Running it day to day: what to watch in normal operation, how to manage level and water make-up, how far the operating range goes, what changes at low current and with frequent starts and stops, and the normal shutdown sequence.
The first start-up is in the quick start chapter. This one picks up after it.
- Recommended point50 A · 50 °C · 4 L/min
- Water use420 mL/h at 50 A
- Make-upYours, by your BoP procedure
First timeRead the four sections in order. The first is what you watch every day; the second is what people most often miss on this product.
Done this beforeThe limits table and the shutdown sequence are enough.
On this pageWhat to watch in normal operation
What to watch in normal operation
Keep the circulation steady and watch four things.
- Flow and temperature
- Confirm the flow is stable (4 L/min recommended) and the temperature is near target (50 °C recommended). If it keeps rising despite available cooling, reduce the current or stop.
- Voltage
- Monitor the stack voltage continuously. A sudden jump or abnormal fluctuation at constant current means reduce the current or stop, then inspect the loop and the conditions.
- Leaks
- Check around the IN, OUT and H2 ports and the external fittings periodically. Wetness or white crystals mean stop, correct the cause, then resume.
- The wet outlet return
- Confirm the OUT return is unobstructed and flows smoothly back to the tank. Gas trapping, gurgling or an unstable return means inspect the routing and the backpressure and correct it before continuing.
Level and water make-up
This is what people most often miss on this product. Unlike a packaged system there is no automatic top-up, so make-up depends on your procedure.
- Electrolysis consumes water.
- In dry-cathode operation with KOH solution fed to the anode loop, water is what is consumed and KOH is not. At 50 A that is 420 mL/h.
- So the tank level falls over time.
- Keep the level high enough for stable circulation and cooling.
- Add DI water to the tank by your external BoP procedure.
- Running at a low level brings pump cavitation and unstable flow.
- If the level gets too low or the circulation becomes unstable, stop and correct it before continuing.
Limits and recommended values
| Parameter | Recommended | Limit |
|---|---|---|
| Current | 50 A | 80 A maximum |
| Stack voltage | About 40 V (BOL at 50 A) | 50.6 V maximum (2.2 V per cell × 23) |
| Electrolyte temperature | 50 °C | Room temperature to 80 °C |
| Electrolyte flow | 4 L/min | 1 to 10 L/min |
| Hydrogen pressure | 0 barg | 10 barg maximum |
Low-current and part-load operation
Running below rated current changes two things: the electrolyte heats less, and the hydrogen-in-oxygen ratio rises.
| What | Why | What to do |
|---|---|---|
| Electrolyte temperature | Less heat is generated, so it does not reach the recommended temperature | Fit a tank heater and put temperature monitoring and over-temperature protection in the external BoP |
| Hydrogen in oxygen (H2-in-O2) | Hydrogen crossing the membrane barely depends on current, while oxygen output is proportional to it. At lower load the same hydrogen mixes into less oxygen | Below 40–50% of rated load, the 2 vol% control limit becomes the practical design limit. Fit at least one of: a minimum-load limit, reduced pressure at low load, or a 2 vol% interlock |
Normal shutdown
- Reduce the current step-wise to 0 A.
- Turn off the DC output.
- Keep circulation running as long as needed to cool down.
- Stop circulation once it has cooled.
- Turn off the tank heater if you used one, and secure the system by your site procedure.
- Do a visual leak check around the ports and fittings.
What this chapter is based on
- HXS-2 datasheetPDF · 1.3 MB
- HXS-2 outline drawingPDF · 481 KB
- Stack integration guidePDF · 449 KB
- HXS-2 user manualOn request
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.