Replies

1. 
   Guest_ | Apr 01, 1999 08:12am | #1

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   John, Two toughts: 1)Some individual breakers just are (or get to be) funky. I've had a 100-amp breaker trip (at 25 amps) when a downstream 30-amp didn't. Replaced it and the problem went away. The free test would be to swap the 20-amp with another 20-amp and see if the problem goes away, stays put, or moves with the breaker. 2) Many flavors of 12 gauge are rated for 25 amps, a few for 30 amps, depending on the temperature ratings of the insulation and how it is installed (raceway, buried, cable, etc.) Check Article 310 after you've looked for the type (THHN, THWN, etc.) and temperature rating (75C, 90C, etc.) printed on the wire. If okay, go to a 25-amp breaker. -David

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   Guest_ | Apr 01, 1999 08:22am | #2

   *John, just a guess and a question.Is the breaker one or two pole (110v or 220v)?Could be the cold is affecting the thermal bi-metal nature of the breaker... it "senses" a greater draw than actually occurs. OR... could the saw be drawing over the rated amperage in a peak spike brought on by the cold? A clamp-on recording type ampmeter would reveal all. I believe Fluke make such a device.

1. 
   Guest_ | Apr 01, 1999 05:00pm | #3

   *The bearings in your saw may be bad. How easy is it to turn the blade by hand (with the power off)? Breakers usually trip at a higher load when cold.

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   Guest_ | Apr 01, 1999 05:49pm | #5

   *Checking amps is tricky. Starting amps are probably 60-80 for a few seconds. Running amps are (should be) close to the name plate on the motor (15-ish?). Some types of motor faults, like a bearing going bad, can be detected in advance by changes in the amp draw or imbalances in 3-phase amp draw. Sounds like a marginal breaker or a saw that is pulling a little too many amps when cold. John: does it trip on start or trip on run? Another general possibility for these kinds of situations: If the motor is at the far end of a wiring run and you have 208 volts at your house (versus 240), the motor could be seeing about 200 volts. At lower voltages, it will pull more amps. The fix is to elimate all wimpy extension cords, run bigger gauge wire in a more direct path, and (worst case) install a "Buck & Boost" transformer from Graingers to get another 15% of voltage. Had to do that once when my equpment was only getting 198 volts on hot afternoons with everything else running. -David

2. 
   JohnKeller | Apr 01, 1999 05:49pm | #4

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   I have added a new workshop onto my home
   I ran 220v and set up a new breaker panel in the shop. I used 12 gage wire and 20A breakers. The problem is when it is cold(below freezing)the breaker that the table saw is on trips. Once I reset the breaker evrything is fine. No other power tools give me this trouble.