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Thread: Oil burner primary control.

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  1. #1
    DIY Junior Member
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    Default Oil burner primary control.

    Just a few simple questions for anyone with oil burner controls experience. Some primary controls are intermittent, some constant and some are interrupted. What would be the differences and how would they affect the burner operation? Can they be interchanged? What would be the determining factor in the decision for chosing one over the other and consequence for installing the wrong one. Thank you in advance.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Sounds like a homework question...have you read your textbook?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Retired HVAC Tech SHill's Avatar
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    Generally, intermittent means that once the burner goes on, after a few seconds of established flame, the ignition transformer cuts out. Constant means just the opposite. The transformer sends a constant spark thru the electrodes. I'm not familiar with the interrupted type.

    Most all controls now a days have the intermittent control. Depending on what unit you have, depends on what type you can use.

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    Engineer Furd's Avatar
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    Close, but not quite correct. Assuming that the question is asked in reference to oil burner primary controls the answers are:

    The terms are really constant ignition, intermittent ignition and interrupted ignition.

    A constant ignition would be a constantly burning source of ignition such as a gas pilot flame. These are only found in commercial and industrial sized equipment, and not very often these days.

    An intermittent ignition would be an ignition source for the main burner that was energized prior to the main fuel valve and remained energized during the entire time the main burner was being fired. In a residential application this would almost always mean the spark ignition transformer would be energized during the entire time the burner was iin operation.

    An interrupted ignition would be an ignition source for the main burner that is stopped some specific time after the main burner fuel valve is opened. In residential service this means the ignition transformer is de-energized after the main flame is established.

    A typical residential system would sequence as this:
    1. Call for heat from thermostat.
    2. Blower motor and ignition transformer are energized.
    3. Blower and fuel pump (common shaft) come up to speed while transformer sparks via electrode gap.
    4. Atomized oil is ignited by spark.
    5. Flame sensor "sees" flame and via electronic circuitry shuts off power to ignition transformer stopping spark.
    6. Burner continues to operate as long as thermostat is calling for heat.
    7. Thermostat is satisfied, burner motor is de-energized, blower and oil pump slow down and oil pump "clean cut-off valve (internal to oil pump) closes stopping flame.

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    Retired HVAC Tech SHill's Avatar
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    I have to disagree with you. The term intermittent means just that, in intervals as when it is just starting up and flame is established, ignition drops out. Check your Honeywell primary control circuits & how they work.

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    Engineer Furd's Avatar
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    Go ahead and disagree, it still won't make you right.

    I am quite familiar with Honeywell primary controls and how they work. The following is a direct quote from my Honeywell Oil Controls Service Handbook.

    Underwriters Laboratories Inc. refers to primary control action as follows:
    1. Continuous ignition-igniter is on as long as the burner is in service, whether the main burner is firing or not.

    2. Intermittent ignition-igniter comes on when burner is energized and stays on as long as the main burner is firing.

    3. Interrupted ignition-igniter comes on when main burner is energized. It goes off automatically when flame is established or after a preset timing period.



    You may be confused because sometimes Honeywell uses the term intermittent ignition instead of the more proper term interrupted ignition. Honeywell's misuse of the proper term does not make it correct. By using the proper terms in the way that Underwriters Laboratories has defined them you can apply the same terms across all manufacturers of primary controls.

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