Light dims when I cut water heater OFF / Brightens when I cut water heater on.

[leeradney]

I wanted to see just how much saving cutting my water heater on and off would gain me. I noticed an interesting phenomenon. When I cut it OFF, the light DIMS in the room that has the breaker box. When I cut it ON, the light BRIGHTENS. This seems backwards to me. Any logical explanations?

Thanks!

 

[iwire]

You may have a bad neutral connection between that breaker and the utility transformer.

 

[kwired]

What is voltage and amps rating of the water heater?

Is there long length of service or feeder conductors involved, or a really small capacity transformer for the load that is connected to it? Your problem is more likely if you have a 120 volt water heater, even with no bad neutral. A long service or feeder can still give some similar effects as voltage is dropped over a long neutral conductor.

 

[GoldDigger]

I wanted to see just how much saving cutting my water heater on and off would gain me. I noticed an interesting phenomenon. When I cut it OFF, the light DIMS in the room that has the breaker box. When I cut it ON, the light BRIGHTENS. This seems backwards to me. Any logical explanations?

Thanks!

Is the water heater element 120V (line to neutral) rather than 240V (line.to line)?
If so and the 120 to the heater comes from the opposite line phase from that feeding the lights, the voltage drop kn the neutral will increase the voltage seen by the lights.
The high neutralize resistance will not be in either branch circuit but could be in feeder, termination of service wires at panel or somewhere on the POCO side.