[Chuck]

If it's at 76% efficiency, and the heat isn't being absorbed, then how is the flue gas below the dew point, and condensating?

The heat was'nt absorbed because it wasn't being produced in the first place. The gas was being burned but it was burning at a cool temp.

When you have 6% O2 the flame temp is 2800°.
When burning at 12% O2 the flame temp is 2000°.

60% or more of the heat transfer in any combustion appliance comes from radiant heat off the flame itself. Which flame in is going to radiate more heat to the HX? The 2800° flame or the 2000° flame?

You can try it sometime, just restrict the air going to a burner to bring your O2 down. You will see your temp rise across the heat exchanger increase which means more btus are being produced. You didn't add any gas but you are getting more btus out of that same amount of gas!!

 

[seatonheating]

The heat was'nt absorbed because it wasn't being produced in the first place. The gas was being burned but it was burning at a cool temp.

When you have 6% O2 the flame temp is 2800°.
When burning at 12% O2 the flame temp is 2000°.

60% or more of the heat transfer in any combustion appliance comes from radiant heat off the flame itself. Which flame in is going to radiate more heat to the HX? The 2800° flame or the 2000° flame?

You can try it sometime, just restrict the air going to a burner to bring your O2 down. You will see your temp rise across the heat exchanger increase which means more btus are being produced. You didn't add any gas but you are getting more btus out of that same amount of gas!!

You are acting like this O2 in can be adjusted on a brand new furnace.

Ok, next install I'm going to install mesh over half of my intake pipe..:gah::gah:


I get what you are saying, but it isn't practical. Time for you to bow out gracefully.

 

[davidr]

You are acting like this O2 in can be adjusted on a brand new furnace.

Ok, next install I'm going to install mesh over half of my intake pipe..:gah::gah:


I get what you are saying, but it isn't practical. Time for you to bow out gracefully.

You might want to consider what he's saying instead of dismissing it.

O2 can be adjusted on a 90% 2 pipe furnace if you know what you're doing and you never have to touch the fuel to do it.

 

[Chuck]

You are acting like this O2 in can be adjusted on a brand new furnace.

Ok, next install I'm going to install mesh over half of my intake pipe..:gah::gah:


I get what you are saying, but it isn't practical. Time for you to bow out gracefully.

I adjust the O2 on every startup and tuneup I do. New, old, natural draft, induced draft, condensing furnace, boiler, etc.... Very practical as it saves the ho money and makes their epuipment last longer.

I would never put a mesh screen in the intake. Their are other ways to adjust air.

As for bowing out I certainly can if its getting too uncomfortable for you.

 

[davidr]

If it's at 76% efficiency, and the heat isn't being absorbed, then how is the flue gas below the dew point, and condensating?

One thing to keep in mind is the different types of efficiencies that are out there and how they are defined.

It looks like Chuck was referring to a furnaces thermal efficiency which is the actual amount of BTUs being delivered from the furnace compared to what it is rated to output.

There are a lot of times that they don't add up.

 

[mike dixon]

the angle of your dangle, is in direct porportion to the heat of your meat, and the mass of your bottom remains at a constant temperature and pressure at all times given the relative humidity, grains of moisture per lb of dry air, and dry bulb, wet bulb is approiate. got it?:angel:

 

[seatonheating]

I adjust the O2 on every startup and tuneup I do. New, old, natural draft, induced draft, condensing furnace, boiler, etc.... Very practical as it saves the ho money and makes their epuipment last longer.

I would never put a mesh screen in the intake. Their are other ways to adjust air.

As for bowing out I certainly can if its getting too uncomfortable for you.

Sure ya do.

 

[ctcont]

Good man

Nice job there is alot goin on there i like the flex connecter here we have to hard pipe everything

 

[edbrown]

So how exactly do you adjust oxygen levels in a 95% furnace? Different restrictor plates in the inducer?

All of out techs use analyzers and adjust the air for atmoshpheric systems, but i have never heard of adjusting the air on a 95%. Have in extreme cases turned down manifold pressure for correct CO levels, etc.

This is a very interesting conversation......

 

[dunkman]

Wow, I guess I'm going to have to change the way I do things. I've been setting them up to 3.5" with the factory orifices for 8 years and now I find out it's wrong?

 

[seatonheating]

Wow, I guess I'm going to have to change the way I do things. I've been setting them up to 3.5" with the factory orifices for 8 years and now I find out it's wrong?

'cause he is a troll and his recommendations are funny. Let's just modify everything!!

Easy there, this can be a very interesting thread if you let it, instead of the above.
Tell you what. I'm going home and adjusting the gas pressures in my water heater because my kids take long showers..... Better combustion will equal more hot water, right?

 

[jeremy-lvhm]

The heat was'nt absorbed because it wasn't being produced in the first place. The gas was being burned but it was burning at a cool temp.

When you have 6% O2 the flame temp is 2800°.
When burning at 12% O2 the flame temp is 2000°.

60% or more of the heat transfer in any combustion appliance comes from radiant heat off the flame itself. Which flame in is going to radiate more heat to the HX? The 2800° flame or the 2000° flame?

You can try it sometime, just restrict the air going to a burner to bring your O2 down. You will see your temp rise across the heat exchanger increase which means more btus are being produced. You didn't add any gas but you are getting more btus out of that same amount of gas!!

I would be interested to see just how high your stack temperature shoots up when you do this as well. The proof would be in the combustion efficiency that pops up in your pretty little meter.

I agree with seaton. Something doesn't add up. And who the hell made that orifice chart? Doesn't look very official to me.

But this thread will live on I'm sure.:cheers:

 

[davidr]

Wow, I guess I'm going to have to change the way I do things. I've been setting them up to 3.5" with the factory orifices for 8 years and now I find out it's wrong?

You might not need to adjust anything.

The combustion readings on the particular piece of equipment that you are working on will give you this information.

There are a lot of furnaces set to operate at 3.5" that are doing a great job.

The problem is 3.5" of pressure assumes a perfectly sized orifice and a certain parameters for the fuel.
If those parameters are met you're good.

 

[davidr]

So how exactly do you adjust oxygen levels in a 95% furnace? Different restrictor plates in the inducer?

All of out techs use analyzers and adjust the air for atmoshpheric systems, but i have never heard of adjusting the air on a 95%. Have in extreme cases turned down manifold pressure for correct CO levels, etc.

This is a very interesting conversation......

You're on the right track here Ed.
It has to do with controlling the amount of intake air and adjusting it for that particular installation.

 

[davidr]

'cause he is a troll and his recommendations are funny. Let's just modify everything!!


Tell you what. I'm going home and adjusting the gas pressures in my water heater because my kids take long showers..... Better combustion will equal more hot water, right?

Pot this is kettle you're black.

Before you start calling someone a troll you might want to go back to the business forum and delete all those hand grenade threads you've started.

Your last statement is correct except it's done by a different method than adjusting gas pressure.
Most water heater gas valves don't have pressure adjustments on them.

 

[davidr]

I would be interested to see just how high your stack temperature shoots up when you do this as well. The proof would be in the combustion efficiency that pops up in your pretty little meter.

I agree with seaton. Something doesn't add up. And who the hell made that orifice chart? Doesn't look very official to me.

But this thread will live on I'm sure.:cheers:

Jeremy you can go to Anderson Forrester http://www.andersonforrester.com/ and get all the orifice charts you want. They are a good source for that type of information.

Watch trusting the combustion efficiency number on a combustion analyzer.
Unless the fuel parameters that are programmed into the analyzer are identical to the fuel you're using the efficiency calculations will be off.

 

[jeremy-lvhm]

You're on the right track here Ed.
It has to do with controlling the amount of intake air and adjusting it for that particular installation.

Um wouldn't this change according to outside temperature as well? The whole thing is flawed and you guys are trying to reinvent the wheel. More oxygen per volume in colder air right? This is why we are running screw driven chiller turbo coolers on power plants in AZ to get more out of our combustion process. SO when you set up and screw with all your furnace settings at 40 outdoor temp and then its -20 out things will change. Just like ANY piece of equipment you cannot make things perfect for all conditions. Test out your theory and you will see it all change at different temperatures.

I know we all like to think we are smarter than the next guy but stop getting out of control. You show me proof on your so called huge savings per customer and maybe I will believe you. A system will not work properly with crappy ass duct work too but most of the time that is ignored. You think you have some sort of magic bullet by with a factory set up furnace? I do not. If this was truly an issue perhaps we should petition the manufacturers to send us a full set of orifices with each and every furnace.:gah:

 

[davidr]

Um wouldn't this change according to outside temperature as well? The whole thing is flawed and you guys are trying to reinvent the wheel. More oxygen per volume in colder air right? This is why we are running screw driven chiller turbo coolers on power plants in AZ to get more out of our combustion process. SO when you set up and screw with all your furnace settings at 40 outdoor temp and then its -20 out things will change. Just like ANY piece of equipment you cannot make things perfect for all conditions. Test out your theory and you will see it all change at different temperatures.

I know we all like to think we are smarter than the next guy but stop getting out of control. You show me proof on your so called huge savings per customer and maybe I will believe you. A system will not work properly with crappy ass duct work too but most of the time that is ignored. You think you have some sort of magic bullet by with a factory set up furnace? I do not. If this was truly an issue perhaps we should petition the manufacturers to send us a full set of orifices with each and every furnace.:gah:

Once the amount of combustion air is set that is it on a resi furnace, no more adjusting required on the air side after that unless you want to split hairs and start setting up a modulating combustion air intake based off of outdoor temperature.

Don't know where the idea that there is some magic bullet came from in my post or any post I make. It sure would be nice if it was that simple unfortunately it's not.
Anyone that's ever been to one of our classes knows there is more to this than what we discuss in an open forum, ductwork is one of those things we are really big on correcting too. There is a huge amount of opportunity out there for correcting messed up stuff.

This definitely doesn't have anything to do with who is smarter than who. Not sure where that came from.

This is about helping each other to learn there is more to this than meets the eye and helping to open those eyes to realize the things that are going on in the field.

Read back to the front of this thread and you will see Chuck asked a simple question and was raked over the coals for it. That is what got out of control in this thread.

 

[jeremy-lvhm]

Actually chuck started with the accusatory attitude first. And why such a question popped on this particular thread is beyond me. This was a simple wall of pride post. From those pictures he had no indication that it wasn't set up to his standards. He was just trying to start a pissing match. And he accomplished it.

It's all laughable to me. I just wanted to poke a hole in his theory. But then I am splitting hairs. I'm pretty sure he started that path.

 

[Adlerberts-Protege]

Actually chuck started with the accusatory attitude first. And why such a question popped on this particular thread is beyond me. This was a simple wall of pride post. From those pictures he had no indication that it wasn't set up to his standards. He was just trying to start a pissing match. And he accomplished it.

It's all laughable to me. I just wanted to poke a hole in his theory. But then I am splitting hairs. I'm pretty sure he started that path.

This is a great thread I wanted to resurrect now that everyone is older and wiser. Thoughts here in 2019?