OPERATION
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 (CUT OUT) (See Figure 2). 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. The CUT OUT set- ting minus the differential setting, equals CUT IN pressure of the operating control.
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Differential | Adjusting |
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Screw |
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Adjusting Screw |
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Scaleplates |
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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 |
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Lever |
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Figure 2 — 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 off boiler.
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 LIMIT PRESSURE CONTROL OPERATION
The high limit is tested in the same manner but with the operating control set above the pressure setting of the high limit. (Figure 3)
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 |
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Reset |
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Screw | Mercury | ||
Lever | |||
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Scaleplates |
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Pressure |
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Setting |
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Indicator |
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Operating |
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Lever |
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Diaphragm |
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Indicator |
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Assembly |
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Figure 3 — Hi Limit Control
OPERATION
RECOMMENDED START-UP PROCEDURES
1.Close globe valve on steam outlet side of boiler. (Customer Supplied)
2.Turn on boiler and allow pressure to build up to operating pressure.
3.Only open globe valve at quarter turns at first, introducing smaller amounts of steam into process. Avoid opening globe valve all at once. This will eliminate the possibility of evacuating the boiler of water caused by the suddenly increased boiling of the water in the vessel as the pressure is reduced. On boilers where constant pres- sure is not maintained, globe valve should be kept partially closed. This will maintain a constant head on the boiler and stabilize any fluctuation in boiler water level.
Note: For best boiler performance, a 1/4” less steam valve
than size of safety valve should be plumbed as close as practi- cable to steam outlet. Where 1/2” safety valve is used on boil- er, a 1/4” steam valve is recommended.
MANUAL BLOWDOWN INSTRUCTIONS
Blowdown is an essential part of boiler operation. It is the best preventative maintenance you can give your boiler and will add years of life to the unit. Make sure a blowdown schedule is estab- lished and followed regularly.
In extremely hard water areas, blowdown is necessary once a day. In soft water areas, once each week. If there is a particular problem which applies to your own local water condition other
than mineral content, take this into consideration in determining which schedule is to be followed.
1.At end of the working day, while boiler is still operating, turn switch to the OFF position and close water supply valve.
2.If
3.It is preferable to connect the blowdown valve directly into a drainage system. If this is done, the boiler can be discharged at operating pressure.
4.When discharge is complete and boiler is drained — (a) close the blowdown valve; (b) open water supply valve; (c) put boiler switch in the ON position; and, (d) close wall mounted safety switch.
5.When refilling is complete, turn off the boiler switch unless further operation is desirable.
6.If you have been supplied with a Manual Reset Low Water control as required in some states, the reset button on the control must be pushed before boiler will begin developing pressure. (Do not push reset until boiler has filled with water.)
The use of chemical boiler cleaning compounds in these boilers voids all warranties unless approved by manufacturer. Some com- pounds will damage copper sheathed heating elements to shorten useful life.
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