Doorbell Oddity


A building has several apartments. Each one has a doorbell, and 4 wires coming to the doorbell. One set is (I assume) for the downstairs main door and the second one is for the door of the apartment.
When I went to replace the old doorbell, the button at the main entry door worked and two wires were connected. The apt. door button didn't work and two wires were disconnected. I couldn't get the apt door bell to work by connecting the two wires to the doorbell at the "rear door" section. In fact one of the wires sparked when I touched it to the terminal.
When I installed the new doorbell, the same thing happened. The entlry door still works when on the "front door" terminal and "transformer", but no joy with the apt door. I put a cheap meter on all four wires to discover which was the transformer wire for each set of two. I got odd readings, something like 50 and 75 volts AC. I figured this was incorrect since the actual voltage should be around 16VAC, and indeed I could touch the wires with no problem.
So what's happening?
Why do I get a higher reading than it should be? Is it because the wires were not connected to anything? Oh, I put the neg test lead into an extension cord on the neutral side (assuming that the plug it was pluged into was wired correctly) and use the pos test lead on the wires coming out of the wall.
What likely caused the arcing when I touched one of the 2nd pair of wires to the doorbell?
Is it likely that the second pair of wires has its own "transformer" lead rather than just taking power from the transformer wire from the first pair?
I assume there's been this problem for a while since the 2nd pair of wires (apt front door) was disconnected. Any way to track down what the problem might be?
Any additional info you need?
--
charles

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Charles Bishop wrote:

For openers, do not use the house outlet neutral for your neg lead. the doorbell trasformer's output has no connection to your AC wiring.
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try this site for basic info:
http://home.howstuffworks.com/doorbell3.htm
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This was helpful, and yet, not helpful. I know how a doorbell works, that the push button is only a switch in one leg of the circuit, but haven't a clue what might be wrong with the setup I've found. I was looking for test suggestions on how to track down the problem.
In short, there are two push buttons, and one works, with its wires on trans and "front door". The second push button has its wires at the doorbell, but unconnected, and that's how I found them. connecting them to trans and rear door doesn't work, and one of them arcs when I touch it to "trans" terminal.
It's possible that there is a problem in the walls, but I'm not sure how to test to see if this is the case.
As usual, sometimes typing out the problem can help. I think I'll disconnect the front door setup and connect the rear door pair and see if this works on its own. I should also check for continuity.
--
charles

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Charles Bishop wrote:

There's a good chance the back door wire was shorted inside the wall. Someone may have driven a nail through it, or it may have just broken and shorted inside the door trim from being pushed in and out too many times when replacing doorbell buttons.
Run a new wire to the back door.
--
Steve Bell
New Life Home Improvement
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