Combustion analysis results question

northernboiler

We were repairing some components on a single pipe steam system today, and unrelated to the job, the customer asked us if we would look at the boiler. He has had to reset the spill switch located on the draft hood from time to time.

I performed a combustion analysis and here are the results.

(allow me to preface this by saying we work mostly on oil. We do a lot of steam, especially repairs but do not do a lot of NG service- on the burner side)



net stack: 265 F

CO2: 3.83

EFF: 80.1%

O2: 14.1%

ex air: 182.7%

CO: 10 ppm

CO air free: 20 ppm



draft: -.0233



Also the flame color looked a bit orange/ reddish to me.

Not blue.



Boiler is a Burnham Independence atmospheric draft with an electronic draft control.

Steam boiler.



Any help or suggestions?

Zman

Underfired

Are the burners clean?

How is the manifold pressure?

Carl

Tim McElwain

First question did you have the analyzer

set for gas?

net stack: 265 F

THIS IS TOO LOW ANYTHING LESS THAN 275 IS A PROBLEM



CO2: 3.83

NORMAL FOR A TYPICAL GAS SYSTEM WOULD BE BETWEEN 8 TO 9.5 CO2. SO THIS READING IS WAY OFF



EFF: 80.1%

THAT NUMBER WITH THE OTHERS IS INSANE

O2: 14.1%

THIS MEANS THE EXCESS AIR IS 150 % OR MORE (YOUR NUMBER 182.7%) IS OFF THE CHART. SO SOMETHING IS DEFINITELY WRONG EITHER WITH YOUR TESTER OR THIS BOILER. NORMAL FOR O2 IS 4.5% TO 7.5% WHICH GIVES EXCESS AIR OF 25 TO 50 %.

ex air: 182.7%

CO: 10 ppm



CO air free: 20 ppm I  SERIOUSLY DOUBT THIS READING.



draft: -.0233



I would check the gas pressure inlet and outlet at the gas valve also clock the burner at the meter. There have to be air leaks or you are not taking the readings correctly. Do you have a draft hood on this equipment? Is the draft hood a part of the boiler or is it in the flue pipe?

northernboiler

Answers:

Yes my Testo was set to Nat Gas.

The draft hood is part of the boiler, before the stack mounted electronic vent damper.

It is a standing pilot boiler.

I am aware the readings were way off. But, again, we work mostly on oil fired boilers.

That being said, I knew based on these readings I needed advice from someone who knows better than I.

I was not about to start, "trying this and that"

This all started because the customer asked, while we were there repairing steam line problems if we could look at the boiler because he has had to reset the spill switch a few time over the few months.

The chimney is lined, it has a rain cap.

However I noticed the flame color when it was running didn't look correct. Too reddish/ yellow. So I took the combustion reading. I drilled a hole above the integrated draft hood and above the damper to obtain the readings.

When I saw these numbers, I stopped there and decided to obtain an opinion and guidance from some more knowledgeable people.

I did not take a wc reading for I need to be sure what range they really need to be .

JStar

Combustion

You need to take the test BEFORE any draft hood. That explains your diluted readings. You can stick the probe up into the draft hood and rest it on top of the boiler sections. Just don't melt the plastic!

icesailor

point of testing:

Not to sound mean but you wouldn't do a oil analysis ABOVE the barometric draft damper.

Draft hoods on gas equipment are a form of draft dampers. For dilution of the heated gasses. I always stuck it into the bottom of the draft hood to get ir=t as far away from the dilution air as I could. Like JStar said, on top of the boiler block, just don't melt the plastic. 

My Bacharach "Insite" has no plastic.

Tim McElwain

Better yet

drill holes through the front of the draft hood one for each section take individual readings and average them out. Seal them up after with high temp RTV sealant.



The yellow from the flame can typically be eliminated by adjusting the primary air shutter for a soft blue flame not roaring not lifting. Make sure all doors are in place when taking the readings.