E18
Schneider Electric
Valve / Actuator Output Failure
Thermostat shows E18 and indicates valve or actuator output fault in hydronic systems.
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Shorted thermal actuator on manifold, Overcurrent on 24 V actuator output, Miswired actuator polarity (for DC actuators), Failed output driver on thermostat or zone controller
How to Fix / Troubleshooting
Safety: Turn off power to the hydronic control circuit and thermostat.
Steps:
- Identify which valve or actuator is controlled by the faulty output (refer to zone labeling and wiring diagram).
- Disconnect the suspect actuator from the thermostat or zone controller and measure its coil resistance; compare to the manufacturer's specification. A very low resistance indicates a shorted actuator.
- Replace any actuator that is shorted or physically damaged (cracked housing, water ingress).
- After replacing the actuator, reconnect and restore power. If E18 persists, the thermostat or zone controller output channel may be damaged and require replacement.
- For multiple actuators on one output, ensure the total current draw does not exceed the Schneider Electric thermostat's rated output; use an external actuator controller if needed.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Hydronic Valve Actuator / Thermostat Actuator Output Channel
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements