Medium
E783 on Navien LCB700

Your boiler has lost communication with its smart thermostat or remote control unit, preventing it from receiving instructions on when to turn on the heating or hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Abnormal operation: OpenTherm remote control

From this model's manual
Verified against the Navien/Navien Lcb700 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Switch off the power supply to the boiler at the fused spur or circuit breaker.Locate the thermostat or remote controller and check that the wiring connections are secure.Wait 5 minutes for the system to reset, then turn the power back on to see if communication is restored.

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Related fault codes

E782View →

All 29 fault codes on the LCB700

Seeing a different code? Every code this model can display, in one place.

E001E003E004E012E016E030E031E046E047E109E110E127E205E302E352E353E407E421E441E445E480E515E517E594E615E740E782E787

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