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-   -   fan assisted flue (http://www.fornobravo.com/forum/f37/fan-assisted-flue-18063.html)

michaelthebaker 07-14-2012 10:26 AM

fan assisted flue
 
I am building a commercial bread/pizza oven indoors, (all my other builds have been mobile outdoor) so i am concerned about the smoke billowing into the restaurant. I wonder if anyone has experience of the smoke draw whilst the oven is warming up, ie before secondary combustion burns the smoke/gas. My flue supplier suggests a variable speed fan mounted on the top of the outdoor flue (6" twin wall) so that the flue will draw until the flue is hot and so will draw without the need for a fan. Problem is the fans are very expensive and so the question is can i do without the fan and rely on the flue to draw the smoke out naturally?
all your help and ideas much appreciated

Michael the baker

david s 07-14-2012 12:14 PM

Re: fan assisted flue
 
See how you go. You can always fit the fan later if smoke is an issue.

shuboyje 07-14-2012 08:16 PM

Re: fan assisted flue
 
Before a powered exhaust I would vastly increase the flue size. 6" is way to small for a commercial oven, unless it is a tiny tiny oven for a commercial operation. With a properly sized flue and a well designed transition an indoor commercial oven shouldn't have issues at even startup. An indoor oven will have no wind to deal with, and generally a taller stack. Both are good for draw.

nissanneill 07-14-2012 09:18 PM

Re: fan assisted flue
 
AS said, a good sized flue transition and an adequate flue is essential for smoke and fume exhaust. My transition is quite large and funnels all the smoke even at start up into the 8" 12 foot flue and that is for a 40" Pompeii. The only time i ever saw smoke exiting the oven opening was when I was using a petrol leaf blower on full throttle to get some stubborn wood alight but that was extreme to sat the least!

Neill

michaelthebaker 07-15-2012 07:46 AM

Re: fan assisted flue
 
hi guys. Thanks for your positive and encouraging replies. The oven is big, 40" wide, 55" deep, so I will go for an 8inch flue as suggested. I am not sure what you mean by the flue transition? The flue is set back from the door opening about 20inches, a little above the door height, but lower than the top of the internal dome, so that gases burn in top of the dome and are (hopefully) drawn up and away. The heat proof smoke fans are over $1000, so I may just put a spinning cowel on the top of the flue pipe to help with the draw. The flue will be approximately 3.5 metres or 14 feet long.
Any further advice much appreciated.

Neil2 07-15-2012 10:19 AM

Re: fan assisted flue
 
"leaf blower on full throttle"

Amazing how much fun you can have with a leaf blower.

nissanneill 07-15-2012 05:55 PM

Re: fan assisted flue
 
Hi Michael

Quote:

I am not sure what you mean by the flue transition?
I have included a picture of my transition and first flue section, of which I have 3 in total length. It is the"funnel" that directs the smoke/gasses up into the flue (the pipe that draws the smoke away and delivers it to the atmosphere or the neighbours).
Mine is made of stainless steel, hence the white plastic protection film and is fairly deep to capture the smoke. An almost flat transition cannot direct the smoKe quick enough and as such it 'overflows the flue out the front of your oven opening.


Neil

Quote:

"leaf blower on full throttle"
Amazing how much fun you can have with a leaf blower.
You should try it but not too aggressively, it really gets it going and if continued, you could melt steel in the oven! Keep the nozzle a little away from the opening (I keep it at ;east a metre away), and aim it at the base of your fire.

Neill


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