help wiring a doorbell transformer

[mikeinaustin]

my old transformer died. it had the normal 1 black, 1 white & 1 ground coming from it to connect to the supply wire (also 1 black, 1 white & a ground). However the new transformer has 2 blacks and 1 ground. Each black wire is exactly identical to each other (no strips, writing all the same, etc). 1 of the black wires comes out of the transformer very near the ground while the other black wire comes out an inch away. I would "assume" that the black wire by the ground is the neutral and the other one is the hot OR that for this transformer it does not matter. However, i don't like to assume. The transformer is a Quorum International 7-30 (16v, 30w). Any one know what i should do in this case?

 

[mahansm]

Connect the two black wires from the transformer to the white and black supply wires. Connect the ground to the bare safety ground.
Connect the output leads to the doorbell as before.

The transformer should have isolated windings. Check with a multimeter on ohms setting across one of the input leads and one of the output leads. If it shows open, you're fine, and polarity does not matter.

Steve Mahan
MSEE (among other things)

 

[Carbon]

Connect one black to black and the other black to white. Polarity does not matter for a doorbell transformer.