Junkers EMS Gateway
6 fault codes documented
Blue LED 1 flash (slow blink) — EMS bus not connected
The blue LED on the Gateway blinks once slowly, then pauses, repeating this pattern. This signifies that the Gateway has booted up but is unable to detect or connect to the EMS bus from your boiler or Heat Pump.
Blue LED 2 flashes — Network not connected, EMS bus is connected
The blue LED on the Gateway blinks twice, then pauses, repeating the sequence. This indicates that the Gateway has successfully detected the EMS bus from your boiler, but it cannot establish a connection to your home's Wi-Fi or Ethernet network.
Blue LED 3 flashes — EMS bus and network both not connected
The blue LED on the Gateway blinks three times, then pauses, repeating the pattern. This indicates a complete lack of communication; the Gateway cannot detect the EMS bus from your boiler or Heat Pump, and it also cannot connect to your home network (Wi-Fi or Ethernet).
No LED on Gateway — No power or hardware issue
The blue LED on the Gateway is completely off after you plug it into the boiler or connect its power plug. This indicates that the device is not receiving power or might have a hardware problem preventing it from booting.
Gateway not functioning — Both jack and screw terminal connected simultaneously
The Gateway may not operate correctly, or it could experience a short circuit on the EMS bus if both the 3.5mm jack connector and the screw terminal are used at the same time to connect the EMS wires. These two connectors are internally hardwired.
Thermostat display not showing anything — EMS wires connected incorrectly
If your thermostat's display, such as an RC310, does not show anything after connecting the EMS Gateway, it indicates an issue with the EMS wire orientation. For some boilers and thermostats, the specific way the EMS wires are connected matters.