Random lockouts on Wayne burner

zepfan

We are having issues with an old Wayne burner model #M-SR. Installed on a Whirlpool forced air furnace. I believe it was installed in the mid 1980's. The homeowner has kept up with the cleaning, and maintenance. The problems started las winter where the burner motor, coupling, and oil primary were all replaced in a span of six weeks. The burner had had no issues so far this winter, up until last week. Since then the homeowner has had to reset it once a day. It went offline this weekend, then the homeowner cleaned the furnace, changed the oil filter, and nozzle, and it stayed online the rest of the weekend. It locked out this morning, the homeowner reset it and it stayed online all day today.

I went by and had the following readings:

smoke- trace to 0
over fire draft- .01-
draft in the stack- .04-
o2- 6.7%
co2- 9.5%
undiluted co- 3ppm
diluted co- 1 ppm
cad cell when firing- 150 ohms
fuel pressure- 105 psi

I cycled the burner probably 10 times and it lite off instantly ever time. The only things that I noticed that were low in the above readings were the co2 being a little low and the cad cell readings being lower then I normally see them. I am used to seeing 400-800 ohms with the burner firing. I still don't think that this would cause this random lockout condition. Any ideas as to what could be causing this would be much appreciated. Thanks to all

STEVEusaPA

With the homeowner working on it, and someone firing the parts cannon at it, who knows?
I don’t understand your smoke number. Is it 0 or is it a trace?
What is your excess air?
Why were all those parts changed? Was there excessive back pressure? Is there a problem in the CAZ?

EBEBRATT-Ed

Check chimney, draft, back pressure, and make sure the furnace is clean.

Also, Run the indoor blower without running the burner with your draft gauge in the burner peep hole. Start and stop the fan a few times. If the draft gauge moves you probably have a bad heat exchanger.

I am thinking back pressure as well as @STEVEusaPA mentioned. Was the coupling melted, motor overheated?

Mid 80s for an oil fired furnace is a long time, pushing 40 years.

Grallert

Nuisance lock outs are the worst. Is there smoke on start up? Is there an iron core ignition transformer in place?

SuperTech

Was a  modern primary control like the Carlin 70200 or Honeywell/Resideo R7284U installed? These will help you troubleshoot the issue by indicating the cause of the fault in the history. 

zepfan

Thanks to all that responded. To clarify the homeowner has just done the general maintenance. Nozzle, oil filter, and furnace cleaning. All the parts were changed last winter because they went bad. The burner was making a ticking sound, the coupling was changed, everything was good. Six weeks later the burner would not attempt to fire, so the original oil primary was replaced with a Honeywell R7884U. All was good. Six weeks later the burner motor locked up, and it was replaced. All was good. Again all these repairs were replaced last winter, and so far this winter the burner has run without issue until last week. since then it has been any every other day lock out. Yes I agree that 40 years is a long time and after this winter the furnace should be replaced. The homeowner if possible would like to limp this unit through another three months.

As far as the excess air and the smoke. The excess air I can get, as I left the combustion test print out at the home, and the smoke is between a 0 of no smoke, and just a slight grey area on the paper. So maybe we could call it a 1. As far as the CAZ I assume this is the electrode gap distance setting? That is right on what the description shows it should be on the burner. What normally should the excess air be on this old of a residential burner?

Also as far as the puff back. I did notice in the 10 + that I cycled the burner that once every 4-5 times there was puff back. The other times it would light off smoothly. Could this be caused by a bad heat exchanger? The draft both over fire and in the stack appeared to be ok.

Thanks again to all

EBEBRATT-Ed

Possible bad HX. What is the oil line installation like . Inside tank, outside tank gravity feed or overhead lines? etc etc

HVACNUT

The MSR is a 3450 retention head burner so it should make it over 10.5% CO2.
Check that over fire draft with blower fan off, then on with burner running. Rule out the heat exchanger. 
Is there oil on the head and nozzle after lockout? Could be a weak ignitor.

zepfan

Thanks for the responses. The oil line installation is single pipe, with the tank located indoors in the next room. The line runs along the floor no more then 25' run to the burner. The pump is a Suntec A2VA-7116 that was replaced in 2020
thanks again

zepfan

The excess air that I measured on this burner was 58.3%. According to the burner manufacturer it should be 50-60% so that appears to be in range

HVACNUT

25-30% excess air.
4.5 - 6.5 O2 as long as 0 smoke and draft is where I want it.
CO should be below 50 ppm.