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HTD
Table 22. Combustion Settings.
Model
Gas Type
High Fire CO
2
Low Fire CO
2
Pressure Differential
1,600
Natural
9.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
Propane
10.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
2,000
Natural
9.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
Propane
10.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
2,500
Natural
9.0% ± 0.2
.25 lower than high fire CO
2
0.9” to .09” wc
Propane
10.0% ± 0.2
.25 lower than high fire CO
2
0.9” to .09” wc
3,000
Natural
9.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc
Propane
10.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc
3,500
Natural
9.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
Propane
10.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
4,000
Natural
9.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
Propane
10.0% ± 0.2
.25 lower than high fire CO
2
0.5” to 1.2” wc*
*Only check the Pressure Differential if there are problems getting the CO
2
in range.
10.C Shutting Down the Unit
Thisstepmustbeperformedbyaqualifiedservice
person.
1. Turn off the main electrical disconnect switch.
2. Close all manual gas valves.
3. If freezing is anticipated, drain the unit and be sure
to also protect the building piping from freezing. All
water must be removed from the heat exchanger or
damage from freezing may occur.
10.D Restarting the Unit
If the system has been drained, see 10.A for instructions
on proper filling and purging.
1. Turn off the main electrical disconnect switch.
2. Close all manual gas valves.
3.
Wait five minutes.
4. Set the aquastat or thermostat to its lowest setting.
5. Open all manual gas valves.
6. Reset all safety switches (pressure switch, manual
reset high limit, etc.).
7. Set the temperature controller to the desired
temperature setting and switch on the electrical
power.
8. The unit will go through a prepurge period and
ignitor warm-up period, followed by ignition.
4. Provide a call for heat to terminals TT-1 and allow
the system to sequence to the Run State. Once
in Run and firing at 100%, using a combustion
analyzer adjust the fuel pressure screw to obtain the
correct CO2 measurements shown in Table 22. If
the CO2 measurement is high, consult the factory
for assistance.
5. During this setup procedure, ensure that the gas fuel
pressure at the entrance to the boiler is equal to or
greater than 4” w.c. while the unit is running at full
firing rate. If the gas pressure is greater than 14”
w.c., turn off the main gas shut-off valve upstream
of the boiler and adjust or replace fuel regulating
components as necessary.
6. Once the high fire is set, adjust the Manual Firing
Rate to 5%
7. Wait until the system stabilizes at the lower rate to
observe the CO2 and CO readings. Refer to Table
22 for the correct ranges. If CO2 is outside of the
specified ranges in the table consult the factory for
assistance.
8. Return to the O2 screen and enable the O2 Trim
9. Return to the manual firing rate control and disable
the manual firing rate.
