Combustion Readings. this months column PHCP Pros

This article contains some good information such as how often test. When contracters say they just at the beginning of the heating season I wonder how they get to every customer that day. Of course there are indirect waters heaters and water heaters that run all year long.

Testing in the proper location is important. Above drafthoods and barometrics is useless information. But where in the drafthood do you measure? If you have a mushroom or round drafthood you locate you probe where the lowest O2 reading of the highest CO reading. The highest flue temperature is the wrong place. If you have a built in rectangular drafthood you have to test each and every burner. On the same piece of equipment with multiple burners I have found one burner underfired, one burner misaligned and several burners not venting properly, When I hear techs tell me they have never seen this I immediately know they are testing incorrectly.

Checking gas pressure first? The burner has to be running to do this and don't we want to know if it is safe? If you understand combustion readings, the combustion tests tell us if we have enough gas or not.

If draft is not proper we are standing in a deadly environment. I thinking living during the testing is more important!

CO Air free is calculated from the O2 reading and the CO as measured. Because the O2 sensor responds faster than the CO sensor you can get all kinds of radical readings. I have had situations where experts?? stated the Air Free CO was the greatest after the burners shutdown. In reality the O2 reading rose faster than the CO. I guess if you want to be sneaky you can scare the customer with that reading. Do CO Alarms measure Air Free? If you don't have an O2 tester or your O2 is bad can you still test with confidence? Yes!Yes!

Can the flue temperature of a condensing boiler be below 140 degrees if it is producing 160 degree hot water? This one I don't have enough experience to comment.

Efficiency. This is the subject manufacturers of combustion analyzer ask me to skip. That was the first discrepancy I discovered in the early 1980's. As I sold combustion analyzers and helped my customers on their initial tune-ups, we noticed that the efficiency on the analyzer didn't go up and sometimes went down and they were saving thousands of dollars. My early customers were most commercial. The efficiency calculation on most/all combustion analyzers is off anywhere from 10% to over 50%. I have shown in class how I can adjust equipment poorly and the analyzer calculates the efficiency at over 90% and the actual meausured efficiency is less 50%.

One additional note, no one that has used a combustion analyzer properly has ever had to go to court.

Good info from From manufacturers rep RL Deppmann blog.

Dirty, plugged mod con HXers are when you may start seeing yellowed, over-heated PVC vent pipe.

@captainco , that might be due to the fact that a lot of installers only measure the gas pressure to the burners when setting up a boiler- if they check anything at all. Like yours, my analyzer has caught a LOT of out-of-tune gas burners.