So I have a main panel (3 phase power), and a 100 amp sub-panel off of that. The sub-panel includes an ~55 amp draw tankless water heater. When it's not used everything is normal. However, when the tankless water heater is engaged, various electronics around the house show side effects:
- The power bar for the TV / entertainment center buzzes loudly
- Many dimmable LED lights on different circuits flicker / fade
- LED lights in the master bathroom buzz loudly
All affected devices are on separate circuits and not tied to the sub-panel or the tankless circuit.
This only happens when the sub-panel tankless heater is active. What's going on? Is it dangerous?