F49 displayed, communication error with external controller or bus

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.

Possible Causes

Short circuit on eBus wiring, Incorrect polarity on Protherm eBus terminals, Too many devices on bus, Faulty external controller

Safety first: Isolate power before working on low‑voltage wiring.

Step 1 – Inspect eBus wiring: Check that the two‑wire bus is correctly connected and not shorted or reversed.
Step 2 – Disconnect external devices: Temporarily disconnect external controllers one by one to identify a faulty device.
Step 3 – Restore basic control: If necessary, run the furnace using its built‑in controls until the bus fault is resolved.

Medium 3/5

eBus Communication Wiring

Check Price on Amazon

We may earn a commission from links on this page.