Getting Ventilation Right

[Vince]

Last year, one of our local Northern California bead makers, John Rizzi, asked me to design the ventilation system for his new combined studio and gallery. He was familiar with my designs using range hoods for small torch installations and had implemented one of those which performed well for him. He had moved up to a larger torch (a GTT Mirage) and was moving his studio to his new gallery and would be having public contact with his workspace and wanted to ensure that the ventilation system was adequate and safe. I agreed to work with him and design the best and most cost-effective system we could.

The first step was a survey of the building that would house the new studio and gallery. I took measurements and photographs of the space and made scale drawings to aid in the design. Here is the space before the equipment was installed.




We discussed the placement of his work bench, the torch position and some special requirements he had such as maximizing the amount of natural light from the existing windows and having space for potentially teaching another person. Several designs were considered and analyzed including the use of a canopy hood that would be high enough to meet the other criteria for space usage. This design was rejected on two counts, the first was that the amount of airflow required would be excessive, and would require a much larger and expensive blower to ensure capture and the second was that the placement of the hood would interfere with the wiring for his low-voltage gallery lighting system.

The design that resulted is shown in the following photo. The hood face opening is 20 inches high by 60 inches long (8.33 square feet) and is inclined 45 degrees from the vertical toward the torch position. The back of the hood is vertical and the top has a pleasant taper toward a 12 inch square base for attaching a 10 inch diameter round duct. The original design specified the use of 22 gauge galvanized steel, but was finally fabricated in brushed stainless steel instead in order to be consistent with the other materials used in the gallery. The fan unit is a roof mounted centrifugal upblast ventilator that moves 1180 CFM at 0� static pressure and 1017 CFM at 0.25� static pressure. It uses a backward inclined wheel type and is rated at a noise level of 13 Sones or about 65-66 dBA sound pressure level.



I took airflow, temperature and acoustical measurements on the hood after it was installed and can report that it performs superbly in all respects. I'll submit more photos in the next post.

[Schermo]

Hey Vince,

This looks like a great set up; obviously excellent ventilation, but also great use of space, and very aesthetically pleasing.

Being insatiably curious, I have a couple questions:
What are the two round shiny silver domes on either side of the window, up near the ceiling? They remind me of fire alarm bells from grade school, but I don't imagine that's what they are. Are they a part of the ventilation system?

Was additional wiring or electrical capability necessary for the ventilation? I notice that there looks like a new fuse box to the left of the window, and a whole lot of conduit. Just wondering what it was for?

Is the hood self-supporting, or does the wall at the back of the bench rise above the work surface, to give support to the hood? Were any additional supports necessary for the 10 inch round duct?

I am starting the process of information gathering to upgrade my studio as my original ventilation was installed when I only had one torch, and it is probably inadequate for when I am teaching with two or three minors going. (I don't have the measuring devices, so I am just guessing, although I've not had any problems yet.) There are a lot of things in the studio that are going to have to be moved around and reconfigured.

So, when are you coming back to Virginia again???

Thanks for showing us John's new studio. It's very inspiring.

Schermo

[PamDugger]

Fantastic, Vince and John. That hood looks like a piece of art in itself!! The dream studio for sure!! Thanks for sharing and I'll be looking for more pictures.
Pam

[Vince]

Ann,

I'll answer all your questions in order.

1. The silver domes on the upper back wall are part of the low-voltage gallery lighting. They basically cover the transformer and connections to the two parallel bus wires that run the length of the gallery onto which movable flood or spotlights can be positioned to illuminate any point. They have nothing to do with the ventilation except that the design needed to avoid intruding into the space occupied by the bus wires.

2. John upgraded the electrical service in the building for his various needs, including a separate circuit for his kiln, but the ventilation as such does not have excessive power requirements. The ventilator uses a 1/4 horsepower 120V AC motor to drive the impeller and would not even require a separate dedicated branch circuit. Conduit is the preferred method of wiring for this sort of installation.

3.The weight of the hood rests on a standard short stud wall that rises on the order of a foot above John's work surface. The hood is fastened to the top of this wall with screws. The top and bench-side surfaces of this part of the wall are sheathed in 1/2 inch thick concrete tile backer board. The bench-side surface is further protected by a ventilated stainless steel shield that has about a two inch air gap to the concrete backer board. Air is scavenged from the hood flow to constantly ventilate this shield and carry away any excess heat to the exhaust. In addition, there are two pieces of Superstrut, also covered in stainless steel, that go from the floor to the top of the hood where the duct is attached. These are bolted to the short wall and to the back of the hood in several places with bolts to stabilize and support the back of the hood. The entire system is very rigid and there is no vibration from loose components in the system except for the damper mechanism at the base of the ventilator. The round duct is also stainless steel and does not require any additional support. All the duct joints are riveted and sealed.

Here is a photo of the back of the hood showing the covered Superstrut supports.




Here is a photo of the detail of the ventilated heat shield looking from the torch position. Two of the bolts fastening the hood to the superstrut can be seen inside the hood face opening.



4. There is no substitute for actually measuring the performance of a system. There is often a difference between theoretical performance and actual, as-built performance. When I measure the systems I either design or am asked to investigate, I always learn something that is of use in the next project.

5. I do not know when I will be next in Virginia.


Vince

[PaulaD]

Vince,

The hood is spectacular!

Paula

[Ellen Black]

Looks FANTASTIC. What a wonderful studio. Thank you for posting the information. Ellen

[balkcumd]

I know this is an old thread but I have a question for Vince about the makeup air.
I am in the process of changing my ventilation again and have been reading as much as I can find about ventilation systems.
I like this system you built here....my question is how did you address the makeup air issue? I have read that a duct, the same size or larger than the size used for evacuation, can be run from outside to the back of the torch bench to supply an adequate amount of fresh air. This duct will not have any fan/blower attached as the plenum blower well create a venturi effect and circulate the fresh air out with the bad eliminating negative pressure in the room. It was stated that supplying it at the bench surface would also help to lesson the issue of temperature changes in the room. Do you think you also need some makeup air from behind you? I read that some of the makeup air should come from behind you.
thanks for any information that you have to share,
Darlene Balkcum

[Nina"Sam"Hibler]

Great Question.
How are you? miss you
Sam

[balkcumd]

Sam, good to here from you...not much torching lately...maybe when I get my ventilation redone!
I do have a class at Flametree with Akihiro Okama in June. Wish you could be there!
Take care