New Studio: Venting Budget Options

[Mouten Keramik]

So me and the wife finally moved into our new (old) house, which has a decent amount of spacious basement for a studio

 

I'm in the process of figuring out where to put everything and how to setup the necessities. One of these is ventilation of the brand new toploaded electric kiln. I was contemplating what the best solution to the venting problem is, since it can get quite expensive, and as far as I know, none of the Kiln distributors in my area offer the downdraft solution (also I feel bad drilling holes in my brand new kiln).

 

So far I think the best budget solution is to get an old vacuumer and make a custom wide nossle for it. The vacuumer would need to be outside, and a hole would need to be installed somwhere in the basement, but that seems quite managable.

 

Can any of you see potential downsides to this solution, other than the need to haul the vacuumer outside, and turning it on, when I fire the kiln? Is there a better budget solution?

 

Thanks in advance.

[Denice]

I had a kiln in a old basement and we couldn't even cut a hole in the wall.  It had foundation issues that had been fixed with steel I beams running vertically and horizontally and the windows had been bricked up.    My kiln was under the dyer vent in the laundry room so my husband added another section to it and put a vent fan in it. You closed it to use the dryer and opened it for firing.  It wasn't perfect there was still some fumes so I didn't work in the basement when I fired. Denice

[Dick White]

I don't think your idea will work. A vacuum has good airflow when the nozzle is small and close to the point where the suction is needed. A kiln is large, with a lot a different spots generating noxious fumes, and you won't be able to put the vacuum nozzle where it would capture all the fumes.

 

You can build a downdraft vent system very easily and cheaper than kiln suppliers if you understand the basic principles. The key item is the air diffuser box underneath the kiln. It operates on the Bernouli principle, the same as a very large, upside down perfume atomizer. The diffuser box is attached to the center of the kiln stand, directly against the bottom of the kiln, and has holes on two opposite sides and the top. The vent fan and pipe is attached to one of the side holes, and the other side hole has some flaps or other adjustment to regulate the amount of air that will flow through the box. When the fan is running, it is pulling a lot of air sideways through the box, which causes a slight low pressure down through the top hole. Since the top of the box is against the bottom of the kiln, the only way for air to get pulled down into the sideways airflow is for there to be a few very small holes in the middle of the bottom of the kiln. Now that there is low pressure in the kiln, some fresh air will be drawn in through cracks between the kiln sections, the peeps, and/or an equal number of small holes drilled through the top of the kiln. This flow of fresh air into and through the kiln and then out into the sideways flow through the diffuser box is what vents the kiln. The much larger volume of air moving sideways will dilute the heat of the small amount of air coming out the bottom of the kiln. The vent fan, which is on or near the wall, blows the now-merely-warm (but stinky) air out into the atmosphere.

 

So, how do we build such a thing with readily available parts. First, the fan is a squirrel cage ventilation fan. I'm not familiar with heating and air conditioning suppliers there in the EU, but here is a picture of one on our side of the pond. https://www.amazon.com/Dayton-1TDP7-PSC-Blower-Volt/dp/B000BK43IY/ref=sr_1_1?s=industrial&ie=UTF8&qid=1468950818&sr=1-1&keywords=squirrel+cage+fanThe pipes are standard round heating or dryer duct, with appropriate corner bends as needed to go where the duct needs to. The diffuser box is a matching standard "T" joint for the duct pipes, attached to a sheet of metal or concrete board (non-flammable) with a hole in the center. The sheet is merely something to attach the T joint to and rest on the kiln stand, and underneath the kiln. The airflow adjustment through the T joint is just a standard HVAC duct damper http://www.homedepot.com/p/Master-Flow-4-in-Inline-Damper-ILD4/205442029 .

[Mouten Keramik]

Thanks for the advice to both of you.

 

Dick: As far as I can tell the Dayton blower you provided a link for, is basically the motor that goes into a cooker hood - it has around the same suction power as well. I guess one could find a used cooking hood motor and use that for the venting system.

 

I've also looked a bit on used suction systems from hair salons - they are about the same size, and the arms provide some flexibility in terms of kiln placement. I can get a motor and two arms for about $350 which is fairly cheap.

[Stephen]

Ya know my two cents is that with the kiln being in the house I would pick something else to do as a project and spend the three hundred on a vent designed for your kiln. The drilling is just a few holes on top and bottom and just like drilling into sheetrock. Make sure to read the kiln manu instructions on hole placement if u go that route. It is really important to get those gases outside properly and the problem with coming up with ur own solution could fail and you not really know it.

[Dick White]

Mouten: The purpose of a kiln venting system is 2-fold - First, to get the noxious and corrosive fumes out of the kiln, and second, to remove all that stinky stuff from the room to outside of the building. Some overhead (updraft) vent systems with a hood will do a good job for the second part, but do nothing to accomplish the first objective of clearing the gases from inside the kiln. In that situation, the fumes just leak out through the cracks, or more likely, don't leak out and stay in the kiln. Thus, an active downdraft system is needed to pull exhaust air through the kiln.

 

The two most common methods are 1) a fan mounted directly on the bottom of the kiln stand to suck air through the kiln and then push it out through a system of ducts leading to the outside. In this system of positive air pressure in the ducts, if there is any flaw or leakage in the ducts (which is highly probably, given the corrosive nature of the gases), the stink will be pushed right back into the room. Not a good thing. Or 2), a fan mounted at the outbound end of the duct creating suction in the duct. For this to work, the volume and velocity of air flowing past the small holes in the kiln must be sufficient to cause a Bernoulli effect down through the holes in the bottom of the kiln, so you will need a stronger fan. This approach has the added protection of not releasing any fumes back into the room through any small flaw in the duct.

 

I have seen self-built systems using a small bath/kitchen vent usually intended for removing humidity and odors, but such vent enclosures have a plastic blade fan with the motor directly in the line of the exhaust flow, and usually don't have enough flow capacity. In the kiln situation, the noxious gases will quickly corrode that motor and then it stops. A squirrel cage fan with the motor outside the airflow is better. From the kiln companies here in the USA, the L&L vent fan is rated at 130CFM and the Skutt vent fan is 140CFM. The Dayton fan I linked to is 146CFM, which is close to the "official" kiln vents. As you mention, you might be able to find a compatible cooking hood vent fan or a hair salon vent fan. Another similar industrial application is greenhouse ventilation. Good luck in your search for a used fan from a commercial setting, it will probably be more durable.

 

Finally, one aspect that is often overlooked. When you are using a vent of any sort, you are creating negative pressure in the room. That negative pressure must be replaced by fresh air coming into the room from somewhere else, an open door or window. The location of that source of incoming fresh air must be far away from the vent outlet. Otherwise, the stinky air going out the vent will be sucked right back into the room through that open window or door. Plan your vents and ducts carefully.

[Mouten Keramik]

Thanks for the responses!

 

The thing is, I've never seen a downdraft venting system applied to any kiln at the potters I've visited. I'm not sure where I would even order a commercial grade downdraft kiln venting. I'll ask the main Danish supplier (thihi) what they usually recommend, but I cannot find a product that would surffice in their Catalogue.

 

Dick: Good point about the air supply! My neighbour is actually a potter as well, whom I visited yesterday. He had a powerful vent for when he sprayed on glaze (but none for the kiln), which required the door to be opened slightly, so new air could enter. If the ventilation was turned on, before the door was opened, it couldn't be opened - powerful stuff!

 

Safety first! New solution to the problem: there's a large wooden shed with a door and a window, behind our carport in the driveway. There's already a CEE outlet which is required for the kiln I've purchased. Maybe it would be best to use the kiln there? The shed is not heated, but it is quite solid. How well does a kiln perform in cold environments? It gets below 0 degrees centigrade during winter. I know the the gasses and fumes would still be present, but it is easier to ventilate naturally, and isn't beneath our living room floor.

 

EDIT: I've found the following recommendation from a british supplier:

 

"Electric kilns, unlike gas or oil, produce no fumes, it is only the products of combustion and volatilisation from clays and glazes that may produce emissions. Harmful fumes are mostly generated at low levels, there will be traces of a variety of materials and smoke arising from combustion of carbonaceous materials. We quote from "The Electric Kiln" by Harry Fraser published by A & C Black: "...the hazard is lowered on account of the air dilution factor of that fraction (of noxious fumes) which escapes from the kiln and it is probable that the concentration of noxious gases in an unventilated room will be of similar hazard to that encountered walking down a busy high street." Certain materials, for example ceramic transfers and lustres can produce more harmful fumes, the manufacturers of these materials will advise on specific hazards but the volume of any toxic emissions is so small that air dilution will render them safe."

 

From that text it sounds like I don't even need a ventilation system? The basement room I plan on using in has two small windows that can be opened, and is about 17 m2 / 183 ft2. The oven is a 70 liters / 18 gal in size.

[Dick White]

It is possible to operate an electric kiln with no vent, but not a good idea in my opinion. Here is a document about kiln venting from one of the main USA kiln manufacturers http://skutt.com/pdf/envirovent2/EV2_Flyer.pdf. Obviously, the electric heat does not have any direct combustion fumes like a gas flame, but the clay itself produces some very smelly sulfide gases during the firing as well as "silent" corrosive flouride and other acidic gases that will begin to slowly destroy other metal and glass (e.g., windows) in the same room. It may be, as the British supplier states, the health hazard is no more than a busy street, but the smell can be very unpleasant and the cumulative damage to your property should not be underestimated.

 

Your new idea of putting the kiln in the outside shed is a good one, with some caveats. A kiln should be located a least .5 m from the wall and the walls should be covered with fireproof materials. The kiln will radiate a lot of heat and you don't want that to accumulate in the wooden walls and suddenly catch fire. The other thing to consider with a shed is the general heat of the kiln will make the small space insufferably hot. Something to keep fresh air moving through the shed is important - door and window open, fans, louvered vents in the walls near peak of the roof, etc. As for cold weather, this would be a problem only if you have an electronic controller for the kiln. The controller circuits begin to malfunction in very cold or very hot conditions. The documentation for your controller will state the manufacturer's tolerances, but you may expect them to be in the range of -10C to +50C. Keeping your operating conditions within the upper range is achieved through adequate circulation of fresh air through the shed and possibly a small fan blowing directly on the control box to keep it cool. The lower limit is more difficult. The issue is not simply that the electronic components are too cold, but the thermocouple in the kiln may give readings at very low temperatures outside the range the controller is programed for and it won't start the kiln.

[susieblue]

Hi Mouton,

 

While it is possible to forego a ventilation system with an electric kiln, it's probably best to play it safe. I have an unvented cone 8 electric toploader in my basement and it does give off some smelly fumes, both bisque and glaze firing. I try to avoid spending time down there while it is firing. I'm not sure I would choose to inhale the fumes from a city street on a regular basis.

 

You also want to keep in mind that venting is supposed to extend the life of your elements which are not terribly cheap to replace. If you are firing only on very rare occasions then maybe you don't really need it but if you plan to do so on any kind of regular basis you'll want to consider a vent system. Downdrafts are probably the most efficient means of venting an electric kiln.

 

I have recently had the good fortune to acquire a motor from a brand new L&L vent system for free (ventilation was already accommodated in an engineer's building plan and the motor became redundant).  Originally I had planned to buy an in-line fan rated for the CFM I need (Although a squirrel-cage one would have worked as well). The one item I could not replicate - though others have-was plenum cup with spring and post, which I purchased ($50) from The Ceramics Shop along with an Amazon purchase of some semi-rigid 3" aluminum ducting. I will attach a reducer and dryer hose to connect the exhaust end to my dryer vent.

 

Here's a couple of links to homemade downdraft vents: http://www.handspiral.com/kiln_vent.

https://www.bluewillowstudio.net/get-your-hands-dirty/to-vent-or-not-to-vent

 

Good luck.

 

 

[Mark C.]

How about a blower hooked up outside with some inside air able to get in?

Mark

[Callie Beller Diesel]

You could run some kind of space heater in an outdoor kiln shed on the days you want to start firing a kiln when it's below 0*C. It'll make loading much more comfortable, as well.