new electric shower - hum?

[dormermike]

Hi

Fitted a new electric shower today as the old one was dead (inlet valve failed).

I used the same circuit etc, like for like replacement. Works fine but seems to make an electrical humming noise, not unlike a transformer or substation.

I'm not familiar with electric showers, this is a backup and unlikely to be used much. Is it normal for them to hum though? It's a Mira sprint 8.5kw

Thanks
Mike

Ps may be being paranoid, better safe than sorry though

 

[Johnmelad]

Do you still get the sound with the shower head removed?

 

[dormermike]

Yep, head off sounds the same

This is not a buzz or crackle btw, just a steady "hum"