Another Shop DC design

[FlyingRon]

OK, I saw the previous thread and I'm working on the DC in my own shop. The room isn't large however the ceilings are up at 17 feet. As a result I don't really want to run things directly overhead. I'm thinking about running a shelf around the shop at about 7 feet and hang the ductwork down below that. The DC will be located outside the shop as show (approximately)
would entail a wye or something to split the run going clockwise and counter clockwise around the room.

Will this work?

 

[ehpoole]

First things:

1) Since the DC is outdoors, what will you be doing for makeup air (we are talking up to 1000 cubic feet per minute of makeup air).

2) Will this space be heated or air conditioned? If so, you will need a substantial air-return path from the dust collector to prevent the loss of heated or cooled shop air.

3) How sensitive to dramatic humidity shifts is your work? If your air is vented outdoors and the makeup air comes from outdoors then you can expect dramatic shifts in shop humidity (even with a humidifier and/or dehumidifier) if the makeup air is drawn from outdoors. On dry winter days your shop humidity will plummet (more so than a basic unconditioned space would have). Similarly, on humid summer days your humiditiy will spike dramatically. Returning your DC air directly to the shop allows you to optimally manage your humidity levels.

4) Will any gas appliances be used in this space? If so, it is critical that makeup air be provided in an efficient manner so as to ensure there is never a negative pressure condition within the shop space (which would draw flue gasses into the shop).

To me these are the most critical startup questions when locating one's DC in an area external to the shop. Once these safety and practical issues are addressed, then all else follows.

 

[FlyingRon]

1) Since the DC is outdoors, what will you be doing for makeup air (we are talking up to 1000 cubic feet per minute of makeup air).

It's outside the shop are but within the same conditioned space. Makeup is as simple as leaving the doors open between the two rooms. The shop is a walled off section of my aircraft hangar.

 

[ehpoole]

In that case, my suggestion for a perimeter setup would be the same as you suggest, to branch out at the DC with a wye. Let one half of the wye service the upper and left walls, the other half the right and lower walls. In this way you can keep your runs as short as possible since you won't have the luxury of reducing distances by cutting diagonally across the ceiling.

 

[FlyingRon]

Good, that's what I was planning on doing. Now I just have to figure out how to get the wye to match up with the two runs of pipe and fit on the the DC.

 

[Alan in Little Washington]

The big problem with a perimeter duct runs is that they require right angle bends which have a big negative impact on CFM. By using diagonals you can use wyes and 45s to totally avoid 90s. In the diagram below there is one diagonal. If all it will draw from, now and in the future is a jointer which does not generate much fine dust, you can probably get away with running the green branch instead of the blue diagonal.

 

[ehpoole]

No one is dissing the diagonal approach, though, in practice, the diagonal approach tends to save only one 45-deg or 90-deg bend versus the majority of the area covered by a split perimeter approach. In the case of the OP, I suspect that the extra 20-ft of straight [vertical] duct the OP would need to implement a diagonal trunk would easily eat away at any performance gained from eliminating one-half of a 90-deg bend (or even a full 90-deg bend) -- not to mention the added cost of an extra 10' of straight duct that would be needed at every single drop point (17-ft ceilings).

The diagonal trunk is a good and convenient choice where it is an option, but there are many shops where a diagonal trunk simply is not compatible with the space -- especially where there are immovable obstacles on the ceiling or where extremely low ceilings (or even resale concerns with respect to lighting layout) are an issue. It is important not to let the quest for perfect optimization stand in the way of the enourmous benefits offered by a still well-designed dust collection system. Every design, even a diagonal trunk, has its pros and cons, all of which are tradeoffs that can be offset by choices elsewhere in the design.

Just my $0.02.

 

[DWSmith]

My 2 cents worth.

Just ordered a Oneida Pro 2000 DC yesterday and since the duct design service is included, I will let them suggest the most efficient design for my shop. The scale drawing is ready to mail out today. We'll see what they recommend rather then cobble together another system.

 

[Alan in Little Washington]

No one is dissing the diagonal approach, though, in practice, the diagonal approach tends to save only one 45-deg or 90-deg bend versus the majority of the area covered by a split perimeter approach. In the case of the OP, I suspect that the extra 20-ft of straight [vertical] duct the OP would need to implement a diagonal trunk would easily eat away at any performance gained from eliminating one-half of a 90-deg bend (or even a full 90-deg bend) -- not to mention the added cost of an extra 10' of straight duct that would be needed at every single drop point (17-ft ceilings).

The diagonal trunk is a good and convenient choice where it is an option, but there are many shops where a diagonal trunk simply is not compatible with the space -- especially where there are immovable obstacles on the ceiling or where extremely low ceilings (or even resale concerns with respect to lighting layout) are an issue. It is important not to let the quest for perfect optimization stand in the way of the enourmous benefits offered by a still well-designed dust collection system. Every design, even a diagonal trunk, has its pros and cons, all of which are tradeoffs that can be offset by choices elsewhere in the design.

Just my $0.02.

I would never run it all the way up to a 17' ceiling. I'd suspend it. Another thing that folks do, whether diagonal or orthogonal is they connect drops to the main with a 90 or tight radius wye, when a 45 wye and sloping drop would be better. I've just seen too many ducting setups where appearance was the goal over performance.