Door Chime Power and Connections


Door bells run on stepped down voltage.  Somewhere in the door bell wiring system is a transformer that takes 110v input and reduces it to something ranging from 8v to 24v.  Check the spec plate on the synch motor to find the intended voltage for your chime, and for best results match your transformer to that voltage. Whatever you do, don’t “test” with 110v line voltage or your test will be short and smoky.   A chime without a clock is pretty tolerant of a range of voltages.  By my trial and error tests, I conclude that the 8v-24v range will operate the solenoids just fine, though at the high end, overpowering can definitely cause non-stop repeat cycling that no amount of adjustment can remedy—so don’t do that.  The other result of high or low voltage is that it will affect ring volume. For chimes with a clock – assuming the AC powered clock is still present and working, it is critical to match the transformer rating to the clock motor rating, which is typically either 20v or 24v.  A functional clock will run with more or less than its rated power, but the accuracy will suffer.

The big problem with 20v transforms is that they seem to be non-existent… at least I’ve never seen one.  I have however, seen lots of 24v transformers used with chimes.  I have one odd-ball vintage NuTone transformer that is capable of delivering 8, 16 or 24volts.  From all this I surmise that 24v volts were regularly used with chimes that have 20v motors.  I have a theory that in situations where a 24 transformer was located at the electrical panel—a very typical set up—the voltage drop over the distance of skinny wires resulted in something close to 20v being delivered at the chime.   Just a theory.

When problems arise, many seem to question the transformer first-- perhaps as a matter of wishful thinking.   Other problems are probably more likely.  A door bell button might be worn out. The house wiring for the system might be compromised.  The connections to the chimes might be wrong.   When in doubt, about wholesomeness of the house circuit, I recommend doing an offline test of the chime.  This requires building a test station consisting of a transformer and door bell button, wired like a miniature version of the house circuit.  It may seem like a lot of work, but could save hundreds in avoiding hiring an electrician to chase down phantom problems.   If you can positively isolate the problem to the house circuit, you may want to replace the door bell buttons and maybe the transformer before hiring professional help..

The chart below decodes the terminology used on various models for identifying the hook-up terminals.  Some are obvious, some not so.  Use this in conjunction with the diagram and it may save you some frustrating trial and error. 





main door

aux door 1

aux door 2

NuTone 1930’s






NuTone 1940’s






NuTone 1940’s










NuTone 1950’s



4-8 NOTE



NuTone 1980’s






Edwards 1950’s






Rittenhouse 610 1 2 3 4  
Rittenhouse 1930's A B C 1








Something that you absolutely must consider when installing or upgrading a chime is that a 3-wire circuit is required  for a motorized chime that rings more than two notes.  The simple two wire circuit adequate for simple 2-note "ding-dong" chimes will not work for the more complex motorized chimes.  If you want to upgrade from a simple 2-note chime to a motorized 3, 4, 8, whatever-note chime, upgrading your house doorbell wiring will be required.   And just to keep things as complicated as possible, if your house has a simple 2 -note chime, but is wired for front and back doors, you will see three wires coming out of the wall, but those three wires are not adequate to run a motorized chime.

BTW, if someone before you (obviously not you because you would know better) installed a motorized chime on  a simple 2-wire circuit, the symptom would be that the chime would run only while the doorbell button is pressed and held.  It would stop the moment the doorbell button is released... a condition which should not be confused with the normal startup lag for a motorized chime.  Simple, right?

Here is the text from 1949 NuTone Jefferson installation instructions:

If possible use present bell wiring.  This eliminates the necessity of installing all new wires from the door pushbuttons to transformer and chime.  However, if you do use your present wiring it will be necessary to connect one more wire from the transformer location to the chime location.  Before installing this new wire, replace your present weak bell transformer with the 24 volt NuTone Transformer packed with this chime.

Attach this new wire to the same transformer terminal to which the door pushbuttons are connected (see wiring diagram). This new wire conducts the 24 volt current to the Telechron motor in the chime mechanism.  This motor is set into operation each time the front door button is pressed and turns until the eight note chime sequence is completed.

And , oh yeah, did you notice that  NuTone clearly specs a 24v transformer for that Telechron motor rated at 20v?

One really oddball thing I have discovered is that some multi-note chimes will not work with a lighted door bell button. The only such model I have encountered is an Edwards 1482 from the early 1940's.  The symptom was that it would start and run just fine, but never stop.  Changing to an unlighted button cured the problem.

I frequently get email from people who say they have a bad transformer, or maybe bad wiring, or a bad chime but just not sure where the problem is... and can I help them figure it out?  It's almost impossible for me to diagnose a chime or house wiring by remote control.  Here's my advice for anyone who wants to debug their own.  Like any multi-variable system, whether its an algebraic equation or fixing your car, the variables need to be solved for one at a time. My own chime test station consists of a miniature of a house door bell circuit, with 110v into a transformer of correct voltage, door bell buttons and appropriate wires.  With this set up I can see all the parts, I can identify each one for sure, and I know that all are wholesome.  If you make a set up like this, you can at least isolate the problem to your chime, or outside your chime, plus you can determine the correct connection scheme by quick trial and error if necessary.   


A  Wiring diagram from NuTone Chimes, seems to work for all "motorized" chimes.  

B  Box for a NuTone Tri-Volt transformer circa 1950.

C  Instruction sheet from Nutone- Scoville includes a list of all chime transformers available.  See anything missing, like maybe a 20v transformer?  More evidence that a 24v brick was used for 20v chimes.


Click on "door chimes" above to see other related topics.