Doorbell Wiring Diagrams

The following doorbell wiring diagrams utilize a NuTone® 2 note doorbell / chime, but the schematics are common practice and should apply to many, if not all brands of doorbell wiring.

The standard low-voltage 18/2 or 20/2  (gauge / # of wires) listed for  doorbell wiring use can be purchased at any home improvement store.

  • Read our article on How to Secure Doorbell Wires
  • If there is no existing doorbell wire and/or adding wire seems like a difficult process, a wireless door chime may be a better solution.

Neither door buttons nor transformer are polarity specific, unless otherwise noted in manufacturers instructions. Either terminal can be mounted to the white or red wire (standard wire colors).

Turn off all power at fuse or breaker box before working.


Standard Nutone 2-Note Wired Door Chime

Standard Nutone 2-Note Wired Door Chime


Single Button Doorbell Wiring Instructions

  • For single button activation, a common transformer is the NuTone C905 (see below). Rating = 16VAC, 10VA (watts).
Single Doorbell Button and Chime Wiring

Single Doorbell Button and Chime Wiring


Double Button Doorbell Wiring Instructions

  • Diagram  for FRONT and REAR door buttons.
  • Use NuTone C907 transformer. Rating = 16VAC, 30VA (watts). Extra watts = extra power = adequate chime  sound, when longer runs of wire on two button applications is typical.
Double Doorbell Button and Chime Wiring

Double Doorbell Button and Chime Wiring


NuTone Door Chime and Transformer FAQ Includes

  • Can a two-note chime be replaced by a 4- or 8-note chime?
  • May two-chimes be on the same pushbutton?
  • What can be done for a two (2) note chime that does not ring loud enough?
  • What is occurring if the chime rings by itself?
  • If an application is to connect two, 2 note chimes together, will 2 transformers be required?
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What’s a Transformer and its Purpose for Doorbell Installation?

A wired doorbell needs power to operate, but the 120VAC from the electrical box is too powerful and un-needed for the application. A transformer steps the 120VAC voltage down to 16-20-24 volts to be compatible with doorbell components voltage ratings.

A transformer can be located inside the bell or chime enclosure, mounted to a junction box as a separate unit (as shown), or fit into a single gang box like a switch, e.g. NuTone C915.

Junction Box Mounting: The transformer will have males threads and a nut; allowing the transformer to mount via one of the junction box knockouts. Power will be delivered from the 120v wires inside the box; connecting to the pigtail wires pre-attached to the doorbell transformer.

Further specific instructions will be included in product packaging.

NuTone / Broan C905K Doorbell Transformer

NuTone / Broan C905K Doorbell Transformer

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