Jethro Bodine:

Sheeez you are asking to die. Hire an electrician Please!!!!

T C:

should never be 2 white wires, should be 1 white, 1 black, 1 grnd. If it is a simple water heater in the shower head, and the voltage is proper for the property wiring. Then bring wiring from source, one wire from shower to source, other wire to other source wire, grnd the grnd wire.

chucky:

Introduction
An electric shower may sound absurd, as electricity is heating water just a few inches higher than your head; but, if installed accurately an electric shower can be a safe and financially sound investment. An electric shower saves money by using only a part of the water that your typical shower or bath uses and only heating the water you need immediately. Read on to learn more.
Instructions
Difficulty: Challenging
Plumbing
Things You’ll Need
Pencil
Power drill
Masonry bit (size dependent on unit manufacturer)
1/2 inch copper branch pipe
Stopcock
T-joint
Steps
1Step OneUse the pattern provided by the manufacturer to mark holes on the wall where you will mount the shower unit. Using your marks as guides, drill pilot holes using the apt sized masonry bit. If the manufacturer does not provide a pattern, you should be able to remove the backing of the shower unit and use the backing itself as a pattern.
2Step TwoDrill a 1/2 inch hole in the shower wall to fit the copper branch pipe that will connect the shower head to the main water valve. Push the pipe through the hole, measure and cut to the proper length. Fit a stopcock to the end of the branch pipe inside of the airing cupboard behind the shower wall. The arrow on the stopcock should be pointing towards the shower head, away from the rising main.
3Step ThreeFit the T-joint to the rising main, only hand-tightening the cap nuts. Measure and cut an extra piece of connecting pipe if necessary to connect the T-joint to the stopcock, joining the branch pipe to the main valve. Once fitted, tense up the cap nuts and other joints well.
4Step FourMount the shower head to the end of the copper branch pipe, attaching the shower unit box to the wall on one side of the shower head where you have made your pilot holes. Connect the flexible spray hose to the shower unit and the shower head.
Tips & Warnings
This article assumes that you have by now installed the basic plumbing for any type of shower. An electric shower will only use the cold water valve, so if you have not plumbed the shower yet, you will only need to plumb one cold water pipe from the main valve. If you are connecting an electric shower to plumbing designed for a regular hot/cold water shower, simply do not connect a hot water heater or turn off the water supply to the hot water valve.
When using a masonry bit to drill pilot holes, place a piece of masking tape over the marks made on the ceramic tiles to prevent the bit from slipping.
Always cover pipe ends with plumbers tape before connecting joints.
Electricity
Things You’ll Need
45 amp double-pole pull-switch
Yellow and green wire sleeving
Steps
1Step OneMake a hole in the ceiling between joists where you will mount the pull-switch. Attach the mounting enter on which you will fasten the pull-switch backplate.
2Step TwoRun a piece of circuit cable up to the ceiling, running it through the mounting enter. Leave at least 6 inches of excess cable at the switch position. For running cable, you can use plastic trunking and attach the plastic sheaths to the wall and ceiling, or run the cable in between studs behind the wall, up through the ceiling and down to the switch.
3Step ThreeAttach the pull-switch backplate and strip the excess cable at the switch position, revealing one black wire, one red wire and a group of bare wires. Twist the bare wires together, the ground wires, and cover them with green and yellow sleeving before attaching them to the “E” terminal of the pull-switch. Then connect the red wire to the “L” terminal and the black wire to the “N” terminal.
4Step FourStrip the cable connected to the shower unit, again revealing one black wire, one red wire and a group of bare wires. Connect the wires located on the shower unit to the “Mains” terminals of the pull-switch. The red wire should connect to the “L” terminal, the black wire should connect to the “N” terminal and bare wires should connect to the “E” terminal. All bare wires should be covered with green or yellow sleeving before attaching them to the terminal.
Tips & Warnings
Refer to the electrical diagram provided with your electric shower or to the resources section below if in doubt.
This article assumes that you have basic electrical understanding and that you have researched the electrical guidelines and set of laws in your area. If you are in doubt about any of the steps higher than, you should friend an electrician.

excellent luck!

Bill:

Some of these answers reckon you are here in the States. I visit Brasil quite often and have installed a few of the shower heads. Both white wires should be 110 and the other is the ground. Make sure the power is off and if possible use wirenuts if you can find them.These have generous resistors in the head and when water flows through it the water is heated up. The quicker you turn on the cold water the cooler the water gets. So for a nice safe hot shower I would turn the water on medium. Delight in and have a cold cervesa for me. We also have these in Ireland and other parts of Europe