Help with Rheem Imperial High efficiency oil furnace

arsenix2001

Hello, forgive the long winded post.  We have an older, mid 90's Rheem updraft oil furnace That had been working flawlessly for the last 30 years until recently it kicked the safety switch. We have a contract with Griffith energy who came out and service the unit. Long story short they ended up replacing the safety switch and eventually the igniters. Afterwards we had noticed oil smell in the vents and they came back out and said that the unit was burning too hot and adjusted the airbands to bring the temperature down.  Fast forward 3 months later and noticed that soot was visible on our chimney as well as in the furnace room outside of the barometric damper.  They sent another technician out who confirmed the wrong size nozzle was put in at the prior "tune up" (when all the issues started) and then opened up and found that the heat exchanger was completely caked with soot and spent the next hour vacuuming and cleaning everything out.  When he left he managed to forget to install the heat shield and screwed up a few other items. 

At this point I no longer trust in their services.  I am fairly proficient and mechanical matters and have been researching this oil furnace intensively for the last week and borrowed a Testo 310 combustion tool from a friend as well as a bachrach smoke tester.  I just want to confirm that my findings are okay as is.  The technician told me that he put a 0.85 burner nozzle in, which is the correct nozzle listed on our panel.
 
I am getting 4% 02, 10ppm CO.  (I did not go far enough to check efficiency. I realized I did not calibrate the unit in fresh air, only in our basement). Will need to reconfirm numbers. Overfire draft was bouncing around between .018 .032 avgs at .025.  breech was more stable at .045  This this was only after a 5-minute burn.  Stack temp at breech was 550 right before shutdown avg 500-520, less 72 degrees ambient for a 480 degree net stack temp.   Smoke test was a number 1 or trace smoke.

The Air band is currently opened to .5. About 1/8th inch and the air shutter is set to 6.  

Should I leave well enough as is? The stack temp seemed a little high and getting trace smoke but I know this unit is on its way out in terms of age.  I mainly wanted to just confirm something was not majorly out of whack.  Is it worth fooling with the air shutter adjustment or barometric damper?

Thanks in advance for any advice.

EBEBRATT-Ed

First of all if your are REALLY getting oil smell from your vents the heat exchanger could be bad. Or the smell if near the furnace could be getting sucked into the return air ductwork and then up into the house but beware of a bad HX at that age and use caution.

Stack temp is ok at 500-520.

Co2 should be 10-12max

Co should be 50 or less (50-100) is allowable but not good

Firing rate depends on correct nozzle size AND pump pressure.

Draft should be -.01-.02 over the fire

I can understand your frustration with your service company. Why not call the service manager or owner and give them some hell and "tell them you want their best technician if they have one".

Steamhead

EBEBRATT-Ed said:

First of all if your are REALLY getting oil smell from your vents the heat exchanger could be bad. Or the smell if near the furnace could be getting sucked into the return air ductwork and then up into the house but beware of a bad HX at that age and use caution.

(snip)

I can understand your frustration with your service company. Why not call the service manager or owner and give them some hell and "tell them you want their best technician if they have one".

Or call an independent service company. Where are you located?

EdTheHeaterMan

I looked at Griffiths website. They look like a pretty large fuel dealer serving most of Maryland and parts of VA. and WV. They should have some experienced oil burner experts, however someone younger needs to be trained on oil heat maintenance. It sounds like you got a trainee that needs more training. This is where all us oil burner experts started. Cleaning heaters. The problem is that no one tells the trainee that they screwed up and therefor they keep making the same mistakes.

OR

Those trainees don't want to keep servicing oil burners while the other technicians do the gas heaters and air conditioners. So if they screw up just enough, maybe they can be reassigned away from oil heat. Without a good training program, Oil Burner Service is becoming a thing of the past.

arsenix2001

Thank you for the comments.  I plan on giving them a call. Coming from a mechanical background myself I guess I just wanted to see it with my own eyes at least to verify that things weren't completely going haywire as they were before.  I have just lost faith since I've had three different technicians out and one of them seems to drop the ball in one way or the other.  It seems like the furnace is running within the spec. The overfire draft and flu draft seam slightly high.  I checked again last night and they were running 0.025 and 0.045 respectively avg.  Friday is supposed to be cooler and I'm going to crank up the unit and let it run for 10-15 minutes straight and recheck measurements.  I am tempted to adjust the barometric slightly but also concerned about creating more soot.  This thankfully at this point I have the tool to check.   If something is way off I think I will just give the service company a call and make sure I'm there when the technician is there to see what he is doing.

arsenix2001

Also I am located in Maryland, Montgomery County.  Any fuel oil smell disappeared after the second tech visit came and made adjustments.  The vents are odorless and I have done an ambient CO test in the furnace room and around the house which so far has come up zero PPM.

pecmsg

arsenix2001 said:

Also I am located in Maryland, Montgomery County.  Any fuel oil smell disappeared after the second tech visit came and made adjustments.  The vents are odorless and I have done an ambient CO test in the furnace room and around the house which so far has come up zero PPM.

How did you test for CO?

arsenix2001

Had the testo 310 set for ambient CO, calibrated in fresh air.  Did not pick up anything in room air.

arsenix2001

Finally was able to run a complete test.  Furnace running 10 minutes.  Unit calibrated in fresh air

O2  4.6%
CO 22 PPM

CO2 12.09%
Excess air 28.8%
Efficiency 80.3%
Stack temp 586 F

Net stack temp 514F
Draft over fire avg .024
Draft between breech and barometric damper .042

Everything look ok?  
Was planning on getting into the heat exchanger with an air gun and vacuum at the end of this heating season just a double check.

EdTheHeaterMan

I dont see a smoke reading. You really need to get a smoke spot tester in order to verify the point at which the reduction of air starts to create a trace of smoke. Without a smoke test you really can't tell if 28% excess ait is burning clean. Once I get the flame adjusted by EYE... I will take a smoke reading to determine if I can use less air or not. No smoke = ability to reduce air a bit more. #1 smoke = not enough air. Trace of smoke = my starting point for best seasonal efficiency. Once I get that trace of smoke, I take the CO2 and or O2 reading. if it is at 12.5% CO2 then I reduce the CO2 1% by opening the air adjustment. This will effectively allow for some dirt build up on the fan and air intake that will reduce the air delivery over the season. by the end of the heating season, that reduction of air into the combustion chamber will have increased the CO2 back up to 12 or 12.5%.

With this procedure you will have the most efficient operation with no soot build up on the heat exchanger over the season of operation. That is your goal. If you have a layer of carbon/soot on the heat exchanger, that equals unburned fuel. The carbon layer also acts as insulation between the flame / hot flue gasses and the heating media on the other side of the heat exchanger. So your CO2 and Stack Temperature may appeat to tell you that the efficiency is 80+% efficient. but that efficiency is only the burnt fuel efficiency. it does not include that wasted fuel that turned into soot. It also does not account for the loss of heat transfer as a result of the insulating quality of soot. I read somewhere that it is estimated that 1/8" soot has the insulation equivalent of a 1" fiberglass batt insulation.

Get a smoke reading... Get a smoke sample tool.

arsenix2001

EdTheHeaterMan said:

I dont see a smoke reading. You really need to get a smoke spot tester in order to verify the point at which the reduction of air starts to create a trace of smoke. Without a smoke test you really can't tell if 28% excess ait is burning clean. Once I get the flame adjusted by EYE... I will take a smoke reading to determine if I can use less air or not. No smoke = ability to reduce air a bit more. #1 smoke = not enough air. Trace of smoke = my starting point for best seasonal efficiency. Once I get that trace of smoke, I take the CO2 and or O2 reading. if it is at 12.5% CO2 then I reduce the CO2 1% by opening the air adjustment. This will effectively allow for some dirt build up on the fan and air intake that will reduce the air delivery over the season. by the end of the heating season, that reduction of air into the combustion chamber will have increased the CO2 back up to 12 or 12.5%. With this procedure you will have the most efficient operation with no soot build up on the heat exchanger over the season of operation. That is your goal. If you have a layer of carbon/soot on the heat exchanger, that equals unburned fuel. The carbon layer also acts as insulation between the flame / hot flue gasses and the heating media on the other side of the heat exchanger. So your CO2 and Stack Temperature may appeat to tell you that the efficiency is 80+% efficient. but that efficiency is only the burnt fuel efficiency. it does not include that wasted fuel that turned into soot. It also does not account for the loss of heat transfer as a result of the insulating quality of soot. I read somewhere that it is estimated that 1/8" soot has the insulation equivalent of a 1" fiberglass batt insulation. Get a smoke reading... Get a smoke sample tool.

Hi Ed, great information.  I forgot to include that I did take a smoke test, 10 pumps with a Bachrach tester.  Was in between 0 and 1 (trace). Closer to zero.  Will definitely be cleaning the heat exchanger again as well as the blower fan this month.