Water heater causes lights to dim

ianbrookes · Sep 14, 2011

please see the attached diagram.

This is a weird one and I am thinking that it is a supply issue. Has anyone seen this before.

The water heater is an instantaneous heater for a basin at 9.5kw and is in the garage. When it is turned on the lights in the house dim for the duration of the water heater being on. (diagram helps to see how garage and house are connected).

I measured the voltage drop as being 242v to 230v when the water heater is turned on. So not enough current ? or something else on the suppliers side ?

I have checked terminals etc and all cables are tight.

The house / garage are semi rural and it is the last house down the lane.

Rockingit · Sep 15, 2011

spark 68 said:
That is for 3 Ph, normally the earthing conductor will not be carrying current (third conductor), I make it 46 A from the table on single Phase.

On my second coffee :ack2:

D'Oh!! You are of course quite right. More coffee required...... Although, that actually increases the voltage drop to 8.26V as the drop value changes from 6.4mV to 7.3mV as well.