Why Do Solenoid Valves Get Hot?
Solenoid valves are widely used for controlling the flow of liquids and gases in industrial, commercial, and domestic systems. A common question is why these valves often feel warm – or even hot – during operation. Understanding the reasons helps ensure safe use and prevents unnecessary concern.
How a Solenoid Valve Works
A solenoid valve uses an electrical coil to generate a magnetic field. This magnetic force lifts or lowers a plunger, opening or closing the valve. When electrical current passes through the coil, energy is converted into heat. This is a normal part of solenoid valve operation.
Reasons Solenoid Valves Become Hot
Electrical Coil Heating
Coils are essentially copper wire windings around a bobine which are typically encapsulated. As current flows generating the magnetic field the electrical resistance generates heat. If you can imagine an old style filament 15 Watt light bulb, after a while these become hot.
The longer the coil is energised, the more heat it builds up.
Duty Cycle
Continuous duty valves are designed to stay powered for long periods, but they will still feel warm.
Intermittent duty coils heat up faster and are not intended for constant energisation.
Power Supply Issues
Excess voltage or incorrect frequency (e.g., 50Hz vs 60Hz mismatch) can cause coils to overheat.
Under voltage can also increase current draw and temperature.
Read more about solenoid coils and duty cycle.
Ambient Conditions
High room temperature or poor ventilation around the valve prevents heat from dissipating.
Enclosed cabinets and hot environments accelerate coil warming.
Incorrect Valve Sizing or Installation
Oversized or undersized valves may force the coil to work harder.
Dirt, scale, or mechanical blockage can trap the plunger, making the coil overheat while trying to move it.
How Hot is Normal?
Many solenoid valve coils run 30–50°C above ambient temperature.
In a room at 20°C, it’s common for a coil to reach 50–70°C, which feels hot to the touch but is within design limits.
Manufacturers specify a maximum coil temperature (often around 80–120°C) that should not be exceeded.
Tips to Reduce Coil Heating
Verify the correct voltage and frequency match the coil rating.
Use continuous duty coils where the valve is powered for long periods.
Ensure good ventilation and avoid installing valves in enclosed, unventilated spaces.
Check for dirt, blockages, or mechanical sticking that increase coil stress (Pull).
Consider using pulsed power or energy-saving coils for long-term energisation.
Consider using low power electric actuated ball valves.
When to Take Action
Some warmth is completely normal, but you should investigate if:
The coil surface is too hot to touch for more than a few seconds.
The plastic housing shows signs of melting, cracking, or discolouration.
This is picture of a burnt out solenoid coil 240v 50Hz coil.
AC (Alternating Current) solenoids have an inrush and holding current.
In this instance the INRUSH 17.6VA, HOLD 15.9VA (VA = Volts Amperes), so 230v with 17.6VA = 0.0765 amp.
The inrush current is higher than the holding current when it is lifting or moving an internal plunger.
When the plunger reaches the fully energised position the coil reduces power consumption to the holding current.
But, if the valve has debris preventing the plunger reaching its fully energised position the coil will continue to draw the increase inrush current - thus over heating.
The valve fails to operate reliably (sticking, buzzing, or weak opening).
In these cases, switch off the power and check electrical ratings, coil type, and valve condition.
Summary.
Solenoid valves get hot primarily because electrical current in the coil generates heat. In most cases this is normal and expected, but overheating can indicate a power mismatch, mechanical issue, or unsuitable coil type. Correct sizing, installation, and ventilation will keep solenoid valves working reliably and safely.