The home has an instant hot whole house water heater with 4 elements fed from a subpanel; each element on 30 Amp 240 Volt breakers. Subpanel is being fed by #2 Alum. on a 100 Amp breaker from 200 Amp main service panel containing all the rest of the homes' service. Subpanel supplies only the instant hot water heater. The problem is that whenever hot water is called for, the lights (especially small 25 watt vanity light bulbs and recess lights on a dimmer)will dim noticably. Anyone have any ideas what might be causing this?
