Duct hose suggestions for venting a Laguna 7 inch collector outside

[Larry Cronin]

Hello,

I have a Laguna 2HP manual clean dust collector (MDC0560-0145) that I am going to vent outside. Who knew besides those that read the manual or measured the outlet pipe that it is 7 inches. Certainly not the guy who yesterday installed the 6 inch vent and purchased the 6 inch hose, blast gate, and clamps. (Another example of why planning is bad)

My questions are:

Could I use a 7 to 6 inch round reducer at the collector and use my 6 inch stuff?

Can I use the Semi Rigid Aluminum Duct and a vent that I can get a the BORG?

Should I purchase some "legit" 7 inch hose and vents from a HVAC place?

Thanks for any help, suggestions, and mild criticism in advance.

Larry C

[Larry Frank]

With that dust collector, using the 6" will be fine.

[Mike Heidrick]

I'd sure try what I had.

[Carl Kona]

Larry,

It depends. It depends on what and how you are using your DC. On the plus side you are eliminating the filter and ducting outside. The downside you are taking a 7" duct ~38 sq. in) and reducing to 6" (~28 sq. in) or ~25% reduction in duct size. As mentioned you can try it and will probably not notice a difference or maybe an improvement. You will get a bigger improvement by using 7". The less restriction the better, but in either case you need to be careful that you don't overload the motor. No restrictions on input or output can allow the motor to spin too freely and draw too much current. If you are attaching a 4" hose to your DC and are venting outside to eliminate filter cleaning then 6 or 7 inch exhaust duct won't matter.

[Carlos Alvarez]

I'm not sure why people make the decisions they do on design, but assume it must matter. My DC setup is 5" pipe going to an Oneida cyclone with 5" inlet. That has a 6" outlet, which mates perfectly with a 3HP motor from Kufo with a 6" inlet. The output from that is bigger, and being rectangular the number is more complicated, but it's clearly bigger than the input. It seems like the out is always more than the in.

[Bill Dufour]

For outlet many use ac flex duct. it is pressure not vac so a cloth sleeve would work cut from a leg of blue jeans.
Bill D.

[Chris Parks]

The exhaust duct should always be bigger than the inlet side, to make the inlet side bigger will only result in slower slower air speed in the duct and no increase in air volume through it. 6" with a two HP unit would be marginal anyway.

[Larry Frank]

I do not think it will make much of a difference at all. If you were running a bigger dust collector with higher flow then maybe.

Technically will there be a difference, yes but small. Practically, there will be no measurable difference.

[Larry Cronin]

Thanks for the suggestions.

I am going to look around a bit today and see if I can find some 7 inch stuff.

If I can and it looks like it may work I might go with that. If it involves ordering and waiting for the 7 inch stuff I think I will just go with the 6.

I will let you know what I end up doing and the results.

Thanks again for the help.


Larry C

[Jim Becker]

You can easily source 7" metal components from an HVAC supply, a dust collection vendor such as Oneida, Air Handling Systems, Kencraft, etc., or even a big-box store if you're talking about reducers, etc.

While a larger outlet is theoretically better, I tend to agree with Larry that for a unit like you have, it's going to be more of a marginal situation rather than a significant improvement. That said, if it's structurally possible to enlarge your pass-through to the outside, by all means, go for it.

[Dan Friedrichs]

1) Figure out if the 6" exhaust is limiting performance in any way: measure the motor current draw (with no exhaust ducting and with your 6" exhaust ducting) and compare. More current = more air being moved. If you find the 6" exhaust is reducing the airflow, you'd probably want to go bigger. But it might not be, depending on the rest of the system.

2) If you need to up-size, there is no reason you need to be exactly 7". Think about it: once it exhausts to outside, it's effectively in an infinite-diameter duct And it doesn't need to be rigid duct, because it's under pressure (not vacuum). So get a piece of 10" insulated HVAC flex duct - or literally anything you can find - and it'll work fine.

[Carlos Alvarez]

1) Figure out if the 6" exhaust is limiting performance in any way: measure the motor current draw (with no exhaust ducting and with your 6" exhaust ducting) and compare. More current = more air being moved. If you find the 6" exhaust is reducing the airflow, you'd probably want to go bigger. But it might not be, depending on the rest of the system.

2) If you need to up-size, there is no reason you need to be exactly 7". Think about it: once it exhausts to outside, it's effectively in an infinite-diameter duct And it doesn't need to be rigid duct, because it's under pressure (not vacuum). So get a piece of 10" insulated HVAC flex duct - or literally anything you can find - and it'll work fine.

1. Great point. Now I wonder if I can use that to fine tune my system. Say, measure it while opening and closing gates, to learn when max airflow is reached? Does it matter to have the 2.5" DP open while the 5" TS is also being used? I'm also always wondered if running only the DP or other 2.5 by itself could actually be bad.

2. To add to this, note that Dan suggested an oversize tube, and I think that's a good idea. 8" is easy to find at the big box.

[Larry Cronin]

Just to wrap it up.

I had a some trouble locating both the 7 inch and 8 inch outside vents that were readily available.

So I am going with the 7inch to 6inch reducer and see how it works.

Thanks for all the suggestions and guidance.

Larry Cronin

[Jim Andrew]

I made my own outside dump, just ran the 8" pipe through a piece of plywood and screwed the pipe to the ply, then made a plywood door hinged on the outside so it closes like a dryer vent. Then made a hood to cover it up to overhang, so rain will not bother it. My 3hp cyclone has a 8" outlet. Used hvac pipe, light gauge is ok as it is pressurized, not vacuum like intake.

[Chris Parks]

The way I look at at us this, if the DE is not very powerful (and 3hp IS marginal) then it needs very good design and any impediment to it working taken away because the DE cannot afford the losses.

If the DE is very strong as a 5hp/15"or 16" impeller would be then the losses are not such a big deal and do not affect the end result noticeably. There is a lot of stuff written and researched on the Ubeaut forum in Australia designed to prevent or minimise these losses for lower performance dust extractors such as bell mouth intakes etc.