Expobar Office: Troubleshooting Machine Back Flow and a Hole in the Heat Exchanger

Learn how to troubleshoot back flow and figure out if there is a hole in the heat exchanger of an Expobar Office espresso machine.

1. Get the machine up to temperature. Once the machine is heated up, pull the intake line out of the water tank. Place a sturdy container or bucket under the hot water tap and open the tap all the way. Once the steam pressure gauge shows “0” or only small amounts of water are coming out of the hot water tap, shut off and unplug the machine.

  • NOTE: Be careful during draining as the water coming out of the tap will be extremely hot. Allow the machine to cool after draining.


2. As shown in the two photos above, there are five Philips head screws that hold on the housing: two on each side and one on the back of the housing in the middle, at the bottom. Remove all five screws and slide off the housing.


3. There are four screws that hold the res support to the frame: two Philips head screws at the top (outlined in yellow above), and two 3mm Allen screws on the bottom (outlined in red above).


4. When lifting off the res support, there is a safety switch for the water tank with two wires attached to it. Please mark the bottom wire with tape or a sharpie. If you need to unplug the switch, you will need to place the correct wire back onto the bottom pole of the switch.

5. In order to run the machine without the water tank attached you need to trip the safety switch. Two ways to do this are represented in the pictures below. You can either get a piece of wire and jump the two wires together, or you can simply leave the res support attached, grab a piece of tape, and press down on the plate, activating the switch, and tape the plate down. Then lay the support down off to the side.


6. The fill probe needs to be grounded out so that the autofill does not turn on and fill the boiler when turning on the machine to perform the test. The first picture below shows the wire that needs to be pulled off the probe. The second picture below shows how the probe needs to be grounded to the ground wire to the right of it so the circuit “thinks” it is full. You can do this with a piece of wire.


7. Use a 17mm open ended wrench to loosen the pipe from the elbow of the intake solenoid.


8. You will need to loosen the other end of the pipe so that you can slightly move it away from the elbow of the solenoid. In the picture below, the pipe connects to a fitting on the bottom of the boiler. Put a 16mm open ended wrench on the fitting to hold and put a 17mm open ended wrench on the fitting for the pipe and loosen it.


9. Separate the pipe outlined in yellow below from the elbow outlined in red below. Then tighten down the pipe on the boiler side that you had just loosened.


10. Disconnect the element wires so that the machine will not heat when you turn it on to perform the test. If the element heats with a dry boiler it will fracture and require replacement.


11. You should now be ready to perform the test. Place a blind basket in your portafilter and insert it into the group. Take your water line and place it into either a container of water if it is easier or the water tank. Turn on the machine and lift the lever to activate the pump. As the machine is running, go back and observe the pipe you disconnected.

12. Look to see which end the water comes out of. If water comes out of the pipe (outlined in yellow in the picture below) then there is a hole in the heat exchanger. If water comes out of the elbow of the solenoid (outlined in red), then water is forcing its way back past the solenoid valve.


13. Once you have determined where the water is coming from, turn off the machine, unplug it, and assemble all connections and wires.

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