Help with Table 13.1

Mike2

Tim, Could you give an explanation of the Tables 13.1 in NFPA 54?  There is some confusion whether the columns for FAN or NAT should be used on oil boilers that are being converted to Natural Gas.  The boilers are natural draft, meaning negative pressure in the flue, but there is a fan in the power burner such as a Carlin EZ Gas.

Tim McElwain

The Power Conversion

burners have nothing to do with pressurizing the flue. The purpose of the motor is to mix air with the gas before burning. It is a Forced draft burner by definition but does not affect what will be a negative pressure in the flue so it is a Nat draft appliance. It would be different if it were fan assisted which means the fan is designed to overcome the internal resistance of the furnace or boiler. That vent however is also a negative pressure vent but would come under the FAN in the chart. All of this falls under Category I.



Is this confusion coming from inspectors or just a discussion among techs?

Mike2

Inspectors

Inspectors say we should follow FAN  column for conversion burners.  Rep for Carlin was under the impression that we should use NAT column.

Tim McElwain

Inspectors wrong

Carlin is correct. Have the inspector give me a call at 401-437-0557 or e-mail me at gastc@cox.net. Or better yet have Carlin talk to them, then have Midco, Wayne, Heatwise etc all conversion burner manufacturers call the inspector.



Many people make the mistake that a power burner powers the flue to make draft. Draft is produced by Delta T (temperature difference0 and height of the flue. In the case of power burners the blower has little to no affect on draft.

Mike2

Carlin

Tim, thanks for the responses.  I was just able to find in the Carlin Gas Burner Guide, page 4,

"Appliances equipped with a gas conversion burner are treated as fan-assisted appliances" 

So I guess that I'll have to follow the FAN column.  I'll have to check Riello's installation guide as well to see if they mention it. 

Tim McElwain

That makes no sense

at all to me???

Jack

Tim, remember in '92

When the venting tables first cme out all the furnace manuf. Decided that they could have one furnace that would do both Cat I and Cat III. That lasted a year or two and then one by one the difficulty of using a Cat I "inducer" to handle side wall vent requirements convinced all the warm air guys to make two separate units.



I'm with you on the NAT col being correct, but what is the static capability of the Carlin...and what kind of mischief could ensue if there is any short cycling, oversizing, etc on this job?

Tim McElwain

Yes I do remember

and there are still a lot of those around as also a few boilers with the same option. Weil McLain CGa and CGs if I am not mistaken.



The good thing with Carlin Burners is that Carlin has done their own testing on many different boilers and offer an Oil and Gas Burner Set-Up Tables for OEM Applications 2010 Edition which takes care of any possibility of incorrect set-up. That of course is provided techs follow their recommendations.