60
RT-SVX063E-EN
of each burner's flame. Color should be blue for
natural gas with a small amount of visible orange.
3. Check the manifold gas pressure of each gas valve
by using the pressure port on the manifold section
downstream of the valve. The manifold pressure for
each valve at High Fire should be set to 3.5" w.c.
(10.0" w.c. for propane).
N
No
otte
e:: On modulating gas units the one-stage valve
just upstream of the modulating valve setting
will be approximately 4.5"w.c. to achieve a
manifold pressure of 3.5" downstream of the
modulating valve on high fire.
If adjustment is needed, adjust the regulator on the
valve. Refer to
, p. 60
for two stage valve on 250 &
350 MBh two stage, and
Figure 35, p. 61
for one
stage valve on all other multi-stage and modulating
burners, for the adjustment screw location. Turn the
screw clockwise to increase the gas pressure or
counterclockwise to decrease the gas pressure.
Combustion Air Analysis
1. Using a flue analyzer make note of the oxygen,
carbon dioxide, and the Air Free CO levels. Take
several samples to assure an accurate reading.
IIm
mp
po
orrtta
an
ntt:: The flue reading should be taken from
center of flue and at least 4 inches down
from the outlet.
2. Compare the measured oxygen level to the
combustion curve in
Figure 34, p. 60
. The oxygen
content of the flue gas should be 4% to 5%. If the
oxygen level is outside this range, contact the
Technical Support for assistance.
Low-Fire Adjustment (250 and 350 MBH
Two Staged only)
1. Use the TEST initiation procedures outlined in the
previous section to operate the furnace in the low-
fire state (1st Stage).
2. Check the manifold gas pressure of the valve by
using the pressure port on the manifold section
downstream of the valve. The manifold pressure for
Low Fire First Stage should be set to 1.2" w.c. (3.0"
w.c. for propane). If adjustment is needed, adjust
the LO regulator on the two stage valve. Refer to
,
p. 60
for the adjustment screw location. Turn the
screw clockwise to increase the gas pressure or
counterclockwise to decrease the gas pressure.
3. Check the oxygen, carbon dioxide, and the Air Free
CO levels after each adjustment.
4. Tap the STOP button on the User Interface to stop
the system operation.
Figure 34.
Natural gas combustion curve (ratio of oxygen to carbon dioxide in percent)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21
Perc
ent
Carbon Diox
ide
Percent Oxygen
A =
A
Curve
Fuel
1,000 BTU per cu ft.
of Natural Gas
S
Stta
arrttu
up
p tth
he
e U
Un
niitt
