Tx51-151(C) NG-LP Conversion Instructions 3
7. Adjust the gas line pressure to ensure the parameters in Table 2-1 are attained under all conditions. If
possible adjust the line pressure to the "Nominal/Desired" value listed in Table 2-1 while the unit is operating
at the maximum modulation rate.
8. Continue observing gas line pressure until combustion analyses is complete in case adjustments need to be
made.
9. Complete pressure testing, remove the ¼”tube from the test port and then return the bleed screw of the Line
Pressure Test Port to the closed position.
The line pressure is a function of the gas supply and is affected solely by field provided
parameters such as line size and regulator settings. Under no circumstances can the boiler gas
valve influence or be used to adjust the gas line pressure.
Failure to close the bleed screw of the Line Pressure Test Port will cause a severe leakage of
gas, resulting in a fire or explosion causing property damage, serious injury or death.
Table 2-1 Line Pressure and Combustion Parameters
Line Pressure (inches wc)
*Note: Observe the combustion products with the burner operating at the maximum modulation rate, CO2 and CO values will
be lower at minimum modulation rate.
Table 2-2 Minimum and Maximum Input Ratings and Respective Modulation Rates
Min. Modulation
Rate (RPM)
Max. Modulation
Rate (RPM)
*Canada: Altitudes between 2000-4500 ft [610-1372 m], de-rate by 10%. Consult local authorities for de-rating for altitudes
above 4500ft [1372 m].
Carbon Monoxide –DO NOT leave the unit operating if producing Carbon Monoxide (CO)
concentrations in excess of 175ppm. Failure to comply may result in serious injury or death.
Manifold Pressure - DO NOT adjust or measure the Manifold Pressure of the boiler. Correct
manifold pressure is factory set. Field adjustment could result in improper burner operation
resulting in fire, explosion, property damage or death.
Adjustment
Throttle / Input Screw Adjustments - The boiler is equipped with a Throttle/Input Adjustment Screw located on the
Gas Valve. It is used to adjust the flow of gas leaving the gas valve entering the Venturi and then the combustion
air stream. Turn the Throttle screw in (clockwise) to reduce the flow of gas, make combustion leaner, and reduce
the concentration of CO2in the flue gases. Turn the Throttle screw out (counterclockwise) to increase the CO2
level and flow of gas in the combustion air stream. Typical adjustment required is 0-1/2 full turns in or out from
the factory setting. See Figures 2-1 and 2-2 for Throttle screw location and Table 2-1 for appropriate CO2levels.
Adjustments to the Throttle/Input-Screw may only be made by a qualified gas technician
while using a calibrated combustion analyzer capable of measuring CO2and CO.
Adjustments may only be performed if the gas line pressure is maintained above minimum
levels throughout the duration of the test, see Table 2-1. Failure to follow these instructions
may result in serious injury or death.
Throttle/Input Adjustment Screw
Increase gas
Turn Counter Clockwise
Decrease gas
Turn Clockwise
