Connecting a Gateway Standard or Regular

Gateway connectors

The Gateway has three connectors:

  • EMS bus screw terminal

  • 3,5mm EMS service jack connector

  • JST connector

EMS Bus Gateway on boiler

The latest Gateway boards have an additional reboot button next to the JST connector.

Preferred order of connection

In short this is the best order in which you should try to connect the Gateway:

  • Service jack (If your boiler has one).

  • If you have a solar or mixer module with a bus OUT: EMS bus wires on EMS OUT terminal of the module.

  • If you don’t have an external module use the same EMS bus terminal as to which the thermostat is connected or should be connected to.

  • External USB adapter.

The service jack provides enough power for the Gateway.

You cannot power this gateway model from the EMS bus itself. If you can’t or won’t use the service jack you have to connect a USB adapter.

Service jack

EMS Bus Gateway on boiler

With the supplied jack cable you can plug in the Gateway to the service jack of the boiler. The entire device is powered via this service jack. So no additional power supply needed. Just the jack cable is all you need. First plug in the cable to the Gateway and then into the boiler. If the Gateway is plugged in, it will start blinking slowly to indicate it’s working and looking for the EMS bus and WiFi network.


If you plug in or unplug the jack cable from the Gateway first instead of the boiler side, you may momentarily shortcut the boiler. It will then reboot, which can cause some clicking noises. Nothing to worry about but just unplug the boiler side first.

EMS/thermostat wires

If your boiler does not have a service jack or it does but you want to mount the EMS Bus Gateway elsewhere you can use the screw terminal to connect to the two EMS bus wires. This can be in parallel with the thermostat or from inside the boiler. You need to power the device by plugging in a USB power supply directly to the Wemos.

To use the screw terminal of an older Gateway remove the top of the case to access the screw terminal by unscrewing the four case screws on the bottom.

Gateway screw connector

It does not matter which EMS wire you connect to which terminal pin, as the Gateway has an internal correction circuit.

You can see here how to locate the correct EMS bus terminals on your boiler: Connecting the Gateway to the boiler side.

If you have a Gateway with a Lolin Wemos V3, you need to remove the plastic tabs on the bottom side of the Wemos so the USB connector of the Wemos will be accessible from the side with the top case attached. If you have a Gateway Regular, the USB connector on the Wemos V2 is already accessible. So you don’t have to remove the tabs.

Wemos mod

After you have connected the EMS bus wires and are sure it works properly you can screw the case top back again. If the Gateway is connected correctly, it will start blinking slowly to indicate it’s working and looking for the EMS bus and WiFi network.

Do not connect both the jack and the screw terminal at the same time. Both connectors are internally hardwired so by connecting both at the same time you can short circuit the bus.

First boot -> Check the LED

If you plug the Gateway into the boiler, the on-board LED will start to blink slow as a sign it has booted and looking for the EMS bus. As soons as it has discovered the EMS bus and your Wi-Fi network, it will light up solid. If the Gateway has already been configured before, the LED will light up solid really quickly after boot. But if it’s new and not connected to your WiFi network yet, it will continue to blink slowly.

The blink speed can be compared at this Youtube video of Gateway LED blink speed 1.

If the light is blinking slowly, then go to Connecting the Gateway to your home network. If you don’t see any LED go to Troubleshooting.