PB Heat MI/MIH series Start-Upprocedures, B.Control Descriptions, D.Adjustment Of Pilot Gas Flow

START-UP PROCEDURES

B.CONTROL DESCRIPTIONS

See Figure 6.1 in Section 6 (Electrical) for locations of these devices.

1.FLAME ROLL-OUT SAFETY SHUT-OFF SWITCH (FLAME ROLL-OUT SWITCH) – A thermally activated switch located between the first burner from the left and the manifold bracket. The flame roll-out safety shut-off switch will sense excessive temperature caused by continued flame roll-out and shut down main burner gas. This is a non-recycling switch that must be replaced once it has been activated and the cause of the roll-out eliminated.

2.VENT SAFETY SHUT-OFF SWITCH (SPILL SWITCH) – A thermally activated, manually resetable switch located in the draft hood relief opening. If venting system becomes partially or totally blocked, the vent safety shut-off switch will sense excessive temperature caused by flue products exiting the draft hood relief opening and shut down main burner gas.

3.LIMIT (AQUASTAT) – A thermally activated, manually adjustable switch located on the left side of the boiler, towards the top and rear. The temperature sensing element is placed in the supply and will shut down main burner gas if the supply water exceeds the preset temperature limit. This is a recycling switch that will automatically reset when the supply water falls below the preset temperature.

4.LOW WATER CUT-OFF (FOR GRAVITY SYSTEMS OR HOT WATER BOILERS INSTALLED ABOVE RADIATION LEVEL) – A level-sensing device (float or probe) located in supply piping near the boiler. If water level in the system drops below the control’s position, it will shut down main burner gas. The control will automatically reset once the water level rises above its position.

C.ADJUSTMENT OF GAS PRESSURE REGULATOR

1.Using the manometer setup installed in part 7A, set manifold pressure as follows for various gases.

a.Natural Gas . . .3.5″ Water Column (0.9 kPa)

b.LP Gas . . . . .10.0″ Water Column (2.5 kPa)

2.To adjust gas pressure, turn adjusting screw of gas pressure regulator counterclockwise to decrease pressure, clockwise to increase pressure. Refer to Figure 7.3 for location of gas pressure regulator. Replace the cap screw when adjustment is complete.

3.In no case should the final manifold pressure vary more than ±0.3 inches water column (0.07 kPa) from the above specified pressures. Any necessary major changes in the flow should be made by changing the size of the burner orifice spuds.

4.When adjustment is complete, turn off boiler, gas flow and electricity to boiler. Remove manometer connection from valve and plug tapping with plug provided. Turn utilities back on and resume checkout. GAS FLOW

D.ADJUSTMENT OF PILOT GAS FLOW

To maximize thermocouple life, particularly on natural gas installations with gas supply pressures above 9″ W.C. (2.2 kPa), reduce the pilot gas flow.

WARNING

Turn off all electric power to the appliance.

Turn Gas Control Knob to “Pilot” position as shown in Figure 7.3.

1.Locate and remove the pilot adjustment cap screw using Figure 7.3.

2.Remove pilot observation port cover on base front panel.

3.Turn the pilot adjustment screw clockwise until the pilot flame extinguishes. Then increase the pilot flow just to the point that the gas valve holds in when relighting the pilot per steps 9 and 10 of Lighting Instructions in Figure 7.5 (turn screw no more than an 1/8 turn).

4.Turn on electric power to the appliance.

NOTICE

The first few turns of the adjustment screw may not cause any change in the pilot flow. Subsequent partial turns of the adjustment screw may have a great impact on pilot flow.

5.Turn Gas Control Knob to “On” position per the Lighting Instructions in Figure 7.5.

6.Verify pilot remains lit after shutdown from a boiler “ON” cycle of at least ten minutes. If pilot extinguishes, follow Lighting Instructions in Figure 7.5 and again slightly increase pilot flow.

7.Make a final slight increase in the size of the pilot to ensure sufficient pilot signal under all operating conditions, just to the point that you observe a slight increase in the size of the flame (no more than an 1/8 turn).

8.Replace adjustment cap screw and observation port cover.

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