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Hey oil guys!

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icy78
icy78 Member Posts: 404
in Oil Heating
Hello all. I agreed to help out a friend in difficult times, BUT i have very rudimentary oil skills. I am pretty good with other heating equipment tho.
He has a MOC-80 Miller furnace in a mobile home from around 1970 I think.
Its running "well" but needs a check
( its been 8 years since its last service.)!
I'll need to get a tune up kit and clean it and I can borrow oil tools from a guy I know, and I can diagnose my combustion analysis.
Now my main question is, apparently this furnace has a unique design....according to the patent from 1963. As such, it doesn't need, and doesn't have,
a barometric damper.
So on the draft side of things, how does the burner get set up without setting flue draft? Does one just get an over the fire draft and how do I prove combustion quality? ( I like to test all I can and feel safe walking away)
In the link, 3rd paragraph down states the furnace can be used for gas or oil models, so I'm assuming there's not a barometric requirement for oil.







There is also only about 14" between the unit top and the ceiling/roof. About 5 ' total flue length.

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,835
    edited October 2022
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    Hello all. I agreed to help out a friend in difficult times, BUT i have very rudimentary oil skills. I am pretty good with other heating equipment tho.
    He has a MOC-80 Miller furnace in a mobile home from around 1970 I think.
    Its running "well" but needs a check
    ( its been 8 years since its last service.)!
    I'll need to get a tune up kit and clean it and I can borrow oil tools from a guy I know, and I can diagnose my combustion analysis.
    Now my main question is, apparently this furnace has a unique design....according to the patent from 1963. As such, it doesn't need, and doesn't have,
    a barometric damper.
    This is because the return air opening is in the same space as the exhaust pipe to the "Roof Jack" (Manufactured Home chimney)
    So on the draft side of things, how does the burner get set up without setting flue draft?
    . That is a direct vent system. Combustion air from under the home and exhaust out the top. Draft is forced by the combustion fan (oil burner fan)
    Does one just get an over the fire draft and how do I prove combustion quality? ( I like to test all I can and feel safe walking away)
    The over fire draft will actually be a positive pressure.
    In the link, 3rd paragraph down states the furnace can be used for gas or oil models, so I'm assuming there's not a barometric requirement for oil.

    Correct NO BAROMETRIC! You can drill a 1/4" hole in the exhaust vent connector and take a smoke reading and use the combustion analyzer for O2, CO2, CO and temperature. That may mean removing the small piece of paneling above the furnace on some homes. BE SURE TO SEAL THE HOLE WITH HIGH TEMPERATURE SILICONE OR RTV CEMENT. The hole will be in a negative pressure zone when the blower comes on and that will suck exhaust gasses thru that hole! Metal duct tape will fall off eventually, so don't us it to seal the hole.

    Hope this helps
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,835
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    I like to use the .60 80° or 90° hollow nozzle for that burner. Delavan A is hollow. or the Delavan .60 90°W also works well. Get extra. I find the most people do not know the proper way to handle a nozzle and will push dirt thru the cindered filter and the nozzle gets partially plugged within a few hours after a tune up/maintenance.

    To avoid this I flush clean fuel thru the high pressure line into a bottle, after changing the oil filter and cleaning the pump strainer(if equipped). Let if flow for 10 seconds after the fuel runs clear. Also I only handle the nozzle by the hex sides. Never touch the orifice or filter sides of the nozzle.

    If you already know this please do not take offense. Just trying to keep the nozzle from getting plugged.

    I also flush the nozzle assembly tube and use a pipe cleaner to force any debris from inside that pipe. Then flush again with water or fuel. I personally do one more step and use a 3/16 flare cap to cap off the open end of the nozzle assembly tube and fill the nozzle adaptor side with clean fuel. Then insert the nozzle into clean oil, then spin it on the adaptor. a small amount of oil squirts out like a squirt from a needle from your doctor giving a flu shot. (adds to the suspense of the process if the customer is watching)

    This also reduces air pockets in the high pressure line that cause after drip.

    But this step is not necessary if you don't have anything to cap off the flare end of the tube.

    Those small diameter orifices and internal slots in the nozzles below .85 GPH can get clogged much easier than the larger ones.

    I hope this helps

    Mr. Ed
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Steamhead
    Steamhead Member Posts: 16,835
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    "Nu-Way"? Didn't realize they were still in business when that furnace was made...............
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • heatdoc1
    heatdoc1 Member Posts: 14
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    Worked on many of these over the years. They are designed to run without a barometric and will usually be -.01 to -.02 over fire with a standard mobile home chimney height as long as the heat exchanger is clear. If you are going to clean it just be prepared for a long job. You need to remove the burner, the lower front of the jacket, the burner mounting plate and the chamber to get to the cleanout on the rear of the unit. Based on the age of the unit I would make sure you have a chamber available as well as the gasket kit for when you put it back together. If it hasn't been taken apart for a while you may snap the bolts. If they are burning kerosene you wont have much buildup to clean but if they were running the old high Sulphur fuel it will most likely be pretty full.
    John Ringel
    Senior Technical Support Specialist
    Energy Kinetics
    EdTheHeaterMan
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
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    Wow brings back memories . 50 year old furnace ....
    I have enough experience to know , that I dont know it all
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,835
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    If you are going for the full service cleaning then these are the 2 parts @heatdoc1 recommends you want to have on hand.

    https://www.supplyhouse.com/Lynn-Manufacturing-1029-Replacement-Combustion-Chamber-for-Miller-Nordyne-Mobile-Home-CMF-MOC-MGC-901818
    https://www.supplyhouse.com/Lynn-Manufacturing-9510-Replacement-Gasket-Kit-for-Miller-Nordyne-Mobile-Home-CMF-MOC-MGC-301205000-660604-688982-689032
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • icy78
    icy78 Member Posts: 404
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    Thank you all for the responses. I have a heck of a lot going on right now and don't really have time to think about what I read here, and respond.
     I will in the near future tho.

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