Transformer installation

My house has a 16V 10VA transformer for the doorbell. I bought a 16V 30VA transformer, and tried to install it. Easy? Simple?

The 10VA transformer is attached through a knockout on the side of the breaker box. The 16V wires are attached to the outside, while the high voltage wires are threaded through the knockout hole.


  • The three high voltage wires are connected directly, without any wiring nuts, to the breaker and the ground bar.
  • The green wire and one of the black wires are attached to the ground bar, and I can’t loosen the screws that hold them to the ground bar. If I can’t loosen the ground bar screws, I will have to cut and strip the existing wires, and use a wiring nut to connect the new transformer wires to the existing wires.
  • The other black wire is attached to a 15A breaker.


  1. Why is the existing 10VA transformer double grounded (ground and one side connected to the ground bar)?
  2. Is it OK to attach a 30VA transformer to a 15A breaker? The circuit only powers the chime solenoid and the video doorbell. They say 10VA is not enough for both, but will they pop a 15A breaker?
  3. I only have small wiring nuts. Will I need to buy larger wiring nuts for the larger gauge wires?

Hi @drepouille. These questions might be better asked to a licensed electrician so they can advise you safely on the proper installation for your new transformer. Other neighbors may chime in if they’ve had similar situations with yours, but if you don’t get an answer from anyone else, a licensed electrician should be able to help answer the questions you asked while ensuring your safety as well. :slight_smile: