Chromalox PQ402-6 service manual Limited Warranty, 2150 N. RULON WHITE BLVD., OGDEN, UT, Phone

LOW WATER CUT-OFF — Like the pressure control, difficul- ties can be broken down into the mechanical and electrical groups.

The mechanical difficulties can be corrected on the high pres- sure 100 psig motor and pump units in the following manner:

1.Remove the cover and test the free movement of the float valve. If the float valve is in the off or down position, then the float is either punctured or dirt and sediment is encrusted in the float chamber. Both of these problems will involve disassem- bly of the float chamber.

2.Check the electrical contacts to determine if they are defective. Defective mercury tube contacts will cause the boiler to fill high- er than normal. This occurrence will require replacement of the mercury tube.

On low pressure feed units, the mechanical test is best made by cleaning the valve seat beneath the float valve linkage to

WATER FEED MECHANISMS — A common problem in this area is boiler flooding, which may be caused by a defective float or solenoid.

The Low Water Cut-Off must be disassembled to check the float valve. The solenoid can be isolated by disconnecting the union after the solenoid and energizing and de-energizing the solenoid. If water comes out continuously or does not come out at all, then the solenoid is defective.

assure that it is properly seated. If the valve seat is scarred or defective, the entire valve seat must be replaced. Also, if the float valve is in the down or “off” position, it may be punctured or encrusted with dirt and the unit must be disassembled.

On all McDonnell-Miller cut-offs, restrictions in the equalizer column can cause burnt out elements. The cause will appear to be a low water condition. Regular blowdown procedures on the equalizer column as well as the boiler will prevent this occur- rence. Correction of the problem can be made by both removing the plug from the side of the column and opening the Low Water Cut-Off blowdown valves. A snake should be used to clean the vertical and horizontal columns.

The electrical trouble shooting should be checked by referring to the Contactors, Elements and Voltages section.

A defective check valve can cause the pump motor to run continuously or cause loss of water pressure. If the pipe between the check valve and the water supply is hot, boiler water is back- ing up through the check valve and the check valve must be replaced. A defective check valve can also prevent water from entering the boiler.

The coupling between the motor and pump may be loose; the entire pump must be replaced if the coupling is excessively worn.

Limited Warranty:

Please refer to the Chromalox limited warranty applicable to this product at http://www.chromalox.com/customer-service/policies/termsofsale.aspx.

2150 N. RULON WHITE BLVD., OGDEN, UT 84404

Phone: 1-800-368-2493 www.chromalox.com