Terminology Glossary

Terminology Glossary


Call this a glossary, index, or compendium! Coffee terminology varies across the industry and we at Black Rabbit Service are no strangers to speaking in a colloquial voice when describing a term, tool, or technique. 

Many of the concepts and terms defined in this guide are directly referenced in Preventative Maintenance and Best Use Practices guides found throughout the 7 Brew Help Center

Espresso Machine:
  1. Autofill/Inlet Valve
    1. Autofill (inlet) valves automatically activate, without user input, when a specific hydraulic circuit calls for water. An example would be the steam boiler fill circuit (managed by the level probe) activating the autofill valve to maintain the appropriate water level for steam production.
  2. Basket
    1. Also known as a portafilter basket. Baskets hold ground coffee in the portafilter during espresso extraction.
    2. Baskets are routinely serviced as part of preventative maintenance.
      1. See: Portafilter
  3. Brew Boiler
    1. Featured on multiboiler espresso machines. Brew boilers (tanks) are fully saturated with water and regulated by a complementing heating circuit. An additional key feature of the brew boiler is the flat surface known as the dispersion block where the diffuser screen and screw thread into.
      1. See: Group Cap, Grouphead, Heating Circuit
  4. Brew Valve
    1. Responsible for water delivery through group head during brew group activation.
      1. See: Solenoid Valve
  5. Bleed Screw
    1. Located on the group cap. Bleed screws are typically used only during initial filling of the fully saturated brew boiler.
      1. See: Brew Boiler, Group Cap
  6. Button Pad / Brew Buttons
    1. Electronic board below a physical button responsible for sending input signals to the CPU. 
    2. One of three physical buttons which can be uniquely programmed to dispense a set amount of water.
  7. Capacitor
    1. Device which stores electrical energy by accumulating charges on two closely spaced surfaces that are insulated from each other. A capacitor creates a phase shift in the electrical current, producing a rotating magnetic field to help the motor start and improve its running efficiency.
      1. See: Pump + Motor
  8. CPU 
    1. Central Processing Units (also known as a circuit or electrical board) are the ‘brain(s)’ of an espresso machine. CPUs receive and send signals from key components as well as store data such as recipes and settings.
  9. Cup Tray
    1. Cup trays, grates, and warmers located on top of the machine and utilize ambient heat to warm cups.
  10. Check Valve
    1. A Check Valve (anti-return valve and denoted by a stylized arrow) is a one-way valve which prevents the backflow of water upstream through a hydraulic path.
    2. It is not uncommon for municipalities to require check valve inspection during equipment installation.  
  11. Diffuser Screen & Screw
    1. Also known as shower/dispersion screens. Diffuser screens & screws soften and disperse water dispensed from the grouphead’s dispersion block to facilitate even espresso extraction.
    2. Diffuser screen & screws are routinely serviced as part of preventative maintenance.
      1. See: Grouphead
  12. Display
    1. User interface feature which shares pertinent information in a digital format. Examples include: brew time, temperature, pressure and other prompts such as error messages/codes.
  13. Drain
    1. Drain hoses are imperative to safely discharge waste water and material such as coffee oils, grounds, and excess milk. Properly routed drain hoses eliminate vacuums and backflow from occurring.
    2. Additionally, drain valves featured on boilers allow for routine draining during maintenance.
      1. See: Tubing
  14. Drip Tray / Drain Box
    1. Located just below the grouphead and attached to drain hoses. Drip trays and drain boxes are catch and drain basins for all excess water and material dispensed or poured as waste. 
  15. Element
    1. Heating elements generate heat when electrical current passes through a resistive material. Elements feature wattage specifications for given boiler applications.
      1. See: Brew & Steam Boiler, Heating Circuit
  16. Expansion Valve
    1. Responsible for relieving excess water pressure during thermal expansion from the brew boiler.
    2. Expansion valves are typically set to ~12bar and routinely serviced.
      1. See: Thermal Expansion
  17. Fitting
    1. Fittings are the joints which connect pipes, tubes, and component assemblies. Common fittings include: compression, flared, a-lok, and quick/push connect (John Guest).
      1. See: Tubing
  18. Flowmeter
    1. Instrument for calculating water volume through a hydraulic path. Water moving through the flowmeter spins an impeller which sends an electromagnetic signal, measured in impulses, to the CPU. Flowmeters are responsible for volumetric accuracy.
      1. See: Group Cap
  19. Flow Restrictor
    1. Also known as a Gicleur, Jet, or Ruby. Restrictors significantly reduce and regulate water flow through a hydraulic circuit. Restrictors are imperative for consistent water debit calculations and extraction quality.
      1. See: Group Cap
  20. Fuse
    1. A fuse is a safety device designed to break a circuit when electrical current exceeds a safe level. This protects equipment from damage caused by overcurrents or short circuits.
  21. Gasket
    1. Composed of various materials per application. Gaskets range from copper crush (washers), to silicone, PTFE (teflon), rubber, and paper in order to form water and steam tight seals.
    2. Various gaskets are routinely serviced as part of preventative maintenance.
  22. Gauge 
    1. Espresso machines feature manometer gauges that indicate pressure via a needle present on the dial. This dial reads the active pressure of either the brew or steam boilers.
  23. Group Cap
    1. Component of the greater brew boiler and grouphead assembly. Group caps house the brew valve, flowmeter, jet, and bleed screw.
  24. Group Gasket
    1. Typically silicon or rubber, group gaskets are the interface between a portafilter and grouphead to form a water tight seal during espresso extraction.
    2. Group gaskets are routinely replaced as part of preventative maintenance.
      1. See: Grouphead
  25. Grouphead
    1. Consisting of several components: dispersion block, bayonet ring, group gasket, diffuser screen & screw, portafilter, and brew buttons. The grouphead is responsible for maintaining thermal stability and water dispensing from the brew boiler during espresso extraction.
      1. See: Brew Boiler, Grouphead
  26. High Limit Thermostat
    1. A high limit thermostat is a safety device designed to break a circuit when boiler temperature exceeds the thermostat's temperature threshold. This protects equipment from damage caused by over temperature or pressure scenarios.
      1. See: Heating Circuit
  27. Hot Water Spout
    1. Spout or wand that delivers hot water on activation.
      1. See: Mix Valve
  28. Level Probe
    1. Found on steam tanks. Level probes are stainless steel rods which respond to water conductivity and regulate water level to a specific depth.
    2. Level probes are routinely serviced as part of preventative maintenance.
      1. See: Autofill/Inlet Valve, Sight Glass, Steam Boiler
  29. Mix Valve
    1. Commonly referred to as a blending valve. Using an adjustable knob, mix valves blend inline cold water with hot, typically steam tank water, for the hot water spout.
      1. See: Hot Water Spout, Solenoid Valve, Steam Boiler
  30. O-Ring
    1. Donut shaped and elastic/malleable. O-rings, often set in a machined groove, are used to form water and steam tight seals between two mechanical surfaces.
    2. Various o-rings are routinely serviced as part of preventative maintenance.
  31. Portafilter 
    1. Consisting of several components: body, handle, spring, basket, and spout. The portafilter is the handheld component of an espresso machine which holds ground coffee and locks into the grouphead during coffee extraction.
      1. See: Basket, Grouphead
  32. Power Switch
    1. Two ON/OFF visual indicators.
      1. ‘O’ (open circuit) is OFF.
      2. ‘I’ (closed circuit) is ON.
  33. Pressure Relief Valve
    1. Typically rated from 2.0 - 2.5 bars, PRV are safety mechanisms designed to discharge steam in the event of a steam boiler over pressure scenario.
    2. PRV are routinely serviced as part of preventative maintenance.
  34. Pump + Motor
    1. The pump and motor assembly are the main pressure delivery component of an espresso machine. Available in several different types, volume capabilities, and power configurations. Pump assemblies draw water from an inline source and produce an adjustable pressure (most often 9 bars). Pump motors utilize a capacitor to activate.
  35. Ribbon Cable
    1. Distinctly different from a wire harness. Ribbon cables are often wide, flat, and contain multiple conducting wires parallel to each other within a flexible ribbon-like cable. Commonly used to connect display assemblies to the CPU.
      1. See: Display, Wire Harness
  36. Shut Off Valve
    1. Various makes and models feature shut off valves within the equipment to disable the hydraulic path or steam track for troubleshooting and service. 
    2. Recommended component and installation check procedure for plumbed coffee equipment.
    3. Shut off valves are independent of a water main and installed as a contingency to isolate a piece of equipment from its plumbed source.
      1. See: Hydraulic Path
  37. Sight Glass
    1. Many makes and models feature glass windows with level indicators (may be a bobber or physical line) for users to view the water level within the steam boiler.
      1. See: Steam Boiler
  38. Solenoid Valve (Electrical)
    1. Solenoid valves are composed of two components, a valve and coil:
      1. The valve, which can be 2-way, 3-way, or proportional controls the direction of water or steam flow and features a plunger and seat which are activated by the coil.
      2. The coil, either AC or DC is a cylindrical coil of copper encased in a square block that upon receiving an electrical charge. Magnetizes and pulls the plunger from its seat… allowing water or steam to flow through valve.
  39. Solid State Relay
    1. A solid state relay (SSR) is an electronic switching device that activates on or off when an external voltage is applied across its control terminals. In short, SSR receive an input signal from the CPU, sent from the temperature probe, in order to provide voltage to its respective heating circuit.
      1. See: Heating Circuit
  40. Steam Boiler
    1. Featured on multiboiler espresso machines. Steam boilers (tanks) utilize an autofill circuit, level probe, and heating circuit to manage a ratio of exceedingly hot water (typically 250°F+) to generate and maintain steam production.
      1. See: Autofill Circuit, Heating Circuit
  41. Steam Tip
    1. Steam tips are the last departure point for steam exiting the steam track. Steam tips are responsible for the volume, rate, and angle of steam while actively steaming milk.
    2. Steam tips are easily removable and feature four precision engineered holes to produce consistent steam flow.
      1. See: Steam Track
  42. Steam Knob
    1. Knob/handle which, when rotated, pushes in a pin that activates the plunger interface within the steam valve.
      1. See: Steam Track, Steam Valve
  43. Steam Valve (Mechanical)
    1. Unlike a solenoid valve, a mechanical steam valve requires manual interaction, via a knob or handle to interface, with a plunger to open or close the steam track.
    2. Mechanical steam valves do not require power to dispense steam and rely on a series of o-rings, pin, plunger, and spring to create a steam tight seal.
    3. Steam valves are routinely serviced as part of preventative maintenance.
      1. See: Steam Track, Steam Knob
  44. Temperature Probe
    1. Featuring two distinct ends: a rod (the probe) and electrical connection. Temperature probes are exposed to conditions within a brew or steam boiler to transmit (a resistance) reading to the CPU. Signaling for the heating circuit to heat or maintain temperature and/or pressure.
      1. See: Heating Circuit
  45. Tubing (Copper, EPDM, Silicone, Stainless)
    1. Responsible for the delivery and disposal of water (various temperatures), steam, and discharge waste. Tubing, ranging in diameter and material, is commonplace throughout an espresso machine. 
      1. See: Fitting
  46. Vacuum Breaker (Anti-suction Valve)
    1. Featured on steam boilers and steam valves (depending on make and model). Vacuum breakers are simple safety valves which form a steam tight seal while under pressure yet open to introduce atmosphere (air) when pressure dissipates. This is particularly crucial for steam boilers to ensure the safe and accurate buildup of pressure and depressurization.
    2. Vacuum breakers are routinely serviced as part of preventative maintenance.
  47. Wire Harness
    1. Commonly a bundle of independent wires sending electrical signals between components. Wiring harnesses may refer to a collection of wires or a singular wire connection between two points.
      1. See: Ribbon Cable