Fuel/Air Adjusment - Harsco Industrial SC-2000 Installation & Owner's Manual

Comfort Heat Operation
Once the desired temperature adjustments are complete, touch the "Home" button to return to the Home Screen.
The Home Screen will now show the temperature setpoint, and will announce the operating condition "Standby",
"Prepurge", "Ignition" at the top of the screen. Ensure that all external control equipment (Remote Enable,
Outdoor Air Temperature Sensor, etc.) selected during the Setup Wizard is installed and properly wired to the
boiler. The boiler is now programmed for Comfort Heat operation. For applications including Domestic Hot
Water (DHW), Cascade, etc., please refer to the NURO Getting Started Guide or NURO Advanced User's Guide.
3.11 Fuel/Air Adjustment
The SC-2000, SC-3000 and SC-4000 boilers are equipped
with a gas/air ratio control valve and a gas safety shut off
control valve, combined into one valve assembly. The valve
functions in series with the variable speed combustion
blower to supply the correct gas/air mixture for optimum
firing performance and efficiency. The combustion blower
speed is controlled automatically by the boiler controller.
The blower speed determines the amount of air flow and the
amount of suction/negative pressure at the gas valves. The
gas valve adjusts gas flow to maintain the proper delivery
pressure at the outlet of the valve.
3.11.1 Gas Pressure Adjustment
See rating plate for the minimum and maximum gas
pressure of the boiler. The supply pressure during main
burner operation must be greater than the minimum
indicated on the rating plate. Nominal gas supply pressure
is 7" w.c. for natural gas. The gas pressure must not exceed
14" w.c. which is the maximum allowable pressure on the
gas train components. Each boiler is furnished with a
manual shut-off valve which has an integrated test port. This
port is located on the upstream side of the valve body for
measuring supply pressure. (Refer to Figure 3.11)
The air flow is pre-set at the factory prior to shipment. Gas flow is dependent primarily on fan speed not upstream
gas pressure. The automatic gas valve may have to be adjusted to obtain proper combustion readings for specific
local conditions. A combustion analyzer must be used. Combustion must be set in accordance with
3.11.2 Combustion Setup and Adjustment
To adjust/tune combustion, use the NURO's "Manual Control Firing Rate" mode. To access, touch the "Info"
button in the lower left corner of the screen, and then touch "Service" in the lower left. Next, touch "Press to
Activate Manual Control" which will open the "Manual Control Firing Rate" mode. This test mode should be used
when adjusting or tuning the gas safety shut off/control valve on the
In this mode a heat request is required. Once the boiler cycles on and is running in "Manual Control Firing Rate",
use the UP and DOWN arrow keys or the slider to force the boiler to operate at low fire or high fire (or anywhere
in-between). To prevent the boiler from cycling off prematurely during adjustment, ensure that any load devices
(air handlers, control valves, radiators, etc.) are in operation and able to shed/dump the heat load created by the
boiler.
Harsco Industrial, Patterson-Kelley Technical Service 1.877.728.5351
Figure 3.11
Gas Valve w/ Test Port
SC-2000, SC-3000
34
Gas Fired Boiler
Table 3.11.2.
or boilers.
SC-4000