that the end result was little to no improvement over using just one blower.

If you attempt to trod this ground again, please carefully document your results and report back.

[Michael W. Clark]

Best bett is to put a blast gate somewhere in the system so you can add resistance. The first fan (the one closest to the hood) is essentially a booster fan. Its purpose in life is to reduce the amount of static pressue the final fan has to overcome. The booster fan can be in the main so that it is carrying all the volume or it can be in a branch that has an unusually high SP drop.

A good example is adding a cyclone to a multibranch system that is already balanced. The main system fan would not be able to overcome the additional SP loss of the cyclone without the booster fan.

[Rollie Kelly]

William,
That is why I added my location. If the weather ever improves maybe we can get together.
Rollie

[William C Rogers]

William,
That is why I added my location. If the weather ever improves maybe we can get together.
Rollie
Would like that, I'm 2-3 months out getting my house/shop together WHICH I HOPE WILL BE BETTER WARMER WEATHER!!!

[Steve Milito]

Ditto on the research.

There was a lengthy thread here several years ago that fully explored the concept of running two DC's in series. There was one poster (a real troll!) who claimed he had done/was doing it, but his understanding of and explanations were contrary to actual blower characteristics and physics. Despite being asked repeatedly, he never provided technical results or photographic evidence supporting his wild claims (he finally disappeared). The general consensus was the lower hp/lower current motor would be allowed to move too much air because of the boost provided by the bigger unit, draw too much current, and likely burn out. Those who tried it experienced quickly popping breakers and some almost burned out the smaller motor. Supposedly Jim Halbert an early pioneer of home cyclones, etc. was partially successful by carefully monitoring and (automatically?) controlling the current through both motors or limiting the air flow (counter productive). He found it difficult to balance the blowers and I believe that the end result was little to no improvement over using just one blower.

If you attempt to trod this ground again, please carefully document your results and report back.

This is really outside of my expertise, but I would think that have the two blowers in parallel would be the correct branch circuit. My concept would be to have both of the blowers connect to a y. I would think you would would want to restrict the flow by having the blowers on smaller legs connected to a larger main. You would probably want some type gate on the smaller blower side to try and balance the flow. I doubt it would work well, but series seems doomed to fail.

[Alan Schaffter]

This is really outside of my expertise, but I would think that have the two blowers in parallel would be the correct branch circuit. My concept would be to have both of the blowers connect to a y. I would think you would would want to restrict the flow by having the blowers on smaller legs connected to a larger main. You would probably want some type gate on the smaller blower side to try and balance the flow. I doubt it would work well, but series seems doomed to fail.

Think about what happens when the output of the two blowers are merged- you have mismatch in CFM and SP which will probably cause back pressure in the lower performing unit. It would be better to just have two separate systems. If the merge was designed like a venturi, you would have a high current situation similar to the series configuration. Also, as I mentioned, adding a gate to balance flow, will actually restrict flow and opposite what you are trying to do in the first place.

[Steve Milito]

Think about what happens when the output of the two blowers are merged- you have mismatch in CFM and SP which will probably cause back pressure in the lower performing unit. It would be better to just have two separate systems. If the merge was designed like a venturi, you would have a high current situation similar to the series configuration. Also, as I mentioned, adding a gate to balance flow, will actually restrict flow and opposite what you are trying to do in the first place.

Just thinking out loud.
In series you are limited to the maximum flow of the smaller unit.
IN parallel, You need to flow restrict one unit so that the SP is equal for both fans. You can then look at the flow on the sp vs flow curve for each fan. You would get the sum of both flows on the other side of the wye minus losses due to turbulence.

I still don't think it's worth the effort.

[Alan Schaffter]

Just thinking out loud.
In series you are limited to the maximum flow of the smaller unit.
IN parallel, You need to flow restrict one unit so that the SP is equal for both fans. You can then look at the flow on the sp vs flow curve for each fan. You would get the sum of both flows on the other side of the wye minus losses due to turbulence.

I still don't think it's worth the effort.

Definitely not worth the effort.

Still not there yet, more than just turbulence- what about pipe diameter after the merge (and possibly a splitter before the blowers if you put them both inline in the main)? Pipe diameter may severely limit your flow. There are a whole host of not so obvious issues. For instance- what happens at start-up if one fan comes up to speed much more quickly? What will be the effects if the system isn't precisely balanced? Will there be dampened or divergent pulsing? With what result? etc., etc. The simplest and most predictable configuration is two completely separate systems.

[Michael W. Clark]

Definitely not worth the effort. .... The simplest and most predictable configuration is two completely separate systems.

I agree given that the OP has two different fans. Parrallel fans really need to be identical to be predictable and to balance with each other. Series fans do not necessarily have to be identical and can be easier to balance and get predictable results.

In series, both fans do not necessarily have to pass the same volume. For example, say you have a large system with a 7" main and one branch is a 4" with a lot of flex, elbows and other losses. You can install a small booster fan (fan from the 1100 DC) in the 4" line along with a blast gate to add aditional resistance as necessary. You would still have to bring some air in one of the other drops to maintain velocity in the 7" main as it would be doubtful that enough air could be drawn through the 4" branch with the booster fan.

[Jim Neeley]

I agree given that the OP has two different fans. Parrallel fans really need to be identical to be predictable and to balance with each other. Series fans do not necessarily have to be identical and can be easier to balance and get predictable results.

In series, both fans do not necessarily have to pass the same volume. For example, say you have a large system with a 7" main and one branch is a 4" with a lot of flex, elbows and other losses. You can install a small booster fan (fan from the 1100 DC) in the 4" line along with a blast gate to add aditional resistance as necessary. You would still have to bring some air in one of the other drops to maintain velocity in the 7" main as it would be doubtful that enough air could be drawn through the 4" branch with the booster fan.

+1 Michael.

If you connected the 1100 to a 4" connection and discharged to the room you could not draw enough air mass into the cyclone to approach overload. Same with the large DC. In either case there may not be enough to keep the velocity up the the large systems mains and you may need to partially open another gate to keep up the flow.

What you would experience with a series connection, however, would be increased flow through the 4" tool compared to hooking the large system up directly, thus the gate wouldn't need to be open so far to maintain velocity in the mains.

[William C Rogers]

This has been interesting. When I posted this I had figured someone has done this and would have information on how to. Evidently not the case. After thinking about it, I agree parallel is not the way to go. Similar to what Jim wants to do I may try the same thing. I bought a used Delta downdraft table years ago and never really use it much, but always wanted to mount it behind my PM 90 lathe for sanding. I have used the big gulp behind the lathe, but never did get a good balance on suction ( too much or too little ) and thought the Delta would provide better area collection overall. Right now my shop is a train wreck. I would be winner in the messiest shop contest. I am guessing about three months out from setting up the dust collection. I will initially check amps as that is easy, and will repost for ideas on where and how to take flow/ pressure measurement if amps are ok. I would also like to use the booster for my table saw. I have two four inch ports hooked to that. One for overarm and one for under cabinet.

Bill

[Bill Space]

Hi.

This may be the thread referred to above:

http://www.sawmillcreek.org/showthread.php?24580-Bill-Pentz-on-Dual-blower-Cyclone

Interesting reading...

[William C Rogers]

Hi.

This may be the thread referred to above:

http://www.sawmillcreek.org/showthread.php?24580-Bill-Pentz-on-Dual-blower-Cyclone

Interesting reading...

Thanks for the link. Yes, interesting. I will re-read when I get ready to try this.

[Wade Lippman]

Unless you will be using several machines at the same time you won't see much of a difference; you will just be using a lot of electricity to make noise.
Sell one of them and buy some nice wood.

[William C Rogers]

You are probably right. I just have a tough time selling stuff. Don't know why, maybe like having backups. Previously I had the Jet 1100 dedicated to the table saw and used the 1900 for everything else. May go back to that.