Middleby Marshall PS570 Inlet Pressure Check, Pilot Pressure Adjustment, Blowers without, opening

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 36863 - Gas Conversion Kit for PS360EWB/WB70 with Midco Burner, Propane to Natural Gas, 1/98

6. INLET PRESSURE CHECK

6.1Check the gas control inlet pressure at the inlet pressure tap. See Figure 6. An inlet pressure of 6-14” (14.9-34.9mbar) is recommended for natural gas operation.

6.2If the inlet pressure is:

•HIGHER THAN 14” W. C. (34.9mbar) - This pressure may damage the combination gas control valve. Decrease the supplied gas pressure.

•LOWER THAN 3” W. C. (7.46mbar) - It may be necessary to increase the supplied gas pressure.

If it is necessary to adjust the gas line pressure, have the customer contact the gas utility supplier.

7. PILOT PRESSURE ADJUSTMENT

7.1Ensure that the main burner primary air supply is properly adjusted for natural gas operation.

•Units with a burner blower air shutter (see Figure 5) should have the shutter opening (at its outside edge) set to 5/16” (7.94mm). A drill bit can be used to check the adjustment of this opening.

•Units without the air shutter (see Figure 5) should have the burner air supply adjustment screw turned 11-17 full revolutions clockwise from the fully closed (counterclockwise) position. The screw is located on the front wall of the burner plenum, and is surrounded by a “MORE AIR” label.

		Figure 5
Insert a 5/16”	Burner blower configurations		Blowers without
(7.94mm) drill			external air shutter
bit to measure
opening
(remove before
operation)	External
		air	OR
	shutter

7.2Before proceeding:

•For a PS360EWB oven, the set point should be reduced below the room temperature.

•For a PS360WB70 oven, set the oven to low flame.

7.3Measure the pilot pressure as shown in Figure 6. The gas pressure should be 5-6” W. C. (12.5-14.9mbar) for proper operation.

7.4If necessary, adjust the pilot pressure as follows:

•Remove the pilot adjustment cap screw.

•Using a screwdriver, turn the inner adjustment screw counterclockwise to increase, or clockwise to decrease, the pilot gas pressure.

•Replace the cap screw and tighten it firmly.

7.5Measure the current across the pilot flame sensor. The current must measure at least 2.0 ∝ A. If the current reading is too low, recheck the pilot pressure as per Step 7.3. If the pressure reading is correct, consult the factory; otherwise, repeat Steps 7.4 and 7.5.

8. MAIN MANIFOLD PRESSURE ADJUSTMENT

8.1With the oven set to high flame, measure the regulated gas pressure to the burner. The outlet pressure should be checked at the main orifice pressure tap. See Figure 6. The gas pressure should be 3” W. C. (7.46mbar) for proper operation.

8.2If necessary, adjust the pressure regulator as follows:

Figure 6

Gas pressure measurement/adjustment locations

Pressure	Pilot tube
regulator cap	connects
screw	here
Inlet pressure	Pilot
	adjustment
tap	cap screw
	Main orifice
	pressure tap
	Pilot pressure
	tap

•Remove the pressure regulator cap screw.

•Using a screwdriver, turn the inner adjustment screw clockwise to increase, or counterclockwise to decrease, the main burner gas pressure.

•Replace the cap screw and tighten it firmly.

8.3Record the final measured regulated gas pressure on the silver conversion information label (included in the kit).

p/n 36862 P. Jan. 98 Rev B Page 3 of 4

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