NFPA 54

NGInstructor

I am looking for other <span style="font-size:12pt">interpretations of the following section of “The National Fuel Gas Code” (NFPA 54) 2009 edition.</span>

<span style="font-size:12pt"> </span>

<span style="font-size:12pt">3.3.32.1 Mechanical Draft.  Draft produced by a fan or an air or steam jet. When a fan is located so as to push the flue gases through the chimney or vent, the draft is forced. When the fan is located as to pull the flue gases through the chimney or vent, the draft is induced. [211, 2006]</span>

<span style="font-size:12pt"> </span>

<span style="font-size:12pt">My interpretation is this:</span>

<span style="font-size:12pt">            An appliance which uses a Burner Motor to pull in Air and mixes with the Natural Gas prior to ignition, and pushes the flue gases into the vent or chimney: is a FORCED DRAFT appliance.</span>

<span style="font-size:12pt">            An appliance which uses a Vent Motor (Inducer Motor) built into the appliance’s flue collector, which pulls the flue gases through the appliance but then pushes them into the chimney or vent is also a FORCED DRAFT appliance.</span>

<span style="font-size:12pt">            A vent or chimney that has a motor in the vent or chimney itself, which pulls the flues gases through the appliance and the vent connector and then out of the vent or chimney is an INDUCED DRAFT appliance.</span>

<span style="font-size:12pt"> </span>

<span style="font-size:12pt">I understand the common theory of forced draft and induced draft appliances but my question is to the verbiage of the above section of the National Fuel Gas Code.</span>

<span style="font-size:12pt"> </span>

<span style="font-size:12pt">Another question is on Venting Categories:</span>

<span style="font-size:12pt">            Would a Natural Gas conversion gun utilizing a Burner Motor and is Non-condensing, which is equipped with a Draft Diverter or Barometric Diverter be considered a;</span>

<span style="font-size:12pt">            Category I        – natural Draft – Non-Condensing appliance</span>

<span style="font-size:12pt">                                                or</span>

<span style="font-size:12pt">            Category III     - Mechanical Draft – Non- Condescending Appliance</span>

Tim McElwain

Mechanical Draft is anytime

draft is created by any means other than natural draft.  It can be forced or induced which is what 3.3.32.1 is defining.



Natural Draft is defined as draft created by Delta "T" (temperature difference in the flue) and the height of the flue. Those are the only two things that can create draft. Many other things can affect draft.



Forced Draft is when the blower is ahead of the combustion process, such as an oil burner or gas conversion burner.



 An appliance which uses a Vent Motor (Inducer Motor) built into the appliance’s flue collector, which pulls the flue gases through the appliance but then pushes them into the chimney or vent is also a FORCED DRAFT appliance.



This is incorrect that is a induced draft appliance. See Category 1 Fan Assisted definition below.





Induced Draft is when the blower is after the combustion process.



There is however a difference when talking about Power Vented this is an induced draft blower which pressurizes the flue after the blower (positive vent pressure) verses normal draft flue condition which is negative such -.01 " W.C. or -.02" W.C etc. Typically a sealed combustion chamber with a dedicated means of getting air for combustion.



Category I Fan Assisted is when the induced draft blower is designed to overcome the resistance of the combustion chamber on an atmospheric gas appliance which is getting its air for combustion from within the space the equipment is installed in or spaces communicating with outdoors.The pressure in the vent will be negative pressure and a vent gas temperature in excess of 275°(F).



A Natural Gas Conversion Burner is a Forced Draft burner which will have a negative pressure in the flue or chimney. All the blower does is premix the gas and air before firing. The blower has very little affect on flue gas pressure. The appliance must still develop natural draft in the flue and chimney for venting purposes. Most conversion burner manufacturers do not want "B" vent used with their burner.



Category III is an appliance which has a positive pressure in the vent with a flue gas temperature above 275° (F) it is non-condensing but will typically require a flue pipe material of AL29 4C stainless steel consistency as it may condense in the flue at times.

Hank C

Coversion Burner

Do you have any documentation on the conversion burner?

Tim McElwain

Hank C not sure what

you want for documentation. I have all the installation instructions for all of the residentail power gas conversion burners. If you are referring to commercial industrial they fall under ANSI Z83.3 standards.



I also have installed over 3,500 Power Gas Conversion Burners in my career and they are always natural draft appliances for venting purposes.

Hank C

Coversion Burner

My thought is that the installation instruction for the conversion burner that he is using would have some instructions on venting.

Unknown

Wow over 3,500 ?

Never doubt Timmie,,,, he really knows his stuff!!!



I mean that in the highest regards Tim!

Tim McElwain

Yes most instructions

for conversion burners refer you to NFPA 54 National Fuel Gas Code. The only thing they may specify exactly is the size of vent based on the BTU (orifice) you are using.



Yes I actually started installing conversion burners with an old timer in South Western Pa when I was 13 years old. He took me under his wing after my dad was killed when I was 9 years old. From 9 to 13 all they would let me do was hang around their shop emptying trash cans after school. They installed coal, oil and natural gas furnaces, boilers and conversion burners. When I turned 13 they had me playing baseball with their company team and put me on the payroll as an apprentice. No child labor concerns in those days. Some of my friends actually went into the coal mines at 13 and 14 years old.