Oil furnace draft question??

rowdydog99January 24, 2008

I have a Tempstar NOMF105D12 furnace. The furnace is setup up to fire at the middle of the three firing rates. 74k output capacity. The flue draft spec in the manual is -0.06 to -0.025" wc. The overfire pressure draft is speced at +0.01 to 0.025" wc. This ranges my draft regulator damper door to be fully open to fully closed. Should I shoot for the middle of the road after doing an initial air shutter adjust.


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You have to have a draft meter to do this. Usually the draft over the fire, while firing, is negative .01 - .02 and the draft at the stack is neg. .02 - .04.

The draft damper is used to set the draft over the fire. It has to be done correctly.

    Bookmark   January 24, 2008 at 4:45PM
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I have a Draftrite gauge and have set the the draft to the following. The flue draft is -0.03" wc and the the overfire pressure draft is set to +0.01" wc. I'm assuming the positive pressure specified in the furnace manual is due to the design of the baffle in the output area of the heat exchanger. Is anyone familiar with setting this type of fire box design with a positive pressure. I have attached a link to the installation manual for this guy which shows the spec for the draft settings.

Thanks for your reply!

    Bookmark   January 25, 2008 at 7:48AM
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I went to the site:
what are you putting in for the login?

    Bookmark   February 1, 2008 at 11:25PM
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I have another way in. Try
look up residential oil furnaces and you can find the manual
NOMF Multi Position Warm Air Oil Furnace French & English Installation and Operation Manual (6-20)


    Bookmark   February 5, 2008 at 11:52AM
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I finally got there. I would agree after looking at the schematics.
They have introduced the baffle assembly and it will add pressure in the firebox. If you set for the max draft; you might longer between cleanouts but you'll send money up your chimney. Middle of the road will save some. Thanks for the links by the way - good info there.

    Bookmark   February 6, 2008 at 3:01PM
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Thanks for the reply. I will try middle of the road and re-check at a the end of season. The net stack temp seems a little high at 490-500 F. Maybe this is all I can expect with this setup.


    Bookmark   February 7, 2008 at 2:45PM
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