Venting dc outside

[paul cottingham]

So, I'm thinking of venting my dc to the outside, and I'm wondering about a few things. I plan to run a cyclone, either a thien style top hat, or an oneida, with the blower from my 1.5 hp dc after it, so I will be pulling from the cyclone. I would then push the air outside, sans filter. I may put in a wye, so I can choose between the filter, and the outside, so i don't lose too much heated or cooled air.

My question is this. Would I lose a significant amount of cfm's if I put 2 90s in about a 6 foot run? I would likely put the blower over the top hat, or cyclone, to keep those runs as short as possible.

Thanks, as always.

[Mike Heidrick]

First your answer: yes

Here is my long answer to questions you never asked

The question should be can you absorb that cost in CFM with your desired setup.

That depends on the size and type of the ductwork, your blower/impellers capacity, the entire run length, its ability to move air, and the loss with your "cyclone".

What do you have now Paul? Have you used this "cyclone" setup type at all? I would definately try it before doing any venting out doors. 1.5hp setup like this will have some real challeges with CFM keeping dust and chips moving in all but the perfect ductwork planning and will have issues with very many drops or lengths of any kind I imagine. There are a lot of variables you need to consider:

the type of 1.5hp blower you have and its impeler size
Its true performance and CFM ability (not what the mfg states on the box)
its inlet options
type of ductwork you will use
wall type in that ductwork
efficiency of air through the ductwork you are dealing with
impacts on the way your ductwork is sealed
ductwork sizes you will use
mains diameter
reduction of mains through your run and when to do that
length of runs
number of runs
branch/Y types
logswept vs short
types of drops
size at the tools
effective blast gates and the length of runs to the gates

All of this is BEFORE we even discuss your "cyclones" cfm cost and effectiveness of the blower through it and the loss you will take in doing so.
So say you manage to get this perfect and your 1.5 can keep up effectivelly then you need to consider air/heat loss and ways to damper/return the air
Also consider your heat/furnace type and the effects of outside venting on that.

This is not meant to be mean - Personally I would be running one line tool to tool with a 1.5 and a thein - not enough "infrastructure" there to warrant a permamnent full shop solution IMO.

I would suggest a book on DC (Sandor's) would be a great reed for you as well. There is math to figure out loss with a 90 and certain CFM requirements you need to have to keep dust and chips in motion.

OR

Just do it and see if it works LOL

[Myk Rian]

A long 90º elbow adds less restriction than a short one.

[Dick Brown]

I am not going into H.P, impeller size, loss in fittings, etc. Will address the heat loss with venting outside,though. I vent outside winter and summer with very little heat loss. Will be the first to admit I don't run my cyclone a lot as I don't do a lot of dust generating work. But the key to preventing loss of your warm air is to minimize the mixing of warm and cold by keeping the cold air supply low to the floor, having sufficient area for the cold air "in" to keep the air stream velocity down and close to the machine as you can that you are taking dust from with your D.C. If you would visulize a cabinet saw with fresh air supplied directly into the cabinet, there would be near zero heat loss in your shop when you were collecting dust from it. All the numbers of XXX CFM / XXX C.F. shop = all your heat gone in XXX min. are worst case scenario, like only warm air and no cold air is being blown out. As we all know, warm air rises. If you collect dust from say 36 inches above the floor and the replacement air comes in at 36" or lower with a low velocity, there will be a warm / cold line at near that 36"point as long as there is not a lot of "stirring." If you want to fine tune your system, save your warm air and vent outside, supplying makeup air low and close to the dust pickup point is something that needs more thought than most folks give it.

[David Kumm]

Everthing Mike said is true. The two ells are likely to produce less resistance than the filters although blowers generally recommend several feet of straight pipe at the outlet before changing direction- at least the larger ones. The bigger issue will be whether the 1.5 hp and impeller are adequate. Dave

[paul cottingham]

Thanks for the thoughtful replies. I am mostly a hand tool guy, but use my planer and jointer quite a bit. I also have chip collection set up for my drill press, mortiser, and router table (seriously, i am mostly a hand tool guy!) They work pretty darn well, I might add, but I would like better performance, if possible, therefore I thought I would try the cyclone and venting out doors route.
I use a thien cyclone for my planer right now, but would MUCH rather run all my dust collection through it. So I thought venting it outside would make up for the extra "strain" on it by yielding some extra cfm's. I have a 1 micron bag right now, which of course clogs up when I look at it sideways.
I hope I am making sense.

[Keith Outten]

I have a very old Grizzly 1 1/2 hp dust collector that I use in a 4" PVC pipe shop system that works well. The exhaust from my DC dumps directly outside to a chip box.
No Bags, No filters, No problems
.

[david brum]

I started venting outside last Fall. It works amazingly well, with no noticeable loss of heat in my shop. Note that I'm also in the Pac NW, so winter is relatively mild. I installed a thermostat/ hygrometer in my shop this winter, and carefully watched to see if there was a change of temperature or humidity after running the DC for long periods. I couldn't determine any difference. The biggest heat drain was when I forgot to close the blast gates all night (many times). It's sort of like leaving a window open. For instance, I could feel a draft coming from my band saw. I plan to install some sort of louvered vent on the outlet before next winter.

On the upside, a smaller DC with no filter or separator restrictions works really well. I don't know the specs, but you'd be getting the performance of a much bigger, more expensive system. There are also no filters to clog, so performance is always at it's best.

On the down side, the outlet shoots out lots of dust and chips at high velocity, so they need need to be contained if the side of your shop is "for show". I build a big box out of scrap OSB, and made a clean out door with a big mesh screen ( screen door mesh from Home Depot). It contains all of the bigger chips and dust. The finer dust mainly drifts away. Works great and super cheap to make.

For me, knowing that there is no fine dust drifting around my shop is comforting, easily worth any insignificant heat loss. Again, I'm not sure this system would work in extreme temps, but it works great in our region.

[Myk Rian]

If you would visulize a cabinet saw with fresh air supplied directly into the cabinet, there would be near zero heat loss in your shop when you were collecting dust from it.

Having a background in HVAC, I don't understand this.
If the DC is connected to the cabinet, and so is the fresh air, all you'll do is draw the fresh air through the DC system. Bypassing the dust entirely.

[Jim Finn]

Having a background in HVAC, I don't understand this.
If the DC is connected to the cabinet, and so is the fresh air, all you'll do is draw the fresh air through the DC system. Bypassing the dust entirely.

Fresh air into the cabinet and exhaust from it will also draw out the dust and not use much air from the conditioned space. When I worked in HVAC in Calif this was common practice in fume hoods.

[paul cottingham]

I live in the pacific northwest as well, so I am not hugely concerned with the loss of heated air. I am going to vent into my backyard, or into my carport (at the bottom of a steep driveway, so, unused) so I will use a separator of some kind so I am only blowing small amounts of fines. I may put a large box around the outlet to confine the fines as well. I suspect that this will give me considerably better collection than I currently have.

[david brum]

I live in the pacific northwest as well, so I am not hugely concerned with the loss of heated air. I am going to vent into my backyard, or into my carport (at the bottom of a steep driveway, so, unused) so I will use a separator of some kind so I am only blowing small amounts of fines. I may put a large box around the outlet to confine the fines as well. I suspect that this will give me considerably better collection than I currently have.

Paul

That sounds like a good plan. I think if you look at the specs, you'll see that a 1.5hp DC with a cyclone and filter is pretty anemic. Eliminating those features makes a huge difference.

[Grant Wilkinson]

Paul: Is your shop in the basement of your house? Are your furnace and hot water tank anywhere nearby? Are they natural gas? If yes, you need to be mindful of sucking air out of their space without replacing it. Been there, done that, wasn't fun.

[paul cottingham]

Yes, my shop is in the basement, but we have a heat pump, and electric hot water, so no worries about CO2. I am not entirely convinced that I need to worry about heat loss all that much, either, to be honest.

[paul cottingham]

That sounds like a good plan. I think if you look at the specs, you'll see that a 1.5hp DC with a cyclone and filter is pretty anemic. Eliminating those features makes a huge difference.

To be sure, my current system 4 " PVC with minimal flex works pretty well. BUT if I can improve it, and include chip extraction, well, that would be peachy.