Expobar Brewtus III Overheating and Wiring Reversal

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by JimK »

Hello espresso fans. This is my first post.

I have an Expobar Brewtus III that was seriously overheating; PID going to 266, steam blasting out of the brew group, etc. This was in spite of the fact that the little power LED on the PID was exhibiting normal behavior, ie blinking on and off around 199-200 and turning off above that point. This should indicate that power is being first periodically interrupted, and then cut off to the boiler. My boiler was continuing to heat.

I traced the failure down to a broken heating element in the boiler with the help of this article on HB Expobar Brewtus 4 overheating

There was water ingress into the copper tube that houses the heating element, and replacing the heating element fixed the problem as in the other HB member's posting.

What concerned me was the fact that the boiler was continuing to heat while both the PID and the SSR (Solid State Relay) were working. As the SSR cycled and eventually shut off current flow, the heating should have stopped. The SSR has its own little green LED that cycles in time with the LED on the PID. The problem turned out to be that my input wiring was reversed (hot and neutral) at the back of the main switch. In this configuration, the SSR in my machine was switching the neutral pathway, and not the hot pathway. This is pretty bad.

In this photo (sorry about cutting off the view of the top of the switch), you can see that my hot input (black) to the bottom of the main power switch is on the left. This was being switched to the blue wires, one of which goes straight to one of the boiler connections; I verified this by tracing the wire and with my volt/ohm meter. Again, note that this photo shows the incorrect connections, with the black wire on the left. I have since reversed the black and white leads and now have the hot lead being switched by the SSR under control of the PID. This would have prevented my system from overheating, but would also have concealed the problem of the broken heating element until it deteriorated to the point that it stopped heating at all.

While the heating element was broken, a significant amount of the return current was probably flowing back through the ground connection rather than all returning through the neutral. This is pretty bad because if there was a failure in the ground path or even much higher resistance, the chassis could have become charged and I could have become the low resistance path to ground. These systems should really be connected through a Ground Fault Circuit Interrupter (GFCI) outlet, which would have detected the current imbalance between the hot and neutral pathways and shut off the outlet. GFCIs are available at big box home stores and are pretty easy to install as long as you are capable of turning off the circuit at the circuit breaker or fuse box and can distinguish hot from neutral from ground wires inside the outlet box.

I have no idea how my wiring got reversed, but it is probably a good thing to check if you are ever inside the machine.