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Draft Control

Paul_9 Member Posts: 1
single vs double acting : why the single for oil &
double for gas. have a double on oil fired barfs back
on ignition. dont like the odor


  • Jim Davis
    Jim Davis Member Posts: 305
    Draft Regulators

    There is probably no logical reason for the difference between single acting and double acting barometrics. Some of the excuses may be oil blows smoke in the house so don't let the barometric open, like it doesn't leak anyway. Or gas fumes are okay in a house but oil fumes aren't? Double acting barometrics relieve positive pressure in flues and down-drafts. It is assumed that down-drafts blow out pilots. Therefore needed on gas not oil. If odors are coming in the building from the barometric it doesn't matter which one you have. Fumes come in because of improper equipment operation and enviromental conditions(negative pressure).
  • Double swing barometrics

    The reason for double swing barometrics on gas is to control the low end of draft when just the pilot is running by itself (no call for heat). The pilot do not forget creates its own products of combustion. The double swing can compensate for the low temperature that is generated by the pilot alone and give some ability to draft and get the pilots products of combustion to vent. Remember draft is created by Height of the vent and Delta "T" (temperature difference) It also important to remember that being able to get some rise on the vent before it goes into the chimney can help to vent the pilot products of combustion. Barometerics should not be used on design gas equipment unless authorized by the equipment manufacturer. Remember we are not design engineers we are installers and service personnel.

    The only time I have ever used barometrics on equipment was when we converted oil or coal boilers to gas with a conversion burner. When we used atmospheric conversion burners we used designed draft hoods in accordance with ANSI Z21.12. The only time we used them with power burners was on outside chimneys on low ranch style homes with 15 foot chimneys. I have also found they work very well with Carlin G3B and G3A gas power conversion burners.

    Some manufacturers show them now on side wall vented equipment or with certain types of systems that put the fan outdoors. They are used to balance the draft and are in accordance with manufacturers instructions. Make sure you read the directions for how to set them up.

    Be careful of arbitrary uses of so called solutions to venting problems. Go to the manufacturers of the equipment for solutions that way you are protected by factory authorized changes to that equipment.

    Interesting by the way is the fact that without the pilot do you still need the double swing. The answer is yes because the code has not authorized you to do otherwise. The truth is however that with out the standing pilot it is not necessary.

    I am sure some will disagree with this approach. As usual I stand my ground 40 years and over 2,000 conversion burner installations and working with one of the most talented combustion engineers Tom Roche of T.C. Roche Associates (now retired) who was the number one distributor of Economite burners for many years. Tom was an engineer who got in the basement with you. I learned a lot from him and continue to study gas combustion every day.
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