Vent Issue?

[ronfire]

I notice that when my kiln gets close to finishing a bisque fire that I have a strong sulphur smell. I have a negative air pressure in the kiln as it will draw in the flame from a lighter at both the top holes as well as a peep hole if I open one.  This is strong enough that it bothers me to be with the kiln in the shop when close to being done.

Why would I smell this if the vent  is drawing in outside air into the kiln?

[Bill Kielb]

1 hour ago, ronfire said:

I notice that when my kiln gets close to finishing a bisque fire that I have a strong sulphur smell. I have a negative air pressure in the kiln as it will draw in the flame from a lighter at both the top holes as well as a peep hole if I open one.  This is strong enough that it bothers me to be with the kiln in the shop when close to being done.

Why would I smell this if the vent  is drawing in outside air into the kiln?

You shouldn’t but typically we see this complaint from wax burn off between 500 - 800 degrees. It’s really hard to influence very tiny lightweight molecules with a downdraft as the slightest updraft from heat rising makes them hard to capture. A hood is the usual solution such as vent a kiln. We experimented  a few years ago when one of our downdrafts died. We created a hybrid design and it definitely improved the situation significantly.

A hood is the typical for sure solution, our hybrid was just to replace the existing with something equal or superior in performance to our broken downdraft on a budget.

Here is a clip of it:

 

[Mark C.]

Is your vent a downdraft no hood or a  updraft  hooded design?

[Bill Kielb]

8 minutes ago, Mark C. said:

Is your vent a downdraft no hood or a  updraft  hooded design?

No, didn’t add hoods which would have been best. So downdraft with above kiln supplementary pickup.  It really was a replacement for the broken downdraft and we added the exhaust grill to pick up as much smell as practical since it cost us virtually nothing to do so and actually made the blower run cooler, so why not was the thought.

[Brandon Franks]

24 minutes ago, Bill Kielb said:

You shouldn’t but typically we see this complaint from wax burn off between 500 - 800 degrees. It’s really hard to influence very tiny lightweight molecules with a downdraft as the slightest updraft from heat rising makes them hard to capture. A hood is the usual solution such as vent a kiln. We experimented  a few years ago when one of our downdrafts died. We created a hybrid design and it definitely improved the situation significantly.

A hood is the typical for sure solution, our hybrid was just to replace the existing with something equal or superior in performance to our broken downdraft on a budget.

Here is a clip of it:

 

That jut gave me a great idea for tomorrow (thank God Home Depot is an *essential store*). My system is... sketchy to put it nicely. Really need to clean out and re-design my whole kiln area. (more quarantine ideas)

 

The flexible venting, while *flexible,* is a real pain to work with. Really wanted to move to the Hard(?) venting since I got my kiln.

 

 

[Bill Kielb]

16 minutes ago, Brandon Franks said:

That jut gave me a great idea for tomorrow (thank God Home Depot is an *essential store*). My system is... sketchy to put it nicely. Really need to clean out and re-design my whole kiln area. (more quarantine ideas)

 

The flexible venting, while *flexible,* is a real pain to work with. Really wanted to move to the Hard(?) venting since I got my kiln.

 

 

Nice kiln area!
Yeah, some of that pressure ductwork is likely leaking. When we design buildings, there is a good reason to put the fan on the roof. It ensures all the ductwork in the building is negative so it cant leak fumes back into the occupied  space. Once you pressurize a piece it’s hard to prevent minor leaks. If you make that neat and tight might be enough to fulfill your needs.

[Brandon Franks]

1 minute ago, Bill Kielb said:

Nice kiln area!
Yeah, some of that pressure ductwork is likely leaking. When we design buildings, there is a good reason to put the fan on the roof. It ensures all the ductwork in the building is negative so it cant leak fumes back into the occupied  space. Once you pressurize a piece it’s hard to prevent minor leaks. If you make that neat and tight might be enough to fulfill your needs.

I don'y have any issues with the leaking or anything (to my knowledge). It's just hard to operate around. It takes up way too much space.

 

Also, there is only one source of air (the kiln) I imagine the air going into that blower system is crazy hot. Want to get some cool air to give it some rest.

 

I don't know why Bailey does not have a system like L&L with the cool air "grab" system. Always thought that air was too hot for the fan. 

[Bill Kielb]

1 minute ago, Brandon Franks said:

I don'y have any issues with the leaking or anything (to my knowledge). It's just hard to operate around. It takes up way too much space.

 

Also, there is only one source of air (the kiln) I imagine the air going into that blower system is crazy hot. Want to get some cool air to give it some rest.

 

I don't know why Bailey does not have a system like L&L with the cool air "grab" system. Always thought that air was too hot for the fan. 

Yes, needs room air and a mixing manifold. Interesting I will look up the Bailey system. Surprised they don’t have a provision for it.

[Brandon Franks]

9 minutes ago, Bill Kielb said:

Yes, needs room air and a mixing manifold. Interesting I will look up the Bailey system. Surprised they don’t have a provision for it.

Always though it was weird. I just followed instructions though. If it failed, I wasn't paying for the replacement.

[neilestrick]

@Brandon Franks Where the duct attaches to the kiln it should be pulling in room air as well as kiln air. If it doesn't, the duct would get way too hot and be a safety issue. Can you post a pic of the connection? Also, Blo-R-Vac dust hose lasts forever. Get the black 250F rated stuff.

@ronfire Check to make sure that there are no cracks in any of your ducts after the vent motor that kiln air could be leaking from, or before the motor that could be spoiling the draft. Also, the hotter the kiln gets the more the lid wants to lift. If the lid is lifting a lot it could be spoiling the draft of the vent system. If that's the case, put a latch on the lid so it can't raise up so much.

Where the duct connects to the kiln you'll get a lot of particulate material building up in the system. Take it apart and make sure it's not clogged up at all.

[Brandon Franks]

3 hours ago, neilestrick said:

@Brandon Franks Where the duct attaches to the kiln it should be pulling in room air as well as kiln air. If it doesn't, the duct would get way too hot and be a safety issue. Can you post a pic of the connection? Also, Blo-R-Vac dust hose lasts forever. Get the black 250F rated stuff.

@ronfire Check to make sure that there are no cracks in any of your ducts after the vent motor that kiln air could be leaking from, or before the motor that could be spoiling the draft. Also, the hotter the kiln gets the more the lid wants to lift. If the lid is lifting a lot it could be spoiling the draft of the vent system. If that's the case, put a latch on the lid so it can't raise up so much.

Where the duct connects to the kiln you'll get a lot of particulate material building up in the system. Take it apart and make sure it's not clogged up at all.

Followed Bailey's instructions. Seems to work fine though. I am going to make a system that pulls cool air from a T joint. The manual says the fan is rated to 500^f (?) that seems a little high.

 

 

[Brandon Franks]

16 hours ago, Bill Kielb said:

You shouldn’t but typically we see this complaint from wax burn off between 500 - 800 degrees. It’s really hard to influence very tiny lightweight molecules with a downdraft as the slightest updraft from heat rising makes them hard to capture. A hood is the usual solution such as vent a kiln. We experimented  a few years ago when one of our downdrafts died. We created a hybrid design and it definitely improved the situation significantly.

A hood is the typical for sure solution, our hybrid was just to replace the existing with something equal or superior in performance to our broken downdraft on a budget.

Here is a clip of it:

 

Bill, do you know the kind of Soffit vent that was used for this? I can only find aluminum ones.

 

Is it aluminum and you just bent it?

[Brandon Franks]

25 minutes ago, Brandon Franks said:

Followed Bailey's instructions. Seems to work fine though. I am going to make a system that pulls cool air from a T joint. The manual says the fan is rated to 500^f (?) that seems a little high.

 

 

Okay so, im going to assume this is bad-

 

Only rust on the intake from the kiln to the fan. Piping from fan to the outside vent has 0 rust.

[Bill Kielb]

46 minutes ago, Brandon Franks said:

Bill, do you know the kind of Soffit vent that was used for this? I can only find aluminum ones.

 

Is it aluminum and you just bent it?

Very lightweight aluminum. Home Depot 2-3 dollars if I recall correctly

[Bill Kielb]

42 minutes ago, Brandon Franks said:

Okay so, im going to assume this is bad-

 

Only rust on the intake from the kiln to the fan. Piping from fan to the outside vent has 0 rust.

Just a note, the room air or dilution air opening is usually placed very near where the manifold is  connected  to the kiln. Having measured these things they usually amount to  one to three 1” diameter holes and are tuned Pretty effectively by way of the smoke test. If you have the equipment the suction generated at the kiln is usually -0.1” WC and I have never seen any size blower discharge more than 20 cfm because of all the suction side restriction.

[neilestrick]

Seems like a really bad idea to not have the kiln air diluted with room air. The duct should be cool enough that you can comfortably touch it. The air should be mixed at the kiln connection. The piece on your kiln looks like an end cap with a hole cut in the middle. I would extend it before making the connection to your flexible duct, and put 3 holes in it like Bill said. Everything will run cooler then. For the kiln itself, you'll want two 1/4" holes through the brick (I think- how many cubic feet is your kiln?).

[ronfire]

Yes mine is a downdraft system. It is done with all metal ducting and no flex with the fan just before the exit through the wall. Might look into adding a room air pickup as well. The fan should be able to handle some heat as it was from a fireplace fan.

 

[neilestrick]

1 hour ago, ronfire said:

Yes mine is a downdraft system. It is done with all metal ducting and no flex with the fan just before the exit through the wall. Might look into adding a room air pickup as well. The fan should be able to handle some heat as it was from a fireplace fan.

 

Especially if it's a small room, a lack of makeup air could be a problem.

[ronfire]

Have my studio in the corner of my 20x40 workshop. Not real airtight with the  12X12 2 section door on the end.  Nice to not have the kiln close to the house and against a concrete wall in a corner. The bad thing is when I do wood projects the dust gets on the pottery projects.

Just checked the hole in the kiln floor and found they are clear so I decreased the amount of room air intake to see if that will help. It is definitely doing some work a the ducts are corroded from the fumes.

Thought of moving the studio to the guest cabin but then I would have to rewire for the kiln. Not willing to carry wares back and forth so I think it will stay where it is for now.

I built the cabin to display and sell pottery from but sale from home was not worth the trouble, so now it is a guest bedroom.

 

[neilestrick]

@ronfire That's a sweet little cabin! I wouldn't mess with moving the kiln out there. Expensive to wire, and hassle to carry pots out there.

[ronfire]

This is the kiln setup now. Was just looking and if I turn the Y  to the other side and an elbow it would draw from above the Kiln as well. The fan is a 2 speed so I would then run it on high.

[Mark C.]

Sweet cabin-leave it alone. I like that foil heat tape-I use a lot of that myself.

That vent should work very well with that short run.

[neilestrick]

It looks like you've to a 4" splitting into two 4", correct? I would reduce them both down to 3", redo the kiln side with 3" all the way to the kiln. Then leave the one side open. If you have the upper one open with them both at 4", you'll ruin the pull from the kiln. Even at 3" you'll want to check the pull in the kiln, you may only want the upper open part way.

[ronfire]

I turned the Y to the other side and opened the end about 1/2 way . The kiln lost most of the draft so I don't think it will work well. I have managed it this way for 4 years, I just don't stay in the garage near the end of the firing when the fumes get troublesome.

Might just put another fan beside and just draw the room air out from around the kiln. Was looking at maybe place this one beside the other fan and vent strait out.

 

 

 

 

[Bill Kielb]

1 hour ago, ronfire said:

I turned the Y to the other side and opened the end about 1/2 way . The kiln lost most of the draft so I don't think it will work well. I have managed it this way for 4 years, I just don't stay in the garage near the end of the firing when the fumes get troublesome.

Might just put another fan beside and just draw the room air out from around the kiln. Was looking at maybe place this one beside the other fan and vent strait out.

 

 

 

 

My experience is that will end up closer to 100 - 125 cfm and 195 is a free air measurement at best. Typical four inch  axial blower rating thing. Actually. If you do install you will likely want to make sure you have accounted for proper makeup air though.