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Doorbell Wiring Diagrams

Learn about every aspect of a wired doorbell system; from how each component works and how they connect. Wiring diagrams include: single and double buttons – single and multiple chimes.



Modern stainless steel doorbell cover
modern doorbells - Contempo Chime Cover *discontinued*

From past to present the common 2-note wired door chime has remained a simple setup. There are three main components: chime, button, and transformer.

Beyond displaying various wiring configurations, we’ll also discuss the relevance of each stage and how all the parts work together to create a chime sound when the doorbell button is pressed.

You’ll notice the Broan-Nutone company, more specifically the NuTone chime and transformers parts used as reference. These are just the products we chose to work with, but the provided wiring diagrams and parts descriptions are universal and should apply to all wired door chime systems.

Applies to All Wired Doorbell Systems

  • Doorbell pushbuttons aren’t polarity specific. Either terminal of the pushbutton can be mounted to the red or white wires shown in the diagram.
  • The transformer doesn’t have an in / out set of terminals. The red wire shown in the diagrams can connect to either terminal of the transformer and pushbutton.
  • Bell wire or Thermostat wire? Either is fine. Bell wire comes as separate individual wires while thermostat wire has a jacket to keep the wires bundled together. Depending on the layout of your home and location of doorbell components, choose if individual or bundled wires work better (ref. single doorbell button wiring diagram).
  • A 20-22 gauge 2 conductor 20/2 wire can handle the electrical load, but I find it to be too thin and fragile. I prefer the extra thickness and durability of 18 gauge 2 conductor 18/2 wire.
  • WARNING: Electrical Hazard. Before beginning work, turn power off at the breaker panel or fuse box to avoid injury. Contact a certified Electrician if unsure of your DIY capabilities.

Wiring a Single Doorbell Chime With a Single Button

  • The NuTone C905 has a rating of 16V – 10VA; these are standard specs for most single 2-note chimes. This is the transformer supplied in contractor grade wired door chime kits.

How to wire a single chime and doorbell button

Wiring a Single Doorbell Chime With Multiple Buttons

  • Add a rear or side door button in addition to the main front door button.
  • All the information for a single chime and doorbell button wiring apply, with the addition of another pushbutton.
  • The rear is only a 1-note chime. You’ll notice a bumper (ref. image in chime parts section below) inside the chime – above the “rear” chime pin – that prevents the top chime bar from being activated. This creates a slightly different sound between the front and rear buttons to indicate which button is being triggered.

How to wire a single chime and double doorbell button

Wiring Multiple Doorbell Chimes With a Single Doorbell Button

  • Strategically placing two or more chimes assures that you hear the doorbell sound throughout the entire home.
  • Powering 2 chimes simultaneously requires a larger transformer, e.g. NuTone C907 with a rating of 16V – 30VA.

How to wire a double chime and single doorbell button

Wiring Multiple Doorbell Chimes With Multiple Buttons

  • Add a rear or side door button in addition to the main front door button.
  • All the information for a double chime and doorbell button wiring apply, with the addition of another pushbutton.
  • The rear is only a 1-note chime. You’ll notice a bumper (ref. image in chime parts section below) inside the chime – above the “rear” chime pin – that prevents the top chime bar from being activated. This creates a slightly different sound between the front and rear buttons to indicate which button is being triggered.

How to wire a double chime and double doorbell button

Common NuTone Door Chime FAQ’s
We wanted to cover the basics and more in this article, but for more answers about NuTone products, reference the Nutone faq page.

  • Can a 2-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 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?

**Consult your specific doorbell brand for further questions.

Wired Doorbell Parts

As mentioned earlier, there are three main stages of a wired doorbell system, plus the wiring to connect all the components.

1) Chime: You can’t have a ding-dong sound without the heart of the doorbell system. There are varying decorative covers, and dimensions may vary between manufacturers, but the fundamental chime design you see here, by NuTone, will remain uniform.

To access the internal chime, most, if not all covers snap on. To remove – pull forward.

Nutone 2-note wired chime

NuTone 2-Note Wired Chime

2) Push-Button: The buttons used to activate the chime are of the momentary switch type. Think of it like this, you could remove the switch and manually touch the two open ended wires together, therefore completing the electrical path to activate the chime. Add the switch, and it achieves the exact same thing, momentarily completing the electrical path when depressed to energize the chime, then breaking the electrical path when released as the internal contacts no longer join.

Doorbell pushbuttons are not polarity specific, therefore either wire can connect to either terminal.

An common rectangle pushbutton is included in many chime kits, but you can upgrade to another pushbutton, including LED buttons, and the wiring will remain the same.

NuTone doorbell pushbutton

NuTone Doorbell Button: Pressing the button creates contact between the metal plates and completes the energized path to the door chime.

3) Transformer: A step-down transformer reduces the 110-120VAC line voltage down to 16-20-24 low-voltage for doorbell component compatibility.

As noted in the wiring diagrams; depending on the door chime, or having multiple chimes, the transformer specs need to comply for chime function.

Broan-Nutone electrical box mounted doorbell transformer

Locating or Installing a Transformer:

  • A transformer can be mounted inside a junction box, e.g. NuTone C915, which may reside directly behind the door chime. This setup can remove the guesswork of locating a remote mounted transformer.
  • A transformer can be mounted to the outside of an electrical junction box. Check basements, crawl spaces and attics for possible locations.
  • Most transformers have screw mount plates as well as the electrical box connector. Check open floor joists or wall studs in the basement, crawl space and attic.

Quick Tips: Essential Electrical Tools

Wire Strippers
Twist Wire Connectors
IDEAL Specialty Wire Connectors
+ 5


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  2. Leann

    August 14, 2017 at 1:12 pm

    I’m changing out my wired doorbell and am confused by the wiring configuration. The main house black wire is connected to a ceramic circular fixture that is mounted to the wall in front of the junction box that’s recessed into the wall in the closet. The ceramic device holds a 3 amp circular fuse that is screwed into it. The doorbell transformer also connects to the back of this 3 amp fuse. The white house wire is connected to the other transformer wire. What is the purpose of this 3 amp fuse configuration?

  3. Spencer

    July 6, 2017 at 10:21 am

    I have an old style 1998 Nutone doorbell on my front door. The chime box just hums when doorbell button depressed. One of the plungers moves but no tone?

    Is this a problem with the chime unit as opposed to the transformer?

  4. John

    August 14, 2016 at 12:05 am

    Hi –

    I just got the Ring Pro and everything is working perfectly…well almost perfectly. My doorbell used to go “Ding/Dong” and now it just goes “Dong”.

    I made sure everything is wired properly and I currently have a NuTone c905.

    Could an upgraded transformer help fix this like the C907? I had my wife press the doorbell and I see the chime goes down first, but does not make contact, and makes contact going up to make the Dong sound.

    Really trying to figure this out – any advice?

  5. Rob

    April 24, 2016 at 8:25 am

    I”m trying to figure out why my new Ring Pro video doorbell won’t sound the mechanical chime while the old Ring doorbell, which I’m told uses much less power, did and my regular doorbell works as well. Tech support is trying to help me, but I think the issue comes down to how my mechanical doorbell is wired. Here are the facts:

    1. Looks like a Nu-tone chime from the mid-80’s.
    2. Has two red wires leading to standard terminals labeled “front” and “transformer”.
    3. I took a voltage meter to the red wires and dectected only trace voltage.
    4. At the chime but simply tied together with a wire nut are two white wires.
    5. I stuck one probe from my voltage meter into the wire nut and the other end to one of the red wires on the chime and got a 19 v reading.

    Is this wiring unusual and does it at all explain why I can’t power the power hungry Pro doorbell?

    Thanks! – Rob

    • Editorial Staff

      April 24, 2016 at 11:47 am

      Hi Rob,
      I apologize, but as of now we haven’t yet tested the Ring Pro Video doorbell. and therefore have no hands-on experience to offer much for diagnostics help.

      Do you know where your doorbell transformer is and the rating of it? Maybe the new Ring doorbell requires a higher powered -output- transformer, like the NuTone C907 mentioned in the double doorbell diagram.

    • Alan

      August 9, 2016 at 7:37 am

      Hi Rob,
      I had the same problem you described, and I debugged it to be caused by a second mechanical chime upstairs. I bypassed the second chime (it was wired in series) and everything is working ok so far now. Good luck

      • Editorial Staff

        August 9, 2016 at 7:42 am

        Hi Alan,
        Thanks for sharing this information.

      • Ken

        August 22, 2016 at 6:50 pm

        How exactly does one “bypass” the second chime? I believe this is the same situation I’m experiencing. I disconnected the “front” and “trans” wires on the second chime, but that just left the circuit open and nothing worked.

  6. Mel

    November 19, 2015 at 5:49 pm

    I just replaced my wired door bell servicing both front and back doors. The three wire coming from the bell is coloured (black, red, and white), but the wires from the buttons and transformer are all one colour (brown) so it is a bit confusing. In any case, once I had it all connected, I ended up with the ding dong at the back door, but I want the ding dong at my front door. When I switch the wires at the bell I only get a dong at both the front and the back doors. I am no electrician so I am puzzled why this is so and wonder how I get the ding dong at my front door. Any advice on this?

    • Editorial Staff

      November 19, 2015 at 6:54 pm

      Hi Mel,
      If your doorbell, transformer, and push buttons are all accessible, I can only recommend following the diagrams shown. I know you may be thinking “great…thanks for nothing”, but there isn’t much else to add. Unfortunately past installers can create chaos and the best answer is to redo what is existing from scratch.

      • Mel

        November 19, 2015 at 7:59 pm

        Unfortunately, The wires are not accessible, but all are gathered to one place that is accessible. Power appears to be delivered okay through the system. Except I need the ding dong and dong interchanged. Any suggestions what I might try? And why doesn’t just exchanging the wires at the bell work to do this? One observation – I don’t know for certain which wires go where, but I have based my best guess on following the wires as far as I could.

      • Editorial Staff

        November 20, 2015 at 8:57 am

        As you mentioned “I don’t know for certain which wires go where”. Therein lies the problem. Who knows what connections, splits, etc. exist. To my knowledge, all basic door chimes aren’t polarity specific, and you are working with low voltage, so at your own risk, you should be able to play musical chairs with the wires until you sort out the right wiring configuration. I’m not sure if the same holds true for electronic chimes.

      • Mel

        November 22, 2015 at 7:13 pm

        Thank you. I’ll try more configurations.

  7. Denise

    November 17, 2015 at 7:17 pm

    I have a door bell chime from the late seventies i removed it to di renos i have four wires from the wall and only three spots to put the there was two wires together how do i connect these wires

    • Editorial Staff

      November 19, 2015 at 6:56 pm

      The wires coming out of the wall could be connected in numerous ways. There is no sure way to tell unless you follow them from point A to B, then follow the diagrams shown to make sure all is wired properly.

  8. Eli

    October 30, 2015 at 3:51 pm

    Doorbell installation: I purchased a #0050500 Transformer and a UT-7580 Doorbell after installing the transformer and the doorbell according the instruction, but only the chime for the front door will work I cannot get the back door to ring when I switch the wiring from the back termnial to the front termnial then the front push button will ring the back door sound, I can only get the back door button to work when the front door button wire is clamp together there are four red wire and four white wire running from transformer to the chime but the chime only have three termnials front, rear, and trans. for the red wire there is no termnial for the white wire.
    Can you help me with this problem?

    • Editorial Staff

      October 30, 2015 at 6:02 pm

      Hi Eli,
      I’ll try and help but many of these projects are hard to sort out without some type of visual. Looking at the UT-7580 Doorbell installation manual, it appears to be the same configuration as the instructions shown in this post, which has me wondering why you have so many wires? You said there are 4 red and 4 white? Something is obviously getting crossed up along the way.

      • Eli

        November 3, 2015 at 10:12 am

        Thank you very much for looking into the matter, the mfg. tech. seem to think that there is a posibility that the wire might be crossup.

        Thanks again,


      • Editorial Staff

        November 4, 2015 at 10:13 am

        I agree with the manufacturer tech. If all parts are installed properly and there is an issue, then product defectiveness may be the issue, but most times there is an error in the installation and / or compatibility. Wiring can be very tricky when swapping out parts as you never know what is going on behind the scenes with the actual wiring. Always best to make sure you can trace the entire wire – from part to part – and confirm all is right.

  9. John S

    September 1, 2015 at 1:51 pm

    Hi Team – I am wiring a new Vivint doorbell to replace my existing, but, this is a bit of a long story. I took off my bell box, and clamped the wiring into my wall, and painted over the hole in the wall. I then took my wiring from the door bell, and tucked in down near the door frame. (I was going to get a wireless doorbell, hence removing the equipment)…….

    Now, I have this new cool Vivint doorbell that Z-Waves into our system, but, it requires a power feed at the door, i.e. the actual doorbell wiring. I know that the hot leg comes from the basement transformer, and the neutral from that same transformer routes to where the original bell box used to be…

    My question is, how easy is it to take the front door bell wiring, and run a straight shot pair (red/white) directly from the transformer to the front door, where the new equipment is? Remember, the front door bell only needs power.

    • Editorial Staff

      September 1, 2015 at 8:02 pm

      Hi John,
      How easy? That varies based on many circumstances and a touch of luck. Our home has conduit installed for electrical, so I have a smooth pathway up the wall and to the doorbell button, then a full open basement where the wires lead to the exposed transformer. Point being? This is a very simple situation if I were to need new wires. Not sure how your situation compares?

      Doorbell buttons are mostly on exterior walls so you may have insulation to contend with. A very common device to use is a fish tape when trying to pull new wires. They’re flexible, yet stiff enough to push through minor obstacles without bending. You may be able to rent one at a Home Depot or other local rental places that carry tools.

      • John S

        September 1, 2015 at 8:30 pm

        I just had my security company here tonight, and, they used the fish wire device, simple. I also traced my basement transformer wiring to where they pair off… I just might be able to join the two pairs that lead to bell box at the same position as splicing the hot and neutral…

        A work in progress….

      • Editorial Staff

        September 2, 2015 at 9:03 am

        Great that things worked out easily enough. Yeah, a simple splice using wire nuts as shown in the article diagrams should work just fine.

  10. Robert

    August 30, 2015 at 3:33 pm

    Black and white for both front and back.

    • Editorial Staff

      August 30, 2015 at 5:37 pm

      Okay, that doesn’t make diagnosing any easier. Red wires at the chime, but not at any doorbell button.

      I’m not sure how comfortable you are with wiring and electricity, but I can assure you this doorbell chime and button combination is at the most basic level. These are not complex electronics you need to worry about damaging. You have very simple momentary switch types at the button and door chime. Which means instead of touching two wires together to complete the circuit, you have a switch plate that makes contact in the same way as touching two wires together when the doorbell button is pushed.

      Point being? You can play around with the wire configuration at the door chime without worry. The door chime is marked rear-trans-front to keep wiring organized just like the wires are colored for easy reference, but can be moved around like someone has done with your doorbell and chime and still work.

      As mentioned earlier, one of the red wires at the chime has to be 12-18v coming from the transformer. Always turn power off at the breaker box to be safe when working with wiring.
      • Connect one of the red wires to TRANS
      • Unwrap the white wires and connect one to the REAR terminal (Maybe they need to stay connected and have both connected to the REAR terminal). Hard to know without seeing and finding the transformer.

      Just keep swapping wire combinations at the door chime and hopefully you get both front and rear doorbell buttons working. That’s if those white wires actually lead to and connect the doorbell buttons. Could be cut somewhere and not connect to anything.

      Hope this helps and let me know if you’re successful.

    • Editorial Staff

      August 30, 2015 at 5:41 pm

      Have you removed the door chime from the wall to see if there is a larger hole in the wall housing the transformer behind the chime?

  11. Robert

    August 30, 2015 at 7:59 am

    I have the exact 2 note door chime used in the illustration. The current wiring has four wires, 2/white and 2/red: the white wires are coupled together and not attached to the doorbell and each of the red wires are connected one to the front and one to the back doorbell terminals. The front doorbell functions properly, but the back doorbell does not ring. Do you have any suggestions on what needs to be done? Also, I have no idea where the transformer is located; the doorbell was installed when I moved to the house.

    • Editorial Staff

      August 30, 2015 at 10:01 am

      Hi Robert,
      Wires are colored coded as a label and reference, but that doesn’t mean a previous installer kept to the standards, so locating the transformer would be very helpful to see what’s truly going on. The transformer shouldn’t be enclosed where you don’t have access. If you have a basement or crawl space, check the floor joists as shown in the transformer image. Another transformer location is near or inside (part of) the door chime itself.

      Do you have a transformer terminal on the door chime? I see no mention of a wire connected to a transformer, which means the transformer might be built-in?

      In the end, if all is fine with the wiring, you might just have a faulty rear door button.

      • Robert

        August 30, 2015 at 12:24 pm

        I have the exact 2 note door chime used in the illustration. The current wiring has four wires, 2/white and 2/red: the white wires are coupled together and not attached to the doorbell and each of the red wires are connected one to the front and one to the back doorbell terminals. The front doorbell functions properly, but the back doorbell does not ring. Do you have any suggestions on what needs to be done? Also, I have no idea where the transformer is located; the doorbell was installed when I moved to the house.

      • Editorial Staff

        August 30, 2015 at 12:26 pm

        If you’ve eliminated faulty parts from the equation, then it’s a simple wiring configuration issue. I’m assuming at some point a resident didn’t want the rear doorbell functioning for whatever reason, and just disconnected at the door chime and reconfigured the wiring; i.e. disconnected white wires and tied them together. Unfortunately, without seeing what’s connected at the transformer we’re just guessing though, so proceed with caution.

        NOTE: The door chime needs power to operate, and both the chime and doorbell buttons needs 12-16V power supplied otherwise they’ll overload and expire, so there has to be a transformer somewhere stepping the power down.

        Since the components aren’t polarity specific, and you don’t know where the transformer is, you can proceed to the trial and error phase without worry of damaging any parts. Obviously one of the red wires is powered from the transformer and the other red wire goes to the doorbell button? In the end one of those red wires should go to the transformer so you know it’s the powered wire.

        Can we take a step back? What color wires exist at the doorbell buttons?

      • Robert

        August 30, 2015 at 5:30 pm

        There is one black and one white on both the front and rear buttons.

  12. Dar

    August 9, 2015 at 4:37 pm

    Installed a new transformer, primary and secondary connections are in place. Need to connect the low-voltage wires on the chime to the Trans and Front connectors, though low-voltage wires (both red) are unmarked from prior connection, therefore I have no way of knowing which is coming from the front door and which is from the transformer. Is there a way to test to determine which is the respective wire from each to connect in the chime box? Or can you offer any suggestions? Thank you!

    • Editorial Staff

      August 9, 2015 at 10:49 pm

      In this case you are dealing with low voltage and parts that shouldn’t suffer any issues if wires are swapped, besides not working. Connect one way, and if that doesn’t work, swap the wires.

  13. Kevin

    July 27, 2015 at 7:17 pm

    Just installed the Nutone doorbell shown above. The transformer is wrapped with a piece of yellow tape..
    I’ve followed the wiring instructions / transformer has power (AC) / wired correctly (I think) / but doesn’t work… does the tape on the transformer mean anything?
    Thanks Kevin.

    • Editorial Staff

      July 27, 2015 at 9:33 pm

      Hi Kevin,
      Some electricians, and others in the trades that do electrical work, may use electrical tape to cover the connections of a switch, or transformer in the situation, as a precaution to avoid terminals being touched and shorted out. Just a preference.

      Did you get the doorbell to work?

  14. Dan

    March 28, 2015 at 1:23 pm

    Outside doorbell has a speaker from inside attached in wiring. I would like a diagram of correct wiring, thanks.

    • Editorial Staff

      March 29, 2015 at 9:32 am

      Hi Dan,
      Without knowing and seeing the existing combination, I’m uncertain as to what directions you require. Maybe this site will give you the answer you need if you can find the brand and model #.

    • Jeff

      June 9, 2016 at 6:51 am


      Did you ever get your Ring Pro to work? I’m trying to determine if I can install my Ring Pro since my doorbell was not wired with the usual 20 awg but instead cat3 24 awg.

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