New Circuit Problem


Old 06-18-01, 12:01 PM
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I just attempet my first 220 circuit and I screwed something up. I hope I can explain clearly.

I added a 2-pole 20 amp CB to my service panel. I have 12/3 wire running upstairs to a thermostat which controls two small baseboard heaters.

I ran the red and black to each pole of the CB. The white went to the neutral bar and the ground to the ground bar (The whites and grounds are separated in my box but appear to be the same thing)

To do a quick test I closed the breaker and tested the red and black wire upstairs and both were hot. (I don't have a meter just a little alarm tester)

Turned power back off and connected the thermostat and the heaters and the breaker tripped right away. I knew something was wrong so I backtracked:

I disconnected both heaters and wired only the line side of the stat. Red-red and black-black only. The white wire was not used so I capped it and the load side of the switch was left disconnected and capped.

With the stat set to OFF I closed the breaker and it tripped again. Does this mean I have a bad stat? I made sure it was a 2-pole 220 volt thermostat. What else could I have done wrong?

It is a new house (5 years old) and I believe I have plenty of capacity on the panel.
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Old 06-18-01, 12:17 PM
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Make sure your source is really wired across the line input of the thermostat, and not between the line in and load out. An ohmmeter would really be useful here to measure the resistance across your stat terminals. A 2 pole stat usually switches one side of the line with the temperature sensing element (bi-metallic) and the other side with a cam when the dial is brought to the "off" position. Listen carefully as you bring the dial up from "off", you should hear a soft click as the cam operated switch makes contact, and another soft click when the dial is brought above the current room temperature. That said, with the dial in the "off" position, no wires in the stat should be making contact together. So try turning your breaker back on with the dial set to "off" (and with the load wires still diconnected from the heaters). If it still trips, your stat IS bad
Old 06-19-01, 07:19 AM
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That should be the answer

You are right about the stat. I do have the click from the off position as well as the temperature click. It is exactly as you described. And it does short when in the OFF position.

As for the line/load part. They make it very clear with red and black leads labeled line and load. I'm going to try to exchange the stat.

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