Venting DC outside - but how ?

[Niels J. Larsen]

I'm currently rebuilding my shop which burned to the ground just after Christmas '05.
I plan on building a Bill Pentz cyclone (thanks to Bill for the excellent work on that!), but here in Denmark recycling the air from a DC through a filter is a big no-no and thus it's almost impossible to find suitable filters.

After reading about a few creekers that have had trouble breathing etc. after doing woodworking for no more than 1½ years I've decided that I want to vent my DC to the outside!

I live in a small town with neighbors close by so I have a few concerns:

1. I don't want to fill up my neighborhood with wood dust, so is there a preferred way of building some sort of container, shroud or whatever you want to call it so I can keep control of the dust ?

2. What about noise ? Will the exhaust automatically mean that I will have the neighbors reaching for their ear muffs when I fire up my DC ? If so - what can I do about that to keep noise at a minimum ?

3. Any other recommendations, heads-up's etc. you might have - please chime in!

Cheers,

Niels

[Cliff Rohrabacher]

here in Denmark recycling the air from a DC through a filter is a big no-no
Wow!! You mean that Denmark has laws prohibiting the use of recirculated air?? And it even reaches into the private homes of the citizens? Does that mean that all commercial buildings must bring in outside air constantly? I'd think it'd make heating costs very high.



and thus it's almost impossible to find suitable filters. Really? Have you tried the internet?? Many people make excellent air filtration units that can go as small as one micron using HEPA filters. Most of the filters I have seen are large square sheets with a cardbord or plastic frame about an inch or so thick. They are in fact ther same filters that many folks use in their residential HVAC systems.



I want to vent my DC to the outside! So long as it's not too cold outside this might be a workable solution




1. I don't want to fill up my neighborhood with wood dust, so is there a preferred way of building some sort of container, shroud or whatever you want to call it so I can keep control of the dust?
You can use a cyclone to catch the heavy stuff. They even make a cyclone like thing that you place on top of a garbage cannister.


2. What about noise ? Will the exhaust automatically mean that I will have the neighbors reaching for their ear muffs when I fire up my DC ? If so - what can I do about that to keep noise at a minimum ? Didn't you say you were fairly remote from neighbors?
How much noise will it take to offend them? Anyway there are impellers that have recurved geometry and they are suppposed to be quieter- a relative term to be sure.

You can also put the impeller& motor in a little shed with sound proofing.


3. Any other recommendations, heads-up's etc. you might have - please chime in! I am still stuck on the issue of Denmark not letting you filter your shop air. Does the whole country just dump whatever they have to the outside?

If noise is a serious problem and you will be filtering the air you evacuate to outside consider the little shed for the impeller coupled with a fairly long exhaust tube with some silencers built in. Silencers can be made from wood in a wood tube A square tube is OK. The down side of a silencer is that it'll consume substantial Delta-P from the impeller.

[Niels J. Larsen]

Wow!! You mean that Denmark has laws prohibiting the use of recirculated air?? And it even reaches into the private homes of the citizens? Does that mean that all commercial buildings must bring in outside air constantly? I'd think it'd make heating costs very high.

I guess I should have put it more clearly: for a company it is illegal to re-use air from a dust collector - i.e. a professional woodworker has to vent his DC to the outside with heavy filtering, cyclone designs etc..
It is possible to buy filters that will actually meet the regulations regarding how much dust there may be in the air etc., so it would be possible to re-use the air, but it's illegal to use - just to be safe (for the sake of the staff in the shop) :)
Due to this, filters of the kind you use in the States are NOT common here.
No, it doesn't reach into private homes, but I'd rather make it right the first time and avoid getting health problems due to too much dust in the air.
Yes, there are actually regulations about how many times pr. hour the air inside a building should be re-circulated. This is partly because of better air for the people who work inside the building, but also about avoiding moisture which could lead to fungus growth and what not in the construction itself.


Really? Have you tried the internet?? Many people make excellent air filtration units that can go as small as one micron using HEPA filters. Most of the filters I have seen are large square sheets with a cardbord or plastic frame about an inch or so thick. They are in fact ther same filters that many folks use in their residential HVAC systems.
No I haven't tried the internet, because if I can come up with a completely safe AND cheaper solution to the dust problem - then why not ? However - if you have a link or two to the products you describe - feel free to provide them to me :D



So long as it's not too cold outside this might be a workable solution
How cold is too cold ? The winters here are relatively warm, but this last one we had periods with temperatures as low as -10 to -15 degrees celsius. My shop will be heated through the floor (tubes with warm water from the central gas heater) and I don't expect the DC to be on for long periods of time.


You can use a cyclone to catch the heavy stuff. They even make a cyclone like thing that you place on top of a garbage cannister.
I plan to use a cyclone - I will build one according to Bill Pentz' plans - as I wrote in my original post ;)


Didn't you say you were fairly remote from neighbors?
How much noise will it take to offend them? Anyway there are impellers that have recurved geometry and they are suppposed to be quieter- a relative term to be sure.

You can also put the impeller& motor in a little shed with sound proofing.

Actually I wrote that my neighbors are close by :D.
Well - how much noise would it take to offend you if were my neighbor (and not woodworking interested) and had to listen to (whatever noise the DC makes) time and time again throughout the calm summer evenings ? :D

I have no idea how much noise this will create, but my plan was to keep the DC inside the shop and then run the exhaust tube through the wall and down through some kind of fine-meshed tube etc. to catch the worst stuff (if any). This tube could be enclosed in some kind of shed with sound proofing (if necessary ?)



I am still stuck on the issue of Denmark not letting you filter your shop air. Does the whole country just dump whatever they have to the outside?

Hmm, let's not get into who does what to the environment - ok ?

No, we dont just "jump whatever we have to the outside". As I wrote in the beginning of this post - there are (very) strict regulations regarding how much dust there may be inside a shop (due to the health of the workers) and also how much dust the DC may dump to the outside.
All DC's here are usually LARGE cyclones with heavy filtering, so the stuff usually ends up in containers ready for pickup by a garbage truck.


If noise is a serious problem and you will be filtering the air you evacuate to outside consider the little shed for the impeller coupled with a fairly long exhaust tube with some silencers built in. Silencers can be made from wood in a wood tube A square tube is OK. The down side of a silencer is that it'll consume substantial Delta-P from the impeller.

Do you vent your DC outside and if so - how did you do it and how much noise does it make when running ?

Cheers,
Niels

[Frank Hagan]

Niels, I don't have my built and installed yet, but I've looked at some of the outside installations, and read some info on both Bill Pentz's site and others. Most of the noise is whereever the motor is with the impeller, so if you can enclose that you can get the noise level down. I'm planning to put the motor/impeller assembly inside the shop, with the cyclone outside.

I'm thinking the cyclone would be efficient enough to collect enough dust that I won't have to go to using filters at all. I may enclose the cyclone in a "box" that baffles the air exiting it and traps any stray dust (one form of dust collection is to have a sudden enlargement in a pipe that slows the air velocity, allowing dust to settle out ... I suppose if you had enough room outside, you could do this without a cyclone at all, but I'm afraid the match is beyond me).

[Niels J. Larsen]

Niels, I don't have my built and installed yet, but I've looked at some of the outside installations, and read some info on both Bill Pentz's site and others. Most of the noise is whereever the motor is with the impeller, so if you can enclose that you can get the noise level down. I'm planning to put the motor/impeller assembly inside the shop, with the cyclone outside.

Good idea about splitting up the motor/impeller and the cyclone itself!
However would that not have a negative effect on the efficiency of the system since you would have to introduce 90 degrees bends in the pipe between the motor/impeller and the cyclone ?


I'm thinking the cyclone would be efficient enough to collect enough dust that I won't have to go to using filters at all. I may enclose the cyclone in a "box" that baffles the air exiting it and traps any stray dust (one form of dust collection is to have a sudden enlargement in a pipe that slows the air velocity, allowing dust to settle out ... I suppose if you had enough room outside, you could do this without a cyclone at all, but I'm afraid the match is beyond me).

Hmm, are you thinking of a box with the sides made of small pieces of wood with a narrow horisontal gap between them ?
That would probably work - and it could even be pretty :D

Cheers,
Niels

[Bill Pentz]

I'm currently rebuilding my shop which burned to the ground just after Christmas '05.
I plan on building a Bill Pentz cyclone (thanks to Bill for the excellent work on that!), but here in Denmark recycling the air from a DC through a filter is a big no-no and thus it's almost impossible to find suitable filters.

After reading about a few creekers that have had trouble breathing etc. after doing woodworking for no more than 1½ years I've decided that I want to vent my DC to the outside!

I live in a small town with neighbors close by so I have a few concerns:

1. I don't want to fill up my neighborhood with wood dust, so is there a preferred way of building some sort of container, shroud or whatever you want to call it so I can keep control of the dust ?

2. What about noise ? Will the exhaust automatically mean that I will have the neighbors reaching for their ear muffs when I fire up my DC ? If so - what can I do about that to keep noise at a minimum ?

3. Any other recommendations, heads-up's etc. you might have - please chime in!
Niels,

Place your cyclone inside your shop and vent the blower output through an insulated duct going outside. An insulated duct and having the blower inside will control most of the noise. The size of the particles coming out of my cyclone design will be invisible. Using a bin sensor to know when it is time to empty the bin or an open filter outside is a good idea because when the bin becomes full the chips go right through the cyclone and could make a mess. Provide an open window, door, or vent that allows makeup air to come inside. The vent whould be at least twice the diameter of your outgoing pipe to minimize whistling and air blast.

Many use a wye fitting and blast gates to let them choose between directing the air to the filters or outside. Farr in Europe does carry the larger filters suitable for indoor use.

bill

[Frank Hagan]

I had a computer crash and have lost my links to the government's dust collection articles ... I'll bet Bill knows them by heart ... but the idea is that you can have dust drop out of the airstream by slowing it down. The heavy stuff falls. If you have too much baffling in it, the dust is just carried along with the air. So a 6" pipe going into a 4' square box, with a 6" pipe outlet, sees the velocity of the air stream fall quite a bit. A lot of dust just falls out of suspension. For the fines coming out of a Pentz cyclone, which is very little, you probably don't need to worry too much about over-engineering a collection box.

But I'm probably over-thinking it, and I do have the blower on the wrong side in my post above. Bill's advice is probably best; keep the cyclone inside and just vent the blower output outside.

[David Rose]

Niels,

I've thought of venting to the outside also. But unless the outside and inside air temperatures are somewhat close, you will have to reheat or recool the makeup air that Bill mentioned with the "open window or door". One of those machines would evacuate the air in my shop pretty quickly. It may be that your heating and cooling costs there are cheaper than ours. But I would expect a substantial increase except when temps are moderate.

I will probably end up with a unit outside in an enclosure, but with return air from the enclosure pumped back into the shop. That probably would not help your situation though, as the air would still be recirculated.

Are there cabinet shops nearby that you could check out to see how they handle this sort of thing?

David

[Niels J. Larsen]

It may be that your heating and cooling costs there are cheaper than ours.

I seriously doubt it - the prices here are outrageous - especially after all the fuss in the MiddleEast.



Are there cabinet shops nearby that you could check out to see how they handle this sort of thing?


The only pro-shops I know of use a system without any filters (due to the regulations).
There are actually a very limited number of non-pro people here in Denmark taking woodworking as seriously as people here on SMC. I'm not sure why, but I haven't met anyone (yet) that would take on the task of building a piece of furniture by themself.

Thanks for all the good advice (everyone) - I will probably do as Bill says - use an insulated exhaust pipe and just let that run outside.

Cheers,
Niels