An important part of espresso making is water flow rate. Yesterday we tackled such an issue on bar. Commercial espresso machines are simply boilers, combined with switches and mechanical valves, a motor (nowadays) and a pump. Yesterday both our motor and pump failed, and we are unsure in which order.

Commercial equipment is normally plumbed in to a water line (it is directly connected to the cities water supply, like a sink or dishwasher). The condition of the water is just as important as the consistency in pressure. At our bar building pressure is high, and we include a pressure regulator/ reducing valve, which steps pressure down with the purpose of smoothing out flow rate. The flow rate of the water is directly connected to the flow rate of the espresso. Normally with commercial espresso machines there is a pump, mounted externally or just outside the machine, which boosts incoming line pressure by a set amount. Any irregularity in the water pressure will simply be boosted by the pump, so incoming pressure will almost directly affect after pump pressure. This is super important, and to the unskilled imagine the espresso machine you see on a daily basis to have a remote pump and motor, normally located under the machine in a cabinet.

There is an electrical cord leading from the machine to the motor. There is a water line leading to the pump (mounted directly on motor), and a line leading to the espresso machine.

The job of the pump is to amplify water pressure so that it may force its way through the coffee structure and extract the “espresso.”

When the burning/electrical fire smell came from the pump motor, we knew we were in trouble. Biking to the roastery we received a new motor and pump, coming back to replace.The motor held a distinctly awful smell, and the pump bearings had seized and would not turn. There are two thoughts- one that the motor overheated and killed the pump bearings, or that the bearings seized on the pump and fried the motor. When we diagnosed the issue the machine was pulling wonderful espresso, but it smelled near death. So since we replaced the unit…

The Pump is responsible for the pressure of water pushing through the coffee grounds. When replacing the pump it is vital to adjust the new pump to create the pressure one wants. Who can trust factory offsets? In this scenario we moved from an arbitrary 114psi to 109psi using the scace device- which is… pretty arbitrary, yet relevant. This calibration tool is our reference point. Lower pressure results in not as much extractive force. This was a fun excersize, and i have to say- it was one of the best days.

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