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[4]

Ventilation in the Shop

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ddickey

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#1
I'm no HVAC expert so please help. I've been told and have read how important ventilation is in the shop. I have a portable A/C unit and a small heater for the winter. I have not used the A/C unit yet due to no exhaust outlet. I'm doing a small renovation in the garage and would like to do some proper ventilation.
Before I call an HVAC guy I want to know what to tell him.
What do I want? Need?
Thanks in advance.
 

pontiac428

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#2
That all depends on what kind of hazards you are trying to control with ventilation. If you do not generate any acute hazards (welding fume, heavy solvent use, painting) you will be well served by a general dilution system that can exhaust four air changes per hour from your shop space. Local vents, like hoods and canopies, are best if they have a very specific purpose that they can be engineered for, but are not very effective against random stuff. I'd be happy to answer on any specifics if you have concerns. Making ventilation assessments and other hazard control recommendations is what I do for a living.
 

ddickey

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#3
Rust is one thing I'd like to control although so far I have not had a real problem with it. I do live in a fairly humid climate though.
I do weld some. I plan on learning to TIG and will do more of that. In the summer it can be done with the garage door open but then if i have a/c going that might not be the smartest thing. In the winter there is no option but to weld indoors or wait until summer. I also have a surface grinder and controlling the grit would be nice but not sure how to go about that. There is a Grit Grabber on CL I will be looking at but that would do nothing for welding fumes of course.
My A/C will need an exhaust path and if you have exhaust you need an intake also, correct? My shop space is ~ 380 ft sq.
 

pontiac428

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#4
Dust control off of a machine like your surface grinder would require a capture vent with a high transport velocity, like what you would see in a wood shop. Unless you are grinding chromium steel or special alloys, the health risk won't justify the cost.
An a/c system with good drainage from the cold side will dry the air in your shop, and heating in the winter will prevent condensation on your machines that lead to rust.
Your main health concern will be with the welding setup. TIG and thermal cutting processes put a lot more chromium-VI into your breathing zone than similar MIG processes, and TIG produces a lot more UV that can ionize various residues on your work pieces/surfaces as a secondary effect. Welding fume extraction systems are affordable enough for the home shop, and can also be fabricated by a HVAC contractor. The idea is to position a flexible 5-6" duct with a flanged end about 4-10" off of your work while welding using clamps or a magnetic base to hold the vent in pace, and exhaust the air outside. Look for 100 linear feet per minute at 6" from the duct face for fume extraction. You can accomplish that on 1/2 hp or less.
Canopy hoods in welding booths are not effective, since the fumes move past your breathing zone from the point of generation to the exhaust vent face. They will contribute to the total air change rate in your shop, but so will general ventilation.
You probably won't need an intake system for your shop (push-pull). There are enough leaks in most buildings to provide makeup air, but you are best off to add a square foot or two worth of passive vents down low in order to keep the power bill down. It won't take much to ventilate a 380 s.f. space. 30-50 CFM worth of throughput from an exhaust fan would do nicely, any more would pull the hat off of your head.
 

ddickey

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#5
Lots a great info. Thanks. I'll talk to an HVAC contractor in town and report back.
 

ddickey

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#6
Could you use the CFM from a welding fume extractor for the grit from a surface grinder? Kind of like a two in one setup?
 

pontiac428

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#7
The air velocity is the determining factor. With the welding fume extractor, you don't want more air movement than you need to remove the fume because you will also remove your (expensive) shielding gas. At the collector face, those systems pull 200-250 linear fpm. For a dust transport system, you're looking for ten times that. Dust systems usually pull a ton of air through small ducts to keep the velocity high enough to keep particles from falling out of the stream. Honestly, I'd rely on housekeeping for your grinder rather than to try to evacuate dust. If you want to go the extra mile, you could fab an enclosure to contain the dust. I'd recommend keeping the machine vacuumed between uses in the home shop, since it's not a 40 hour per week occupational exposure. Its use in a hobby capacity is highly unlikely to lead to illness.
 

f350ca

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#8
Won't solve your makeup air for the air conditioner, but I installed a air exchanger with heat recovery in my shop a couple of years ago. Made the world of difference. It removes the smoke from welding and the plasma cutter as well as fumes from painting. A simple washable filter sprayed with Pam on the shop inlet takes care of keeping the heat exchanger clean. They're not cheap but keeps the air breathable in the winter. The shop stays cool about 18 deg C in the summer, so I can't open the doors in hot humid weather or the cool machinery is instanly covered in condensation. Hence it gets used year round.

Greg
 

ddickey

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#9
The HVAC estimator/sales guy just left. He suggested that I run a cooling and heat duct from my into my garage since my utility room is right behind the garage. There are no cars that will fit to CO would never be a problem. The problem is I have a down flow system. It is old though from around 1990. He suggested a new furnace an A/C unit. Big bucks though. You'd still need exhaust though. He also suggested a mini cool which also heats. IDK.
 

pontiac428

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#10
So the HVAC guy wanted to redo your whole house system instead of just selling you a small wood burning stove and bidding to install an exhaust fan up high to address the needs in your shop? Well, that's capitalism for you. As small as your shop is, you could get away with an attic fan on a switch in the uppermost vertical wall and a pair of eve vent grilles in the lower opposite wall. I wouldn't make a habit of welding in an enclosed space without mechanical ventilation, that will shorten your lifespan, even as an occasional hobby.
 

ddickey

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#11
The welding exhauster is something I'm pretty sure I will do.
He certainly wasn't pushy but he took one look at my 30 year old furnace then came up with the idea. It is old but works fine. I was not prepared to even consider the price he quoted like 12 or 13 grand. ouch. I will call the other company in town and see how they go about it.
 

f350ca

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#12
I'd opt for a separate system and not circulate air from the house. Maybe no CO2 but the fumes from machining and welding wouldn't go well in the house, not even my house.

Greg
 

ddickey

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#13
There wouldn't be any welding fumes as I'll have a proper exhaust for that. I don't think there would be any way to get fumes into the house though. Maybe when it shuts off but I would thunk there would be some sort of swing check valve/flapper in the system. My gut is telling me this is not a very great idea. What if I can't cool my garage down enough or heat it up. Your house will get very cool or very warm, possibly.
We'll see what the other contractor has to say.
 

ddickey

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#14
Second contractor came today.
His suggestion was to use my portable AC unit and vent it out a hole in the garage door. If that doesn't work well we could always go with a split mini cool system at a price of ~$4000. Man I had no idea how expensive this stuff was. Maybe I should reconsider and do the work myself.
anyway he didn't see the need for any exhaust but if I wanted one it would be $200 to plum it out the roof.
He actually was the original contractor of my house (townhouse). He said the reason my furnace has lasted for 28 years is because it's all stainless. My AC is original, 30 year old Magic Chef.
He also suggested a new furnace and AC but at a more reasonable price ~ $6000. This might be something I need to do.
The welding fume extraction would be a separate project.
 

pontiac428

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#15
For <400 square feet, you probably have less expensive options for heat and a/c. Of course, a nice unit that's slightly overpowered and cleanly installed is a wonderful thing. Running a fan-powered exhaust is really the key for keeping your health protected from the welding, oil mists, and other things we do in shop space. There again, the costs should be low considering the size of the area you're working with. If I were in your position, I don't think I'd be willing to plunk down thousands where a window unit a/c, a good radiant heater or wood stove, and an exhaust fan would do.
 
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#16
Don't rush into a new furnace , if your old ones working well keep it . It's made better then any new one.. mines about sixty and the furnace guys love it over the new ones . The firebox is four times the thickness of the new improved type. I agree you should exhaust the welding fumes and the heat in summer , air conditioning and heat in the shop is mandatory , we need to get away don't we. I've only ever had portable heat propane fan forced , it warmed the shop but the concrete stayed frozen rising right through me . Of course my weldings all outside. Guess I'm no real help
 

ddickey

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#17
No your opinion matters much. I tend to agree if it ain't broke don'fix it. The contractor didn't really agree with that though.
 

Ray C

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#18
Sounds like you're working in an area like mine -which is a 2.5 car attached garage dedicated to the shop. Here in MD, our winters are not as bad as yours. I insulated the walls and ceiling and put up drywall. The two overhead doors are insulated too. I get by with a 20k BTU propane heater. There are enough air gaps in the overhead doors that I get plenty of outside air. I also have CO2 and smoke detectors to be on the safe side.

In the summer, it gets way too hot to even consider getting AC.

Now, the message I really want to convey....

Effective last month, I stopped using hand held grinders and doing stick/MIG welding in the shop. I have vacuum for the bench grinder and tool grinder. I only use the hand grinders outside or open the door and blast the particles outside. Same with welding... TIG welding is fine. It makes no mess to speak of. The smoke and mess left behind from the other welding is way too much to keep-up with. It turns your shop into a filthy pigsty mess in a matter of minutes. -Tired of the mess and I just spent 3 weeks cleaning the place and from one end to the other, I must have picked-up 50 lbs of grit and welding splatter. The white walls are all yellow too from welding smoke.

Just passing along my experiences (and probably obvious frustration from working in tight quarters)...

Ray
 
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