A doorbell transformer, like any other electrical transformer, reduces or transforms currents of electricity. Most doorbells don't require a lot of power, so the doorbell transformer defuses the current, reducing the standard 120 volts of electricity to usually about 16 volts to prevent an overload in the chime of the doorbell. Installing your own doorbell transformer sounds like a complicated task, but with a few ordinary tools, this is an update that you can do yourself.
Step 1 - Locate the Transformer
The most difficult step in replacing any transformer is finding it. The best way to do this is to start at the push button, and trace it back to the location it's hardwired into. Usually, if the doorbell is wired down, it will be hardwired into the basement or crawlspace. Conversely, if it's wired up, it's most likely in the attic.
After you've found the transformer, you'll need to remove the old one. The most important part of the following step is to find the electrical panel in the circuit breaker that coordinates to the doorbell. Make sure it is turned off before going any further.
Step 2 - Remove the Old Transformer
Once you have switched the power off to the proper panel in the circuit breaker, remove the transformer from the wall joist with a screw gun. Make sure to pay close attention to which lines are going where. You may want to trace them back to the front door, the back door, the chime, etc. Once you've gotten them sorted, label them. In order to guarantee a fresh, solid connection, you'll want to use the wire strippers to snip the wires, then use them to peel back about 3/4-inch of the wire casing.
Step 3 - Identify the Wires
One side of the transformer, where the power supply enters, should be marked hot, neutral, and ground. You might want to use a voltmeter to verify this, but generally, the hot wire will be black, the neutral wire will be white, and the bare copper is most likely the ground. Once you've verified the hot wire, make sure to turn the power off again.
Step 4 - Install the New Transformer
Use a screwdriver to attach the hot wire to the ground wire. The other side of the transformer will be for the outlet of energy. There will usually be two, or sometimes three screws there. One is for the push buttons, another will be for the chime, and if there's a third, it will be for any external units, such as speakers. It is important to make sure that all of the push button wires go to the same screw, so strip them back if necessary and twist them together before screwing them down. There will only be one chime. If there are multiple speakers, those wires should be twisted together as well. Once all of the wires are attached, simply use the screw gun to reattach the new transformer in the same location on the wall joist.
That's it. Now you can hear your friends dropping by to congratulate you on a job well done.