#11  
Old 02-11-2008, 12:01 AM
Il Pizzaiolo
 
Join Date: Dec 2006
Location: Mishigame & Iberia
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Default Re: Damper and door questions

My oven chimney did come with a damper and I use it everytime I fire up the oven. I tend to season the oven for a longer period of time so after the fire is going, I tend to set the damper at 1/2 closed. I believe this keeps some more heat inside the oven.

A damper allows you to shut down the oven for baking but you can also cover the chimney with a bucket or wet blanket or something to seal it once you take the fire out. The damper also helps if you want to smoke things. The chickens I recently did were nicely smoked by the 1/2 damper technique.

And with all that soot, you get to see it turn white when it's pizza time

XJ
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  #12  
Old 02-11-2008, 01:59 AM
Journeyman
 
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Default Re: Damper and door questions

I am just reading this thread now. Sorry by the delay.
My oven has a chimney damper, that is used when the fire is 'in regime'. The combined use of the damper and door (loosely closed) helps to maintain the flames bright and alive and highest temperature, using little wood.

Luis
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  #13  
Old 02-11-2008, 06:44 PM
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Default Re: Damper and door questions

This asks an interesting question. When we are firing our ovens, and the fire is breathing in air through the open door, how much air is the fire getting from the vent and chimney?

I tried to kill a fire in an oven that had been build in-correctly, where the door sealed the vent opening, not the oven chamber. The fire continued drawing in air through the vent and chimney and just kept burning. It was a bad design, but it showed how the oven can take air "in" where you thought it would only go "out".

Still, I don't see how a chimney damper gives you more control over airflow than a well-positioned door.

James
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Old 02-12-2008, 08:33 AM
Il Pizzaiolo
 
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Default Re: Damper and door questions

James, I don't believe any air is coming from my chimney. That's where the smoke and heat is going. A damper helps you keep the heat in and burn less wood. Open and it can get hotter when you want it.

Having used one for years on woodstoves and fireplaces, you get the fire burning and once it is, you can damper it back. A good fireplace or woodstove is an airtight which takes in primary and secondary air to the fire. You also damper down the air supply at the door, so it's a balancing act. Without the damper you burn much more wood.

Now, I have not used a WFO without a door and chimney. Others may have different experiences.

XJ
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  #15  
Old 02-12-2008, 10:50 AM
Journeyman
 
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Default Re: Damper and door questions

I agree with XJ.
Just to clarify a little more, when the chimney has a correct relation respect to the oven dimensions, the flue of hot air and flames is vigorously drawing out and up, do not letting space to air return and forcing the air to enter by the lower part of the landing area.
If the chimney is completely opened, the flue is maximum and hotter and there is more wood consuming.
When the oven temperature is the adequate to your needs, the use of the damper let you to regulate this flue.

Luis
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  #16  
Old 02-12-2008, 05:52 PM
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Default Re: Damper and door questions

Enquiring minds want to know.

Just how do I know if I need a damper?

When I fire my oven I can see that roughly the upper half of the oven is full of smoke and the bottom half is clear. I presume the bottom half is air coming in from the opening. Should it be more like 1/4 clear and 3/4 smoky?

So far the oven heats up in about 45 minutes with a good steady fire. Could a damper help it to heat up faster?

Thanks!
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Old 02-12-2008, 07:27 PM
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Il Pizzaiolo
 
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Default Re: Damper and door questions

Christo, good question. You'd think there'd be an authoratative or scientific recipe for the perfect fireplace/oven. I've got a feeling that some engineer (or many), somewhere, has done the work, but I've yet to see it on a web page. I've done many searches, but perhaps not used the correct terminology to find what I was looking for.
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Old 02-12-2008, 07:58 PM
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Default Re: Damper and door questions

It appears that controlling your airflow, either down the chimney or through the door gives you more precise control of the oven heat. Here is a link to a ceramic BBQ that claims you can adjust and control the heat by adusting the bottom and top dampers.

FAQ

It looks like the object is to contain the heat filled smoke to warm the entire cooking chamber. The trick appears to be balancing the need for oxygen for combustion with the desire to trap all the heat possible. My thoughts are that using a damper is like fine tuning your oven. It works just fine without one, but you can tweak and adjust your oven with one.

I'm starting to think of this as hedging your bets. If your chimney diameter/ height/ transition/ etc is too big for your oven, you can make an adjustment without having to rebuild your oven.

Just what I need, one more thing to twiddle with while I'm trying to cook

Last edited by brokencookie; 02-12-2008 at 08:03 PM.
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  #19  
Old 02-12-2008, 11:23 PM
Il Pizzaiolo
 
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Default Re: Damper and door questions

I believe that's it...more control and flexibility. The hottest fires in my woodstove was with the chimney damper closed and the door dampers open. I would get a surface temperature between 500 and 600 F.

All dampers are wide open when you start your fire. I would then reduce the flow to the primary air and the chimney damper, leaving the secondary air open as that burns off the gases above the fire.

A wood fired oven may be different, particularly if you're only firing for a short period for pizzas. There you're using a big fire and curling the flames to heat the hearth or cook the pizzas! And I believe some of the pizza ovens don't even use a chimney.

For other cooking, roasts & bread, etc when the oven will operate for hours, you'll get the benefit of a damper, holding heat and using less wood.

Now chimney height....yes, once warmed the taller chimney tends to draw better and again, I think a damper is beneficial. Even in my short chimney I can dial down the damper until smoke comes out the top of the door crack, then open a bit, that's the sweet spot. I do want a taller chimney though to improve on this draw.
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  #20  
Old 02-13-2008, 05:33 AM
Journeyman
 
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Default Re: Damper and door questions

Look out you mob, an' settle eh.
Fellers, you all have good points on this "air-flow" thing.
I reckoned James had missed the point re fire and fires when warming up. (If you care to look, I actually asked about increasing exhaust efficiency.),when he said that he couldn't see how a chimney damper may be usefull.

Mate, depends at what stage of firing one uses it. Very pertinent to each individual setup .And once you're up to temp, you guard that temp like you'd guard an illicit fling.
I must admit to being a tad bemused by this thread. Here I am in a climate that ever-so-rarely drops below 18*C. One of our masochistic mates (a bloody sheila, eh, god bless her adventurous little arr,soul), was cooking in minus 30*.!!! Crappers eh!!
[Sorry Love, you're totally bonkers. Love ya, eh, and tellumfukum.]
X Jim runs close to my thoughts. Authority over 'gas in' cf 'gas out' is a bit like street cars cf race cars. fine tuning, each to their own
Mates.To those of us wot cook in caves: shall we raise a glass to James?
I'd like to think we could. Tomato juice/vodka, and all things in between?
So fill yer glass and sip to Jimmy, eh.
Not often that The Boss is so honest as this pric, eh. If he doesn't know, then he'll ask.
And I reckon I'd be proud to have him visit my humpy.
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