ventilation for a big torch

[glass addict]

I need some help. I've been reading lots of the ventilation threads, but could sure use some guidance from the experts. I have a GTT delta elite. Most of the time I'll be using the center fire only, but I'd like to start getting into goblet making. (Took a class years ago, but it took awhile to save up for the big torch.)

Any suggestions on hoods and fans? Does it matter what size the exhaust air is as long as it's equal to the fresh air? (and piped with smooth piping).

I've also heard that the delta elite puts out so much heat that it tends to burn out fan motors.

I really appreciate any help and guidance.

Thanks in advance,
Mary

[MikeAurelius]

Nothing is going to change as far as the exhaust system is concerned: the size of the torch has nothing to do with the size of the exhaust system. As long as the fan is properly sized for the hood being used (100 to 125 CFM per square foot of hood area), you don't need to worry about anything else.

As far as burning out motors, yes, if the the motor is in the airstream, there is a very good chance that the motor will burn out if you are using the Delta at max capacity. Many of the Grainger fans have the motor external to the fan (some have the motor in the suction airstream, and these should not be used). You should also stay away from in-line duct fans as well. Any fan with the motor in the airstream will burn out in fairly short order.

[vetropod]

You might want to think about moving your new torch further from the wall than your old one - that bad boy is definitely going to put out some heat! 8-[

Have fun and melt some serious glass!!!


Wes.

[boroburner]

I have had a delta, used with inline fans and have had no heat issues. Fans are about 3ft from the opening in the hood and have no melting of equiptment. Infact with a 10" duct, and a 1000CFM inline fan i can put my hand at the exaust port opening(interior) and it feels no differnt than the ambiant air within the shop.

As for makeup air...... you dont really need it, unless your
A: in a sealed room
B: Have a HONKING fan going, and it is stressed and fighting for air.
As long as the fan is running, makeup air will passivly enter and circulate thru your shop. If by chance you feel you need more air, just open a window, i wouldnt bother with a fan.

Mike........ i know the formula of 100-125CFM per sf is reccommended for lampworking, is there any kind of specs on the reccommended hood size for larger torches? Im pretty confident if i had a 5sf opening a 600cfm fan on it that it just wouldnt quite handle a delta. Any thoughts?

[Dale M.]

aI have had a delta, used with inline fans and have had no heat issues. Fans are about 3ft from the opening in the hood and have no melting of equiptment. Infact with a 10" duct, and a 1000CFM inline fan i can put my hand at the exaust port opening(interior) and it feels no differnt than the ambiant air within the shop.

As for makeup air...... you dont really need it, unless your
A: in a sealed room
B: Have a HONKING fan going, and it is stressed and fighting for air.
As long as the fan is running, makeup air will passivly enter and circulate thru your shop. If by chance you feel you need more air, just open a window, i wouldnt bother with a fan.

Mike........ i know the formula of 100-125CFM per sf is reccommended for lampworking, is there any kind of specs on the reccommended hood size for larger torches? Im pretty confident if i had a 5sf opening a 600cfm fan on it that it just wouldnt quite handle a delta. Any thoughts?

I have several concerns about you statements...

Make up air needs to be consistent with volume of air you are exhausting...

IF you are running 400 cfm air out exhaust(for example) , you have to guarantee pretty close to 400cfm of make up air...Passive air entry is not a solution.... You MUST have a open door or window or ducted in make up air... There is no alternative.

As for volume of combustion by products from torch, it will not be any more than volume of fuel and oxygen you are putting into torch, so if you are running 2 cfm of fuel and 10 cfm of oxygen (I know numbers are not right- but this is for example only) your torch is only putting 25 cfm of byproducts into ventilation stream... This would mean you are only drawing 12cfm less makeup air from fresh air intake as you are trying to pushing out your exhaust...

Going back to 400cfm exhaust example, if your exhaust is pumping out 400cfm and your torch will produce 12cfm of gases in the exhaust flow and makeup air will be 388 cfm of air flow...

Again number will vary due to combined volume (cfm) of fuel and oxygen you are running though torch...

Dale

[boroburner]

yes i agree 100% that makeup has to be = to that which you are exausting.

Thus the....... "if the fan is straining, open a window".

I was just saying that there is no need, unless you are running a retardedly HUGE fan, to have make up air delivered mechanicly, ie. with a fan.

[boroburner]

IMO hood design is probably the most important part of a good ventalation system. If possible have sides and a back on you hood. This will direct air flow and will greatly increase the effiency of your entire system.

[MikeAurelius]

Mike........ i know the formula of 100-125CFM per sf is reccommended for lampworking, is there any kind of specs on the reccommended hood size for larger torches? Im pretty confident if i had a 5sf opening a 600cfm fan on it that it just wouldnt quite handle a delta. Any thoughts?

Nope, not necessary. Use the rule of thumb and you'll be fine. What will happen is that your outflow stream of exhausted air will be substantially hotter than, say a Nortel Minor.

Back when I had my commercial studio up and running, I did a test with a variety of torches. We were running hoods with about 4 square feet of area, and the fan was 495 CFM (as I remember).

With the smaller torches, air stream temperature was a constant room temperature - this was with Minor's, midranges, the smaller GTT torches etc.

Then we tested with a Mirage and then with a CC+. Air temperature in the air stream shot up to 165+ F fairly fast when the outer rings were running. There was no change in the quality of the air in the studio, we had plenty of fresh air. This is why I say that in-line fans are not going to last long - a goodly percentage of them are designed for a maximum of 145 F. If they run much more than that, they overheat and the motor burns out in pretty short order.

My design criteria takes into account the fact that I never know what torch will ever be run in a system. A beadmaker may start out with a Hot Head or Minor, but there is a natural tendancy to move to bigger and bigger torches as they become more proficient and want to extend themselves. Not everyone does this, but to say that a beadmaker will never change torches is not a design element I want to put into my system designs.

I'm also going to take issue with your statement about "if your fan is straining". How will you know that? Many times the fan doesn't strain because it is pulling its needed air from dry plumbing vents, or backdrafting the hot water heater or furnace.

There should ALWAYS be an open window or door, or a duct from the outside supply fresh air into the studio any time the lampworking ventilation system is running. You should never rely on the air inside the house as a source of fresh air.

[gwacie]

Just curious. Does it matter how big the open window is? If so how would you figure it?

[boroburner]

should be equal to the diameter of the ducting your using i would imagine.

[Dale M.]

Window opening should be equal to or a little larger than the size (in square inches) of your exhaust duct...

So if you use a 10 inch duct for exhaust, that is a cross section of 78.5 square inches so if you have a window that is 24 inches wide, it should be open at least 3.5 to 4 inches ( 84 to 96 square inches)

(Edited to change 8 inch duct to 10 inch duct to correct calculation error)

Dale

[boroburner]

Air temperature in the air stream shot up to 165+ F fairly fast when the outer rings were running. There was no change in the quality of the air in the studio, we had plenty of fresh air. This is why I say that in-line fans are not going to last long - a goodly percentage of them are designed for a maximum of 145 F. If they run much more than that, they overheat and the motor burns out in pretty short order.



huh....... ill have to stick a thermometer in my outtake and see what the temp is. Never though of that.

Doesnt fan CFM play a role in the temp? The more air you pull the cooler itll be?

[boroburner]

Thought id clarify-by inline fan i was refering to something along the line of the elicent brand.

[gwacie]

Thanks Dale, that makes sense.

[MikeAurelius]

Just curious. Does it matter how big the open window is? If so how would you figure it?

Well, an 8" round duct can handle 350 CFM without restriction, so I use that as my basis for calculations. That's 50 square inches. So if your fan draws 350 CFM, you need to open your window to allow 50 square inches of area.

[MikeAurelius]

huh....... ill have to stick a thermometer in my outtake and see what the temp is. Never though of that.

Doesnt fan CFM play a role in the temp? The more air you pull the cooler itll be?

Of course it does, but you also pay a price for that -- draw in too much fresh air and you start affecting the "climate" of the workspace, even if it is ducted into the workspace.

I don't believe in fan overkill. A properly sized fan for the hood (100 to 125 CFM per square foot of hood opening) will do the job quite nicely.

[boroburner]

Are there any reccomendations for placing hoods (distance) over workspaces? i know there is a formula for light stregnth based on distance from source. Im assuming there is probably one for air.

[MikeAurelius]

Not in this particular case. You want enough room under the hood to work, but not so high that you are drawing more room air than you are workspace air.

I typically recommend 36 inches minimum to 54 inches maximum.

[glass addict]

Thank you all for you help. It's going to take me awhile to digest it all, but it's good eating (he, he).

Thanks again, I really appreciate it!!!

Mary

[MikeAurelius]

You bet, Mary! Good Luck!