North American 6423 Dual-Fuel™
Fire• All Burners

Sheet 6423

Light oil can be burned as standby or primary fuel in the larger 
sizes of 4423 Gas Burners by adding a 5423 Atomizer to an 
existing burner or by specifying a 6423 Dual-Fuel Burner for a 
new installation.

6423 Burners have the same 4423 "Fire•All" suitablility for a 
wide variety of industrial furnaces, from low temperature ovens 
to high temperature forge, heat treat, etc. applications. When 
burning oil, these burners are not as fl exible re air/fuel ratio as 
they are on gas. But oil operations with 200% excess air can be 
realized at 12-16 osi main air, somewhat less XSA at lower inputs.

Gas go es through the atomizer in a 6423 Burner, so atomizing 
air is not available when burning gas: Thus, total air capacity is 
greater when burning oil (by the amount of the atomizing air 

-- see tables below). An approved 3-way valve must be installed 
in the line feeding the gas/atomizing air connection to assure 
that the non-used medium is completely shut off . Gas pressure 
requirements at the burner are higher than they are for a 4423 
Burner, but a standard cross-connected regulator system is 
satisfactory.

PILOT, FLAME SUPERVISION

A 4021-12 pilot tip lights the burner satisfactorily with 8-22 osi 
pilot air pressure (3-10"w.c. mixture pressure.) Use a UV fl ame 
detectcor -- fl ame rods are not satisfactory.

See Bulletin 4423/4424 for construction and other characteristics.  

Table 1. CAPACITIES, FLAME LENGTHS

Table 2. MAIN AN ATOMIZING AIR CAPACITIES

designation 

Btu/h HHV 

oil, gph 

Btu/h HHV 

gas,cfh 

oil 

gas

 6423-2 

277,000 

2.1 

234,000 

234 

13 

8

 6423-3-A 

396,000 

3.0 

354,000 

354 

16 

17

 6423-3-B 

475,000 

3.6 

432,000 

432 

18 

17

Burner

Burner

burning oil 



burning gas 



fl ame length, in.

pressure at burner, osi

main air, cfh

pressure at burner, osi

atomizing air, cfh



  based on 132,000 Btu/gallon oil with 16 osi main and atomizing air at the burner.



 based on 1,000 Btu/cf natural gas with 16 osi main air at the burner (atomizing air not available with burning gas).

designation 1  5  6  8  12  16  14 16 20 

22 24

 6423-2 

585  1300  1430  1650  2010  2340 

440  470  525  550  575

 6423-3-A 

885  1980  2160  2500  3050  3540 

440  470  525  550  575

 6423-3-B 

1080  2410  2640 3050  3720  4320 

440  470  525  550  575

ENERG

Y | C

OMBUSITION