Doorbell transformers sold by Heath Zenith and Broan Nutone contain terminals labeled for 24 volts as well as lower settings of 8V, 10V, 16V and 20V. While old transformers topped out at 8 to 16 or even 20 Pine, those versions with a top range of 24V can serve larger homes that need longer wire runs, with no drop in voltage. The units allow you to power chimes with numerous notes or your very own downloaded music, as well as a doorbell push buttons at both the front and a back door. Transformers of any voltage step down your home’s 120V system to lower voltages, to lower your electric use and protect your house from fire.
Shut the power off on the circuit which serves either the existing transformer or a junction box which you intend to tap into to get a new transformer setup. Verify the electricity is off by tapping on the incoming cable using a low-voltage contact tester.
Unscrew the faceplate of this junction box and, if it also functions a lighting unit, pull that to the side, where it can dangle by its stiff wires. Remove the old transformer, if present, by twirling its locknut, removing its wire nuts and untwisting its pigtail wires in the home power supply wires. Set it aside. If this is a new setup, flick away among the available junction box knockouts using a screwdriver.
Thread the 24V transformer’s pigtail wires through the knockout. Press the male threads of this NuTone 24V transformer through the knockout, and securely hand-tighten a locknut over them. For your Heath Zenith, press the clamp through the knockout and tighten its screw against the border of the junction box.
Connect the black transformer wire to the black home wire, as well as the white wire to the white cord, and insulate each using a wire nut. Connect the green wire to the green or to the bare power supply wire. All these are average instructions, which you need to verify with the manufacturer’s directions. Refasten the faceplate.
Connect existing low-voltage, 18-gauge, paired wires, typically white and red, if existing, one to each of the two lower brass screws marked 24V on the transformer. If this is a replacement, turn on the power and then test your work. In a new install, continue with extra actions.
Run new 18/2 cable to your doorbell button rated for 24V. Strip slightly more than the usual half-inch the ends off. Wrap and fasten the red wire to a brass screw — it doesn’t matter which one.
Run a low-voltage cable in the doorbell button to the approximate area you want to attach a 24V-rated chime. Return to the doorbell, and attach the red wire in the second cable to the free screw on the doorbell button. Twist the two white wires together and insulate them in a wire nut.
Return to this chime, and set the red wire on the brass screw labeled the white wire on the screw labeled Trans. If you want a back-door doorbell, run a separate low-voltage wire from a single backdoor doorbell button screw to the transformer, and another one in the second doorbell screw to the chime’s screw labeled Rear.
Fasten the chime to the wall after the manufacturer’s arrows embossed on a plate on the back of the chime. You may have one choice vertically and one choice horizontally. Analyze your new transformer by pressing the front doorbell button and the back button, which will suffice otherwise.