Tft285 NG-LP Conversion Instructions
3
2.0 Gas Valve and Burner Setup
Failure to perform the Gas Valve and Burner Setup correctly may result in incorrect
operation, component failure, property damage, serious injury or death.
Operating Sequence
Prior to commencing the Gas Valve and Burner Setup, perform the following operating sequence check:
1.
Turn the supply of gas to the boiler off.
2.
Set the thermostat to the highest setting.
3.
Ensure the combustion fan pre-purges for a short time prior to activating the igniter.
4.
Ensure the combustion fan post-purges for at least 5 seconds prior to reactivating the igniter.
5.
Set the thermostat to the lowest setting and continue with the Gas Valve and Burner Setup procedure outlined
below.
Gas Line Pressure
The boiler gas valve is equipped with a Line Pressure Test Port; see Figure 1-1. Use the following procedure to
measure the gas line pressure to the boiler to ensure it falls within the range given in Table 2-1:
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 Figure 1-1.
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.
Turn the gas supply to the boiler on and check for gas leaks.
5.
Observe the line pressure under static conditions and compare it to Table 2-1. The pressure will be greatest
under static conditions.
6.
With all other gas appliances in the application running, operate the burner to the maximum modulation rate
(See Table 2-2) and compare the observed line pressure with Table 2-1. The pressure will be lowest during
the maximum flow of gas.
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, see Table 2-2.
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, remove the 1/4” tubing 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
Gas
Line Pressure (inches wc)
CO
2
(%)*
CO (ppm)
Max.
Nominal/Desired
Min.
Max.
Min.
Max.
Natural
7
4
10.5
8.9
9.5
175
Propane
11
8
13
10.2
10.8
175
1
Combustion calibration must only be performed with the burner operating at maximum modulation rate.
2
Combustion values listed are for burner operation at maximum modulation rate; CO
2
and CO values will be lower at minimum
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 2-2 Minimum and Maximum Input Ratings and Respective Modulation Rates
Model
Min. Modulation Rate (RPM)
Max. Modulation Rate (RPM)
Input (MBH)
Min
Max
1
Tft285
1000
7300
28.5
285
1
Canada: Altitudes between 2000-4500 ft, de-rate by 10%. Consult local authorities for de-rating for altitudes above 4500ft.
Carbon Monoxide
- Never leave the unit operating while producing Carbon Monoxide (CO)
concentrations in excess of 175ppm. Failure to follow this warning 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.
