OLR105A12C Oil furnace combustion analysis

mlm71570

Hello all, I have a question about idea settings for this furnace. i recently purchased a testo 310 analyzer and was able to get the following readings: O2=5.7, CO=4ppm, flue gas temp=506 F , EFF=83% , draft of -023, excess air= 34.9%, CO2=11.43%. Just a few notes, the nozzle is a .65 70a, which should be a .60 70b. Also i was not able to get the draft any higher as the manufacturer says the range is .03-.06 negative. i do not have access to above the flame for readings on this furnace. Please let me know if i am close with settings. Thanks

EBEBRATT-Ed

Your readings look pretty good. -.02 over the fire draft if you can maintain that should be ok. As far as the nozzle goes these are your readings with a "A" nozzle which is hollow. If the burner is recommended with a "B" nozzle which is solid I would try it. Do not make any adjustments and see which one gives you a better readings. The manufacturer doesn't always know best.

If the furnace and flue and chimney are clean and your draft regulator is basically closed then you are getting all the draft you can.

If the draft becomes marginal you could try to reduce the input slightly by installing a .60 nozzle (and readjust air) which could give you more draft. a reduction in input (less air and oil) should give you more draft unless it drops your stack temperature too much which a low stack temp can reduce your draft but I don't think that will happen.

You didn't mention a smoke test but you want to be at 0-trace of smoke.

Make sure you use your test equipment to verify combustion.

mlm71570

Thanks for the response. Let me clarify that my -02. was NOT over the fire but in the flue. I cleaned the flue and base of chimney but i was not able to clean the heat exchanger, i checked nozzle and spark though. I did do a smoke test but when i get it to a 0-trace ( adding more air) , the CO,O2 and flue temp go up. So i got it to about a 1-2 and was wondering what would be the MAX CO ppm, max O2 and Flue temp if i add more air. Basically i just want to make sure that i am not on the wrong side of settings.

STEVEusaPA

1 or 2 smoke is not good. Was the spot black, or wet/yellowish?
Did you try the correct nozzle and confirm pump pressure? This is probably most important. Ed was leading towards the start of a nozzle substitution test.
Does it require an low fire baffle, and if so, is it installed?
Did you check the z dimension?
Why couldn't you clean the heat exchanger? This to me would be a deterrent to proper draft.
Why can't you get an over fire draft reading?
For air, the easier way to make sure you're on the right side of the curve would be to close the shutter a few settings, and do a smoke test (you want to see black), then start opening the shutter and rechecking until it clears up. You should always be at true zero smoke.
-What does the end cone look like? Any cracks, warped, dirty?
-How about venting? Describe the flue pipe from unit to chimney base (length, elbows, tees, etc).
-What type of chimney, and how high?

mlm71570

The spot was not black. I have not gotten a nozzle as of yet, probably get one in the next day or so. i will need to get a gauge to check pressure. It is a AFG burner with F0 head, which i believe it has a low fire baffle, but i will confirm. Z dimension? do you mean the z2000 tool, if so yes i did and reset it. I looked around for clean outs but i was only able to locate a plate above burner which i vacuumed out ( it had very little soot in there). Should i remove burner and clean pot? or do i need to take apart furnace? there is a glass sight window and i didnt want to drill a hole on case. Should i remove glass sight and use this port? how far do i put probe in? End cone? As for venting, its a old 30' approx masonry chimney with approx 10-12' of flue pipe and (1) elbow. I was able to get to a trace of smoke but my question was how high do you go with regards to CO,O2 and flue temp? thanks for all these great questions! As Ed was leading to, i will change nozzle and retest and will let you know the readings without changing anything.

STEVEusaPA

I wouldn't pull the burner unless you saw lots of soot in the clean out or thru the flue pipe. You could easily damage the chamber with a vacuum.
Un bolt the access door. I use a garden hose, attached to my vacuum. You should be able to push it more than half way around the heat exchanger from each direction.
The sight glass should unscrew to take an overfire measurement. Over fire draft should be 0 to +. 035. And flue, as you mentioned -.035 to -.06 for chimneys.

Chimney connectors are not suppose to be longer than 10', and the Total Equivalent Pipe Length of the connector is not to exceed 75% of the chimney's height.
Here's a manual for the furnace:
http://www.utcccs-cdn.com/hvac/docs/1011/Public/05/X40083_Rev_Z_ICP_22115.pdf
And here's an article about proper flue pipe design, right from Dragon's excellent book. I recommend making copies of the charts, they are great for troubleshooting.
http://fueloilnews.com/2016/06/23/flue-pipe-design/

As far as final numbers, here's what I do, after you put in the proper nozzle, confirm pump pressure (calling for 156psi on your unit), band/shutter 0/7.5. Confirmed nothing on end cone, not cracked.
-Run unit for 10 minutes
-Check and adjust draft to specs. Over fire is more important than at breech.
-Lower shutter to 6 (if you're starting at 7.5).
-Do a proper smoke test. A proper smoke test is taking 3 seconds to pull, hold for 3 seconds, return for 1 second-repeat 10 times. Pumping too fast will give you a false reading.
--At this point you should see a readable smoke number. Open shutter one number, repeat until you have a 0 smoke.
Then I check combustion with the analyzer. After that, I will open the shutter until the CO2 drops 1% point.
-Now see where you are with your numbers, excess air, CO and efficiency.

If you have poor CO2 numbers, or really high excess air and/or high CO, I would investigate a cracked heat exchanger. At this point I would check draft/numbers with blower motor on and off. If they differ, then I would pull the burner and start looking for the crack.
Keep in mind when you pull the burner, you are probably going to have to replace the gasket-hopefully you have some on hand.

mlm71570

Steve, thank you for the response. i will let you and ed know once i change nozzle and check pressure.

mlm71570

Steve,
I finally got around to changing nozzle and vacuumed around heat exchanger like you suggested. These are the settings I was able to get which I think seem too high. 0-1 smoke; 0/7.5-8 air; 7.2 o2; 10.3% co2; 48.8% excess air; co 1ppm. When i close down air i get better readings but more smoke. What should i do?