Technical/Service Questions & Answers
In keeping with its mission to enhance industry education & training, NORA’s R&D and Technical Service teams are available to answer your questions regarding the safe, reliable & efficient operation of your customer’s system.
Q – I accidentally set my analyzer for propane when doing a combustion test on an oil system. I spotted it and changed the fuel setting to oil. What would have happened if I did not notice the error?
Before answering your question, let’s review how combustion analyzers work.
Almost all analyzers work by measuring the O2 content of the flue gas and calculating a CO2 equivalent based on the fuel it is set for.
Some UEI brand analyzers use an optical CO2 sensor and read CO2 directly, if you were using one of these, no worries! Your CO2 number would be correct although your efficiency number would be wrong.
Assuming you were not using a UEI, your CO2 reading would be about 1.1% less than it actually was. This is a pretty substantial difference. If you set the unit for what you thought was 12% CO2 and it was 13.1% CO2 it could lead to a bad situation.
Alternatively, you could use O2 to adjust and you would always be right, regardless of the fuel. This is why it’s important to always set for a trace amount of smoke to determine which side of the curve you are on and then increase the air until you drop the CO2 from 1% to 1.5%.
It’s a good practice to always double check to be sure that you have the analyzer set for the correct fuel and have it calibrated according the manufacturer’s instructions.
Q – Curious if anybody has noticed on new equipment or even on tuneups a much lower amount of air then even suggested on air band to get desired 11-12 CO2 readings? I’ve been seeing new equipment coming through and
noticed the desired setting on the testo and zero smoke has always obtained by cutting off more air. So we trust our
eyes and our equipment and we see a 1.05 firing rate with a 0.75 setting on air band. I get that air band is guide but this seems to be a new trend. We are ultra low sulfur 20% blend.
Thanks for the question, since you mentioned a GPH setting on the air band, I’m going to assume you’re referring to a particular brand of burner although the question is applicable to all burners.
OEM (Original Equipment Manufacturer) burners are assembled to the appliance manufacturers specifications (mounting, pump pressure, nozzle, air settings etc.) for a specific appliance. As you have noticed, these initial settings often provide too much combustion air.
With new equipment this is done intentionally to provide a safety margin on the initial startup (no one can be sure of the unique conditions of each installation regarding draft, air temperature and other variables) so having conservative air band settings prevents smoke and soot formation before you’ve had the chance to begin the proper adjustment procedure.
Regarding tune-ups and service calls, it is important to remember that the manufacturer settings are a starting point and will not provide perfect combustion on every job.
To properly adjust the burner, once steady state has been reached:
1. Adjust the barometric draft regulator to the manufacturer’s recommendations, usually -.02? W.C. over-fire draft.
2. Set the burner air shutter/band to obtain a trace of smoke at steady-state operation.
3. At the trace level, measure the CO2%. Assume you have 13.0% CO2.
Now open the air shutter until this level drops to 12% CO2. Check the smoke level again, you should have zero smoke. Dropping the CO2 1% from a trace smoke setting will allow a safe margin before smoke generation begins due to draft variations, lint accumulation on the fan and/or air gate, heavier oil being delivered, or other adverse variables that may be encountered.
Always use OEM specs as a starting point and then adjust as necessary to the desired results using combustion testing equipment and remember that pump pressure testing must be conducted at the pump outlet, NOT at the bleeder!You mentioned that your company supplies ultra-low sulfur B20. At the B20 level, CO2 will be less than 1/10th percent lower than with #2 oil with the same air settings. Keeping in mind the 3/10ths percent plus/minus margin of error for combustion analyzers, this is indistinguishable.
Q: Does UV rays from the sun affect #2 heating oil? i.e., as would be stored in a white plastic drum.
Yes, exposure to light will accelerate degradation of #2 oil. It should NOT be stored in a container that will be exposed to sunlight.
Q – I recently read a sticker on a new oil tank and it said, “Do not transfer oil from the old tank to this new tank.”This makes no sense, what are we supposed to do, pay to throw away oil that the customer paid for and then charge them for new oil?
Research has shown that transferring oil from an older tank, even when filtered, can move “microbes” into the new tank.
These microbes multiply at a rapid rate and excrete acidic substances that can lead to failure of the tank, filters, oil lines and other components. A few years ago, UL changed the labeling requirements to remind installers that transferring fuel often leads to premature tank failure, sometimes within one year.
It is best to delay non-emergency tank replacements until the oil level is low and a minimal amount of oil has to be disposed of.
If a tank is leaking and/or needs to be replaced ASAP, installers should consider using a temporary tank to enable the customer to use up as much of the oil as possible.
While this does complicate the replacement process, it is much better than risking failure of the new tank and additional cost (including clean up expenses) and inconvenience for the customer.