Why Do Our Lights Go Dim When Our Shower is On?

loveandlight

We have recently had a new 9kw electric shower fitted. It works fine except every time one of us has a shower all the lights in the house go slightly dim!
We have spoken to our electrician about it and he says that this is normal as the shower is using up a lot of electricity. Is this true? Or does anyone know what the problem could be?

weekendwarrior

It is quite common for this to happen. I was told that it may depend on which phase you are connected to!

orainsear

It's nothing to worry about. Without being too technical, a 9 kW load will cause a slight voltage drop in the electrical system, say 2.5 - 10 volts. The human eye is very good at detecting changes in brightness and a filament bulb can dim quite significantly for a relatively small voltage drop.

ManAtHome

Wow - a genuine MSE shower, automatically turns down all the stuff you won't be using when you're using it...

YorkshireBoy

weekendwarrior wrote:

I was told that it may depend on which phase you are connected to!

Possibly, since throughout industry it's a fact that more equipment is connected to the red phase, than to yellow or blue (I'm working in old money, just in case there are any pedants looking in!).

Other factors include...

1. How far the property is from the distribution transformer (the further away the worse the problem), and

2. The age of the supply cable to the property (older terraced properties were often supplied with very small, compared to nowadays, CSA cables and one cable would often feed 4-6 houses in the terrace).