Solenoid Valve
// How it works — de-energized vs energized — troubleshooting
DE-ENERGIZED STATE
○ Coil: 0VDC — off
○ Plunger: retracted by spring
○ Spool: spring position
→ P connects to B
→ A vents through EA
Cylinder: RETRACTED
Fail-safe position: this state
// Quick Specs & Field Notes
Electrical Specs
Voltage: 120VAC (crystallizer solenoids)
Good coil resistance: 85–120Ω
Shorted coil: <10Ω — replace immediately
Open/burned coil: ∞ ohms — replace
Response time: 10–50 milliseconds
Current draw: ~0.1–0.2A at 120VAC
Good coil resistance: 85–120Ω
Shorted coil: <10Ω — replace immediately
Open/burned coil: ∞ ohms — replace
Response time: 10–50 milliseconds
Current draw: ~0.1–0.2A at 120VAC
Pneumatic Specs
Supply pressure: 80–120 PSI
Minimum to operate: 20 PSI
Maximum: 150 PSI
You'll hear: Sharp click when energizing
Warm coil: Normal — hot coil is NOT normal
Manual override: Red/yellow button on top
Minimum to operate: 20 PSI
Maximum: 150 PSI
You'll hear: Sharp click when energizing
Warm coil: Normal — hot coil is NOT normal
Manual override: Red/yellow button on top
// Troubleshooting Reference
| Symptom | Likely Cause | First Check |
|---|---|---|
| No click, coil cold | No voltage reaching coil | 120VAC at terminals — check relay/triac output, fuse, wiring |
| No click, voltage present | Open coil (burned) | Ohm test: should read 85–120Ω. ∞ = replace coil |
| Click but air won't switch | Plunger or spool stuck | Push manual override — does air switch? Then it's mechanical |
| Coil very hot, trips breaker | Shorted coil | Ohm test: <10Ω = short. Replace immediately (fire hazard) |
| Buzzing / humming | AC hum or loose plunger | Verify DC coil on DC supply. Check plunger seats fully |
| Leaks air when de-energized | Worn spool seals | Listen at exhaust ports — rebuild or replace valve body |
| Dextrose buildup on plunger | Product contamination | Clean with air or replace valve body. Monthly maintenance |
// 04_Limit_Switches/Solenoid_Valve_How_It_Works.html │ INSTRUMENTATION FIELD MANUAL