D.C. input

[Kenneth Reidy]

Hi All,

I have two questions concerning dust port sizes and Y connections.:

I am setting up a new shop and routing the main 8" spiral pipe branch into a 16"x16" cast trench in the slab. The new layout includes running from the 5HP DC unit tying into it a table saw with an existing 4" port, a 8" jointer with the same port configuration and then a 16" jointer that I will fabricate a 6" port, after that it goes into a W at the opposite wall with risers going up the wall feeding a 6" horizontal run for each leg of the W. The question is do I change the 4" ports on the TS, Jointer, 15" planer to 6"?

Next question is from the Y's I intend on using flex house, is this a sane approach?

There are a few more questions but I would be delighted to get some confirmation on the two above.

All responses humbly appreciated.

Many thanks,
Ken
Corrales, NM

[Michael W. Clark]

My first question would be do you have enough DC to deliver 1400 CFM? Maybe you do if you don't have a cyclone? That is what it will take in an 8" line to keep the dust flowing without dropping out in the duct. Are you running multiple branches at the same time?

A simple way to consider your port sizing is that if you are always pulling through the 8" duct, you need to be pulling from a combination of branches with roughly the same area. For example, 1400 CFM through a 4" port is 16,000 FPM, requiring about 16" SP and you don't have enough fan for that. You need four (4) 4" ports open to support the 8" duct. This is not exact by any means as it will also depend on your system layout, but something to consider.

[Kenneth Reidy]

My first question would be do you have enough DC to deliver 1400 CFM? Maybe you do if you don't have a cyclone? That is what it will take in an 8" line to keep the dust flowing without dropping out in the duct. Are you running multiple branches at the same time?

A simple way to consider your port sizing is that if you are always pulling through the 8" duct, you need to be pulling from a combination of branches with roughly the same area. For example, 1400 CFM through a 4" port is 16,000 FPM, requiring about 16" SP and you don't have enough fan for that. You need four (4) 4" ports open to support the 8" duct. This is not exact by any means as it will also depend on your system layout, but something to consider.

Hi Michael,

Fortunately the CFM is 1,850. 2.5 SF (w/ filter). My shop is basically a one person operation with usually only 2 machines running simultaneously and 90% of the time only one. My main concern is that the system would run more efficiently with the 6" dust ports or should I retaining the 4" ports where originally equipped. I had a mechanical engineer say that if the machinery functions well with the 4" port, go with it. He was emphatic that I shouldn't go to 6" ports.. After reading Bill Penz, it is my belief that he believes that an increase in port size is needed. Since I want to install the DC system just once, I would like to get some input on the best way to go.

Thanks,
Ken

[james manutes]

My impression is a mechanical eng. is not an expert in DC do's/ don'ts . What DC unit are you using ? It' actual CFM will give you the data for 8" , 6" , 4" , what to not do .

[Mike Heidrick]

id run 6" drops to those tools then convert. Change only if you need to. Too many variables for us to guess what you need to do.

[Michael W. Clark]

My impression is a mechanical eng. is not an expert in DC do's/ don'ts .

Depends on the mechanical engineer and their experience....

[Michael W. Clark]

Hi Michael,

Fortunately the CFM is 1,850. 2.5 SF (w/ filter). My shop is basically a one person operation with usually only 2 machines running simultaneously and 90% of the time only one. My main concern is that the system would run more efficiently with the 6" dust ports or should I retaining the 4" ports where originally equipped. I had a mechanical engineer say that if the machinery functions well with the 4" port, go with it. He was emphatic that I shouldn't go to 6" ports.. After reading Bill Penz, it is my belief that he believes that an increase in port size is needed. Since I want to install the DC system just once, I would like to get some input on the best way to go.

Thanks,
Ken

What is 2.5 SF? Your collector may be rated 1850 CFM but it likely won't pull that much flow when connected to your system. For a 5HP unit, I would target 800 ACFM and run 6" everywhere. If you have to wye to a 4" port, have the other side of that wye open (at least partially) as well. Run (2) 4" ports, or a 5" and 3" all the time. Its not going to be perfect but it will better balance the system.

If you can sketch what you have and are considering, others may be able to offer more insight as to arrangement.

[Bill Dufour]

Is there pipe in the trench or is the trench the duct?
Bill D