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

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?
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You need to purchase a CO meter or combustion efficiency meter and play with it. You will get all the answers you wish. Bubba
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Bubba wrote:

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.
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Actually it does, your just too ignorant to know it.
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Noon-Air wrote:

And his id. is "HVAC Guy" He must be a quack.
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Sounds like a home inspector wanting to make a blanket indictment of HVAC techs in the 70's and 80's.
--
Ron Paul or more of the same.

http://www.ronpaul2008.com /
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What about his too ignorant?
You're going to have to learn to spell and punctuate, if you want to convince others of their ignorance.
--

Christopher A. Young
.
.

"Noon-Air" < snipped-for-privacy@comcast.net> wrote in message
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pot calling the kettle ?????

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Stormin wouldn't know proper combustion if it burnt his ass.
wrote:

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The Freon Cowboy wrote:

You all can look at "his ignorant" if you want, but for me I'll just keep my eyes on my own "ignorant" thank you very much.
--
Zyp



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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
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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
.
.

"HVAC Guy" < snipped-for-privacy@Guy.com> wrote in message news: snipped-for-privacy@Guy.com...
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On Wed, 31 Oct 2007 18:14:07 -0500, "Stormin Mormon"

You dont know jack shit about combustion so why dont you keep your mouth shut.
I changed my handle just so you see this.
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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?
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ftwhd1 wrote:

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

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.

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

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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HVAC Guy wrote:

HVAC Guy;
Both of those reasons are not "reasons" to set the burner shutter all the way open. It is likely the furance was never adjusted properly in the first place. It is likely that many a plumber or furance repair person cared either. They opened it all the way knowing that was probably safest.
BTW: during the 1970's to 1978 we only had one furance efficiency. After 1979, intermittent pilots came about in an effort to conserve on fuel. By 1981, induced draft and slimer heat exchanger's came. By 1988 pilotless ignition known as Hot Surface Ignition started appearing. Today we have a host of choices for furnaces depending on what the homeowner / client want's to pay. Highend, variable speed 96% AFUE furnaces are expensive and not many homeowners are willing to flip the bill for one of these. Fossil fuel burning furnaces now can be combined with Heat Pumps to offer a better way to save fuel and money.
If you would like to learn more, why don't you take a class at your local Community College? Or possible seek information through your utility company [the one suppling your fuel].
--
Zyp



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ftwhd1 wrote:

You may be too hard on him. This type of equipment may be rare in his area. I know it is in mine. Heat strips or heatpumps is about it here, if there is heat at all.
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wrote:

homeowner Im pretty much done with him. If he wanted to have a reasonable disscussion about combustion then he needs to learn the lingo which he unwilling to do.
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No.
-zero
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