HydroXpandHandbook

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Quick start

HXB-V1 · updated 2026-10-01

From delivery to your first hydrogen: what to prepare, the ports, filling electrolyte, the first start-up, and the acceptance check.

The sequence from delivery to your first hydrogen and the acceptance check. Half a day is enough once everything on the checklist is at hand.

Before installing, review the site space, ventilation and utility requirements in Installation and battery limits.

  • TimeHalf a day
  • People1 (2 recommended for handling electrolyte)
  • PPEEye protection · alkali-resistant gloves
  • Prior knowledgeNone needed
  • AcceptanceNo leaks · stable flow and level
How to read this chapter

First timeWork through the steps in order. Practical notes explain the reasoning and common mistakes; the last two sections cover acceptance and what to record.

Done this beforeThe acceptance check and the records are what you need. Recommended setpoints and operating ranges are in the operation chapter.

On this page1. What to prepare

1. What to prepare

Installation and battery limitsCheck site space, ventilation and utility requirements
  • 1 × PCRuns the control app (HXB HMI). The app ships with the system; ask us if you need the latest version.
  • 1 × Ethernet cableConnects the PC directly to the system.
  • 1 × AC power cordC19 plug. The inlet on the system is C20.
  • TubingOne electrolyte and water inlet, one electrolyte drain, two hydrogen outlets, one oxygen outlet.
  • ElectrolyteAbout 5 L of 0.1 M KOH for the first fill, made up in DI water from KOH of 95% purity or better.
  • DI waterFor automatic make-up during operation. Recommended ASTM D1193 Type II (1.0 µS/cm or below at 25 °C), maximum 30 µS/cm.

Photos show the type of item only. Tubing photo by Best Tech Nick 25, water container photo by Safilol222299 (Wikimedia Commons, CC BY-SA 4.0, background removed and edited). Both edited versions are released under CC BY-SA 4.0.

Mixing the electrolyte

0.1 M KOH contains about 5.6 g of pure KOH per 1 L of final solution. Adjust the weighed amount for reagent purity, dissolve in DI water, cool to room temperature, then make up to a final volume of 1 L.

  1. Wear protective equipment

    Wear eye protection and alkali-resistant gloves. If it contacts skin, rinse immediately with running water; alkali burns hurt later than they start.

  2. Add KOH to water

    Always add the KOH to the water, never the other way round: reversing the order causes violent local heating and splashing. Add it a little at a time and stir.

  3. Cool to room temperature

    The solution gets hot as it dissolves. Let it cool to room temperature before it goes into the system.

Water and electrolyte care

Feed-water quality
Take feed water from a stable, well-maintained purification system, and avoid sources high in organics, silica or particulates. Type III or IV water can be used for short-term testing, but it shortens maintenance intervals and accelerates degradation.
When to replace electrolyte
Replace the electrolyte on condition and performance trend rather than on a fixed interval, because KOH is not consumed during operation the way water is. Replace it if you see discolouration or solids, or if the voltage trend shifts at a comparable operating point.

Before you start

  • All five lines are connected and each runs to a safe place.
  • Power and Ethernet are connected and the control app finds the system.
  • The electrolyte for the first fill and the DI water for make-up are ready.
  • You are wearing eye protection and alkali-resistant gloves.

2. Identify the front-panel ports

Start with the labels on the front panel. Every fluid port is a 1/4-inch double-ferrule fitting. Naming can differ between revisions, so follow the labels on your own unit.

Line drawing of the HXB-V1 front panel. Five fluid ports (1 H2O IN, 2 O2 OUT, 3 H2 OUT, 4 H2 VENT, 5 DRAIN) and six electrical interfaces (6 Reset, 7 status LED, 8 External sensor port, 9 main switch, 10 Ethernet, 11 power inlet) are numbered 1 to 11. The fluid ports are spread across the upper left, upper centre, lower centre and lower left; the electrical interfaces are grouped in a column on the right.
Figure 4-1 HXB-V1 front panel and port layout. The labels are engraved in English. Layout can differ between revisions, so follow the labels on your own unit.
No.LabelWhat passes throughConnection
1H2O INDI water in. The first electrolyte fill also goes in here1/4-inch double ferrule
2O2 OUTOxygen out1/4-inch double ferrule
3H2 OUTHydrogen out. This is the product line to your point of use1/4-inch double ferrule
4H2 VENTHydrogen leaves here in an emergency. Never fit a valve or plug it1/4-inch double ferrule
5DRAINElectrolyte out1/4-inch double ferrule
6ResetThe red button. Restarts the controller into STANDBY. Press it to release an emergency stop. It is not a button for stopping operation—
7LEDShows the operating state. How to read it is in the operation chapter—
8ExternalFor an external hydrogen or oxygen sensorAnalog signal
9ON/OFFMain power on and off—
10EthernetHow the control app reaches the systemRJ45
11PowerMains power cordC20 inlet
PortFunction
H2O INElectrolyte for the first fill, then water make-up
H2 OUTHydrogen outlet
O2 OUTOxygen outlet
H2 VENTHydrogen vent and relief outlet for emergency release
DRAINElectrolyte drain. Connect a hose only while draining
EthernetRJ45 for the control app, connected to the PC
PowerC20 AC inlet
Power switchSystem main power
LEDSystem status. What each state means is in the operation chapter
External portOptional. Analogue input for an external hydrogen or oxygen sensor
ResetRed button. Restarts the controller, releases an emergency stop

3. Connect the tubing

Connect every line you need before operating.

Routing of the five lines from the HXB-V1 front panel. 1 H2O IN goes to a reservoir: electrolyte at first, then DI water. 2 O2 OUT rises to a safe area for oxygen, and 3 H2 OUT rises separately to a safe area or approved downstream equipment for hydrogen. 4 H2 VENT rises in its own line to a safe area with no valve or plug. 5 DRAIN stays capped, with a hose fitted only while draining.
Figure 4-2 Tubing routes. Numbers match figure 4-1. Keep the hydrogen and oxygen lines separate and route gas lines upward.
  1. Electrolyte and water inlet
    • Connect tubing to H2O IN.
    • Leave the free end ready to place in a reservoir: electrolyte at first, then DI water.
  2. Hydrogen outlet
    • Route H2 OUT to a well-ventilated safe area or to approved downstream equipment, following your site rules.
    • Route H2 VENT to a well-ventilated safe area as well.
  3. Oxygen outlet
    • Route O2 OUT to a well-ventilated safe area, keeping the lines separate so the gases cannot mix.
  4. Electrolyte drain
    • Keep DRAIN capped during normal operation.
    • Connect a drain line only when you are draining.

4. Power on and connect the PC

Close-up of the lower right of the HXB-V1 front panel. 1 Plug the C19 cord into the C20 inlet and switch the main power on. 2 Set the PC to the static IP 192.168.121.4 with subnet mask 255.255.255.0. 3 Connect the front RJ45 Ethernet port to the PC with an Ethernet cable.
Figure 4-3 Power and PC connection. The numbers in squares are the step numbers below.
  1. Connect power.
    • Plug the AC cord into the C20 inlet.
    • Switch the main power ON.
  2. Set the PC network to a static IP.
    • IP address 192.168.121.4
    • Subnet mask 255.255.255.0
    • These addresses are the same on every HXB-V1. Units are told apart by the Device ID on the rear label.
    • To run several units from one PC, tell us when you order. We set a different static IP on each unit before shipping and give you the list of addresses.
  3. Connect the PC to the system with the Ethernet cable.

5. Create a project

  1. Launch the app and Project Manager opens.
  2. Click New Project.
  3. Enter the project details.
    • Project name
    • Description, optional
    • Device ID, exactly as printed on the label on the rear panel.
  4. Click Create, then click Start on that project in the list.
  5. Confirm two things on the top bar.
    • Connection = ONLINE
    • Logging = ON
PRACTICAL NOTESWhat setting a static IP actually does
  • Normally a router hands your PC an address. This system does not do that, so you set the address on the PC side by hand and the two can then find each other. That is what the address in the previous step is for.
  • That Ethernet port becomes dedicated to the system: your office network and the internet will not work through it. If you need both, add a USB Ethernet adapter so you have two ports.
  • To undo it, switch the same setting back to automatic.

6. Fill and prime the electrolyte

Work from the P&ID screen in the app. This is a first-time-only procedure.

Concept diagram of filling and priming in three stages. 1 With flow at 0 and room temperature, electrolyte control ON runs only the make-up pump, which fills the internal tank from the electrolyte reservoir on H2O IN; circulation to the stack is still idle. 2 At two thirds, a flow of 4 L/min starts circulation, which fills the inside of the stack while make-up keeps topping up the tank. 3 When the tank is full, the H2O IN line moves to the DI water reservoir and stays there for operation.
Figure 4-4 Electrolyte fill and priming sequence. A simplified concept diagram; the P&ID screen in the control app shows the actual layout.
  1. Prepare about 5 L of electrolyte for the first fill.
  2. Submerge the free end of the H2O IN line fully in the electrolyte.
  3. Set the targets in Electrolyte Control and click Apply.
    • Leave the temperature at room temperature. No heating yet.
    • Leave the flow at 0. No circulation yet.
  4. Turn Electrolyte Control ON.
    • The make-up pump fills the internal tank automatically and the tank graphic on the P&ID fills with blue.
  5. When the tank reaches two thirds, start circulation to fill the inside of the stack.
    • Leave Electrolyte Control ON, enter a flow of 4 L/min and click Apply.
  6. Continue until the tank is full.
    • Make-up keeps topping the tank up while circulation fills the stack.
  7. Move the H2O IN line to the DI water reservoir.
    • Keep it there from now on. Topping up with water, not electrolyte, is the normal operating configuration.

What electrolyte control actually does

The shape of the filling procedure makes sense once you understand this one switch.

Raising the flow to 4 L/min once the tank is two thirds full works the same way: circulation starts pushing liquid through the inside of the stack while make-up keeps topping the tank up.

The step-by-step actionsFilling, warm-up and start-up in order

7. Warm up

  1. Keep Electrolyte Control ON.
  2. Enter a temperature of 50 °C and click Apply.
    • This is the recommended value.
  3. Confirm on the P&ID that the cartridge heater turns on and heating begins.

8. Start electrolysis

  1. Confirm the system is ready for power.
    • Electrolyte level is in the normal range.
    • Flow is stable at the setpoint of 4 L/min.
  2. Enter voltage and current in Power Control and click Apply.
    • 46 V and 50 A are recommended, not required.
  3. Turn Power Control ON.

9. Check

Watch either the P&ID or the Dashboard.

  • Stack voltage and current respond to your targets.
  • Electrolyte level stays in the normal range.
  • Flow stays stable near the setpoint.
  • Temperature climbs toward the setpoint.

What normal looks like during warm-up

For a setting of 46 V and 50 A.

  • At first the electrolyte is cold and the voltage limit is reached first: voltage sits at 46 V and current stays below 50 A.
  • As the temperature rises the current target is reached: current holds at 50 A and voltage drops below 46 V.
Concept diagram of normal behaviour during warm-up with 46 V and 50 A set. Voltage is on top, current below, and the horizontal axis is time and electrolyte temperature. While the electrolyte is cold, voltage sits at 46 V and current climbs below 50 A. As it warms, current reaches 50 A and from then on voltage falls below 46 V.
Figure 4-5 Normal behaviour during warm-up. A concept diagram of the shape only, not a measured curve; how long it takes depends on the installation.
Operation and controlDay-to-day operation, LED states and recommended rangesTroubleshootingWhat to check when the readings look wrong

Acceptance

Check the following once electrolysis is running. If all three hold, treat the commissioning as accepted.

Leaks
No visible electrolyte leakage at the fittings or ports.
Flow and level
Flow is stable at the setpoint and the electrolyte level stays in the normal range.
Voltage and current
They respond to the targets you set.

How it behaves while warming up

With 46 V and 50 A set. If it moves like this, it is behaving normally.

  • At first the electrolyte is cold and the voltage limit is reached first: voltage sits at 46 V and current stays below 50 A.
  • As it warms the current target is reached: current holds at 50 A and voltage drops below 46 V.

What to write down

What you record now becomes the baseline for judging whether performance has changed. Without a baseline you cannot tell, months later, whether the voltage has risen.

  • The date and who ran it
  • The electrolyte specification and the date it was made up
  • The stack voltage and current once settled, with the electrolyte temperature and flow at that moment
  • How those compare with the factory acceptance test figures
  • Any alarm that appeared during commissioning

What this chapter is based on

Resource library →

TroubleshootingWhat to check first when voltage jumps or pressure and flow become unstable, with causes and actions for four symptoms.

Ask the engineer who built it

If your case is not covered here, send us the operating condition and what you observed. The engineer who designed the system answers directly.

Technical enquiry