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Doorbell Wiring Diagrams

The provided wiring diagrams are based on the NuTone 2-note door chime, but the common wiring configurations should pertain to all other brands of chimes as well.

**Please consult your specific brand of chime for reference.

NuTone Door Chime and Transformer FAQ…

  • 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?
  • If an application is to connect two, 2 note chimes together, will 2 transformers be required?
  • What is occurring if the chime rings by itself?

**Find many more common questions and answers at NuTone

WARNING: Electrical Hazard. Turn off power at breaker panel or fuse box to avoid injury. Contact a certified Electrician or HVAC tech if unsure of your DIY capabilities.
NOTE: Use solid copper (not stranded) low-voltage wiring (18/2 thru 22/2). Available at any local home improvement store.

Single Button Doorbell Wiring Instructions

  • For single button activation, a common transformer is the NuTone C905 (see end of article). Rating = 16VAC, 10VA (watts).
  • Neither door buttons nor transformer are polarity specific, unless otherwise noted in manufacturer’s instructions. Either terminal can be mounted to the red or white bell wire (typical wire colors).

**Find complete specs on the C905 at Nutone.

How to wire a doorbell with one button
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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.
  • 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 (typical wire colors).

**Find complete specs on the C907 at Nutone.

Front and rear doorbell wiring diagrams

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 mounted several ways:

  • Located inside the bell or chime enclosure.
  • Installed into a single electrical gang box like a switch, e.g. NuTone C915.
  • Wall mounted via the 4 screw holes in the mounting plate.
  • Mounted to a junction box.
Further Reading:  Luxello Modern LED Doorbell Buttons

Junction Box Transformer Mounting (as shown):

The transformer will either have males threads and a nut; allowing the transformer to mount via one of the junction box knockouts, or use a quick install lock-mount. 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
Tags : doorbell