Service manual

SC Series Boilers – Installation and Service Manual
20
3.6 GAS MANIFOLD PRESSURE
These boilers are factory equipped for operation at altitudes ranging from 0 to 2,000 feet above sea level.
The designated manifold pressures for sea level application are as shown in the table below.
Model Natural Gas Propane
All Models for 0 to 2,000 feet altitude
3.5” W.C. 9” W.C.
Please note that the manifold pressure must be measured without referencing the gas valve
venter to the air chamber (see Manifold Pressure Adjustment below). A 1/8” NPT tapping is provided
on the gas valve for connecting a manometer to check this pressure. Both natural gas and propane
models are furnished with gas valves which have a built in gas pressure regulator. If necessary, adjust to
the proper value by removing cap and turning adjusting screw clockwise to increase manifold pressure or
counterclockwise to decrease manifold pressure.
Use at Altitudes above 2000 feet
For altitudes above 2,000 feet above sea level, the input rating of the boiler must be reduced as shown in
the table in Section 3.7.
In Canada, for boiler applications at altitudes in the range of 2000 to 4500 feet above sea level, the high
altitude input rate must be achieved by changing the orifice size. The manifold pressure should be
adjusted to the value as shown in the table above.
In USA, for boiler installations at altitudes above 2000 feet, the input rating of the boiler may be achieved
by adjusting the manifold pressure or by changing orifice size.
The conversion of a boiler from sea level to high altitude must be performed by a qualified heating
installer, service technician or gas supplier and in accordance with the requirements of Section 2.2 of this
manual. A conversion data plate, indicating that the boiler has been converted for high altitude use, shall
be attached adjacent to the rating plate. The correct conversion information must be entered on the
conversion data plate by the installer.
After the boiler has been converted for high altitude use, the input must be verified following the input rate
test as described in Section 3.7.
Manifold Pressure Adjustment
1. Adjust airflow as per section 3.5 of the manual
2. Ensure gas inlet pressure is set correctly
3. Connect a manometer to the gas valve outlet
pressure tap
4. With the boiler running for few minutes, disconnect
the tube B from the orifice on the gas valve venter
and plug or clamp shut the end of tube B. The
manometer should show the manifold pressure
required on the rating plate or conversion data
plate.
5. If the manifold pressure is not equal to the value
required, remove the pressure regulator adjustment
cap screw on the gas valve
6. Using a screwdriver turn the inner adjustment
screw clockwise 3 to increase or counterclockwise
4 to decrease it
7. Replace cap screw and tighten firmly
8. Reconnect tube B to the regulator vent orifice A.