Sterling RF-90 Primary Air Shutter Adjustment, Gas Input Rate, Main Burner Orifice Schedule

= 75,000

PRIMARY AIR SHUTTER ADJUSTMENT

Primary air adjustment is made at the factory. No field adjustments are necessary.

GAS INPUT RATE

Check the gas input rate as follows (Refer to General Safety Information section for metric conversions).

Never overfire 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.

2.PROPANE GAS: An exact manifold pressure of 10.0 inches 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 specified in Tables 5 & 6.

Table 5 - Main Burner Orifice Schedule*

	TYPE OF GAS	NATURAL	PROPANE
*
	HEATING VALUE	1075 BTU/Ft3	2500 BTU/Ft3
INPUT		(40.1 MJ/m3)	(93.1 MJ/m3)

3600 (Sec. per Hr.) X BTU/Cu. Ft.

Time (Sec.)

For example:

= Input Rate

IN	MANIFOLD	3.5" W.C.	10" W.C.	NO. OF
1000				BURNER
	PRESSURE	(0.87kPA)	(2.49 kPA)
BTU				ORIFICES
30	FT 3/HR	28	12	2
	ORIFICE DRILL	49	57
45	FT 3/HR	42	18	3

Assume the BTU content of one cubic foot of gas is 1000, and that it takes 48 seconds to burn one cubic foot of gas.

3600 x 1000

48

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 inches W.C. (0.9 kPa). 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 below 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.

	ORIFICE DRILL	49	57
60	FT 3/HR	56	24	4
	ORIFICE DRILL	49	57
75	FT 3/HR	70	30	5
	ORIFICE DRILL	49	57
90	FT 3/HR	84	36	5
	ORIFICE DRILL	47	55

*This schedule is for units 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 orificed to 90% of the normal altitude rating, and be so marked in accordance with ETL certification.

TUBULAR UNIT HEATER

HIGH ALTITUDE DERATION

This Tubular Unit Heater has been manufactured utilizing standard burner orifices and a normal manifold pressure setting as per the specifications shown on your unit rating plate (refer to Tables 3, 5 and 6).

All unit deration must be done through field adjustments by a qualified technician (refer to Table 6). Once the proper adjustments are made in the field, attach label #J17-06459 to the unit, and record adjusted manifold pressure, altitude of the unit installation and the technician’s name and date on the label using a permanent marker.

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