CMS question

[vaking]

Just got myself new 12" CMS. Put it together, turned it on and noticed something I don't like. It has a motor rated at 15Amp. I have 2 circuits in my shop, both are 20Amps. On one circuit the braker opens up instantly the moment I turn this thing on. On the other circuit it runs without popping up the breaker even together with my DC on the same circuit. However, the motor for CMS feels warm after one minute of working with no load. I have not yet sunk its teeth into wood at all. I believe BT motor is also around 15 Amps and have been running the BT on both those circuits.
Do I have a defective braker or the motor on the brand new CMS is bad? This is my first CMS, don't know much about these beasts yet. Is it supposed to get warm in 1 minute of idle spinning? And what will it do if it actually touches the wood? I can probably get my multimeter and start measuring amps.

[maxparot]

Mitersaw motors are not designed for and kind of continueous running. They are design for start and stop operation. Warm isn't anything to worry about. As for your breaker I'd check to see if anything else is using that circuit. If the saw runs on one circuit but not the other then I'd say the saw is fine. 15 amps is typical.

[just4funsies]

Your BT and your CMS may not have EXACTLY the same load characteristics, which might explain why the BT works on both circuits, but the CMS does not. The fact that the CMS works on one circuit, but not the other, indicates a possible wiring problem or breaker going bad. If all else is equal (meaning no other loads on either circuit), I would look at the circuit breaker on the circuit that trips with the CMS. Is it the same type as the one that holds (some have built-in time delays, others do not)? If so, swap them, to see if the tripping problem moves with the breaker. If it does, replace the breaker (it's weak). If it stays with the circuit, look for a loose or bad connection (burned insulation, crispy wire-nut, loose terminal screw, etc.). Smaller wire or significantly longer wiring distance could also be the culprit in the circuit with the tripping problem.

CAVEAT: When working on power circuits, ALWAYS: Turn OFF the main breaker or service disconnect, Check the main circuits with a meter to make SURE they're dead, and then CONTINUE to treat all circuits like they're HOT while you're working. Better to be safe (you won't get a chance to be sorry. You'll be DEAD...).

[ted van halen]

CAVEAT: When working on power circuits, ALWAYS: Turn OFF the main breaker or service disconnect, Check the main circuits with a meter to make SURE they're dead, and then CONTINUE to treat all circuits like they're HOT while you're working. Better to be safe (you won't get a chance to be sorry. You'll be DEAD...).

Ain't that the truth. I had my heat pump replaced years ago. HVAC guy killed the breaker & went to unhook the air handler in the closet. Next thing I know ...BZZZZ...BZZZZ...smoke....FIRE... from the breaker box. I thought for sure I got a dead HVAC guy who also is a friend of mine in my closet now. He walks out & says he ALWAYS pushes the hot to ground w/ very well insulated lineman pliers. Turns out the breaker did not open up. 2nd time in 30+ years that happened to him. 60 amps, he would've been toast if not for that one precaution. It wasn't the safest thing to do, but it saved his life.

Ted

[sacherjj]

I would prefer taking the hot to ground with a $10 meter. That makes less arcs and smoke.

[ted van halen]

I would prefer taking the hot to ground with a $10 meter. That makes less arcs and smoke.

I'm w/ you on that. I asked why he didn't use the meter & I'm not sure what he said but it must've made sense at the time. Like I said, not the safest thing to do. I sure wouldn't.

[wreckwriter]

kinda off topic but not really....

Back in the early 80s I worked in an anodizing shop. One day the heater in a rinse tank shorted out sometime prior to me reaching in to grab a rack of parts that had been rinsing.

Luckily the foreman realized I was being smoked and body blocked me away from the tank. I flew across the room with the 40 lb rack of parts still locked in my hand. Voltage later measured above 200 in the water.

One night in the hospital for observation but no apparent lasting damage. I'm REAL careful with electricity these days....

[scorrpio]

As they say, the fastest way to find and pop the correct breaker is to stick a fork into the outlet before opening it.

I said fastest, not safest.

[davehenry]

I've got the same problem with the two lines in my garage. The thickness planner sets one breaker off half of the time. Traced it to a weak breaker. Now only the DC gets plugged into that one and it hasn't flipped yet.

[LinuxRandal]

As they say, the fastest way to find and pop the correct breaker is to stick a fork into the outlet before opening it.

I said fastest, not safest.

Or you could do what my brother did when he was two, he's never liked electricity since. He pee'd on an outlet, if it had been a full stream, instead of a dribble....

[Tom Miller]

Do I have a defective braker or the motor on the brand new CMS is bad?

Given that the other breaker works with it, I'd guess the breaker is the problem. At start up, motors can draw many times their rated current. You may have a breaker that's become a little quick on the trigger finger.

Also, concerning the warm motor: unless it smells like there's something burning, I wouldn't give a second thought.

Enjoy your new CMS!

Regards,
Tom

[JimD]

I would check out the Ground Fault outlet. If you house is new enough, it will have these in the garage or basement as the first outlet on the circuit. I had one of these that tripped prematurely routinely. If it is really your breaker tripping prematurely, I would double check the wire on these circuits to make sure it is 12 gauge as it should be in a 20 amp circuit and if the wire is correct, change the breaker. 20 amp breakers should never trip on 15 amps. The startup current could be a bit above the running current but it seems like you have a breaker or outlet that is trip happy. It happens.

Jim