Troubleshooting

Solenoid Valves

CAUTION - Dangerous hydraulic pressures may develop if a hand valve is installed in the liquid line head of the solenoid valve and the hand valve is closed while the solenoid valve is closed. Also the line between these two valves should be pumped down completely before disassembling the solenoid valve for service. There are only four possible malfunctions.
1. Coil burnout.
2. Failure to open.
3. Failure to close.
4. Solenoid valve noise.

1. COIL BURNOUT :
Coil burnout are extremely rare unless caused by one of the following:
A) Improper electrical characteristics
B) Continuous over voltage, more than 10%
C) Under voltage of less than 15%. This applies only if the operating conditions are such that reduced MOPD causes stalling of the plunger, which results in excessive current draw.
D) Incomplete magnetic circuit due to the omission of parts such as: Coil housing, Coil plate, Enclosing tube, Sleeves or Plunger.
E) Mechanical interference with movement of plunger which may be caused by a deformed enclosing tube. F) Continuous operation of a standard solenoid on a steam application where a high temperature coil is required.

2. FAILURE TO OPEN :
A) Solenoid valve assembled incorrectly. Check the location of the coil sleeves, coil plate, and the coil. Each part must be positioned correctly if the valve is to function properly.
B) System operating pressure to high. Check the actual pressure differential across the valve against the nameplate MOPD rating. If the actual pressure differential exceeds the nameplate rating, a valve with a higher MOPD rating must be used.
C) Dirt of sludge causing the valve to stick. Dismantle the valve and completely clean the interior and components parts. Install appropriate Strainer of proper capacity to prevent foreign material from reaching the valve.
D) Low voltage. The voltage applied to the solenoid coil must be at least 85% of the rated nameplate voltage. If the voltage is found to be lower, the cost of the voltage drops must be determined and corrected. Common causes of voltage drops are undersized supply lines, other loads connected in series with the solenoid coil, loose connections and faulty control switches.
E) Coil burnout. Prolonged exposure to excessive ambient temperature can cause coil burnout. If the valve cannot be relocated to a space at a more reasonable temperature the use of a special high temperature coil is advisable.

3. FAILURE TO CLOSE :
A) Dirt or sludge causing the valve to stick. Dismantle the valve and completely clean the interior and component parts. Install appropriate Strainer of proper capacity to prevent foreign material from reaching the valve.
B) Electrical circuit closed because of faulty switch or relay contacts. Repair or replace the faulty controls.
C) Congealed oil causing valve to stick. Refrigerant oil should be of the proper type for the temperature range of the system. This is particularly true of low temperature application, clean interior of valve thoroughly. Change to oil of proper viscosity at system operating temperature .
D) Held open by the manual lift stem.
E) In pilot operated valves, damaged pilot port may prevent closing.

4. SOLENOID VALVE NOISE :
A partially open solenoid valve is apt to develop a mechanical chatter which may be amplified to an objectionable level by the system piping. This type of noise can be caused by low voltage, excessive pressure differential or foreign material, causing the valve to Hang in a partially open position. The noise can usually be eliminated by removing the cause of the sticking. A solenoid valve with a loose or mis-assembled coil and housing can exhibit an electrical hum. This type of noise is corrected by either tightening the coil housing nut securely, or by reassembling the valve parts in their proper order. Rarely, this may be caused by loose coil sleeves in which cases deforming them slightly will eliminate the hum.