myenergi zappi [Bad Voltage Range]

Bad Voltage Range is code 31, and the screen usually adds which way it went, Over Voltage or Under Voltage. myenergi’s meaning is that the zappi has detected that the supply voltage is too high or too low and has disconnected the EV to protect it, and their action carries the same condition they attach to the PEN fault: unplug the EV, make sure that the fault has been removed, and then hold the button to reset. That condition is the important part. The installation manual gives the numbers: the nominal supply is 230 volts, and the zappi trips its output if the measured voltage is more than 12 per cent above or below that for five seconds — roughly 202 to 258 volts — showing Over Voltage! or Under Voltage!, and it resets automatically once the voltage returns to the acceptable range of 230 volts plus or minus ten per cent, which is also the rated supply range in the specifications.

When the mains sits outside that band there is nothing in the charger to fix; resetting into the same supply produces the same code. The cause is either the incoming supply itself, which the distribution network operator is obliged to keep between 216 and 253 volts, or the installation, where a long or undersized cable run to the charger drops enough voltage under 32 amps to trip the low end while the rest of the house reads normal — the IET have written about exactly this, because the open-PEN detection that BS 7671 permits works on the voltage at the charging point, and voltage drop in the installation’s own cable can take that below 207 volts and cause unwanted tripping on a supply that is perfectly healthy at the meter.

Over-voltage on a UK supply is most often seen in the middle of a sunny day on a street with a lot of solar exporting into the same substation. Under-voltage is more often the evening peak or the cable. Code 31 that appears at the same times of day is telling you which. A UK chargepoint disconnecting on voltage is also doing part of its job against a lost PEN conductor, which is why it will not simply ride through a bad reading.

1. 1

   Read the screen and note whether it says Over or Under, and what time it happened. The pattern is most of the diagnosis.

2. 2

   Unplug the EV. Wait for the supply to settle, then press and hold the menu button to reset if the unit has not already reset itself — the installation manual says it resets automatically once the voltage is back inside 230 V ±10%. myenergi say to make sure the fault has been removed first, so a reset during the same conditions will not hold.

3. 3

   If it recurs only under charging and the house voltage is fine, ask the installer to check the voltage drop on the charger circuit. That is a measurement at the zappi under load, not an owner job — and UK Power Networks ask owners to have their own equipment checked by the installer or an electrician before reporting a charger voltage issue to them.

4. 4

   If it recurs at the same time of day, note the dates and times and report it to your distribution network operator. UK Power Networks describe the process: they check for known network problems, send an engineer, and if needed fit a recording device for two weeks.