What does an arc fault circuit breaker do?

This is not necessary unless you are installing a new power outlet, or moving one.

You can as long as the breaker box is still readily accessible! Something temporary like a picture or calendar would be fine—just don't build anything permanent around it that will...

You can and it's not a bad practice at all. In fact, that's your only option if there are no external settings on the water heater itself.

Did you allow access to the data. Check the iPhone, unlock the screen and allow access in the popup of the iPhone OS.

Yes, it's a good idea to have everything fully documented. The person could always go back on their word so better to be safe than sorry.

The short answer is, probably not. The wires coming out of that breaker may not be thick enough to handle 20 amps and you risk fire. If you can guarantee...

Place the compass point at one end of the arc. Strike arcs of a given radius on each side of the circle's arc. Place the compass point at the other...

Treat the arc as if it were a straight line segment, and perform the operation shown in the article above. You can also strike arcs only on the outside of...

Divide the diameter by 2. That gives you the radius. Multiply the radius by the arc length, then divide by 2 again. That gives you the sector area.

As shown above, the formula is (60°/360°) π (3)² = (1/6)(3.14159)(9). The area will be expressed in square feet.