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Which chart for sizing vents.

Assuming noncondensing, which chart gets used for sizing vents on gas fired, power burner , barometric damper equipped appliances....fan or natural.  I believe they are CAT 1, but it really doesn't make sense they would be lumped with draft hoods since draft hood equipped appliances have much larger volumes of gases to vent due to the draft hood air entering the venting system   Does it change when it is pressure fired?  I suspect these are CAT 3 appliances.   The venting charts I have seen do not specifically call out CAT 1 for natural and CAT 3 for fan assisted, even in the codes.
The Steam Whisperer (Formerly Boilerpro)

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Comments

  • Tim McElwain
    Tim McElwain Member Posts: 4,481
    The answer to your question is

    the power burners installation instructions should give the size. That being said a conversion has always been a CAT I appliance the blower on the burner has nothing to do with powering the vent as its purpose is to pre mix gas and air before ignition.

    Which chart for sizing vents.

    but it really doesn't make sense they would be lumped with draft hoods since draft hood equipped appliances have much larger volumes of gases to vent due to the draft hood air entering the venting system WITH THE DOUBLE SWING BAROMETRIC YOU HAVE CONTROL OVER DILUTION AIR BUT THAT DOES NOT CHANGE THE CATEGORY AS CATEGORY IS BASED ON SEVERAL THINGS SUCH AS STACK TEMP, EFFICIENCY, ETC.



      Does it change when it is pressure fired?  I suspect these are CAT 3 appliances.   IF THEY ARE THEN THEY MUST USE STAINLESS STEEL VENTING AND BE SEALED TIGHT. THEY ARE NOT THEY ARE CATEGORY I. LOOK UP THE FOUR CATEGORY'S AS TO ALL THE REQUIREMENTS.



    The venting charts I have seen do not specifically call out CAT 1 for natural and CAT 3 for fan assisted, even in the codes. THAT IS NOT TRUE IF YOU LOOK AT NFPA 54 CODES YOU HAVE "NAT" FOR NATURAL DRAFT "FAN" FOR FAN ASSISTED (WHICH MEANS THE ONLY PURPOSE OF THE INDUCED DRAFT FAN IS TO OVERCOME THE INTERNAL RESISTANCE OFFERED BY THE SECTIONS OR HEAT EXCHANGER) THE PRESSURE AT THE BREACH IS STILL NEGATIVE. THEN THERE IS A COLUMN FOR "FAN/NAT".