How the FizzWizz Works
How the FizzWizz controls carbonation — the three pneumatic circuits, the carbonation calculation, and why temperature accuracy matters.
How the FizzWizz works
The FizzWizz holds a brite tank at the pressure needed to reach your target carbonation level. Understanding the three pneumatic circuits and the calculation behind them makes the rest of this documentation much easier to follow — and makes troubleshooting far faster, because most problems trace back to one of the circuits described here.
The carbonation calculation
Carbonation is a function of pressure and temperature. For a given temperature, there is exactly one equilibrium pressure that holds a given volume of dissolved CO₂.
The FizzWizz works the calculation in this direction:
- You enter a target carbonation level, in volumes of CO₂.
- The unit reads product temperature from the WizzTemp probe.
- It reads tank pressure from the Brite pressure transducer.
- It calculates the finish pressure required to reach your target at that temperature.
- It adds CO₂ through the carbonation stone until the tank reaches that pressure, then holds it.
Because temperature changes shift the required pressure, the FizzWizz recalculates continuously. A tank that warms up overnight needs more pressure to hold the same carbonation — and the unit adjusts automatically.
This is why temperature accuracy is critical. A probe that reads warm makes the FizzWizz calculate less CO₂ than needed, and the beer is systematically under-carbonated. See the Slushy WizzTemp Test to verify the probe.
The three pneumatic circuits
Gas reaches the tank through three separate circuits. Each one has a distinct job, and each is tested by a different part of the Health Check.
| Circuit | Path | What it does |
|---|---|---|
| CO₂ inlet | Regulator → CO₂ check valve → Manifold | Supplies gas to everything else. Tested in Check 2. |
| Stone (carbonation) | CO₂-in solenoid → Flow controller → Stone hose → Inline check valve → Isolation valve → Sanitary check valve → Carbonation stone | Delivers metered CO₂ into the tank through the stone. Tested in Check 7. |
| Arm (head transfer) | Head_Transfer solenoid → Arm hose → Separator → Tank head | Applies and senses head pressure. Tested in Check 6. |
The full diagram and a component-by-component glossary are on the Pneumatics Schematic page.
CO₂ inlet circuit
Your CO₂ supply connects to the CO₂_In port through a regulator, typically set to 30–40 psi. Gas passes a check valve — a one-way valve that prevents reverse flow back toward the regulator if the supply runs out — and enters the internal manifold.
The manifold distributes gas to the three solenoids. A CO₂ reg psi reading on the display shows the pressure at this inlet.
Stone circuit
This is the circuit that actually carbonates the beer. Gas passes through the CO₂-in solenoid, is metered by the flow controller (the vertical flow meter with the adjustment knob), travels down the stone hose, and enters the tank through the carbonation stone.
Three valves protect this circuit from product flowing back into the FizzWizz:
- The inline check valve, in the stone hose
- The stone isolation valve, a manual valve that isolates the stone
- The sanitary check valve, immediately before the stone on the wetted side
Carbonation stones are porous ceramic. Because the pores are small (0.5 micron on the WizzStone-Combo), the stone produces very fine bubbles and high CO₂ transfer — but the same small pores make it prone to clogging, which is why regular cleaning matters so much.
Arm circuit
The arm circuit connects the FizzWizz to the tank head rather than to the beer. It has two jobs: applying head pressure during packaging, and sensing the tank's head space pressure.
Gas passes through the Head_Transfer solenoid and down the arm hose to a separator before reaching the tank head. The separator catches liquid and foam before it can travel back up the arm hose — and it is the single most important component for protecting the unit.
The Brite psi reading on the display shows pressure in this circuit.
Solenoids and the front panel
Three solenoids control gas flow. Each is operated by one button, and the mapping is fixed:
| Button | Solenoid operated | Port |
|---|---|---|
| Up | Head_Transfer | ARM |
| Down | CO₂_in | STONE |
| Enter | Vent | Vent valve |
The button you press determines which solenoid opens, but which port gas comes out of depends on where the CO₂ supply is connected. When CO₂ is on CO₂_In, pressing Down sends gas to the Stone port. Move the CO₂ supply to the ARM port and the same button opens the same solenoid, but the gas now appears at a different place. That reversal is deliberate — it is what lets the Health Check isolate a stuck solenoid from a blocked hose.
Why fluid ingress is the main failure mode
Pressure transducer and solenoid failures are usually not component defects — they are the downstream consequence of fluid reaching parts that were never meant to see it. The separator, the inline check valve, and the sanitary check valve exist solely to prevent this. If you find fluid inside the unit, replacing the failed transducer or solenoid without also establishing how the fluid got in will simply produce the same failure again.
This is the single most important thing to understand about the FizzWizz. It is also why the Arm Circuit & Separator page exists, and why the troubleshooting guides ask about fluid ingress and separator condition before recommending parts.