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Burner air intake adjustment and flame color, flame length and combustion flow

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Burner air intake adjustment and flame color, flame length and combustion flow HVAC Guy 10-31-2007
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Posted by Bubba on October 31, 2007, 10:07 pm

>Bubba wrote:
>
>> You need to purchase a CO meter or combustion efficiency meter and
>> play with it. You will get all the answers you wish.
>
>That's doesn't answer my question about the general differences
>between the fully open and fully closed positions and their effect on
>combustion velocity and furnace efficiency, and if the desire to
>prevent condensation in the chimney plays (played) a role in the
>setting of the burner air intake baffle.

Actually, I did answer your question. Your problem in understanding is
that Im not going to just spoon feed it to you and shove it up your
ass. Experiment you dip. Do what I said. Get a simple carbon monoxide
tester and stick it in a flue. Now slowly adjust the air mixture. If
you have any clue at all, you will soon understand that you can do a
pretty awesome job of tuning the air fuel mixture of a burner as long
as you understand the basics of a fuel and air mixture.
Now bite me and go do your homework.
Bubba

Posted by Stormin Mormon on October 31, 2007, 7:14 pm
When I worked for Sears, my trainer told me we left the air intakes wide
open, less likely to produce carbon monoxide. The rest of the reasons, I've
not heard one way or the other.

--

Christopher A. Young
.
.


The burners of older natural gas furnaces usually have a round plate
that can be rotated to either open or closed positions, allowing a
variable amount of combustion air to enter the burner along with the
gas.

If the plate is fully open, the resulting flames seem shorter, faster,
uniform height, and uniform color (blue).

If the plate is fully closed, the flames are longer, slower, variable
height, and more red in color.

It seems that usually the plates are rotated fully open.

Is it true that back when natural gas was cheap, these intake plates
are usually set fully open to create a faster-moving combustion flow
to help increase exhaust temperatures that would help to prevent
chimney condensation, and that by closing the plates you are
increasing the efficiency of the furnace by slowing the combustion
flow and allowing more of the heat to be transfered to the heat
exchanger instead of escaping out the flue?



Posted by ftwhd1 on October 31, 2007, 8:47 pm
On Wed, 31 Oct 2007 18:14:07 -0500, "Stormin Mormon"

>When I worked for Sears, my trainer told me we left the air intakes wide
>open, less likely to produce carbon monoxide. The rest of the reasons, I've
>not heard one way or the other.

You dont know jack shit about combustion so why dont you keep your
mouth shut.

I changed my handle just so you see this.

Posted by ftwhd1 on October 31, 2007, 9:02 pm

>
>The burners of older natural gas furnaces usually have a round plate
>that can be rotated to either open or closed positions, allowing a
>variable amount of combustion air to enter the burner along with the
>gas.
>
>If the plate is fully open, the resulting flames seem shorter, faster,
>uniform height, and uniform color (blue).
>
>If the plate is fully closed, the flames are longer, slower, variable
>height, and more red in color.
>
>It seems that usually the plates are rotated fully open.
>
>Is it true that back when natural gas was cheap, these intake plates
>are usually set fully open to create a faster-moving combustion flow
>to help increase exhaust temperatures that would help to prevent
>chimney condensation, and that by closing the plates you are
>increasing the efficiency of the furnace by slowing the combustion
>flow and allowing more of the heat to be transfered to the heat
>exchanger instead of escaping out the flue?

Oh theres your original post... :)

I must say for an hvac guy you dont seem very well educated on
combustion. It would seem that in order for you to fully understand
what is goiung on you need to start with the basics. Like the
combustion triangle and progress from there.

Learn terms like excess, primary and secondary air, what they are,
where they come from and the effects on combustion. Learn about fuel
to air ratios . I suggest looking up Backarack <sp> on the web. They
have some good info on combustion in the training room.

The questions you are asking are indicative of a lack of knowledge
which is fine but beyond the scope of this NG imo. Have you
considered formal training on the subject?



Posted by HVAC Guy on October 31, 2007, 9:43 pm
ftwhd1 wrote:

> Oh theres your original post... :)
>
> I must say for an hvac guy you dont seem very well educated on
> combustion.

It's just a handle I made up for this thread. Don't focus on it.
Focus on the questions.

> It would seem that in order for you to fully understand
> what is goiung on you need to start with the basics.

I'm asking direct questions here regarding the effects of setting the
air baffles either fully open or fully closed and historically were
they set fully open for reasons other than correct combustion or best
efficiency.

I now have 2 possible reasons why in years past the default of
fully-open may have been routinely used:

1) prevent chimney condensation by keeping combustion flow high
resulting in higher flue and chimney temps

2) keep combustion flow high to create enough passive exhaust flow to
overcome possible air imbalances that might lead to flue back-flow in
a well-sealed house.

Both situations sacrifice efficiency in favor of either safety or a
reduction in future chimney maintainence, and at the time (20, 30
years ago) both seemed rational based on the price of NG and the
relatively low efficiencies of the furnaces at the time.

> Learn terms like excess, primary and secondary air,

I could do that, but that wouldn't answer my questions regarding what
was done by techs in the field, working on actual furnaces.

> The questions you are asking are indicative of a lack of
> knowledge

They are indicative of a lack of being an hvac tech and experiencing
first-hand what was actually done by techs 20 or 30 years ago as they
serviced and adjusted low to mid-efficiency furnaces or even what a
tech would do today when servicing or adjusting a 20, 30 or even 40
year old furnace.

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