Sterling TC - Manual (Page 23)

23
OPERATION
PRIMARY AIR SHUTTER ADJUSTMENT
Primary air adjustment is made at the factory. No fi eld adjustments are necessary.
GAS INPUT RATE
2. PROPANE GAS: An exact manifold pressure of
10.0" W.C. (2.5 kPa) must be maintained for proper
operation of the unit heater. If the unit is equipped
with a pressure regulator on the combination gas
valve, follow steps "a" through "d" above. If the unit
is not so equipped, the propane gas supply system
pressure must be regulated to attain this manifold
operating pressure.
3. The adjusted manifold pressure should not vary
more than 10% from pressure specifi ed in Table 8.
Table 8 - Main Burner Orifi ce Schedule*
*This schedule is for units at operating at normal altitudes of 2000 ft. (610m)
or less.
When installed in Canada, any references to deration at altitudes in excess
of 2000 ft. (610m) are to be ignored. At altitudes of 2000 to 4500 ft. (610 to
1372m), the unit heaters must be fi eld derated to 90% of the normal altitude
rating, and be so marked in accordance with ETL certifi cation. See Table 8A
for fi eld deration information.
Check the gas input rate as follows (Refer to General
Safety Information section for metric conversions).
Never overfi re the unit heater, as this
may cause unsatisfactory operation, or shorten the
life of the heater.
1. Turn off all gas appliances that use gas through the
same meter as the unit heater.
2. Turn the gas on to the unit heater.
3. Clock the time in seconds required to burn 1 cubic
foot of gas by checking the gas meter.
4. Insert the time required to burn one cubic foot of
gas into the following formula and compute the input
rate.
3600 (Sec. per Hr.) X BTU/Cu. Ft.
= Input Rate
Time (Sec.)
For example:
Assume the BTU content of one cubic foot of gas is
1000, and that it takes 18 seconds to burn one cubic
foot of gas.
3600 x 1000
= 200,000
18
NOTICE: If the computation exceeds, or is less than
95% of the gas BTU/hr. input rating (see Table 1),
adjust the gas pressure.
Adjust the gas pressure as follows:
1. NATURAL GAS: Best results are obtained when
the unit heater is operating at its full rated input
with the manifold pressure of 3.5" W.C. (0.9 kPa).
Adjustment of the pressure regulator is not normally
necessary since it is preset at the factory. However,
fi eld adjustment may be made as follows:
a. Attach manometer at the pressure tap plug
adjacent to the control outlet.
b. Remove the regulator adjustment screw cap,
located on the combination gas valve.
c. With a small screwdriver, rotate the adjustment
screw counterclockwise to decrease pressure, or
clockwise to increase pressure.
d. Replace regulator adjustment screw cap.
INPUT
IN
1,000
BTU
TYPE OF GAS NATURAL PROPANE
NO. OF
BURNER
ORIFICES
HEATING VALUE
1050 BTU/Ft3
(39.1 MJ/m3)
2500 BTU/Ft3
(93.1 MJ/m3)
MANIFOLD
PRESSURE 3.5" W.C. 10" W.C.
(0.87kPA) (2.49kPA)
100
FT3/HR 93 40
4
ORIFICE DRILL 42 53
125
FT3/HR 116 50
5
ORIFICE DRILL 42 53
150
FT3/HR 140 60
6
ORIFICE DRILL 42 53
175
FT3/HR 163 70
7
ORIFICE DRILL 42 53
200
FT3/HR 186 80
8
ORIFICE DRILL 42 53
250
FT3/HR 233 100
9
ORIFICE DRILL 42 53
300
FT3/HR 280 120
10
ORIFICE DRILL 42 53
350
FT3/HR 326 140
11
ORIFICE DRILL 42 53
400
FT3/HR 372 160
12
ORIFICE DRILL 42 53