Basic Troubleshooting

Gateway plugged in to service jack but…

…no LED at all

If the LED is always off, there either is no power or the firmware is wrong, corrupt or has a wrong setting.

  • No power on the Service jack -> Plug in a power adapter to the Gateway directly. The LED should start blinking now.

  • You are shortcutting the bus or the jack. -> unplug the Gateway and wait 2 min before plugging it back in.

  • No firmware or firmware update error -> Reload a stable firmware image.

  • LED is turned off in the firmware settings -> Log in to the web interface and turn it on.

…LED keeps blinking forever

If the LED keeps blinking forever with 3 beeps this means it cannot find the EMS bus AND the WiFi network.

  • Boiler with no EMS bus -> The Gateway is only compatible with the EMS bus.

  • EMS wires not connected or faulty -> Reconnect the jack cable or otherwise connect the screw terminal of the Gateway to the thermostat wires.

  • WiFi network disconnected.

…LED turns solid but start blinking again after a while.

In this case the EMS bus was found at some point, but due to either intermittency problems the communication was lost. Or the Gateway lost its connection to the WiFi network.

  • Bus wires not connected properly -> Reconnect the EMS bus wires.

  • Insufficient power -> Use another power supply

…LED turns solid but web interface says ‘TX not working’.

In this case the EMS bus was found, but the Gateway cannot communicate with the bus.

  • Bus wires not connected properly -> Reconnect the EMS bus wires.

  • Service jack cable not connected properly -> unplug and replug the cable, reboot the Gateway.

  • TX mode is wrong -> For some boilers TX mode 1 EMS is not the correct mode, try mode 2 or 3.

  • You hacked together your own board -> TX getting to work is very tricky!

…LED is blinking or is solid but cannot connect to the web interface or with Telnet.

This is likely caused by network communication issues.

  • You are not connecting to the right IP or if using Telnet not on port 23 -> Change to the IP address of the Gateway and to port 23.

  • Your laptop (with Telnet) is not on the same network as the Gateway -> The Gateway should be on either your home network or it is in access point mode. In the latter case connect your laptop to the ‘ems-esp’ Wi-Fi network.

…the boiler reboots once on insertion of the cable

This usually happens when you insert the cable into the boiler and then into the Gateway. If the reboot happens once, you can ignore it.

…the boiler reboots continuously or intermittently

In this case the cable does not fit properly on either the boiler side or the Gateway side. Press the cable firmly into the connector or try another cable.

Gateway connected to the EMS wires but…

…the boiler reboots continuously or intermittently

  • Shortcut of the wires or not enough power on the bus. Check the wires. Try the service jack or a USB adapter.

…the boiler or thermostat gives an error code like BUS ERROR or A01, A51

  • Only for the Premium II: There is not enough power available on the bus for the Gateway. Try the service jack or a USB adapter. If you have a module like a solar or mixer module with a BUS OUT terminal you can connect the Gateway there.

…the boiler starts heating by itself

  • Some boilers like the Bosch Condens 2500 accept either a on/off or EMS thermostat on the same terminal. If you have an on/off thermostat but you also connect the Gateway, the boiler detect a device on the bus and goes into EMS mode. But the Gateway is not a thermostat and the boiler starts heating anyway.

… the Gateway often disconnects from the WiFi

  • You have bad WiFi reception where the Gateway is located.

  • Only for the Premium II: There is not enough power available on the bus for the Gateway. Try the service jack or a USB adapter. If you have a module like a solar or mixer module with a BUS OUT terminal you can connect the Gateway there.

  • If you have an Asus router: turn off IGMP snooping, Band steering.

  • If you have a Unifi system: when WiFi reception is low, Unifi may kick the ESP from the channel so it can reconnect. However, this reconnect is then at another channel which the ESP chip does not like. There is no good solution for this yet.

…My RC310 or other thermostat turns off, or the bus stops working after a few minutes

Reverse the wires on the screw terminal of the Gateway. The RC310 is polarity sensitive.

…the bus stops suddenly stopped working with an E32 connected

Remove the E32 and powercycle the boiler. See if the bus works again. Connect the E32. If the problem persists and you have a 2021 or 2022 E32, contact me.

Gateway connects to home network but MQTT is not connected

There can be a range of issues.

  • Wrong IP -> Set the correct IP of your MQTT broker. This is not always the same IP address as your home automation system.

  • Wrong user/password -> Make sure the MQTT authentication is set right or not at all.

  • Wrong port -> the MQTT port is 1883 by default. If you need to change this you have to build the firmware yourself.

  • MQTT broker is not running -> Make sure the broker is running on the target machine.

  • MQTT broker is not installed -> Install a MQTT broker like Mosquitto on the target machine.

Gateway connects to home network but MQTT gives the error ‘TCP Disconnected’

You have (updated to) Mosquitto 2.0. The default configuration of Mosquitto version 2.0 now only accepts (anonymous) clients from local host (the same machine Mosquitto is running on). So if you have previously used an older version of Mosquitto with no additional config, Mosquitto will now deny external connections from for instance the Gateway/EMS-ESP. In order to accept clients outside of local host you need to add a listener on port 1883 and add an authentication method. Google around on how to do it (See f.i.

MQTT is connected but seemingly no response

  • You are listening or publishing to the wrong MQTT topics -> verify the topic string.

MQTT is disconnecting all the time after I upgraded the ESP module or Gateway

  • You are using the same MQTT client ID of the old Gateway, while the old ESP is still active.->Turn off the old ESP module.

My E32 has no Ethernet or no EMS bus after an firmware update/error

The problem here is that the board profile is not correctly set to the E32. If it is set incorrectly, EMS-ESP is looking on the wrong pins for the EMS bus and it does not know Ethernet is available. You have to go to Settings->board profile and set the board profile to any other than E32, save. Next set it to E32, save and reboot. This will bring back Ethernet and EMS bus.

The WiFi connection drops when it is connected to a Unifi access point

Your Gateway is connected to a Unifi access point, and it disconnect with ‘REASON code=auth expire’. This a common problem with the WiFi library of the ESP32, there are no really good solutions. The problem is caused when the Gateway tries to reconnect to an access point. -> Try to fix the Gateway to a specific access point and channel.

MQTT seems unstable and WiFi drops intermittently and the Gateway does not reconnect

Firmware versions 3.6.0 to 3.6.3 can have issues staying connected to a mesh network. Specifically Fritzbox systems may be affected. Please use the network settings and fill in the BSSID of the mesh node or access point to which the Gateway should connect. This has solved the problem for most users.

When I try to set a parameter on my Junkers/Worcester boiler, nothing happens

Some Junkers/Worcester boilers do not allow changes to be made from the bus. Others only allow temperatures to be set lower than the dial setting on the front of the boiler -> Set the dial higher or to max.

More troubleshooting

For more troubleshooting see Proddy’s EMS-ESP Wiki [1]. Or send me an email via the webshop.