Shower/outside light strange

[gazdkw82]

was talking with a friend of mine who has a strange situation. Every time he turns his shower on the outside light by the garage turns off. If he leaves the shower running and turns the garage light on and off at the light switch it comes back on again. He asked me if I knew what it was....

Only thing I could think of was possibly a voltage spike?

Something related to neutral? Possibly a borrowed neutral?

He says the light is on a daylight sensor so maybe that's faulty but I'm unsure how it could be related to the shower

Any thoughts?

 

[davesparks]

My initial guess would be the voltage drop when the shower is switched on, assuming it's an electric shower, is causing it.
Do the lights in the rest of the house get perceptibly dimmer when the shower is switched on?

This was a normal occurrence at my parents house as it is out in the sticks fed via an overhead line from a small pole mount transformer serving around a dozen houses. So voltage dips with load we're quite common and would cause this kind of behaviour.

 

[gazdkw82]

If this is the case then maybe upgrading the shower cable csa would reduce voltage drop?

 

[davesparks]

If this is the case then maybe upgrading the shower cable csa would reduce voltage drop?

It would only reduce the voltage drop on the shower cable, which won't help at all with the garage light problem. If I am correct then the voltage drop is occurring on the distributing main and service cable external to the property. There is nothing you can do about this.

 

[gazdkw82]

Ah I what you mean now.

How I would this for sure? Is there a way to measure it?

 

[davesparks]

Ah I what you mean now.

How I would this for sure? Is there a way to measure it?

Yes you can measure the voltage at the incoming side of the main switch with the shower on and off to establish the voltage drop on the incoming supply. This will vary throughout the day between times of heavy usuage on the distributing main.

 

[gazdkw82]

Ok cool thanks for the help

 

[gazdkw82]

There must be something that could be done to change this situation.

If you had a call from a customer with the same problem what would you suggest?

 

[davesparks]

There must be something that could be done to change this situation.

If you had a call from a customer with the same problem what would you suggest?

I would test to confirm that this is being caused by the situation I have described above. And if I'm happy that it is not the result of a fault and not something that can/will be corrected then I would recommend changing the light sensor for one which does not switch off when there is a voltage dip.

 

[gazdkw82]

Ah I see. Makes sense