Sterling RT - Manual (Page 18)

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1. With unit fi ring, remove the pilot adjustment cap.
2. Adjust the pilot screw to provide properly sized
fl ame.
PILOT ADJUSTMENT
3. A proper pilot flame is a soft steady flame that
envelopes 3/8 to 1/2 inch (9.5 to 12.7 mm) of the
fl ame sensor.
4. Replace the pilot adjustment cap.
For correct air adjustment, close the air shutter until
yellow tips in the flame appear. Then open the air
shutter to the point just beyond the position where
yellow tipping disappears.
PRIMARY AIR SHUTTER ADJUSTMENT
After the unit has been operated for at least 15
minutes, adjust the primary air flow to the burners.
Turn the friction-locked, manually-rotated air shutters
clockwise to close, or counterclockwise to open.
When shipped from the factory, all gas fired units are
equipped for the average BTU of the gas stamped on
the rating plate.
Since the BTU content of gases
varies in many localities, the input must be checked
after installation of the unit. If the unit is overfi red,
the overheating will substantially shorten the life of
the heat exchanger. Never exceed the input on the
rating plate.
The input may be checked by either the meter method
or the pressure of the gas in the manifold. A 1/8 inch
pipe tap is available on the body of the gas valve.
Never overfi re the unit heater, as this
may cause unsatisfactory operation or shorten the
life of the heater.
METER METHOD OF CHECKING INPUT:
1. Obtain the heating value of the gas from the
local utility. This should be in BTU per cubic foot
(MJ/m
3 ).
2. Determine the cubic feet per minute of the gas as
shown in the following example. The rating plate
input should be taken from the unit as stamped on
the plate.
EXAMPLE: Assume this is a unit having an input of
250,000 BTU/hr. and the heating value of the gas to
be used in the furnace is 1000 BTU/hr.
GAS INPUT ADJUSTMENT
250,000 BTU/hr.
INPUT=
1000 BTU/cu. ft. x 60 min/hr
= 41.7 cu feet per min.
Before checking the unit input, all other gas
appliances connected to the same meter must be
turned off.
3. Fire the unit according to instructions.
4. Observe on the meter dial the cubic feet of gas for
a period of fi ve minutes. This should be 41.7 cu ft.
per min. x 5 minutes, or 20.8 cu. feet. Minor input
adjustments can be made by moving the regulator
screw clockwise for increased input and counter-
clockwise for decreased input. Any appreciable
adjustment in input should be made by re-orifi cing.
MANIFOLD PRESSURE METHOD
OF CHECKING INPUT
1. Close the manual gas valve on the unit.
2. Install a 1/8 inch pipe connection in the tapped
hold provided on the valve body and a “U” tube or
manometer by means or a rubber hose.
3. Fire the unit and observe the pressure.
4. Small variations in gas pressure adjustment can
be made by means of the pressure regulator.
Remove the cap from the regulator. Turning the
screw clockwise will increase the input, and turning
it counterclockwise will decrease the input. The
adjusted manifold pressure should not vary more
than 10% from the pressures specifi ed in chart 5.