Installing a new doorbell transformer

Before you start a replacement, verify that the transformer has power by checking the terminals with a voltage tester. If the meter is reading over 10volts, you may have a damaged wire between the transformer and the doorbell. Voltage tester. Cordless drill. Check the instructions that are included with your doorbell chime to confirm the wiring requirements. Since the transformer is a low power device, it is often installed on an existing circuit on the side of a junction box. The transformer should be located near the doorbell.

If you are installing it onto an existing junction box, make sure that the circuit or circuits feeding that box are off and test the wires. Remove a knockout on the side of the junction box by tapping the edge with a flat screwdriver and twisting it off with a pair of pliers. If your transformer has a threaded nipple you can slide this into the hole and secure it with a locknut.

Other transformers need to be mounted to a new electrical box sized for a switch. Remove the wire nuts from existing circuit and connect the black wire from the transformer to the black circuit wire and connect the wires with a larger wire nut. Repeat for the white and green wires respectively. Carefully bend the wires into the box and replace the junction box cover plate.

The wiring from the transformer to the doorbell button and chime are usually 18 gauge AWG or larger depending on the voltage requirements. For existing systems 2-wire thermostat wire is often used to complete this circuit. If you are replacing the transformer you simply need to reconnect the wires to the terminals on the outside of the transformer. Go to 5. If you are installing a new doorbell, you will need to run the low voltage wire to the door bell and the chime.

Cut a 2 inch square hole in the drywall and push a fish tape up from the basement to the hole. Attach 2 pieces of 18 AWG wire, the same color, to the end of the fish tape and secure it with a piece of electrical tape and pull the tape back down through the hole.

One wire should reach to the doorbell button and the other to the transformer. Running the wire for the doorbell to the outside can be more difficult. It is best to remove the trim and run the wiring behind it. Leave the wire stick out about 4 or 5 inches. Slide the wire through the hole in the trim and reattach the trim to the door. It is important to keep track of which wire is going to the chime and which is going to the button.

This article has been viewed 43, times. Often enough, replacing a faulty transformer is a fairly straightforward job. Turn off the power first, disconnect the transformer's wiring, and dismount it. Then bring it to the hardware store and purchase a matching replacement.

Tip: If you have trouble finding the transformer, remove the chime box the indoor doorbell unit from the wall. If the wires that run through a hole in the wall to the transformer lead up, the transformer is in the attic.

If they lead down, the transformer is in your basement or crawl space. Tip: Transformers have various specifications, so take yours to the hardware or home improvement store after removing it. Ask an employee at the store to help you find a match. Safety Precaution: Call an electrician if there is no grounding wire, bar, or screw inside the junction box.

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Learn why people trust wikiHow. Download Article Explore this Article parts. Tips and Warnings. Things You'll Need. Related Articles. Part 1. All rights reserved. This image may not be used by other entities without the express written consent of wikiHow, Inc. Rule out issues with the doorbell switch, chime box, and wiring. Before attempting to replace the transformer, ensure the problem isn't with another part of the doorbell. First, remove the wires from the doorbell switch the button mechanism , and touch them together.

If the doorbell rings, the switch needs to be replaced. Remove the cover, have a helper press the doorbell button, and test the chime with a low-voltage meter. If the tester lights up, there's something wrong with the chime.

Look for buildup in the mechanism, and clean any grime with rubbing alcohol. If that doesn't do the trick, you'll need to replace the chime. If the tester doesn't light up, the chime isn't receiving power, which means the issue is either with the transformer or the wiring between the transformer and chime.

Find the transformer in the basement or attic near the electrical panel. Doorbell transformers are usually located on or near the main electrical panel.

Look in the area around your panel for a small black or silver metal box attached to a beam or to the panel itself. Check behind insulation, especially if you suspect the transformer is in the attic. While less common, the transformer may be under or inside the chime, so check there if you can't find it near your electrical panel or heating and cooling system. If the transformer is attached to the panel itself, it may be trickier to replace or require you to disassemble the panel. Shut off the circuit breaker or fuse at the main panel.

Before attempting your repair, find the circuit breaker or fuse that supplies power to the transformer. Flip the circuit breaker switch off, or twist and remove the fuse from your fuse box. If you have a fuse box, pull out the main fuse block, or a large rectangular block with a handle at the top of the panel. Before you turn off main power, have a headlamp or flashlight handy so you can find your way to the transformer and make the repair.

Hold a no-contact voltage meter to the transformer to make sure you turned off the right circuit. You can purchase a voltage meter online or at your local hardware store.

Part 2. Remove the transformer junction box cover, if necessary. Doorbell transformers are typically mounted on a silver metal junction box, which will likely have a cover.

The cover may snap off, or you may need to loosen screws to remove it. The 2 sets of wires are connected by wire caps, which are plastic cylinder-shaped covers. Disconnect the wires that supply power to the transformer.

Untwist the caps that connect the wires running from the transformer with those that lead to the electrical panel. The green wire is connected either to a green or brown wire or to a metal ground bar or screw. This grounding wire helps prevent electrical overloads. Unscrew the wires that connect the transformer to the doorbell.