Problems installing doorbell transformer

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  #1  
Old 01-28-17, 12:03 PM
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Problems installing doorbell transformer

Installing a new 16VAC doorbell transformer. House only had a wireless doorbell before. I bought this one: Wired Door Bell Transformer-216597 - The Home Depot

I am mounting it to an existing box that has nothing in it yet, other than the incoming line. The line has a white, black and bare copper (ground) wire. The voltage between

white-black is 0V
black-ground is 120V
white-ground is 0V

The transformer has 3 wires, black, white and green. Instructions say to wire white-white, black-black, green-ground. When I do that and turn on the power, the breaker trips. I disconnected the transformer and tested the continuity on the transformer and the black and white lines are shorted. I went back to Home Depot and tested the continuity of the other transformers on the shelf, and all the whites and blacks were shorted. So I guess this is by design. But I can't wire this to my house because it is shorting my house black and white together and tripping the breaker.

Since there is 120V between the house black and ground, I tried wiring the transformer black-black, green-ground, white hanging loose. The breaker does not trip and the output reads 16V as needed. But the white neutral on the transformer isn't connected to anything, and it is not wired per mfr instructions.

What am I missing?
 
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Old 01-28-17, 12:15 PM
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Is this a box and cable you installed. If so where does the cable come from. The white is obviously not a neutral. Ground can not (safely) be used as a neutral.
and tested the continuity of the other transformers on the shelf, and all the whites and blacks were shorted.
I doubt it. You have to check with your multimeter set to the lowest ohm scale. Reading should be between 50-200 ohms. Check the battery(ies) in your multimeter.

Main thing now though is full details on the cable you are trying to use.
 
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Old 01-28-17, 01:24 PM
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Go back to the box this cable came from. check the connection on the white wire.
 
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Old 01-28-17, 01:40 PM
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Be very careful.


The transformer has 3 wires, black, white and green. Instructions say to wire white-white, black-black, green-ground. When I do that and turn on the power, the breaker trips.
I see it as the ground is possibly hot.
 
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Old 01-28-17, 01:41 PM
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Is this a box and cable you installed. If so where does the cable come from. The white is obviously not a neutral. Ground can not (safely) be used as a neutral.
No I did not install it. It's a line that is on the same circuit as bedroom outlets. Some of those outlets work and some do not.

You have to check with your multimeter set to the lowest ohm scale. Reading should be between 50-200 ohms. Check the battery(ies) in your multimeter.
I had the scale set too high. The reading is 150 ohms black-white.

What should these line measurements be?

white-black is 0V
black-ground is 120V
white-ground is 0V
 
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Old 01-28-17, 01:51 PM
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Black to white should be 120. Black to ground 120, White to ground 0. I would look for the last working outlet and the next one in line for a loose wire, either in wire nut or a backstabed wire. all backstabed wires should be moved to screws.
 
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Old 01-28-17, 02:00 PM
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I will replace all the outlets and report back. I already have the new receptacles (I am working on several upgrades currently). I will only use screw terminals.
 
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Old 01-28-17, 04:21 PM
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I will replace all the outlets and report back.
No magic parts to fail inside regular receptacles. The problem will be a bad or reversed connection probably at the supply to the chime transformer box.
 
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Old 01-28-17, 05:00 PM
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I mean, I am replacing all my receptacles anyway (from brown to white), so any loose or broken connections will be found and fixed.
 
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Old 01-28-17, 06:22 PM
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so any loose or broken connections will be found and fixed.
You also need to look for an incorrect connection at the box supplying the chime.
I am mounting it to an existing box that has nothing in it yet
A bit off topic but where is this box. You are saying it was already there? Could you post a picture of ut and the wires inside. http://www.doityourself.com/forum/li...rt-images.html
 
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Old 01-29-17, 11:18 AM
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A bit off topic but where is this box. You are saying it was already there? Could you post a picture of ut and the wires inside.
Yes, it was already in the wall. I am replacing it with a 2-gang and putting the xformer in one side instead of mounting the xformer to the side of the box. There is not much to see, but here it is.

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Old 01-29-17, 11:55 AM
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The transformer is not made to mount inside a box. They mount on the outside, typically on an exposed box.

You also need to keep the line voltage separate from the low voltage.
 
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Old 01-29-17, 12:28 PM
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Now you know why I asked where the box was. As PCBoss wrote that won't work. In addition to the code violation there might be heat build up from the transformer.

Is there a near by receptacle box that the cable in the box comes from?

The chime transformer is often mounted on a box in an unfinished attic or basement. Sometimes to side of the breaker box if the breaker box is located inside. You could also place it in a closet using a recessed box and cover plate with a half inch knockout for the " nipple on the transformer.
 
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Old 01-30-17, 12:13 PM
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I am all set! I found the bad outlet in one of the bedrooms. Looked like it shorted out at some point because wires were burnt and brittle. Cut them back and replaced receptacle. All outlets working. Voltages at chime box measure per standard. Thanks all for the help
 
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Old 01-30-17, 12:27 PM
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But you can not install it that way so you are not set.
 
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Old 01-30-17, 12:37 PM
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Are you talking about the mounting of the xfmr? A lot of people mount them to the outside of a box inside the wall. I ran it for a while on the counter and it hardly gets even warm under load. I am using the metal box with one side off to get the whole thing neater, better support, and be able to get to the xfmr easily if I need to (with the hybrid wall plate). What difference does it make if it's on the outside of the box, against insulation in the wall, or the way I did it? Also, I do not have the lv and hv lines together.
 
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Old 01-30-17, 02:04 PM
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Those transformers should not be mounted in a wall or inside a box.
 
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Old 01-30-17, 03:15 PM
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I am using the metal box with one side off to get the whole thing neater, better support,
You can't remove one side of a metal box. It is a code violation to modify the box and creates a fire hazard because the box can no longer contain a spark or fire.
 
 

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