Rapid 7500 136 Installation, operation & service manual - page 46
7500-S
ERIES
I
NSTALLATION
, O
PERATION
AND
S
ERVICE
M
ANUAL
34 of 143
for standard
bu
rner collar
diameter / flange size. Cons
u
lt factory for non-
standard
bu
rners as collar diameters / flanges may
v
ary.
Table 13: Combustion Air Duct Collar Sizin
g
When d
u
cting o
u
tside com
bu
stion air to the
bu
rner
air inlet, se
v
eral considerations m
u
st
b
e taken in
acco
u
nt:
• Temperat
u
re
v
ariations
w
hen
u
sing o
u
tside fresh
air: Changes in air temperat
u
re affect density of
the air and the
v
ol
u
me of air deli
v
ered to the
com
bu
stion process. This m
u
st
b
e taken in
acco
u
nt
w
hen performing com
bu
stion
performance. For example: For each 30° F (33.3°
C) change in the air temperat
u
re, a 1% change in
the oxygen reading
w
ill
b
e experienced.
• Condensation in the fresh air d
u
ct: A drain
connection is req
u
ired in the lo
w
est point of the
d
u
ct or the d
u
ct m
u
st
b
e pitched a minim
u
m of a
0.25" (.6 cm) per foot (30.5 cm) a
w
ay from the
bu
rner for condensate drainage.
• D
u
ct Sizing: Size the fresh air d
u
ct to pro
v
ide a
minim
u
m of 20 CFM (34 m
3
/h) per 10,000 Bt
u
/hr
(2,931 kW) of inp
u
t firing rate. The
v
elocity of the
air m
u
st not exceed 1000 FPM (5.0 m/s) and
ca
u
se less than 0.1"
w
c (<.25>
b
ar) press
u
re
drop, incl
u
ding all screens, filters and fittings. The
inlet to this d
u
ct m
u
st
b
e protected from
w
eather
(rain, sno
w
and/or ice) and m
u
st ha
v
e an inlet
screen to protect from pest and de
b
ris.
FIGURE 19: "Type J" Burner with Ultraviolet Scanner - Natural Gas or LPG
Burner Type
Gas
Oil and Gas/Oil
Type
Size - Outer
Dimensions
Max
Input
Max
Input
Max
Input
Max
Input
(in)
(cm)
(MBH) (kW)
(MBH)
(kW)
Ro
u
nd
6.0
15.2
1075
315
1360
398.6
Ro
u
nd
8.0
20.3
2200
644.8
2200
644.8
Sq
u
are
8.0
20.3
5250 1538.6
5250
1538.6
Sq
u
are
12.0
30.5
5600
1641.2
5600
1641.2