Hot Solenoid Coils – Causes, Problems & Solution
Why do solenoid coils get hot?
It is completely normal for many solenoid valve coils to become hot during operation, especially when energised continuously for long periods. Standard DIN 43650A coils can often reach surface temperatures of +70°C to +90°C depending on:
→ Coil wattage
→ Ambient temperature
→ Duty cycle
→ Valve media temperature
→ Ventilation and enclosure design
→ Supply voltage stability
In confined spaces or hard-water applications, excessive coil temperature can create several long-term reliability problems.
Common Problems Caused by Hot Solenoid Coils
1. Reduced Coil Life
Continuous high temperatures accelerate insulation ageing and internal winding degradation.
Possible symptoms:
→ Premature coil failure
→ Reduced magnetic performance
→ Intermittent operation
→ Burnt or discoloured coils
2. Increased Heat Inside Panels & Enclosures
Multiple continuously powered valves inside cabinets or compact machinery can significantly raise internal temperatures.
This may affect:
→ PLCs
→ Sensors
→ Pneumatic controls
→ Electrical reliability
→ Cooling requirements
3. Limescale Build-Up in Hard Water Areas
One overlooked issue is heat transfer into the valve body and pipework.
In hard water applications, excessive valve temperature can accelerate:
→ Calcium deposits
→ Mineral scaling
→ Internal sticking
→ Reduced flow
→ Valve seizure
This is particularly common on:
→ WRAS water valves
→ Coffee machines
→ Wash systems
→ Steam/hot water equipment
→ RO and filtration systems
4. Higher Energy Consumption
Traditional continuously energised solenoid coils consume full holding power permanently, even after the valve has opened.
This results in:
→ Unnecessary energy use
→ Increased running costs
→ Excess heat generation
Solution – PWM Energy Saving DIN 43650A Connector (24vDC)
We now offer a practical solution using a PWM (Pulse Width Modulation) DIN 43650A energy-saving connector for 24vDC solenoid valves.
After initial energisation, the PWM circuit automatically reduces coil holding power whilst maintaining reliable valve operation.
Benefits include:
→ Dramatically reduced coil temperatures
→ Lower power consumption
→ Extended coil lifespan
→ Reduced enclosure heat build-up
→ Reduced limescale formation in hard water systems
→ Improved long-term reliability
→ Reduced operating costs
Real-World Temperature Reduction
During testing, standard continuously energised coils reached temperatures approaching +90°C after approximately 20 minutes.
With the PWM connector fitted:
→ Coil temperature rise became minimal
→ Surface temperature was almost undetectable even after more than 1 hour energised
→ Valve operation remained reliable
This can provide a major advantage in applications where valves remain powered for long periods.
Typical Applications
Recommended for:
→ WRAS water solenoid valves
→ Hard water areas
→ Continuously energised valves
→ Compact machinery
→ Enclosed control cabinets
→ OEM equipment
→ Process systems
→ Energy-conscious installations
Important Information
→ Suitable for 24vDC solenoid coils only
→ DIN 43650A / Form A connection
→ Holding power adjustable via jumper settings
→ Helps reduce coil operating temperature substantially
→ Easy retrofit installation on compatible valves