I've successfully installed my Ring Door Bell Pro yesterday.

Ring Door Bell Pro integrates with an existing door chime. I used a voltmeter and confirmed the transformer's output voltage is 19 V AC.

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Due to the Ring Door Bell Pro size, my installation at the entrance door exposes two wires going to the unit. The wires are safe; however, someone can pull them hard and they can short. I tested and when I short the wires, they spark.

I am thinking to add a fuse right after the transformer. this way, if I am not at home, and any short circuit happens by an intruder, there is no risk of fire in my basement where the transformer is.

What is the proper fuse model, type, number ar amp for such application? It would be nice if I can buy it from HomeDepot

  • \$\begingroup\$ Since the manufacturer provides no useful information for answering this, you need to ask them. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 6 '17 at 14:59
  • \$\begingroup\$ Any run of cable should be protected by a fuse. Check if the transformer has an integrated fuse/cutout. If so then there's not danger. If not then the installation wasn't safe to begin with. \$\endgroup\$ – ratchet freak Jul 6 '17 at 15:05
  • \$\begingroup\$ Since the action of the bell push is to short the two wires together, you don't need a fuse to protect against a short. You do need a fuse on the mains side of the bell transformer, but that should already be fuse protected. If the transformer mains side is already fuse protected, then you don't need any more. If it is not then look at the VA rating for the transformer and use a slow blow fuse about 3-5 times the maximum current on the mains side. \$\endgroup\$ – Jack Creasey Jul 6 '17 at 16:18

The Buss Fuses "Fuseology" article will help you select a fuse. Fuses are more complicated than you might expect.

You will probably find that the doorbell transformer has an internal fuse.

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  • \$\begingroup\$ If the wires are pulled then they won't be connected to the transformer anymore, i.e. any fuse in the transformer won't help. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 6 '17 at 16:23
  • \$\begingroup\$ Most transformers (that I know of, inex) draw at most a single amp. A 19V, 1A Transformer should then pull ~19W. \$\endgroup\$ – IceMage Feb 5 '19 at 22:33

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