What should you be looking at when doing a combustion analysis? (The basics!)
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- Опубликовано: 1 май 2024
- Download a Free copy of the mQ Combustion Quick Start Guide: measurequick.com/resources/#c...
We often get the questions, "What are you looking at when you perform a combustion analysis?" In this video we cover just that. Combustion all comes down to fundamentals. If you have not used an analyzer before, or you are just looking to buy your first one, this video will help you understand how the readings relate to each other and what changes as you make combustion adjustments.
More about the Sauermann Combustion Analyzer
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Best explanation video I've seen yet, thank you sir.
Thanks Jim, always enjoy your videos.
Great info, got the combustion guide downloaded 👍🏻
I love it. This is a great visual on how adjusting the fuel input effects combustion. I will be sharing this with my team!
Thanks for the important info!
Great info. Jim. Thank you.
God bless you sir. Relying on your education to do my job better.
Thank you very Much Jim Happy Thanksgiving !
Hi Jim on point as usual. When you cranked up the gas the flames coming out of the roof vent were spectacular- I live next door. I wanted to mention, because you forgot to, that you were wearing the official combustion testing shirt. We should put the link up.
Just got my Bluflame today, hope I can get some gas furnaces commissioned before heating season is up!
Would love to see a video on clocking an LP fired furnace. My process is painful and a huge time suck.
I would love to see you do a combustion test with the fieldpiece cat85.
I love your videos on technical subjects as you give very thorough explanations.
But just today I found one by "tradestutor" titled "combustion analysis for natural gas". It would be great to hear your version of that material as I don't think you have ever specifically taught the what the numbers mean and why we need certain numbers. THANK YOU
Great video. Thank you! You've shown us readings at proper gas pressure and at higher gas pressure. What would the Co Air free reading be if the pressure is at 3" or even 2.5" wc?
This was great do you have one on what it would look like when the heat exchanger is cracked?
Great video, I would like to find an analyzer that can output the raw data for CO ppm, O2% at each sample time point as well as showing the final computed results. Some units will make graphs of the raw data, but can they export it to a csv file or equivalent numeric format?
This year I would like to master the combustion air zone. Can’t seem to get it into my routine.
I love the mQ app, the graph updates are a really nice touch too.
all I can say is “THANKS “!
I travelled multistate for a large industrial and institutional contractor for decades. On occasion I worked with commercial, and residential equipment.
The primary owner and president of our division had been my fire dept,/EMS Capt. prior to my moving to a different dept. (I also have over 4 decades in public safety services)
You touched on static and air flow.
IMHO, prior to combustion analysis or sub cooling/superheat, these should be the two first system checks.
Our company was founded in 1867 and we had several people involved in design, draftsman, engineers, and architectural firms, in our design/ build projects. We had acquired several early 'warm air' companies and their large patented furnaces. We had blowers large enough to crawl in to and pretend that you were a gerbil ---.we had dual duct constant volume, single duct mixed air, vav, vortex dampers, and were involved with early VFD inverters and venturi systems for more precise air control. Most in residential and commercial services will never deal with this variety of air distribution.
Static pressure readings above manufacturer's design should be evaluated and corrected or one is wasting their time and the customers money.
It saddens me to see the percentage of residential and commercial installations that were never properly designed and commissioned. What is worse is hearing stories of multiple contractors recommending and installing larger capacity equipment on systems that can't handle what they have. I recently scrapped a 100k propane furnace for a friend who implants pacemaker probes in surgery. He and his wife had purchased a faux log cabin style home that had wild temperature swings. When their furnace started shutting down on safeties and two companies came out and changed pressure switches, roll outs, and boards without success, I received a call for help.
Their 100k furnace had four ten inch by four inch supply boots and discharge registers for return air. And the spare bedroom supply and return had been closed "to try to help the rest of the house" as that room wasn't being used.
All sections of the primary cell were cracked. They also regularly used a wood stove to save on propane costs. They thought that the intermittent chirping of the co detector was due to their opening and closing of their wood stove.
Very lucky that we weren't called in our other capacity with big red trucks and bags with zippers.
Was just asked to do a casual walk through of another friends new cape cod style home. The hacks that did the HVAC made the usual bottom plate, floor, and top plate cuts, and panning to facilitate return air flow back down to the panned return joist space which connected to the return duct. This return, from a roughly 150 Sq ft room, was restricted to 8" by 3.5" going into a first floor stud space in which the studs didn't line up. Sadly, due to the open concept kitchen/dining/living room, they had made no provision for the other bedroom's return air pathway other than a transfer above the door.
There were two 14" X 6" wall returns, one mounted low in the master bedroom (4- 10"X 4" supplies: 2 in bedroom, one in bath, and one in master walk in closet) and one in the south upstairs bedroom. The other bedroom had the 14" X 6" transfer.
There was also a 30" X 6" low return in the kitchen wall. The hand scribbled 'plans' showed a 30" X 6" in the master. I had questioned the general contractor's supervisor, who sort of took offense that I could possibly question his sub's calculations. A return visit revealed an additional 14" X 6" in the master and dining room floor (both within a few feet of the existing low wall return, but nothing to remedy the lack of upstairs return. A few large, high wall returns and a connecting duct through the knee wall space, dropped through a chase in a corner of the first floor laundry or master bedroom closet to connect to the return duct would make a world of difference. Oh well. Calls to the builder's GM have not been returned and the new owner is already talking about a lawsuit.
Truly sad.
My point? Without adequate airflow one can chase their tail on commissioning.
Nice video regarding flue gas readings.
Love to hear our large blowers spooling up and the modulating power or ribbon burners firing off.
Stay safe.
This is why comments sections are just as awesome as awesome videos.
Thanks for the insights.
You can have 40 HVAC techs with 40 years of experience each but no one single person among them has all of the knowledge.
Just curious what your starting gas pressure was and what you dialed it up to in this video? Great info Jim
3.2 adjusted up to 3.7ish.
Can anyone tell me if u can do a combustion analysis in 1st stag on a 2 stage furnace?..if so what should o2 and co2 readings be?..its a trane xv80 gas furnace..thanks
Great vid thank you
How would the appliance get damaged with Low input?
Condensing in primary heat exchanger/vent pipe
Thank you
Will TPI ever be supported?
If measuring gas flow by clocking the meter shows that the furnace is operating at the nameplate BTU, then why even check the gas pressure?
Is it even possible for a furnace to be operating at the nameplate BTU but have the gas pressure outside of the manufacturer-specified range?
Where would I find the chart for a high efficiency gas furnace
Let's do a high efficient video one day Jim!
(Though we'll have to use my TPI DC710 🤪)
Where can I get that sheet for reference?
Jim we are waiting for some new videos way overdue. Even though I saw you at the symposium can never get enough learning. If you remember me I'm the Jewish guy from new York. We had a little chat at the symposium. I actually have a question how can I reach out to you?
Jim@measurequick.com
I know this particular video is about combustion analysis but I have a question about when will the testo 550i 557s manifolds will interact with measurequick?
That is in Testos ballpark at the moment. We will be in contact with them about this again soon.
Why do you clock the gas meter in addition to using a combustion analyzer? Wouldn’t using the combustion analyzer be a more accurate way of dialing in you gas pressure than by clocking the meter?
No, not without an exact excess air required from the manufacture. Sometimes the excess air also includes air for dilution. You could easily end up over fired.
How do you seal the whole in the flue pipe?
Also if the flue pressure is bouncing between positive and negative what would fix it?
Depends on the material. Silicone plug in most applications. They are available through TruTech Tools.
Bouncing usually indicates that you are too close to the induced draft motor. 10-12” upstream from the fan outlet is ideal.
How do you seal the hole in the flue pipe? We use double wall flue pipes so putting a piece of tape over the hole still leaves a hole on the inside and im pretty sure it won't pass inspection like that. We arent allowed to use screws in the flue pipe so I dont believe leaving a taped up hole in it would be ok?
trutechguy.files.wordpress.com/2011/01/4-letters-on-b-vent-testing.pdf
Basically make the outer hole larger then the inner, seal the inner with high temp caulk and the outer with foil tape. Above is a link to letter from the manufacturer from TruTechTools.
I've noticed many systems that have high Excess Air and O2 readings and therefor push the gas pressure to the upper 3.8" limit and often still can't get the correct readings. It tells me I should probably be increasing my orifice size? Also, should there be noticeable differences between sealed and non-sealed combustion furnaces?
Sometimes the excess air and dilution air are combined on 80+ appliances making the overall reading of excess air high. Don’t adjust an appliance on the 02 reading. Clock the meter and get check the input. At a 3.5 nominal you have 3.2-3.8” to work with. Outside of that range increase or decrease orifice size. Proper input and temp rise are the key to proper operation.
@@measureQuick
Since you said it has been on the low side of stack temp and temp rise and the gas pressure adjustment was counterproductive, is a change in orifice size what you are leaning towards for this particular furnace?
@@jrsmyth9761 I can get the input correct within the allowable range, I also have the temp rise at the high end. Everything is correct, it just has a very low stack temperature. It is the way that it is designed.
When you say high excess air what kind of percentages are you looking at?
I brought an ancient bryant down from over 200% to 175% by fixing gasket leaks but I can't find the LP specs for manifold pressure for that model. The opinions from bloggers are mind-numbing bordering on dangerous.
@@measureQuick Hi Jim. Whenever I see/hear 3.5, I don't know whether to scream or cry. It seems like LP is child that is kept in the closet. We love your stuff, but 90% of the presenters out there only talk in terms of NG. I did see the mfg conversion chart you kindly showed at 11:30, but the rating plates on ancient machines are never updated so unless each machine is standarized then unclocked, unrated LP doesn't fit the 3.5 standard setpoint because too many techs have made too many turns on that screw before us (so as to imply that the factory setting is unknown). I've been consuming your videos like sugar-coated breakfast cereal. Currently excess air has been my nemesis. In your seminar at HVAC school channel you started to speak about your 2-stage with excess air but we didn't get to hear how you resolved it. The Carrier inspection guides are a good start but can be vague. That's where a lifetime of experience makes the sun come out and the blue birds sing.
So, how are we preventing flue gas condensation on these Goodman furnaces with such a low stack temp? On this particular furnace, increasing fuel seems to create excessive CO, and reducing airflow may exceed mfg. specified range. Would orifice increase have the same affect on CO as the increased pressure did? I would think the difference would be velocity comparing the two methods to increase gas. So, would the velocity reduction by changing orifices have a different affect on the CO? It amazes me that some of these mfgs. get away with making such garbage equipment. Are they making the unit so cheap that the heat exchanger can't handle a 60° temperature rise?
cut fan speed i think, get closer to the high end of the rise range if it's something like 20-50f.
60f rise is high.
If I find high coaf like 120 ppm what should I do to get the coaf lowered. Or should I condemn the unit with those readiings
Check the input, manifold pressure, burner alignment, for flame impingement, check the venting, check burner cleanliness, etc.
@@measureQuick thanks alot I appreciate it I work for Goettl btw thanks for all your work you implement into mq (DD)
Understand the chemistry is important but not every one can afford to have comb-analyzer. Careful but practical way to adjust the gas output pressure by looking at the gas burner flame, will be helpful.
You cannot see issues with a flame until it is in very bad condition. A combustion analyzer is required for appliances.
This stack temperature seems to point to incorrect orifice size. By increasing the Gas Pressure your taking the O2% out of range. That being said, I would be curious about the orifice in this furnace. The ratio seems off. I'm in Alberta and we are at 2200 ft approx. Our furnaces are derated at the supplier by a orifice size. And I do CA on every furnace I touch, never seen a brand mid at that low of stack temperature!! Also are we so focused on co "air free", that appears to be a theoretical number. The Co value is the real actual number Im concerned with. CO air free is not even possible.
So the orifice is close to being oversized as furnaces are set by rated input. It is spot on. The low stack temp is likely due to the rated temperature rise of 15-45 degrees. That is a really low rise range for an 80+ furnace in my opinion. COaf is what you should be concerned with. It is a apples to apples measurement that removes the affect of dilution. It is not a theoretical number as much as a number that reflects the absolute CO reading at 0% O2 rather then relative to a wide range of O2 and the resulting dilution of the CO. CO is in ppm (Parts/million) so adding more ok reduces the ppm without changing the actual amount of CO. So you could have what looks like a safe CO number on a very dangerous appliance because the O2 is diluting the gasses.
@@measureQuick Thank you for your reply.
I agree a 30º T rise seems odd. I understand manufacturers do offer different tonnage of air per unit but it certainly can be a issue when a unit has low BTU size with high air tonnage. in other words, the contractor chooses a unit more for AC than Heating, but that is where the equipment selection process should be more thought out as this is an example of the downside of poor equipment selection.
I will have to digest your explanation of the COaf number and learn more👍
Thanks again
Hello Mr. Jim
I was paying attention when you were adjusting gas pressure to reduce or increase gas flow, however the rating 80% gas efficacy rating did not improve to 80% I understand you mention condensation built up when it gets over 84% I am sure that will cause rust in heat exchanger vent pipe. what is the best course of action to reduce efficiency when you doing combustion analyses?
Thank You Very Much
The only thing that you could do is to increase temperature rise by lowering the blower speed. The input has to be within 2%. In this case, I think there is a manufacturing/design issue.