Calculating combustion efficiency on oil fired systems

GW

I didn't follow that; maybe I'm a little slow.

Anyway, the only affect your low temps will have is a "higher" number in terms of combustion efficiency. The flue gas temp has a direct relation to the medium of which the appliance is heating (water, air). The combustion test doesn't make a distinction between water temps, so you obviously will have higher efficiency numbers at lower boiler temps. It is what it is; keep in mind these are man-made numbers, so don't get all excited when your new install is showing 89.6% efficient.

Anyone with half a clue knows you can easily massage the efficiency numbers just by moving the magic wand around in the flue (hood, pipe, either one). My main goal is to make sure the appliance is safe (co), second goal is to make sure the temp, o2/co2 is normal for whatever I'm working on, third goal is to instill faith (in the new appliance) for the home owner.

Once the o2/co2 numbers stabilize, and your co stabilizes, you're at steady state. If anyone says you have to be at full temp to achieve this, I would have to disagree from a "real world" perspective.


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Ray Landry_2

At what BOILER WATER temperature do you guys set up your oil burners (particualary buderus) I've always set up at 180 but when using outdoor reset should combustion numbers be taken at lower boiler temps to ensure proper co2 zero smoke ect ect?

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lee_7

boiler temp should not matter for combustion effiency test. Unit needs to run to steady state of combustion for proper test.

Alan R. Mercurio_3

Just my opinion, but for what it’s worth when testing for combustion efficiency regardless of boiler temperature I’d be more interested in the steady state flue temperature. Grant it the boiler temperature will have an effect on your combustion results but your question is about combustion efficiency. I hope I have made some sense?

Your friend in the industry,
Alan R. Mercurio

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Ray Landry_2

Thanks guys for the input. I now realize I mis-worded myself when I asked the question intially. Let me try again. My conern is with the quality of the fire in a three pass cast iron oil boiler firing with an out door reset control. I realize what you are all saying about waiting until all of your combustion numbers even out and you're at steady state, but couldn't one argue that boiler water temperature does have much to do with your stack results as it will directly effect the net stack temp, your 02 may not stabilize, your co could be through the roof ect. I know what it takes to make a boiler safe once steady state is achieved, but again if you've got a temperature maintaning boiler firing on a heater curve (IE:Buderus G115) that on a should day only fires to 115 degrees, does this make for a bad fire and lead to sooting because the numbers can't equalize as they did during the stack results? Maybe I'm way over thinking this one help me out here guys! It also occurs to me that with a properly sized boiler even a boiler firing to 115 degrees on a shoulder day probably will have some sort of steady state burn achieved, but what if there is no draw on the boiler and it's just firing to maintain?

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Ray Landry_2

Thanks guys for the input. I now realize I mis-worded myself when I asked the question intially. Let me try again. My conern is with the quality of the fire in a three pass cast iron oil boiler firing with an out door reset control. I realize what you are all saying about waiting until all of your combustion numbers even out and you're at steady state, but couldn't one argue that boiler water temperature does have much to do with your stack results as it will directly effect the net stack temp, your 02 may not stabilize, your co could be through the roof ect. I know what it takes to make a boiler safe once steady state is achieved, but again if you've got a temperature maintaning boiler firing on a heater curve (IE:Buderus G115) that on a should day only fires to 115 degrees, does this make for a bad fire and lead to sooting because the numbers can't equalize as they did during the stack results? Maybe I'm way over thinking this one help me out here guys! It also occurs to me that with a properly sized boiler even a boiler firing to 115 degrees on a shoulder day probably will have some sort of steady state burn achieved, but what if there is no draw on the boiler and it's just firing to maintain?

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EBEBRATT-Ed

Well?????????? I'm not convinced. Some boilers produce better #s when they are hot. Cold combustion is no good. The exception to this is condensing boilers. Most of the time you can get better numbers when the enviroment you are burning in is hot. jmho


ED