What should you be looking at when doing a combustion analysis? (The basics!)

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

[marksplace]

Best explanation video I've seen yet, thank you sir.

[hvacslayer]

Great info, got the combustion guide downloaded 👍🏻

[Andrewfixit]

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.

[jericosha]

God bless you sir. Relying on your education to do my job better.

[kieffersheatingcoolingv.]

Thanks Jim, always enjoy your videos.

[texasstarniles]

Thank you very Much Jim Happy Thanksgiving !

[MrBdogg]

I would love to see you do a combustion test with the fieldpiece cat85.

[michaelmaclachlan]

Just got my Bluflame today, hope I can get some gas furnaces commissioned before heating season is up!

[ThomasGray-fs]

checking CO at start up and shut down can tell you if you are having trouble with a gas valve not closing soon enough on shut down, or if you are having delayed ignition on startup

[bobpaulino]

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.

[staticpressurenerd]

I love it. This is a great visual on how adjusting the fuel input effects combustion. I will be sharing this with my team!

[RJMaker]

Would love to see a video on clocking an LP fired furnace. My process is painful and a huge time suck.

[taephillips]

This was great do you have one on what it would look like when the heat exchanger is cracked?

[LouisWilen]

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?

[billb.]

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

[lee-johnson]

Just curious what your starting gas pressure was and what you dialed it up to in this video? Great info Jim

[pubchat]

Great vid thank you

How would the appliance get damaged with Low input?

[takleung]

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?

[frankmashione]

This year I would like to master the combustion air zone. Can’t seem to get it into my routine.

[tactifoo]

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?