[Stoves] Excess air

[lannych at bellsouth.net]

How do you get a sample from hot moist exhaust without whacking out the meter.
Mine took 30 minutes to recover.


> On Oct 27, 2014, at 9:14 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Lanny
>  
> That is a very sensible question.
>  
> IF you take the simplest form of the equation it is
>  
>     Measured O2    s
> 21 - Measured O2
>  
> If you only have an O2 meter, you can still make a lot of progress. Note the picture of my checking the EA in the large TLUD:
>  
> <image001.png>
>  
> It is just on the side of the flame where on air from the room can get to the nozzle.
>  
> It would have been better it there was a pot on, and the sample taken from the edge of the pot like this:
>  
> From experience, it is more difficult to keep the EA to a constant level in a wood stove than for other fuels because it is not as predictable and it evolves its chemical composition unevenly.
>  
> If you can get 100% EA, the O2 reading will be 10.5%. If you plug 10.5 into the formula above you get 100% as the answer. You will start to get smoke and CO in higher concentrations at 50% EA in a wood stove, in almost all cases. At 200% EA which is an O2 reading of 14%, you will again start to lose a lot of combustion efficiency.
>  
> If you are able to keep the EA between 75 and 150%, a range of 2:1, it will be about as good as it is going to get with whatever architecture you have at the time. At 100% EA held constant, you can play with the architecture and get the CO level down more and more. When it is extremely low, it is likely the PM has also disappeared with steady state combustion.
>  
> The O2 reading for 75-150% can be determined by working that formula backwards. It is O2= 9 to 12.6%.
>  
> A more accurate formula is
>  
>     Measured O2 - CO/2    s
> 21 - (Measured O2- CO/2)
>  
> If the CO is high, it makes a significant difference (measurable).
>  
> There are more sophisticated formulae involving more gasses if you are measuring them.
>  
> Regards
> Crispin
>  
>  
>  
> For a wood fired cooking stove, burning wood, How much excess air is reasonable and what O2 readings would that be?
>  
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