Thread: Dust extraction in a cold climate

Originally Posted by Xfigio

A key principal of dust extraction is to move large volumes of air from inside the shed where the dust is, and vent it outside. The resulting low pressure zone in the shed then draws outside air into the shed.
In the case of places like Tassie, and many of the inland areas at lower latitudes, that new air coming into the shed can be icy in the cooler months! Safety concerns mean we can't wear gloves or long sleeved jumpers etc.
At times, as detailed in another post, I just resort to my face mask, but that has its own issues.
I'm interested in any thoughts or strategies to overcome this conundrum.

This problem is far more common than not with most woodworkers in North America and Europe in this position.
There are DC filters that can filter down to a low enough level to be quite safe.
The problem with conventional DCs where the collection bags are under pressure is they leak - a dust detector can help pick up leaks would useful.

Cyclonic systems are better because their collection chambers are under vacuum but the impeller and motor need to be a decent size to overcome the back pressure that cyclones generate.
The cyclones also need to be efficient at removing chips and fine dust otherwise the filters will be rapidly overloaded and clog.
Clearvue cyclones are specifically designed be efficient and the filters they recommend are very effective but they can't easily be transferred to other DCs.

I don't live in a cold area, but I've often wondered how an infra red heater might do in these situations. They warm you directly with infra red rays rather than indirectly through heating the air in your workshop. Might work if you are wanting to exhaust dust collector air outside...

Originally Posted by Oddy

I don't live in a cold area, but I've often wondered how an infra red heater might do in these situations.

We have them (same idea, just a newer technology) in some sports centres where spectators (parents) sit whilst the kids are generating their own body heat. They are outstanding, as long as you're directly inline with the heating path. This is with very high ceilings though. Where I've experienced them in lower ceilings, they make your head uncomfortably warm?
I wonder how they would go mounted horizontally, shooting across the workshop at torso height.
Good thought!

Originally Posted by Oddy

I don't live in a cold area, but I've often wondered how an infra red heater might do in these situations. They warm you directly with infra red rays rather than indirectly through heating the air in your workshop. Might work if you are wanting to exhaust dust collector air outside...

Probably better than nothing. However, if there really is the 1000 CFM sweeping up dust around an operator, then the number of kilojoules of heat being extracted is considerable and will overwhelm the heater (it will cool that as well).

I think it depends on the activity, short bursts are not going to make too much of a difference, its when undertaking prolonged woody activities like turning that it would become significant.

Leaks in DCs used to be expensive and a PITA to monitor but these days with small PM2.5 dust detectors available (2017 Mini LED LCD Plantower PMS7003 G7 laser PM2.5 detector meter with battery | eBay) the cost is reasonable so it would be possible to at least know if a DC was leaking or not extracting adequately. Finding and fixing leaks is another problem.

This is not something I would recommend to an asthmatic or someone with other breathing difficulties but t is an option.

Originally Posted by BobL

...the number of kilojoules of heat being extracted is considerable and will overwhelm the heater ...

Bob, the point with these heaters is that it is not the air being heated so you are not extracting any heat in that way. They work through electromagnetic radiation - directly heating surfaces they are facing i.e. you if you are standing in front of it. The first I saw one of these things was at the Bendigo wool show this winter. It was cold for a brass monkey that weekend and all the exhibit halls / marques were wide open to the weather - so the air in the building was freezing, but stand in front of one of these panels and it was like heaven.
Infrared electric panel heaters: Herschel Select & Select XL

Originally Posted by Oddy

Bob, the point with these heaters is that it is not the air being heated so you are not extracting any heat in that way. They work through electromagnetic radiation - directly heating surfaces they are facing i.e. you if you are standing in front of it. The first I saw one of these things was at the Bendigo wool show this winter. It was cold for a brass monkey that weekend and all the exhibit halls / marques were wide open to the weather - so the air in the building was freezing, but stand in front of one of these panels and it was like heaven.
Infrared electric panel heaters: Herschel Select & Select XL

Sure I under stand how they work
BUT
Try it with 1000 CFM of cold air going past you.
I agree the IR won't be lost to the air but I'm guessing the moving cold air will strip warmth from your skin and clothing faster than the IR heaters can heat it up.
Like I said worth a try but I expect limited success.

In some cases like a TS or a BS the 1000 CFM is not directly being drawn past an operator but on something like a Lathe the 1000 CFM should be straight past.

I have a couple of IR lamps in the shed - I can do some tests.

Hummmmm . . . .might have to wait till next winter as there is not much cold air around.

Fire up the air conditioner Bob and then do the test.

Lance in industrial settings in climates like mine, -40C in winter, you'll find that they will use cartridge filters that are housed in a large box with a hopper below to collect the dust. The box, depending on system size, will house 4 or more filters with the air moving from the outside of the filter to the inside and then out of the box. A HEPA filter can be added for even better filtration. They work best with a Cyclone, like Bob mentioned, before the cartridge box. This is basically the approach I will be taking while I make my system in the coming months. The downside for hobby woodworkers is the lack of space for the machines but they can be setup outside the shed and enclosed in an insulated addition with the filtered air returning to the workspace.

Pete

Originally Posted by Oddy

I don't live in a cold area, but I've often wondered how an infra red heater might do in these situations. They warm you directly with infra red rays rather than indirectly through heating the air in your workshop. Might work if you are wanting to exhaust dust collector air outside...

It depends on how you define cold.
Last winter we had a few weeks when the maximum temperature was -25 degrees, the mins were down around -40. More normally the daytime max during winter is around -10, with the mins around -25. At those temperatures, even if you can keep the body warm with insulation and infrared heating the air is too cold for gluing.
My "shed" is one bay of a 3 bay garage. The garage has underfloor hearing and sits at around 15 degrees C, but when the car comes back in, suddenly there's a tonne and a half of metal at -20 (or colder) sucking the heat out of the air. I've had a few instances where epoxy was still tacky 8 hours after application.

As Bob mentioned, the dust control "solution" is to use high efficiency filters and recirculate the filtered air. This winter I'm adding a room air filter to deal with dust from hand sanding.

I live with winter cold, usually no worse than -20C. It isn't possible to heat incoming make-up air to satisfy any DC, without enormous expense.
Even at -5C, I cannot imagine being brave enough to leave the shop doors flapping open.
QC Inspector plans a recirculating system. Good plan. I endured many Stoon winters with Februarys of -40. I use a ShopVac on small power tools.

Otherwise, we all wait until summer and open the doors with fans (and every blood sucking flying bug known to Man).

Thanks for the responses from the northern latitudes. You do indeed operate at an extreme significantly beyond our worst cold. Your insights are appreciated.

Originally Posted by ian

It depends on how you define cold.

Yes - not talking about Canadian winters. More like 0 deg C to 10 deg C. There aren't too many places in Australia that get colder than that on a winter's day.

Originally Posted by QC Inspector

Fire up the air conditioner Bob and then do the test.

Good idea, except my AC is quite small and doesn't generate the 1000 CFM of cold air to do the test.

I thought about the test and have come up with the following.
I'll have to wait for a coolish winters day ( we do get down to zero about a dozen times each year) and rig up an IR lamp shining say ~1m above me and check the skin say on the back of my left hand with an IR gun. Once it has stabilised, turn on the DC and see what happens.

Blimey, I just realised I reached 20,000 posts!
At 5 minutes per post that 100,000 minutes , 1667 hours, 69 days, 2% of my time during the 11 years of WWF membership, gone!
Not to mention posts in the MW and other forums.
And think of all that hot air that could have been used to heat sheds.

The size of this problem depends on a couple of things, how long the extractor stays on and how warm the building is. OS it is common for the building to be heated 24/7 and if you could do that to a large extent the problem can be minimised if the extractor is used sporadically as needed the amount of air removed has little long term (relatively) effect. The building mass is what is costly to heat and the temperature of the building takes a long time to change when compared to air. if the building is up to temperature and the air temp drops because the extractor is turned on the air will very quickly be raised back to the same temp as the building because it is heated by the building. This of course also depends on the insulation of the building and in Oz we generally do not have anything like adequate insulation, in fact far from it.

I agree good insulation helps enormously, but insulation is only part of the answer because heat retention by a shed also depends on the structural design, mass and type of materials used in its construction. The outer skin and even the frame in contact with the outer skin of a metal clad metal shed will usually be closer to the outside than inside temperatures and being metallic gain and lose thermal energy rapidly. Hence even if that shed is insulated the the walls and roof contribute very little to the total thermal mass of the building and then only thermal masses that can store heat are the, floor, shed contents, and the internal air. To retain significant amounts of thermal energy inside a shed requires a structure like double brick, or insulation and internal cladding, preferably with something that has a significant thermal mass.

Running a DC for short bursts works for folks that have a DC that can capture most of the dust at source which requires 6" ducting and a reasonably powerful DC. If they can't do that then they either have to live with dust, or ventilate by running their DC for longer, use other forms of ventilation, or use quality filters and vent internally.