Cylinder not heating as expected
Pin down exactly what the customer means, then follow the matching checks.
Use this guide when the cylinder heats, but not to the level, at the times or to the temperature the customer expects. Most of these are settings, external controls or heat source set points rather than hardware, so start by pinning down which of these five behaviours you're dealing with.
Which best describes the behaviour?
Heats at the wrong times
Check the app for anything that changes when the cylinder heats: smart or manual schedule, Boost, maintain levels, tariff windows, holiday mode, the sterilisation cycle and the PV diverter schedule.
- Correct the settings and explain them to the customer. See App settings causing unexpected heating. Mixergy support can also adjust settings remotely and monitor the cylinder for 24 hours.
Overheating or always on
Is it heating constantly to 100%, or does the heat source never stop calling for heat?
- If so, something outside the Mixergy system is calling for heat, such as an external programmer or a wiring fault. Check and correct it.
Stuck at low charge
Is the charge stuck at around 10 to 30%, even on Boost, on electric heating?
- If yes, these are classic top-up pump symptoms. See Charge stuck at 10 to 30% (top-up pump).
- If not, and it heats but stops early, follow the checks below.
Stops early
Does electric heating stop early with an amber warning, or does the immersion trip before reaching target temperature?
- If yes, the thermostat probe probably needs repositioning. The board is live, so this needs a competent engineer. Contact Mixergy support before you go further.
- If the cylinder heats indirectly, the heat source may not be reaching temperature. Confirm the boiler flow is at least 10°C above the Mixergy target. If the boiler can't reach it, refer it to a boiler engineer. Otherwise, contact Mixergy support for a data check.
Reaches temperature but runs out quickly
Is the target charge or temperature simply set too low for how the household uses hot water?
- If yes, raise the target charge or temperature, or add a scheduled heat, and show the customer how Boost and maintain levels work.
- If not, suspect destratification, for example a third-party diverter overheating the top of the cylinder before the pump mixes it away at speed. Contact Mixergy support so they can review the charge data and diverter setup.