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Power vent timing

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SeanR
SeanR Member Posts: 1
in Oil Heating
For those of you out there that use power venters on oil burner setups, how long is the recommended time for the post purge cycle?

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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
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    3 minutes is a good start
    steve
    billtwocase
  • billtwocase
    billtwocase Member Posts: 2,385
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    3-5 minutes. Is the burner's control also post purging? No need to if it is
  • captainco
    captainco Member Posts: 793
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    I sold a lot of power venters and a 90% condensing oil furnaces. Like it or not the minimum post-purge we could get by with to eliminate smells and after-drip was 8 minutes. Gas can get by with 3-5 minutes not oil.

    The furnaces I sold came with 5 minutes timers and we had to change everyone to 8-10 minutes.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
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    Wow 8 minutes.
    steve
  • captainco
    captainco Member Posts: 793
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    Much of it had to do with the combustion chamber radianting back into the airtube and heating up the oil in the drawer assembly and creating a delayed afterdrip. This was discovered by a rise in the CO readings more than 30 seconds after the burner shutdown. Sometimes it just had to do with smells and overcoming negative building pressures.
  • billtwocase
    billtwocase Member Posts: 2,385
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    Keyword is condensing unit. Non condensing oil unit 3-5 is sufficient
  • captainco
    captainco Member Posts: 793
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    Field Controls has an adjustable post-purge timer on their PVO Power Venter for oil and it goes up to 10 minutes, thanks to me. I am sure with a really short flue 3-5 might work but not on longer flues. 8 minutes work every time to prevent the combustion chamber from radiating enough heat back into the airtube and eliminating afterdrip. Without testing for CO for at least a minute after shutdown you wouldn't know if you had this problem or not. That is when trial and error on setting the timing began.

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