Gas Valve and Burner Set-up
│
Tx I&O Manual
34
Gas Line Pressure Test
The boiler gas valve is equipped with a line pressure test port; see Figures 9-1 & 9-2. Use the following
procedure to measure the gas line pressure to the boiler to ensure if falls within the range given in Table 9-1:
1.
Turn the supply of gas to the boiler off.
2.
Open the bleed screw of the line pressure test port approximately 1-1/2 turns. This port is directly
connected to the gas line feeding the boiler. See Figures 9-1 & 9-2.
3.
Force 1/4
ID tubing over the housing of the line pressure test port; install the other end of the tubing to an
appropriate line pressure test gauge or manometer. Ensure both ends of the tubing make a tight connection.
4.
Open the supply of gas to the boiler and check for gas leaks.
5.
Observe the line pressure under static conditions and compare it to Table 9-1. The pressure will be greatest
under static conditions.
6.
With all other gas appliances in the application running, operate the burner to the maximum firing rate (See
Table 9-2) and compare the observed line pressure with Table 9-1. The pressure will be lowest during the
maximum flow of gas.
7.
Adjust the gas line pressure to ensure the parameters in Table 9-1 are attained under all conditions (See
NOTICE below). If possible adjust the line pressure to the "Nominal/Desired" value listed in Table 9-1,
while the unit is operating at the maximum modulation rate, see Table 9-2.
8.
Continue observing the gas line pressure until the completion of the combustion analyses, in case
adjustments need to be made.
9.
Complete pressure testing, 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 9-1 Line Pressure and Combustion Parameters
Gas
Line Pressure (inches w.c.)
Model
CO
2
(%)
CO (ppm)
Max.
Nominal/Desired
Min.
Max.
Min.
Max.
Natural
7
4
10.5
All Tx models
9.0
9.8
175
Propane
11
8
13
All Tx models
10.0
10.8
175
Notes:
1
Combustion calibration must only be performed with the burner operating at maximum modulation rate; when tested at
minimum modulation rate the CO
2
must be 0.4-0.8% lower than CO
2
at maximum modulation rate.
Table 9-2 Minimum and Maximum Modulation Rates
Model
Appliance Number
Min. Modulation Rate (RPM)
Max. Modulation Rate (RPM)
Tx51
1
1380
5460
Tx81
2
1260
5700
Tx101
3
1260
5820
Tx151
4
1380
6420
Tx151C
5
1380
6420
Tx200
6
1020
5280
Tx200C
7
1020
5280
Notes:
1
Use Installer Menu setting 2-15 to force the burner to operate at the max. (2-15 = 3) and min. (2-15 = 1)
modulation rates; see Section 17.0 DISPLAY MENU GUIDE.
