Trane SFHJ090-162 - Page 166

Unit Startup
166 RT-SVX24J-EN
for the required manifold pressure during low-fire
operation. If it needs adjusting, remove the cap
covering the low-fire adjustment screw on the gas
valve. Refer to Figure 118, p. 167 for the adjustment
screw location.Turn the screw clockwise to increase
the
gas pressure or
counterclockwise to decrease the
gas pressure.
Note: Do not adjust the combustion air damper while
the furnace is operating
at low-fire.
4. Check the carbon dioxide levels after each adjustment.
5. Press the STOP key at the Human Interface Module in
the unit control panel to
stop the system operation.
Figure 116. 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
0123456789101112131415161718192021
Percent Oxygen
Percent Carbon Dioxide
Curve Fuel
A = 1,000 BTU per cu. ft.
of Natural Gas.
A
Table 48. Recommended manifold pressures and CO
2
levels during furnace operation
2-STAGE MODULATING
MBH
FIRING
RATES
% CO2
NAT GAS
MANIF
PRESS
“W.C.
% CO2
PROPANE
MANIF
PRESS
“W.C. MBH
FIRING
RATE
% CO2
NAT GAS
MANIF
PRESS
“W.C.
% CO2
PROPANE
MANIF
PRESS
“W.C.
850 100% 8.0-9.0 3.0-3.5 9.0-10.0 3.0-3.5 850 100% 8.0-9.0 3.0- 3.5 7.8-8.4 1.7-2.2
510 60% 5.0 -7.0 0.8-0.95 5.0-7.0 1.5-3.0 85 10% 5.0 -7.0 0.8- 0.9.5 2.0-3.0 .1-.2
1100 100% 8.0-9.0 3.0-3.3 9.0-10.0 3.0-3.3 1100 100% 7.0-9.0 .8-.9 8.5-9.5 .5-.75
550 50% 5.0 -7.0 0.8-0.95 5.0-7.0 0.8-0.95 55 5% 1.5-3.0 .05-1.0 1.5-2.5 .02-.04
1800 100% 7.0- 8.0 1.5- 1.8 N/A N/A 1800 100% 7.0-9.0 1.5- 1.8 N/A N/A
900 50% 5.0- 7.0 0.5- 0.7 N/A N/A 90 5% 1.5-3.0 .05-1.0 N/A N/A
2500 100% 7.5- 8.5 2.0- 2.5 N/A N/A 2500 100% 7.0-9.0 2.0- 2.5 N/A N/A
1250 50% 5.0- 7.0 0.5- 0.7 N/A N/A 125 5% 1.5-3.0 .05-1.0 N/A N/A