Shower causing lights to dim??

[Hagarbloke]

Hi all,

Hoping you can shed some light on an issue I have with our new shower. We moved into our new house about 8 months ago and the original shower was completely knackered so I've replaced it with a 9.5kW unit. The cable feeding it is 10mm2 and there's a 40 amp breaker in the CU. The shower works fine, but what I'm finding is that when the shower is fired up the light in the bathroom dims slightly, not alot but it's noticeable. What could cause this given that the shower is on a seperate circuit to the lights??

Thanks in advance......Matt

 

[TicklyT]

probably the load of the shower, which is likely to be the heaviest single load connected to your CU, causes the supply voltage to drop a tad. The effect is more noticable on incandescent lamps, as the light output is proportional to the square of the voltage.

 

[Hagarbloke]

So is that quite normal? If a voltage drop is occurring due to a heavy load, wouldn't that imply that there was an inadequate conductor somewhere adding resistance to the circuit, and thus the resulting drop in voltage? I'm not that experienced with household electrics, I'm an electronics engineer by trade.

 

[ColJack]

wiggle the meter tails and listen for crackling noises..
might be a lose neutral..

it might also be that you've got undersized supply cables or your starting voltage isn't that great..

 

[Hagarbloke]

wiggle the meter tails and listen for crackling noises..
might be a lose neutral..

it might also be that you've got undersized supply cables or your starting voltage isn't that great..

By undersized supply cables do you mean the cables between the meter and the CU ColJack? I ask because obviously the lighting is on a seperate supply from the CU, so the only thing that could cause a drop in voltage would be inadequate cabling here? Am I right to think this?

 

[RF Lighting]

It's more likely the cable from the substation transformer to your house which is a bit on the small side

 

[Steve]

Replace the lights in the bathroom with CFL (energy saving) types. These aren't affected by voltage drop (to a point).

Seriously, dont worry about it. Our lights always dimmed when the showers on.

 

[Hagarbloke]

Great, thanks for your advice.