Example C:

 

Select a mixer for a 4682-6-C burner with 8 osi 

(14"w.c.) air and 8"wc mixture pressure. This arrangement 
necessitates a cross-connected regulator and high gas pressure 
because air pressure drop is <66% of its air pressure. 

 

Capacity of a 4682-6-C at 8"w.c. mixture pressure is 

1,200,000 Btu/h. (divide by 100= 12,000 scfh air) Pressure drop 
across the mixer = 8 osi (14"wc) minus 8"w.c. mp = 6"w.c. From 
the capacity 

Chart 1B

, a 3065-6-S0 Mixer would serve the 

purpose, as would a 3065-7-20. For minimum cost and size (both 
mixer and burner nozzle are 3" NPT) use the 

3065-6-S0

 mixer. 

The gas pressure required upstream of the ratio regulator = 14" 
w.c. + 6"w.c. = 20" wc = 11.5 osi (use 12-16 osi)

Example D:

 

Select a mixer for 3,000 scfh air) burner with 8 osi 

air and 8"w.c. mixture pressure. (This arrangement necessitates 
a cross-connected regulator and 12-16 osi gas pressure.) Pressure 
drop across the mixer = 8 osi (14"w.c.) minus 8"wc mixture 
pressure = 6"w.c. 

 

From the capacity 

Chart 1A

, a 

3065-3-S0

 or a 

3065-4-8

 

could be used. Which mixer to choose depends on a number of 
factors. 
     - The 

3065-3-S0

 uses 1

½  

" pipe and the 

3065-4-8

 uses 

       2" pipe
     - If at any time the system capacity needs to be increased,  
       the capacity of the 

3065-4-8

 can be increased by using a  

       smaller displacement rod. The 

3065-0-S0

 with its -0 rod is  

       already is at the maximum capacity. 
     - In most cases pick the mixer with the same pipe size as  
       the burner, but the 

3065-4-8

 mixer off ers more sizing             

       options if fi eld conditions require a new displacement rod  
       choice.

Example E1:

 

An existing system uses a 

3065-5-17

 mixer to feed 

four (4) 4682-2-A burner nozzles, with a zero governor ratio 
control for natural gas. What mixer is needed if the burners are 
changed to four (4) 4682-2-B burner nozzles to increase the 
system capacity?

 

Since these are standard size nozzles with zero governor ratio 

control, use 

Table 2

. Find the -2-B nozzle row move right and 

fi nd the 4 nozzle column. Find the 

3065-5-12

 Mixer from the list. 

Since the mixers are both the 3065-5 size, only the displacement 
rod needs to be changed.

Example E2:

 

An existing system uses a 

3065-5-17

 mixer to 

feed four (4) 4682-2-A burner nozzles with a zero governor ratio 
control for natural gas. What mixer is needed if the burners are 
changed to four (4) 4682-2-D burner nozzles to increase the 
system capacity.

 

Since these are standard size burner nozzles with zero 

governor ratio control, use 

Table 2

. Find the -2-D burner row, 

move right and fi nd the 4 burner column. Pick the 

3065-6-18

 

mixer from the list. This is a new mixer size which requires larger 
pipe (but maybe a 3065-5-S_ will work) from 

Table 3B

, the 

orifi ce throat area of a 

3065-6-18 

is (1.040 in2). A 

3065-5-S15

 

is (1.055 in2). So use the 

3065-5-S15

 because only the mixer 

needs to be changed and not the piping. 

Note:

 The other system 

components still need to be checked to see if they are suitable 
for use with the higher capacity. Due to more pressure drop 
through the piping it may be necessary to cross connect the ratio 
regulator. 

Example G:

 

Select a mixer for a 2,300,000 Btu/h (divide by 

100= 23,000 scfh air) burner with 8 osi air and 4"w.c. mixture 
pressure. (zero governor ratio control for natural gas) Pressure 
drop across the mixer = 8 osi (14"w.c.) minus 4"wc mp = 10"w.c.

 

From the capacity 

Chart 1B

, a 

3065-8

 with between a 

#56

 

and a 

#64

 rod or a 

3065-7-S

 with between no rod and a #38 

rod (21,000 cfh capacity) could be used. For minimum cost and 
size, use a 

3065-7-S

.

Eff ective mixer throat area = for a 

3065-7-S38

  = 2.652 sq. in. 

(from 

Table 3B

)

(A), Throat area, unknown mixer 

=

 Capacity, unknown mixer

      Throat area, known mixer        Capacity, known mixer

(A)

2.652

23,000 scfh

21,000 scfh

=

From 

Table 3B

 use 

3065-7-S34

 mixer.

A = 2.90 sq. in.

3065 Sizing Examples continued

Bulletin 3065

page 14

Catalog Combustion 2021 - Page 0041

Fives Group
FIVES GROUP
FIVES GROUP-FIVES GROUP-0041-0045

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5 3065-0-0 Fives Group Request Quote
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7 3065-5-_ Fives Group Request Quote
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