We recently had our Peerless wb/wv-03 serviced and a new Beckett burned installed. The combustion tests after the new burner are showing a pretty good loss of efficiency and higher flue temp.
2021 Results
02 - 5.7%
CO - 20ppm
Eff - 84.9%
C02 - 11.43%
Flue Temp - 431
Ambient Air - 62.8
Excess Air - 34.9%
2022 Results
02 - 6.0%
CO - 22ppm
Eff - 85.8%
C02 - 11.19%
Flue Temp - 359
Ambient Air - 67.1
Excess Air - 40.2%
2023 New Burner Results
02 - 5.8%
CO - 48ppm
Eff - 81.4%
C02 - 11.3%
Flue Temp - 542
Ambient Air - 57.8
Excess Air - 35.5%
The company is telling me the higher efficiency numbers from previous years are because the previous company was cheating the test and not letting the flue get up to temp. If a flue temp of 542 ok, or is it high? I agree that the higher the flue temp the lower the efficiency as more heat is just going up the flue. The Peerless is from 1996 and we were originally looking at replacing it, during the site visit the company said it looks great and the efficiency numbers are still great(looking at previous combustion test slips) and that all that is needed is a new liner and a new burner and we will be set for another 10 years easy. I thought this was great, till I saw the new combustion test results.
Does this burner need a different nozzle? Does the flue draft need to be adjusted? Were the previous combustion tests just bogus and the new company is right?
Comparing 2023 test results to earlier years is not meaningful because 2023 has the new burner. If any year test was not completely automatic, it could be biased by the technician. Ask the company that did the 2023 test for the calibration certificate on the instrument used for the test. If the certificate is more than 1 year old I would ask for a retest using an instrument with calibration within the last year. You could also ask the 2023 company how they know the old burner was not at maximum temperature when testing performed. Sounds like BS to me.
Page 17 are the burner settings they are looking for.
IMO a lot of those numbers don't mean much for an oil burner. You want STACK TEMP., SMOKE, DRAFT (over fire & smoke pipe) CO2. The results of these settings and readings determine your boilers efficiency.
The tests can be fudged by adjusting the air or not letting the boiler completely heat up to get the proper stack temp as the last service tech mentioned. or depending on the equipment if it is calibrated properly. I think the 542 seems a little high but the 359 seems low and is suggesting either too much air which will give you a cooler fire or the stack therm. removed too early. The 542 could possibly have a nozzle that is a little too large for the boiler, producing a higher stack or it could be right for a 26 yr. old boiler even with a new burner. Your efficiency also depends how the boiler is designed and baffled to slow down the wasted heat to the chimney.
The new results. 2023 New Burner Results 02 - 5.8% CO - 48ppm Eff - 81.4% C02 - 11.3% Flue Temp - 542 Ambient Air - 57.8 Excess Air - 35.5%
What they are not giving you is over fire draft when the unit is running. What this shows is the last company has too much air on the boiler.
CO2 should be between 12 - 12.5%. This will be less air on the boiler, and lower stack. As long s the stack is a minimum of 350f your stack temp is good.
The overfire draft should be less than -0.04 but I would suggest -0.02.
Please post a picture of boiler and show vent hole where tested and the draft regulator.
Can any HVAC tech provide the equation the test instrument uses for calculating efficiency? Without it, how does the tech know which measured parameter to adjust for the greatest increase in efficiency? What are the parameters for an efficiency of 100 percent?
Anybody with a combustion analyzer should be able to perform the test. If qualified, they should also understand what to do with the results.
The two big ones are CO2 and Overfire draft. The reason I say that is adjusting air to get a different CO2 will affect the flue temp (vent) temperature as will Overfire draft.
Always adjust the draft first with boiler running before adjusting air/CO2
Recheck draft.
On chart below Frozen13 data 84.9% correlates stack chart temp 431 less 70 F room temp,
DH does not use data or ask maker of his Weil-McLain 1957 boiler anything. His measured stack temp is 350F minus 70F room= 270 F for 86% on boiler rated for 1.5 GPH
Boilers are heat exchanges and manufacturer BTU rating are maximum. Easiest way to increase efficiency is with smaller oil nozzle to reduce firing rate BTU’s. DH uses nozzle and pressure for 0.80 GPH, and not 1.50 GPH rated.
On most oil non condensing oil burners max efficiency is less than 86% when adjusted properly. Using measured stack temp, less boiler room temperature find efficiency on chart.
Thank you all for the info. The burner sounds like it's running better than our old one and the installation work looks great. We mainly heat with wood so don't burn a lot of oil, to begin with. I think we will leave it as is for now and see what the combustion test results are during its first service this spring/summer. Thank you again for all the info and I'll be asking for additional testing parameters during it's first service.
Had to put on a new air vent canister on my boiler today, there's a little blk plastic cap on the top of the vent, do I keep it closed tight or do I turn it to loosen it up a little?
I understand that this valve doesn,t have a built in check valve thus allowing water to back up upstream in the system. If this is the case does that eliminate the need for an expansion tank.
01-13-23, 12:26 PM
