The mains has been restored but the generator is still running

This is something which we get asked a lot about.

So you’ve had a power cut and the generator kicked in automatically as it is supposed to but now you are told that the mains power has been restored and yet the generator is still running. Here’s a run down of some possible causes:

  • Check the AMF panel. It might be that the changeover panel has switched back over to mains and the generator is just running through its cool down period. This is a preset time and is generally around 5 minutes. Have a look at the AMF panel to see whether your load is powered by the generator or the mains.
  • Mains power is still not yet within acceptable limits. After a power cut it is common for the mains to come back but not be quite within the acceptable range. For example you may have 230V on L1 but you could have 180V on L2 and 0V on L3. Most changeover panels monitor all 3 phases and are therefore clever enough to realise that the mains power is still not correct and will therefore continue to run on generator to keep your operations working. If your AMF panel has a display, you can check the voltages of all three phases on the mains as well as the frequency and this will highlight whether the mains is there or not.
  • AMF Reset. Sometimes the changeover panel needs a reset for it to realise that the mains power has been restored. This doesn’t happen often but it can happen.

When your building is being powered by your generator, it is a good idea to monitor the mains voltages every now and then to see whether mains has been restored. Of course the generator will happily run and you might even find that the cost of the fuel is less than what you pay for your electricity usage.

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