PRE-OPERATION CHECK
Pump | |
Alarm Switch | |
| Low Water |
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| Terminals |
Alarm | Adjusting | |
Screws | ||
Circuit | ||
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Terminals |
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Pump |
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Circuit |
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Terminals | Pump | |
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Line | Switch | |
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Figure 11 – Automatic Reset Low Water Cutoff Junction Box
NOTES
1.Motor, Solenoid Valve and Dotted Control Wiring are included if Motor and Pump package is supplied. Solenoid Valve only is sup- plied with 99117 Water feed.
2.1/3 HP Motor is controlled directly without use of Motor Starter.
After proper wiring and piping of boiler system is complete, testing of controls can start. Before testing controls, it is recommended that all contactor fusing be removed. This is to prevent possible element fail- ure under test conditions.
CAUTION: Be sure all electrical connections are tight before energizing boiler. Reset all manual reset con- trols by pushing reset buttons on: (1) high limit control located on top of boiler and (2)
A.McDONNELL & MILLER LOW WATER CUTOFF CON-
TROL OPERATION AND TESTING
1.Be sure all valves from incoming water supply are fully open. Turn boiler switch to “ON” position, pump or solenoid valve will ener- gize, allowing boiler to fill with water. Proper water level is auto- matically reached with level control supplied. Pump or solenoid feed will shut off at proper water level. Contactor(s) will energize, supplying power voltage to elements.
2.Checking operation of pump switch. (Figure 11) With water level visible in sight glass, partially open drain valve at bottom of boil- er. If automatic blowdown supplied, push manual blowdown switch until valve open light is on, hold for few seconds. Water level will fall, allowing float to trip pump switch to “ON” position. Close drain valve or release manual blowdown switch. Pump motor or solenoid valve will energize and water level will resume to normal level in sight glass.
3.Checking low water cutout switch operation, open drain valve completely. If automatic blowdown supplied, push in and hold manual blowdown switch until water level falls enough to trip cutout switch. Close drain valve or release manual blowdown switch. If low water cutout is automatic reset, pump or solenoid will return water level to normal. If low water cutout is manual reset, then manual reset button on McDonnell & Miller low water cutoff control must be pushed to complete circuit. Turn off boiler.
Reinstall contactor fuses.
Pump
For pump motors 1/2 h.p. Single Phase or less, or D.C. 1/4 h.p. or less,
wire as main line switch.
Line
Wiring Diagram – McDonnell & Miller Low Water Cutoff and Pump Control
B. ADJUSTING OPERATING PRESSURE CONTROLS
1.Chromalox boilers are supplied with operating and high limit pres- sure controls. One is used for controlling the operating pressure of the boiler while the other is used as a high limit control. To deter- mine the difference in the controls, the high limit has a manual reset lever on top of the case. Also, there is no differential scale present.
2.On all controls, the pressure adjusting screw on the top of the case sets the desired pressure. Turning the screw counterclockwise reduces the pressure setting (see Figure 12). High limit control should be set at 10 psig above the operating pressure of the boiler.
3.The differential adjusting screw on the operating control is set in the same manner as the pressure adjusting screw. This scale set- ting, plus the main scale setting, equals cutout pressure of the oper- ating control. (Scale A thru F equals 3 psi per letter. L9l B only) L404A Differential is indicated on Scale Plate.
| Pressure |
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| Adjusting | Mercury | ||
Differential | Screw |
| Switch | |
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Adjusting |
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Screw |
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Differential |
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Setting |
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Indicator |
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Pressure |
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Setting |
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Indicator |
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Operating Lever |
| Index Mark | ||
Diaphragm Assembly Leveling | ||||
Pointer | ||||
| Indicator | |||
Figure 12 – Pressure Control
To check operation of the controls, close steam outlet valve and adjust operating pressure control to a low pressure setting. Also, set high limit control at 10 psig above operating pressure control.
Turn on boiler and allow pressure to build up. When pressure gauge reading approaches set point of pressure control, the switch will trip and shut off boiler. Turn boiler main switch to “OFF".
To reset pressure control, bleed off enough pressure in the boiler by opening steam outlet drain, or blowdown valve to allow the operating control to reset.
4.HIGH LIMlT PRESSURE CONTROL OPERATION. The high limit is tested in the same manner but with the operating con- trol set above the pressure setting of the high limit. (Figure 13)
CAUTION: THIS IS FOR TEST PURPOSES ONLY!
When the high limit trips turn off boiler and reset high limit to proper setting, the manual reset level must be pushed to resume operation upon startup.
Pressure | Manual |
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Adjusting | Reset | Mercury | |
Screw | Lever | ||
Switch | |||
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Scaleplate
Pressure
Setting
Indicator
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| Index | |
Operating Lever | Leveling | Mark | |
| Pointer | ||
Diaphragm | Indicator | ||
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Assembly |
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Wiring Diagram – McDonnell & Miller Low Water Cutoff and Pump Control
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