wwhitney
In the Trades
I reviewed all your posts in this thread, the details have changed a bit over time. And taking a voltage measurement between the black and red is the way to confirm that you have 240V at the water heater, vs say some wiring error that puts both the black and the red on one leg of the supply, providing 0V between them.
So how about a diagram that shows all the details as you currently understand them: the panel, the switch box, the water heater junction box, the size and type of cable between each of those, and how the wires are connected at each location.
But as a basic comment, certainly if you have 120/240V at your water heater (which would require 10/3, not 10/2), and your 3800W 240V heater is currently operating at 120V (so 950W), you can switch it to operate at 240V and get ~4 times the heating power.
And a 20A breaker is fine for a 3800W heater: the limit for a tank water heater on a 20A/240V circuit is 80% * 20A * 240V = 3840W. So 3800W elements are made for precisely this application.
Lastly, a single pole switch is fine as a _controller_ for a 2-wire 240V load, but not as a _disconnect_. A controller is just for turning the appliance on or off, which breaking a single conductor will do. While a disconnect is to remove all power downstream to make it safe to work on, which requires breaking both conductors. So the 20A double breaker would be your disconnect.
Cheers, Wayne
So how about a diagram that shows all the details as you currently understand them: the panel, the switch box, the water heater junction box, the size and type of cable between each of those, and how the wires are connected at each location.
But as a basic comment, certainly if you have 120/240V at your water heater (which would require 10/3, not 10/2), and your 3800W 240V heater is currently operating at 120V (so 950W), you can switch it to operate at 240V and get ~4 times the heating power.
And a 20A breaker is fine for a 3800W heater: the limit for a tank water heater on a 20A/240V circuit is 80% * 20A * 240V = 3840W. So 3800W elements are made for precisely this application.
Lastly, a single pole switch is fine as a _controller_ for a 2-wire 240V load, but not as a _disconnect_. A controller is just for turning the appliance on or off, which breaking a single conductor will do. While a disconnect is to remove all power downstream to make it safe to work on, which requires breaking both conductors. So the 20A double breaker would be your disconnect.
Cheers, Wayne