ventilation for enclosed dust extractor?

[Trav]

Hi all

I am setting up my workshop again after a 3 year hiatus in Italy. It's good fun!

I have a plan to vent my dusty 'outside' the workshop, which is into a small enclosed hallway that I can separate from the main workshop by building a simple door. It can vent directly to the exterior of the house through a solid timber exterior door.

My concern is that the 'hallway' is not big - 0.93m wide x 1.25m deep x 2.20m high. It will only house the dusty, plus a small compressor (because of the noise). Is this small size likely to be a problem? Should I vent it through the solid door to the outside? Any thoughts on the ventilation needed?

Thanks

Trav

[Pat]

Trav, I am about to consign my dusty to a 1.52*.78*1.8 shed at the back of my new shed. I will evaluate it's performance an may add a couple of vents to gain airflow.

I don't think any shed or hallway is totally air tight so I'll wait and see.

[mic-d]

Hi Trav, if I understand correctly, you'll have some ductwork run through that new door into the hallway right? You must either have the external door open when the dusty is running or at least cut a hole to vent the air the dusty has sucked through. You can't have a sealed cavity or there's nowhere for the air to go. I don't know the rule of thumb, but to minimise back pressure (and pushing dirty air back into the workshop), the bigger the duct the better, I certainly wouldn't go smaller than about a 8" diameter vent and in mine I went the whole hog and installed a 600mm diameter exhaust duct!
If you've realised this and you're really asking about cooling ventilation for the motor, well the exchange of air produced by the dust extractor is all that is needed.

[BobL]

Venting is of course essential for both devices but you may want to think about specifically venting the waste air across the DC motor and compressor or they will overheat.
Mine is 1.8 x 0.6 x 2.4-5.
Details here. The DC enclosure stuff starts at post 127.
My baffled vent is 200 x 500 mm which is >5 times the cross sectional area of a 6" duct.

My compressor enclosure is separate and has dedicated 100 CFM ventilation which kicks in while the compressor recharges.
Details in the same thread above.

[mic-d]

compressor maybe, but the dusty won't overheat. The motor has a fan which blows by air from the cabinet air, the cabinet air is very rapidly exchanged with fresh that the impeller has sucked in, so the cabinet air is always the cooler air of the workshop, so the cooling is the same as if the cabinet wasn't there. I have been running my 3hp dusty in a tiny cabinet for 18months and there is no problem. We've been through this before Bob and you've agreed and supported this in the past, so why change your tune?

[BobL]

compressor maybe, but the dusty won't overheat. The motor has a fan which blows by air from the cabinet air, the cabinet air is very rapidly exchanged with fresh that the impeller has sucked in, so the cabinet air is always the cooler air of the workshop, so the cooling is the same as if the cabinet wasn't there. I have been running my 3hp dusty in a tiny cabinet for 18months and there is no problem. We've been through this before Bob and you've agreed and supported this in the past, so why change your tune?

I still agree with you
It's just that I have seen an enclosure where the bags were separated from the blower and so had no air exchange and it was tripping out on hot days. The reason it was done this way was the enclosure was on the flimsy side and still leaking a lot of noise so the owner decided to encase the blower and motor.

[mic-d]

I still agree with you
It's just that I have seen an enclosure where the bags were separated from the blower and so had no air exchange and it was tripping out on hot days. The reason it was done this way was the enclosure was on the flimsy side and still leaking a lot of noise so the owner decided to encase the blower and motor.

Ah, it wasn't clear to me that Trav was planning to separate the bags (thus air stream) from the motor. I thought the whole this was going in a little hallway.

[BobL]

Ah, it wasn't clear to me that Trav was planning to separate the bags (thus air stream) from the motor. I thought the whole this was going in a little hallway.

Correct. My post was more of a reaction to recently seeing that other setup I was referring to. Sorry I should have stuck to the topic.

Trav, one way to keep the compressor from overheating on hot days would be to run the DC every now and then.

I'm not sure about the compressor in the same room as the DC. The air in the hallway is going to be permanently chokka with fine dust which will go straight through the compressor filter and enter the compressor. Long term then effects might be detrimental to the compressor. If you can arrange it I would suggest a duct to external air so that the compressor gets external air.

[Trav]

Thanks guys

Yes, you're right, the whole dusty will go into the little hallway. I've attached a plan to help show what I mean.

The red line is the new door I will install, the yellow arrow is the location of the external door and the blue lines are the approx. location of the 100mm ducting. Before anyone comments, it will run along the floor and I know it will be a tripping hazard near the TS, but as that is the outfeed side of the saw and I don't use the space for anything else, it is a risk I can manage. The ducting can't go across the roof as the garage tilt door goes in that space. The other ducting run doesn't pose a hazard as the door to the finishing room is more than a 100mm step up.

I will vent through the door - as this door is visible from the front of the house (in fact, it is right at the front of the house) I need to make sure it looks OK from the outside. There are some door vents that you can get from the big shed that might be ok. Size and airflow will be a challenge.

I agree about the risks of the dust on the compressor - from a sonic point of view it makes sense to co-locate the dusty and compressor, but the reality may not be quite so simple. I might just leave it loose in the workshop for the moment - I don't use it that much so the sound is not a particular problem. I was simply hoping to take advantage of the effort I will go to to isolate the dusty for both sound and dust.

Trav

[BobL]

Looks OK to me.

If you put the compressor right next to the vent it should be able to suck air back through the vent and then it would not be so bad for it.

I know this maybe too much work but one way to make a large area vent is to make simple frame that sits inside the door frame and then attach the old door to the front of the frame but offset with a gap of 25 mm all the way around. This will provide a cross sectional area of 1.5 sq ft which is more than enough to accommodate the air flow from 4" ducting. You could even go to 15 mm if needed. You might want to cover the gap with some flywire to reduce creepy crawlie infestation.

[Trav]

Thanks Bob.

Good idea to get the airflow needed, but SWMBO will never go for it! I think I will find some through-door metal plates that can be fixed to the door and can give enough airflow. I'm aiming for two vents at this stage -one low down next to the compressor as you suggested and one higher up the door.

Will post some pics when I'm done. It shouldn't be a huge job. Next I need to work out how to build the door in such a way to minimise the sound transfer, without costing a bomb.

Trav

[BobL]

Thanks Bob.

Good idea to get the airflow needed, but SWMBO will never go for it! I think I will find some through-door metal plates that can be fixed to the door and can give enough airflow. I'm aiming for two vents at this stage -one low down next to the compressor as you suggested and one higher up the door.

Will post some pics when I'm done. It shouldn't be a huge job. Next I need to work out how to build the door in such a way to minimise the sound transfer, without costing a bomb.

Trav

If you mean those ~230 x 150 mm galv metal plates with 4 horizontal slots in them then you will need at least 4 of these to match with the 2X area of of a 4" duct. The problem with those is they will let thru some noise so you may need to build some baffles on the back of the door. If you are not sure what I mean just ask. Also even if the door is not solid you may want to think about using an old foam mattress that you can fix to the back of the door.