Sterling TD - Manual (Page 26)

26
GAS INPUT RATE
Check the gas input rate as follows (Refer to General
Safety Information section for metric conversions).
Never over-fi re the duct furnace, 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 duct furnace.
2. Turn the gas on to the duct furnace.
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 1 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 2),
adjust the gas pressure.
Adjust the gas manifold pressure as follows:
1. NATURAL GAS: Best results are obtained when the
duct furnace is operating at its full rated input with a
manifold pressure of 3.5 inch WC (0.9kPa). Adjustment
of the pressure regulator is not normally necessary
since it is preset at the factory. However, field
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.
2. PROPANE (LP) GAS: An exact manifold pressure of
10.0 inch WC (2.5 kPa) must be maintained for proper
operation of the duct furnace. If the duct furnace is
equipped with a pressure regulator on the combination
gas valve, follow steps “a” through “d” above. If the
duct furnace is not so equipped, the propane gas
supply system pressure must be regulated to attain
this manifold operating pressure.
OPERATION (continued)
Table 7 - Main Burner Orifi ce Schedule – Standard
Altitude*
TUBULAR DUCT FURNACE
HIGH ALTITUDE DERATION
This Tubular duct furnace has been manufactured utilizing
standard burner orifi ces and a normal manifold pressure
setting as per the specifi cations shown on your unit rating
plate.
All unit deration must be done through fi eld adjustments
by a qualifi ed technician. Once the proper adjustments
are made in the fi eld, attach label #J17-06459 to the unit,
and record adjusted manifold pressure, altitude of the unit
installation, the technician’s name, and the date on the
label using a permanent marker.
Refer to installation instruction section Gas Input Rate for
adjusting the manifold pressure.
INPUT
IN
1000
BTU
2500 BTU/Ft 3
(93.1 MJ/m 3 )
PROPANE TYPE OF GAS NATURAL
HEATING VALUE
1050 BTU/Ft 3
(39.1 MJ/m 3 )
3.5 INCH WC
(0.87kPA)
10 INCH WC
(2.49 kPA)
NUMBER
OF BURNER
ORIFICES
MANIFOLD
PRESSURE
2
3
4
5
6
7
8
100
150
200
250
300
350
400
FT 3 /HR
ORIFICE DRILL
FT 3 /HR
ORIFICE DRILL
FT 3 /HR
ORIFICE DRILL
FT 3 /HR
ORIFICE DRILL
FT 3 /HR
ORIFICE DRILL
FT 3 /HR
ORIFICE DRILL
FT 3 /HR
ORIFICE DRILL
93
3.40mm
140
3.40mm
186
3.40mm
233
3.40mm
280
3.40mm
326
3.40mm
372
3.40mm
40
45
60
45
80
45
100
45
120
45
140
45
140
45
*This schedule is for units at operating at normal altitudes of 2,000 feet
(610m) or less.
When installed in Canada, any references to deration at altitudes in excess of
2000 feet (610m) are to be ignored. At altitudes of 2,000 to 4,500 feet (610 to
1372m), the unit must be fi eld derated and be so marked in accordance with
ETL certifi cation. See Table 7A for fi eld deration information.