Sterling TF-250, TF-400, TF-150, TF-300, TF-200 Primary Air Shutter Adjustment, Gas Input Rate

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 Table 5.

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)
IN	MANIFOLD			NO. OF
		3.5" W.C.	10" W.C.

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

Time (Sec.)

For example:

= Input Rate

1000	PRESSURE	(0.87kPA)	(2.49 kPA)	BURNER
BTU				ORIFICES
100	FT 3/HR	93	40	4
	ORIFICE DRILL	42	53
125	FT 3/HR	116	50	5
	ORIFICE DRILL	42	53

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

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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 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 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.

150	FT 3/HR	140	60	6
	ORIFICE DRILL	42	53
175	FT 3/HR	163	70	7
	ORIFICE DRILL	42	53
200	FT 3/HR	186	80	8
	ORIFICE DRILL	42	53
250	FT 3/HR	233	100	10
	ORIFICE DRILL	42	53
300	FT 3/HR	280	120	12
	ORIFICE DRILL	42	53
350	FT 3/HR	326	140	14
	ORIFICE DRILL	42	53
400	FT 3/HR	372	160	16
	ORIFICE DRILL	42	53

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

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